Synthesis of thiadiazole derivatives bearing hydrazone moieties and evaluation of their pharmacological effects on anxiety, depression, and nociception parameters in mice

Article abstract of DOI:10.1007/s12272-012-0410-6

Novel thiadiazole derivatives bearing hydrazone moieties were synthesized through the reaction of 2-[(5-methyl-1,3,4-thiadiazol-2-yl)thio)]acetohydrazide with aldehydes/ketones. The chemical structures of the compounds were elucidated by 1H-NMR, 13C-NMR,

Full text of DOI:10.1007/s12272-012-0410-6

Arch Pharm Res Vol 35, No 4, 659-669, 2012
DOI 10.1007/s12272-012-0410-6
Synthesis of Thiadiazole Derivatives Bearing Hydrazone Moieties and
Evaluation of Their Pharmacological Effects on Anxiety, Depression,
and Nociception Parameters in Mice
1
2
1
·
1
1
Özgür Devrim Can , Mehlika Dilek Alt
l
ntop , Ümide Demir Özkay , Umut Irfan Üçel , Bürge Do g˘ ruer ,
2
and Zafer As
l
m Kaplanc
l l
kl
1
2
Department of Pharmacology, Faculty of Pharmacy, Anadolu University, 26470 Eski ¸s ehir, Turkey and Department of
Pharmaceutical Chemistry, Faculty of Pharmacy, Anadolu University, 26470 Eski ¸s ehir, Turkey
(Received August 16, 2011/Revised December 1, 2011/Accepted December 2, 2011)
Novel thiadiazole derivatives bearing hydrazone moieties were synthesized through the reac-
tion of 2-[(5-methyl-1,3,4-thiadiazol-2-yl)thio)]acetohydrazide with aldehydes/ketones. The
1
13
chemical structures of the compounds were elucidated by H-NMR, C-NMR, MS-FAB spec-
tral data, and elemental analyses. Behavioral effects of the test compounds in mice were
examined by hole-board, activity cage, tail suspension and modified forced swimming tests
(MFST). Antinociceptive activities were evaluated using the hot-plate and tail-clip methods.
Results of the experiments indicated that the test compounds did not significantly change the
exploratory behaviors or locomotor activities of animals in the hole-board and activity cage
tests, respectively. Administration of the reference drug fluoxetine (10 mg/kg) and compounds
3
a
,
3b
suspension and MFST tests, indicating the antidepressant-like effects of these derivatives.
Morphine (10 mg/kg) and compounds 3a 3b 3c 3d 3e 3j 3k, and 3l increased the reaction
, 3c, 3j, 3k, and 3l significantly shortened the immobility times of animals in the tail
,
,
,
,
,
,
times of mice in both the hot-plate and tail-clip tests, indicating the antinociceptive effects of
these compounds. To the best of our knowledge, this is the first study of central nervous sys-
tem activities of chemical compounds carrying thiadiazole and hydrazone moieties together on
their structures.
Key words: Thiadiazole, Hydrazone, Antidepressant, Antinociceptive, Tail suspension, Forced
swimming test, Hot-plate, Tail-clip
INTRODUCTION
al., 2009). Numerous studies have confirmed that the
,3,4-thiadiazole derivatives exhibit a broad CNS-
1
Thiadiazole, a 5-member diunsaturated ring struc- related activity spectrum, including antidepressant
ture containing 2 nitrogen atoms and 1 sulphur atom, (Brufani et al., 1994; Varvaresou et al., 1998; Clerici
occurs in 4 isomeric forms. These forms are 1,2,3-thia- and Pocar, 2001; Yusuf et al., 2008; Pattanayak et al.,
diazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, and 1,3,4- 2009; Sharma et al., 2011), anxiolytic (Clerici and Pocar,
thiadiazole.
2001; Pattanayak et al., 2009; Sharma et al., 2011),
en et al., 2007; Pandey et
A considerable amount of research has been carried and analgesic (Salgin-Göks
¸
out on the effects of thiadiazoles on the central nervous al., 2011) effects. Anticonvulsant properties have also
system (CNS). Among thiadiazole derivatives, 1,3,4- been reported for various thiadiazole derivatives
thiadiazoles have received a great deal of attention as (Chapleo et al., 1986; Stillings et al., 1986; Pattanayak
important pharmacophores in drug design (Siddiqui et et al., 2009; Rajak et al., 2009; Sharma et al., 2011).
Moreover, acetazolamide, one of the currently used anti-
Correspondence to: Özgür Devrim Can, Department of Pharmaco-
logy, Faculty of Pharmacy, Anadolu University, 26470 Eskisehir,
¸
Turkey
Tel: 90-222-335-0580 ext 3751, Fax: 90-222-335-0750
E-mail: ozgurdt@anadolu.edu.tr
convulsant drugs, has 1,3,4-thiadiazole nuclei in its
structure (Chufán et al., 1999).
In addition to thiadiazoles, hydrazides and hydrazones
show CNS-related effects, particularly antidepressant
659

660
Ö. D. Can et al.
activity (Ergenç et al., 1998). Irreversible and non- a VG Quattro mass spectrometer (Agilent). Elemental
selective monoamine oxidase (MAO) inhibitory drugs, analyses were performed on a Perkin Elmer EAL 240
iproniazid, isocarboxazid, and nialamide are examples elemental analyser (Perkin-Elmer).
of clinically used antidepressant agents with hydrazide
groups (Rollas and Küçükgüzel, 2007). Moreover, anti- General procedure for synthesis of compounds
convulsant (Ragavendran et al., 2007) and analgesic
(
Silva et al., 2004; Salgin-Göks
¸
en et al., 2007) activities Ethyl 2-[(5-methyl-1,3,4-thiadiazol-2-yl)thio]acet-
have been reported for various hydrazide/hydrazone ate (1)
derivative compounds.
A mixture of 5-methyl-1,3,4-thiadiazole-2-thiol (0.05
The CNS-related activities of both thiadiazole and mol) and ethyl chloroacetate (0.05 mol) in the pre-
hydrazone moieties prompted us to synthesize novel sence of potassium carbonate (0.05 mol) in acetone was
compounds bearing both of these biolabile components refluxed for 10 h. The reaction mixture was cooled and
on their structures in our search for new pharmacolo- filtered, and the crude product was dissolved in water
gically active drug candidates. We combined thiadia- and then extracted with ether (Kidwai and Kumar,
zole and hydrazone moieties by a thioether group. 1996).
This method increases lipophilicity of CNS-targeted
drugs, thereby enhancing passage across the blood- 2-[(5-Methyl-1,3,4-thiadiazol-2-yl)thio)]acetohy-
brain barrier and improving drug delivery to sites of drazide (2)
action (Waterbeemd and Mannhold, 1996; Silverman,
004).
We used a bioisosteric replacement approach for perature for 3 h and then filtered (Kidwai and Kumar,
A mixture of the ester (
hydrate (0.1 mol) in ethanol was stirred at room tem-
1) (0.05 mol) and hydrazine
2
designing the new compounds. Bioisosteric replace- 1996).
ment can be defined as the rational modification of a
part of a biologically active molecule to elicit similar 2-[(5-Methyl-1,3,4-thiadiazol-2-yl)thio]-N'-[(aryl)
biological activity. The bioisosteric replacement of methylidene/ethylidene]acetohydrazide (3a-o)
benzene with a heteroaromatic ring resulted in analo-
A mixture of the hydrazide (2) (0.01 mol) and al-
gues maintaining the same biological activity within a dehydes/ketones (0.01 mol) was refluxed in ethanol for
series of different pharmacological agents, lending great 5 h, filtered and crystallized from ethanol.
importance to ring-equivalent bioisosteres. Pyridine,
furan, and thiophene, which are structurally related 2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(pyridin-
to benzene, are widely used as ring equivalents in drug 2-yl)methylene]acetohydrazide (3a)
1
development (Patani and LaVoie, 1996; Lima and
H-NMR (500 MHz, DMSO-
d
6
): 2.65-2.69 (3H, s, CH
), 7.42-8.81 (5H, m, -N
we used these bioisosteres to derive our chemical com- =CH-, pyridine), 11.93 and 12.04 (1H, two s, N-H).
3
),
Barreiro, 2005; Ciapetti and Giethlen, 2008). Therefore, 3.97 and 4.63 (2H, two s, S-CH
2
13
pounds.
In summary, our research group aimed to synthesize (CH
novel thiadiazole derivatives bearing hydrazone moie- (C), 145.67 (CH), 150.92 (CH), 154.16 (C), 165.93 (C),
ties and examine their effects on pain perception and 170.55 (C). For C11 OS calculated: C, 45.03; H,
C-NMR (125 MHz, DMSO-
d ): 15.76 (CH ), 36.44
6 3
2
), 120.99 (CH), 126.11 (CH), 137.57 (CH), 139.91
H
11
N
5
2
depression and anxiety parameters in mice. We also 3.78; N, 23.87; found: C, 45.00; H, 3.80; N, 23.85. MS
+
investigated structure-activity relationships in differ- (FAB) [M+1] : m/z 294.
ent bioisostere substitutions.
2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(pyridin-
MATERIALS AND METHODS
3-yl)methylene]acetohydrazide (3b)
H-NMR (500 MHz, DMSO-d6): 2.67-2.69 (3H, s, CH3),
1
Chemistry
Materials
4.20 and 4.61 (2H, two s, S-CH
=CH-, pyridine), 11.90 (1H, s, N-H). C-NMR (125 MHz,
2
), 7.47-8.86 (5H, m, -N
13
All reagents were purchased from commercial sup- DMSO-d6): 15.75 (CH ), 36.54 (CH ), 125.16 (CH),
3
2
pliers and used without further purification. Melting 131.13 (C), 134.75 (CH), 142.43 (C), 145.88 (CH),
points were determined with an Electrothermal 9100 149.93 (CH), 151.98 (CH), 164.76 (C), 169.98 (C). For
melting point apparatus (Weiss-Gallenkamp) and were C H N OS calculated: C, 45.03; H, 3.78; N, 23.87;
1
1
11
5
2
1
13
+
uncorrected. H-NMR and C-NMR spectra were re- found: C, 45.04; H, 3.81; N, 23.88. MS (FAB) [M+1] :
corded on a Bruker 500 MHz and 125 MHz spectrometer m/z 294.
(Bruker), respectively. Mass spectra were recorded on

Effect of Thiadiazole Derivatives on CNS of Mice
661
2
-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(pyridin- 164.22 (C), 169.22 (C). For C H N OS calculated: C,
11 12 4 3
4
-yl)methylene]acetohydrazide (3c)
42.29; H, 3.87; N, 17.93; found: C, 42.31; H, 3.89; N,
), 4.21 17.91. MS (FAB) [M+1] : m/z 313.
1
+
H-NMR (500 MHz, DMSO-
d
6
): 2.67 (3H, s, CH
3
and 4.63 (2H, two s, S-CH ), 7.65-8.66 (5H, m, -N=CH-,
2
13
pyridine), 12.03 (1H, s, N-H). C-NMR (125 MHz, 2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(1H-pyr-
DMSO- ): 15.75 (CH ), 36.43 (CH ), 122.07 (2CH), rol-2-yl)methylene]acetohydrazide (3h)
42.39 (C), 142.77 (C), 146.15 (CH), 151.64 (2CH),
65.06 (C), 170.23 (C). For C11 OS calculated: C, and 4.52 (2H, two s, S-CH
5.03; H, 3.78; N, 23.87; found: C, 45.05; H, 3.79; N, pyrrole), 11.20 (1H, br, pyrrole N-H), 11.42 and 11.68
d
6
3
2
1
1
1
4
2
H-NMR (500 MHz, DMSO-d6): 2.68 (3H, s, CH ), 4.20
3
H
11
N
5
2
2
), 6.10-8.11 (4H, m, -N=CH-,
+
13
3.90. MS (FAB) [M+1] : m/z 294.
(1H, two s, N-H). C-NMR (125 MHz, DMSO-d6):
7.98 (CH ), 38.74 (CH ), 112.56 (CH), 116.11 (CH),
1
3
2
2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(furan-2- 125.49 (CH), 130.44 (C), 140.04 (C), 143.87 (CH), 165.94
yl)methylene)]acetohydrazide (3d)
H-NMR (500 MHz, DMSO-d6): 2.68 (3H, s, CH ), 4.16 H, 3.94; N, 24.89; found: C, 42.72; H, 3.94; N, 24.84.
(C), 171.34 (C). For C H N OS calculated: C, 42.69;
10 11 5 2
1
3
+
2
and 4.54 (2H, two s, S-CH ), 6.63-8.09 (4H, m, -N=CH-, MS (FAB) [M+1] : m/z 282.
13
furan), 11.69 and 11.75 (1H, two s, N-H). C-NMR (125
MHz, DMSO-d6): 15.76 (CH ), 36.61 (CH ), 113.31 (CH), 2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(1-methyl-
3
2
1
15.06 (CH), 135.32 (CH), 138.31 (CH), 146.50 (C), 1H-pyrrol-2-yl)methylene]acetohydrazide (3i)
1
150.29 (C), 164.47 (C), 169.51 (C). For C H N O S
H-NMR (500 MHz, DMSO-d6): 2.68 (3H, s, CH ), 3.85
10
10
4
2
2
3
calculated: C, 42.54; H, 3.57; N, 19.84; found: C, 42.55; (3H, s, CH ), 4.13 and 4.52 (2H, two s, S-CH ), 6.10-
3
2
+
13
H, 3.60; N, 19.85. MS (FAB) [M+1] : m/z 283.
8.11 (4H, m, -N=CH-, pyrrole), 11.42 (1H, s, N-H). C-
NMR (125 MHz, DMSO-d6): 20.52 (CH ), 41.67 (CH ),
3
3
2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(thiophen-
41.97 (CH ), 114.01 (CH), 121.24 (CH), 132.65 (CH),
2
2
-yl)methylene)]acetohydrazide (3e)
134.34 (C), 143.40 (CH), 146.53 (C), 168.53 (C), 173.79
1
H-NMR (500 MHz, DMSO-d6): 2.68 (3H, s, CH ), 4.15 (C). For C H N OS calculated: C, 44.73; H, 4.44; N,
3
11 13
5
2
and 4.50 (2H, two s, S-CH ), 7.13-8.42 (4H, m, -N=CH-, 23.71; found: C, 44.75; H, 4.42; N, 23.72. MS (FAB)
2
13
+
thiophene), 11.72 and 11.76 (1H, two s, N-H). C-NMR [M+1] : m/z 296.
125 MHz, DMSO- 6): 15.76 (CH ), 36.41 (CH ), 129.12
CH), 129.19 (CH), 129.97 (CH), 130.40 (CH), 140.36 2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(1H-indol-
C), 143.69 (C), 164.37 (C), 169.35 (C). For C10 OS 3-yl)methylene]acetohydrazide (3j)
(
d
3
2
(
(
H
10
N
4
3
1
calculated: C, 40.25; H, 3.38; N, 18.78; found: C, 40.27;
H, 3.40; N, 18.75. MS (FAB) [M+1] : m/z 299.
6 3
H-NMR (500 MHz, DMSO-d ): 2.69 (3H, s, CH ), 4.28
+
and 4.74 (2H, two s, S-CH ), 7.08-8.50 (6H, m, -N=CH-,
2
indole), 10.72 (1H, s, indole N-H), 11.51 (1H, s, N-H).
13
2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(5-methyl-
6 3
C-NMR (125 MHz, DMSO-d ): 15.76 (CH ), 37.10
furan-2-yl)methylene]acetohydrazide (3f)
(CH ), 110.40 (C), 111.10 (CH), 119.80 (CH), 121.70
), 2.68 (CH), 121.80 (CH), 126.30 (C), 130.70 (CH), 137.10 (C),
2
), 6.26- 142.70 (C), 143.30 (CH), 164.20 (C), 170.20 (C). For
2
1
H-NMR (500 MHz, DMSO-
3H, s, CH ), 4.17 and 4.53 (2H, two s, S-CH
.98 (3H, m, -N=CH-, furan), 11.60 and 11.66 (1H, two C H N OS calculated: C, 50.74; H, 3.95; N, 21.13;
6
d ): 2.34 (3H, s, CH
3
(
3
7
1
4
13
5
2
13
+
s, N-H). C-NMR (125 MHz, DMSO-
d
6
): 14.11 (CH
), 109.72 (CH), 116.86 (CH), m/z 332.
35.45 (CH), 138.17 (C), 148.78 (C), 156.06 (C), 164.29
calculated: C, 44.58; 2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(naphtha-
H, 4.08; N, 18.90; found: C, 44.60; H, 4.11; N, 18.93. len-1-yl)methylene]acetohydrazide (3k)
3
), found: C, 50.72; H, 3.97; N, 21.11. MS (FAB) [M+1] :
3 2
15.76 (CH ), 36.66 (CH
1
12 4 2 2
(C), 169.30 (C). For C11H N O S
+
1
MS (FAB) [M+1] : m/z 297.
H-NMR (500 MHz, DMSO-d6): 2.68 (3H, s, CH ), 4.22
3
2
and 4.67 (2H, two s, S-CH ), 7.58-8.85 (8H, m, -N=CH-,
13
2
-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(5-methyl- naphthalene), 11.78 (1H, br, N-H). C-NMR (125 MHz,
thiophen-2-yl)methylene]acetohydrazide (3g)
DMSO-d6): 20.55 (CH ), 41.64 (CH ), 129.69 (CH),
3 2
1
H-NMR (500 MHz, DMSO-
), 4.14 and 4.47 (2H, two s, S-CH
.32 (3H, m, -N=CH-, thiophene), 11.64 and 11.67 (1H, (C), 139.60 (C), 149.76 (CH), 169.37 (C), 174.46 (C).
d
6
): 2.47 (3H, s, CH
3
), 2.68 130.39 (CH), 131.54 (CH), 131.59 (CH), 132.34 (CH),
(
8
3H, s, CH
3
2
), 6.82- 133.31 (CH), 133.44 (C), 134.48 (C), 134.84 (CH), 134.90
13
two s, N-H). C-NMR (125 MHz, DMSO-d6): 15.76 For C H N OS calculated: C, 56.12; H, 4.12; N,
16
14
4
2
(
CH
3 3 2
), 19.15 (CH ), 36.46 (CH ), 127.58 (CH), 132.33 16.36; found: C, 56.13; H, 4.10; N, 16.39. MS (FAB)
+
(CH), 137.65 (CH), 140.55 (C), 143.92 (C), 144.46 (C), [M+1] : m/z 343.

662
Ö. D. Can et al.
o
2
-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[(biphen- trolled temperature (25 ± 1 C) and a 12-h light/dark
yl-4-yl)methylene]acetohydrazide (3l)
cycle. Temperature, sound, and light conditions were
1
H-NMR (500 MHz, DMSO-d ): 2.67 (3H, s, CH ), 4.19 not altered during the course of the experiments.
6 3
and 4.62 (2H, two s, S-CH ), 7.39-8.25 (10H, -N=CH-,
All animals were acclimatised to the laboratory
biphenyl), 11.79 (1H, s, N-H). C-NMR (125 MHz, environment at least 48 h before the experiments.
DMSO- ): 15.76 (CH ), 36.63 (CH ), 127.93 (2CH), Food was withdrawn 12 h before experiments in order
28.30 (CH), 128.78 (2CH), 129.01 (2CH), 129.16 (2CH), to avoid food interference with substance absorption,
2
13
d
6
3
2
1
1
34.31 (C), 140.63 (C), 142.84 (C), 144.85 (C), 148.12 although water was allowed ad libitum. The experi-
OS calcul- mental protocols were approved by the Local Ethical
ated: C, 58.67; H, 4.38; N, 15.21; found: C, 58.70; H, Committee on Animal Experimentation of Eskisehir
(CH), 167.07 (C), 169.77 (C). For C18
H N
16 4
2
¸
+
4.41; N, 15.19. MS (FAB) [M+1] : m/z 369.
Anadolu University, Turkey.
2-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[1-(furan-
Administration of compounds
2
-yl)ethylidene]acetohydrazide (3m)
Animals were randomly divided into the following
), 2.67 groups: control group, reference drug-treated group and
1
H-NMR (500 MHz, DMSO-
d
6
): 2.22 (3H, s, CH
3
(
3H, s, CH ), 4.27 and 4.56 (2H, two s, S-CH ), 6.60- test compound-treated groups (n = 6 animals/group).
3
2
7
.81 (3H, m, furan), 10.71 and 10.94 (1H, two s, N-H).
C-NMR (125 MHz, DMSO-d ): 13.88 (CH
6 3
Behavioral tests and nociceptive measurements were
), 15.75 performed in different groups of animals. In behavioral
CH ), 37.17 (CH ), 112.26 (CH), 113.07 (CH), 142.12 tests, control solution, reference drug fluoxetine (Flx,
1
3
(
3
2
(CH), 145.84 (2C), 152.96 (C), 164.91 (C), 170.38 (C). For 10 mg/kg), and the test compounds (100 mg/kg) were
11 12 4 2 2
C H N O S
calculated: C, 44.58; H, 4.08; N, 18.90; injected intraperitoneally (i.p) for 3 times; 24, 5 and
found: C, 44.60; H, 4.11; N, 18.88. MS (FAB) [M+1] : 0.5 h before testing (Can et al., 2009).
m/z 297. For nociceptive measurements, control solution, the
+
reference drug morphine sulphate (10 mg/kg), and the
test compounds (100 mg/kg) were injected (i.p) once,
30 min before testing (Kaplancikli et al., 2009).
2
-(5-Methyl-1,3,4-thiadiazol-2-ylthio)-N'-[1-(thio-
phen-2-yl)ethylidene]acetohydrazide (3n)
1
H-NMR (500 MHz, DMSO-
6 3
d ): 2.29 (3H, s, CH ), 2.68
(
3H, s, CH ), 4.26 and 4.52 (2H, two s, S-CH ), 7.09-7.61 Behavioral tests
3
2
(
3H, m, thiophene), 10.75 and 11.00 (1H, two s, N-H).
Assessment of exploratory behavior
Exploratory behavior of mice was screened using
13
C-NMR (125 MHz, DMSO-
CH ), 37.05 (CH
CH), 144.52 (C), 146.49 (C), 150.64 (C), 164.71 (C), No. 6650) consisted of gray Perspex panels (40 cm
6 3
d ): 14.68 (CH ), 15.76
(
(
1
3
3
2
), 128.79 (CH), 129.48 (CH), 129.77 hole-board tests. The hole-board apparatus (Ugo Basile,
40
calculated: C, 42.29; H, cm, 2.2 cm thick) with 16 equidistant holes 3 cm in
.87; N, 17.93; found: C, 42.31; H, 3.85; N, 17.91. MS diameter in the floor. Head-dipping was measured by
×
12 4 3
70.19 (C). For C11H N OS
+
(FAB) [M+1] : m/z 313.
infrared cells placed under the holes. In hole-board
testing, each mouse was individually placed in the
centre of the apparatus facing away from the observer
and allowed to explore freely for 5 min. Total number
6 3
d ): 2.31 (3H, s, CH ), 2.69 of head-dips, latencies prior to the first head-dips, and
2
-(5-methyl-1,3,4-thiadiazol-2-ylthio)-N'-[1-(1H-in-
dol-3-yl)ethylidene]acetohydrazide (3o)
1
H-NMR (500 MHz, DMSO-
2
3H, s, CH ), 4.28 and 4.74 (2H, two s, S-CH ), 7.08-8.50 total number of explored holes were recorded during
(
3
(
1
d
5H, m, indole), 10.72 (1H, s, indole N-H), 11.47 and the test session (Takeda et al., 1998; Can et al., 2010).
13
1.51 (1H, two s, N-H). C-NMR (125 MHz, DMSO-
): 14.75 (CH ), 15.76 (CH ), 37.10 (CH ), 111.10 (CH),
12.50 (C), 119.80 (CH), 121.70 (CH), 121.80 (CH),
6
3
3
2
Assessment of spontaneous locomotor activity
Spontaneous locomotor activities of mice were moni-
1
1
26.30 (C), 127.10 (CH), 137.10 (C), 142.70 (C), 164.20 tored in activity cage apparatus (Ugo Basile, No. 7420)
OS calculated: containing 2 pairs of 16 photocells placed 3 cm and 12
C, 52.15; H, 4.38; N, 20.27; found: C, 52.13; H, 4.40; N, cm above the floor under a transparent cover. Inter-
(C), 165.80 (C), 170.20 (C). For C15
H N
15 5
2
+
2
0.25. MS (FAB) [M+1] : m/z 346.
ruptions of light beams during vertical and horizontal
movements of the animals were automatically recorded
for 5 min (Can et al., 2009).
Pharmacology
Animals
Adult BALB/c mice weighing 30-35 g were used for
all tests. Animals were housed in a room with con-
Assessment of antidepressant activity
Antidepressant-like activity of the test compounds

Effect of Thiadiazole Derivatives on CNS of Mice
663
was screened using tail suspension and modified passed before the mouse began biting the clamp was
forced swimming tests (MFST). Tail suspension tests recorded by a stopwatch. A sensitivity test was carried
were performed similarly to tests described by Steru out before the experimental session, and animals that
et al. (Steru et al., 1985). Mice were dangled from their did not respond to the clamp within 10 sec were
tails using adhesive tape placed approximately 1 cm excluded from the experiments. Maximum latency
from the tip of the tail and attached to an applicator time (cut-off time) for the tail-clip tests was chosen as
stick. Then, the mice were hung approximately 30 cm 10 sec to avoid possible tissue damage. Analgesia was
above a table and were considered immobile only expressed as a percentage of the maximum possible
when they did not make struggling movements and effect (MPE %), according the following equation (Can
hung passively. Immobility time for each animal was et al., 2010):
recorded by a stopwatch during the last 4 min of a 6-
min test (Can et al., 2011).
In MFST tests, mice were forced to swim individual-
ly in a glass cylinder (diameter, 12 cm; height, 30 cm)
containing 20 cm of water at 25 ± 1 C. Twenty-four Statistical analyses
MPE % = [(post drug latency
− pre drug latency)/
(cut-off time pre drug latency)] × 100.
−
o
hours prior to the MFST, animals were exposed to a
Statistical analyses of the experimental data were
pre-test for 15 min. In test session, swimming (hori- performed using GraphPad Prism 3.0 software (Graph-
zontal movement on the surface of the water and Pad Software). Experimental data were evaluated by
crossing into another quadrant), climbing (upward- one-way analysis of variance (ANOVA) followed post
directed movements of the forepaws along the side of hoc by Tukey’s honestly significantly different (HSD)
the swim chamber), and immobility (the minimum test. The results are presented as mean ± S.E.M. Dif-
movement required to keep the head above water) ferences between data sets were considered significant
times over 5-sec intervals were recorded for 5 min by when the
a stopwatch (Cryan et al., 2002; Tanaka and Telegdy,
p value was less than 0.05.
2
008; Kaplancikli et al., 2010).
The water in the cylinder was changed after testing
RESULTS
each animal to minimise the influence of secreted alarm Chemistry
substances. Following the training and the test sessions,
the animals were dried in a heated enclosure.
Initially, ethyl 2-[(5-methyl-1,3,4-thiadiazol-2-yl)thio)]
acetate ( ) was synthesized by the reaction of 5-
1
methyl-1,3,4-thiadiazole-2-thiol with ethyl chloroacet-
ate in the presence of potassium carbonate. Then, this
Assessment of antinociceptive activity
The antinociceptive action of the tested compounds ester (
in mice was evaluated using hot-plate and tail-clip zide derivative (
tests. The response to thermal stimuli was tested rivative ( ) with various aldehydes/ketones produced
1) was converted to the corresponding hydra-
2). The treatment of the hydrazide de-
2
using a hot-plate analgesia meter (Ugo Basile, 7280) the target compounds (3a-o). These reactions are
o
maintained at 55 ± 1 C. Delay of nociceptive re- summarized in Scheme 1, and some properties of the
sponses, such as licking or shaking the paws was compounds (3a-o) are given in Table I.
recorded as the reaction time. A cut-off latency time
of 30 sec was imposed for each measurement to avoid firmed by H-NMR, C-NMR, mass spectral data, and
The structures of the compounds (3a-o) were con-
1
13
lesions to the skin and unnecessary suffering (Woolfre elemental analyses.
1
and MacDonald, 1944; Pavin et al., 2011).
In the H-NMR spectra of the compounds (3a-o), the
Effects of the test compounds on nociceptive percep- signal due to the hydrazone proton appeared in the
tion were calculated by converting hot-plate reaction region of 11.0-13.8 ppm. The signal due to the -S-CH
2
-
times to percentage antinociceptive activity according protons was observed in the region of 4.0-5.0 ppm. In
1
to the following previously described equation (Can et the H-NMR spectra of some compounds, N-H and -S-
al., 2010):
CH
2
- protons gave rise to 2 singlet peaks in accordance
and isomers (Özdemir et
with the presence of the
al., 2009; Despaigne et al., 2010). The signal due to
the methyl protons attached to the thiadiazole ring
E
Z
Analgesia % = [(post drug latency
−
×
pre drug latency)
100
/pre-drug latency]
Tail-clip tests were applied for measuring mechan- was observed in the region of 2.6-2.7 ppm. The other
ical antinociceptive activities of the compounds aromatic and aliphatic protons were observed at the
(
D’Amour and Smith, 1941). A metal artery clamp expected regions.
In 3C-NMR spectra, the signal due to the -S-CH2-
1
was applied to the tail of mouse, and the time that

664
Ö. D. Can et al.
Scheme 1. Synthesis of thiadiazole derivatives (3a-o).
Table I. Some properties of the synthesized compounds (3a-o
)
o
Compound
R
Ar
Yield (%)
M.p. ( C)
Molecular formula Molecular weight
3
a
H
H
H
H
H
H
H
H
H
H
H
H
2-pyridyl
3-pyridyl
4-pyridyl
2-furyl
thiophen-2-yl
5-methyl-2-furyl
5-methylthiophen-2-yl
1H-pyrrol-2-yl
1-methyl-1H-pyrrol-2-yl
1H-indol-3-yl
1-naphthyl
biphenyl-4-yl
2-furyl
thiophen-2-yl
1H-indol-3-yl
70
80
90
85
95
85
70
72
80
90
95
90
70
78
75
137-138
170-171
183-185
164-165
190-191
138-139
154-156
207-208
151-152
249-250
170-172
161-163
140-141
139-140
242-246
C
C
C
11
11
11
H
H
H
11
11
11
N
N
N
5
5
5
OS
OS
OS
2
2
2
293
293
293
282
298
296
312
281
295
331
342
368
296
312
345
3b
3
c
3d
C
C
C
C
C
C
C
C
C
10
10
11
11
H
H
H
H
H
H
H
H
H
10
10
12
12
N
4
2
O S
2
3
3
e
f
N
4
OS
3
N
4
2
O S
2
3g
N
4
N
5
N
5
N
5
N
4
N
4
OS
3
2
2
2
2
2
3h
10
11
14
16
18
11
13
13
14
16
OS
OS
OS
OS
OS
3
3
i
j
3k
3
l
3m
CH
CH
CH
3
C
C
C
11
H
12
N
4
2
O S
2
3n
3
11
H
H
12
N
N
4
OS
OS
3
3o
3
15
15
5
2
carbon appeared at 35-40 ppm. The signal due to the dipping behaviors, latency to first head-dippings and
hydrazone carbon was observed at 168-172 ppm. The total number of explored holes. Similarly, activity cage
signal due to the methyl carbon attached to the tests showed no specific changes between the spontan-
thiadiazole ring was observed in the region of 15.0- eous locomotor activities of animals injected with
20.0 ppm. The other aromatic and aliphatic carbons control solution and those injected with test compounds
were observed in the expected regions.
(Table III).
In the mass spectra of all compounds (3a-o), M+1
Fig. 1 illustrates the effects of the test compounds
peaks were observed. All compounds provided satis- on immobility times of mice in the tail-suspension
factory elemental analysis results.
test. Administration of the reference drug (Flx) and
compounds 3a 3b 3c 3j 3k, and 3l significantly
shortened the immobility times of animals as com-
,
,
,
,
Pharmacology
Results obtained from the hole-board tests are given pared to controls. Fig. 2 shows that the same test com-
in Table II. In this test, none of the test compounds pounds significantly decreased immobility and increased
significantly changed the total numbers of head- the swimming times in the MFST. Climbing times in

Effect of Thiadiazole Derivatives on CNS of Mice
665
Table II. Effects of the test compounds on exploratory
behavior of mice in hole-board tests
Total
Latency to Total numbers
Groups
Control
Dose
-
number of first head-
head-dips
22.3 ± 1.9
of holes
explored
dip (s)
5.9 ± 1.2
5.3 ± 0.8
7.4 ± 1.1
8.4 ± 0.9
7.3 ± 1.4
7.8 ± 0.9
6.7 ± 1.0
7.5 ± 1.1
6.7 ± 1.2
8.3 ± 1.3
7.3 ± 1.6
6.3 ± 1.1
8.2 ± 1.3
7.2 ± 0.9
7.4 ± 1.2
7.9 ± 1.1
8.3 ± 0.9
8.8 ± 1.0
9.7 ± 1.2
8.5 ± 0.9
7.5 ± 1.2
8.0 ± 1.6
8.2 ± 1.5
9.2 ± 1.4
7.8 ± 1.2
8.5 ± 1.1
7.2 ± 1.0
7.5 ± 0.6
8.5 ± 0.8
6.8 ± 1.6
7.5 ± 0.7
8.0 ± 0.9
3a
100 mg/kg 21.3 ± 1.8
100 mg/kg 19.0 ± 1.6
100 mg/kg 19.7 ± 2.1
100 mg/kg 22.0 ± 2.1
100 mg/kg 20.5 ± 2.6
100 mg/kg 19.0 ± 2.7
100 mg/kg 20.3 ± 2.4
100 mg/kg 20.0 ± 2.5
100 mg/kg 20.5 ± 1.7
100 mg/kg 19.8 ± 3.4
100 mg/kg 22.5 ± 1.2
100 mg/kg 20.8 ± 1.9
100 mg/kg 19.2 ± 2.9
100 mg/kg 18.7 ± 2.0
100 mg/kg 20.5 ± 2.4
3b
3
c
3d
3
e
3
f
3g
3h
Fig. 1. Effects of the test compounds on immobility time of
mice in tail suspension tests. Values are given as mean ±
3
i
3
j
S.E.M. Significance against control values, *
p < 0.05, **p <
3k
&
0
.01, *** < 0.001; significance against Flx group,
p
p
< 0.05;
a
3
l
significance against 3c group,
post-hoc Tukey test, n = 6.
p < 0.05. One-way ANOVA,
3m
3n
3o
Figs. 3 and 4 illustrate the effects of the test com-
pounds on the reaction times of mice to noxious stimuli
in hot-plate and tail-clip tests, respectively. Significant
increases in reaction times were observed following
Values are given as mean ± S.E.M. One-way ANOVA, post-
hoc Tukey’s test, n = 6.
Table III. Effects of the test compounds on spontaneous
locomotor activity parameters of mice in activity cage
tests
administration of compounds 3a, 3b, 3c, 3d, 3e, 3j,
3k, and 3l at 100 mg/kg doses. Morphine sulphate (10
mg/kg) also increased reaction times in both tests, as
expected.
Tested compounds exhibited negligible toxicity; they
incurred neither deaths nor undesirable side effects
such as ataxia, paralysis, convulsions, and diarrhea
when administered at dose of 100 mg/kg.
Number of
horizontal
movements
Number of
vertical
movements
Groups
Control
Dose
-
464.3 ± 63.5
457.7 ± 57.7
544.5 ± 62.9 102.7 ± 16.2
94.7 ± 11.6
83.2 ± 14.4
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
a
b
c
d
e
f
g
h
i
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
100 mg/kg
361.5 ± 52.3
468.7 ± 65.5
563.7 ± 45.1
415.2 ± 77.7
407.0 ± 52.1
447.5 ± 63.1
524.8 ± 43.1
378.0 ± 49.9
551.5 ± 54.1
366.7 ± 70.1
392.8 ± 54.3
414.2 ± 44.0
494.7 ± 47.9
71.2 ± 12.3
65.8 ± 16.3
94.8 ± 13.5
78.2 ± 11.6
73.7 ± 13.1
84.7 ± 11.0
89.7 ± 14.0
74.8 ± 16.0
87.5 ± 21.2
70.8 ± 12.1
67.0 ± 14.3
94.5 ± 11.8
68.8 ± 10.6
DISCUSSION
We synthesized thiadiazole derivatives bearing hy-
drazone moieties and investigated their effects on
behavioral and nociceptive parameters in mice. Puta-
tive effects of the test compounds on exploratory be-
havior and spontaneous locomotor activity were ex-
amined by hole-board and activity cage tests, respec-
tively. MFST and tail suspension tests were used for
assessments of depression parameters. Potential anti-
nociceptive effects of the compounds were evaluated
using the hot-plate and tail-clip methods.
j
k
l
m
n
o
As illustrated in Table II, tested compounds did not
cause any significant changes in the exploratory para-
meters of mice in hole-board tests. These results indi-
cated that neither anxiolytic nor sedative effects were
Values are given as mean ± S.E.M. One-way ANOVA, post-
hoc Tukey test, n = 6.
the MFST were not changed. Flx exhibited an antide- induced by these derivatives when administered at a
pressant effect, evidenced by decreased immobility and dose of 100 mg/kg. The results obtained from the hole-
increased swimming times, as expected (Cryan et al., board tests were recapitulated by the findings of the
2002).
activity cage tests. In activity cage tests, administra-

666
Ö. D. Can et al.
Fig. 3. Effects of the test compounds on response latency of
mice in hot-plate test. Values are given as mean ± S.E.M.
Significance against control values, *
**
.001; significance against 3c group,
One-way ANOVA, post-hoc Tukey test, n = 6.
p
< 0.05, **p < 0.01,
&&&
*
0
p
< 0.001; significance against morphine group
p <
a
b
p
< 0.05,
p
< 0.01.
Fig. 4. Effects of the test compounds on response latency of
mice in tail-clip test. Values are given as mean ± S.E.M. Sig-
nificance against control values, *
p
< 0.05, **
p
< 0.01, ***
p
Fig. 2. Effects of the test compounds on (
swimming, and ( ) climbing time of mice in MFST. Values
are given as mean ± S.E.M. Significance against control
values, * < 0.05, ** < 0.01, *** < 0.001; significance against
Flx group,
A) immobility, (B)
&
&
<
0.001; significance against morphine group
p
< 0.01,
C
&
&&
a
p
< 0.001; significance against 3c group, p < 0.05. One-
way ANOVA, post-hoc Tukey test, n = 6.
p
p
p
&
&&
&&&
p
< 0.05,
p
< 0.01,
p < 0.001, significance
a
against 3c group,
Tukey test, n = 6.
p < 0.05. One-way ANOVA, post-hoc
and increased swimming times without changes in the
climbing durations indicated that the antidepressant-
like effects exhibited by 3a, 3b, 3c, 3j, 3k, and 3l in
tion of the test compounds did not alter the total num- this study (Fig. 2) may be related to serotonergic,
bers of the horizontal or vertical locomotor activities rather than noradrenergic mechanisms in the CNS
(Table III). Collectively, these data indicate that the (Cryan et al., 2002). Involvement of the serotonergic
behavioral experimental results in this study were not system in the antidepressant activity should be con-
attributable to motor alterations caused by the test firmed with further studies, such as depleting neuronal
compounds.
Tail suspension tests showed that compounds 3a
3c 3j 3k, and 3l significantly shortened immobil-
serotonin by p-chlorophenylalanine pretreatment or
measuring serotonin levels in limbic areas of the brain.
Significant increases in reaction times of animals
,
3b,
,
,
ity times of animals and showed antidepressant-like against noxious stimuli after administration of com-
activities (Fig. 1). MFST results confirmed these find- pounds 3a 3b 3c 3d 3e 3j 3k, and 3l indicated the
,
,
,
,
,
,
ings and provided additional information related to a presence of antinociceptive activities in hot-plate (Fig.
possible mechanism of activity. Decreased immobility 3) and tail-clip tests (Fig. 4). Hot-plate and tail-clip

Effect of Thiadiazole Derivatives on CNS of Mice
667
tests have been reported as a measure centrally medi- Compound 3j, having a 1H-indol-3-yl group substitu-
ated, transient pain. As reported previously, the hot- tion only, exhibited significant antidepressant-like
plate test predominantly measures responses organized effects, whereas compound 3o, with a methyl substitu-
supraspinally, whereas the tail-clip test mainly measures tion in addition to a 1H-indol-3-yl group, was ineffec-
spinal reflexes (Wong et al., 1994; Gabra and Sirois, tive. We concluded that substitution of the hydrazone
2003). The tested compounds prolonged the response carbon with an additional methyl group caused a loss
times of animals in both hot-plate and tail-clip tests. of antidepressant activity.
We therefore suggest that their antinociceptive activities
Structure-antinociceptive activity relationships were
are related to both supraspinal and spinal mechanisms. similar to the structure-antidepressant activity rela-
In the present study, 100 mg/kg doses of compounds tionships observed for compounds 3a
, 3b, 3c, 3j, 3k,
3a,
3b 3c 3j 3k, and 3l showed both antidepressant and 3l. In terms of the antinociceptive effect, com-
,
,
,
and centrally mediated antinociceptive activities. pound 3c was statistically more active than 3a and
Antidepressants that increase monoamine levels in 3b. Compounds 3d and 3e, which were substituted by
CNS synaptic clefts activate descending inhibitory 2-furyl and thiophen-2-yl groups, respectively, also
nociceptive pathways and thus show analgesic activity showed antinociception effects. This finding indicated
(Korzeniewska-Rybicka and Plaznik, 2000). We may that substitution by furyl and thiophen-2-yl groups
speculate that compounds 3a 3b 3c 3j 3k, and 3l did not add to the strength of antidepressant activity,
,
,
,
,
exert both antidepressant and antinociceptive effects but did add an antinociceptive potential. For com-
by activating the monoaminergic system in the CNS. pounds 3m and 3n, which are further methyl substi-
This hypothesis is supported by the results of the tuted derivatives of compounds 3d and 3e respectively,
MFST, which suggested that test compounds activate lack of an antinociceptive effect indicated that methyl
central serotonergic mechanisms. However, the exact substitution abolished antinociceptive activity. These
mecha- nism underlying the test compound activity results illustrated once more the importance of sub-
must be clarified with further detailed studies.
In contrast to compounds 3a 3b 3c 3j 3k, and 3l, activity.
compounds 3d and 3e did not exhibit significant In summary, the results of the present study provide
stitutions on chemical structure for pharmacological
,
,
,
,
effects in the depression tests. On the other hand, these scientific evidence of the antidepressant and anti-
two compounds increased the reaction times in hot- nociceptive activity potential of thiadiazole derivatives
plate and tail-clip tests and exhibited significant anti- with hydrazone moieties, supporting our initial hypo-
nociceptive activities, which were related to both su- thesis. Furthermore, our results suggest that the active
praspinal and spinal mechanisms. Their mechanisms test compounds show serotonergic system-related anti-
of action in the CNS seems to be different from those depressant activities and centrally mediated anti-
of compounds 3a, 3b, 3c, 3j, 3k, and 3l, which showed nociceptive activities. To the best of our knowledge,
both antidepressant and antinociceptive activities in this is the first study of the CNS activities of chemical
the present study. The exact mode of action for test compounds carrying both thiadiazole and hydrazone
compounds 3d and 3e should be clarified with further moieties on their structures.
detailed investigations.
Among these pharmacologically active compounds, currently used to treat various neuropathic pain syn-
is substituted by 1H-indol-3-yl, 3k by 1-naphthyl, dromes (Watson et al., 2011; Dharmshaktu et al.,
and 3l by biphenyl-4-yl. Additionally, compounds 3a
2012). Therefore, our results may have implications
, and 3c are 2-, 3-, and 4-pyridyl group substituted for the synthesis and development of new drugs
Antidepressants with antinociceptive effects are
3j
,
3b
derivatives, respectively. The results of the depression targeted to treat chronic neuropathic pain.
tests showed that substitution by 1H-indol-3-yl, 1-
naphthyl, biphenyl-4-yl, or pyridyl groups adds an REFERENCES
antidepressant activity potential to the tested com-
pounds. Among pyridyl substituted derivatives, the 4- Brufani, M., Loche, A., Perlini, V., and Pocar, D., Preparation
pyridyl group substituted derivative 3c was found to
be statistically more active than 3a and 3b. These
results suggest that substitution with a 4-pyridyl group,
but not 2 or 3-pyridyl, increased the antidepressant
activity of the compounds.
of 2-amino-5-[(ar)alkylthio]thiadiazoles as antidepressant.
EUR. Patent 579,129 (1994).
Can, O. D., Ozkay, U. D., Kaplancikli, Z. A., and Oztürk, Y.,
Effects of some 1,3,5-trisubstitued-2-pyrazoline derivatives
on depression and anxiety parameters of mice. Arch.
Pharm. Res., 32, 1293-1299 (2009).
Another interesting structure-antidepressant activity
Can, O. D., Ozkay, U. D., Oztürk, N., and Oztürk, Y., Effects
relationship was observed in compounds 3j and 3o
.

668
Ö. D. Can et al.
of hawthorn seed and pulp extracts on the central nervous
system. Pharm. Biol., 48, 924-931 (2010).
Can, O. D., Ismail, I. B., Öztürk, Y., Öztürk, N., Potoog
Korzeniewska-Rybicka, I. and Plaznik, A., Supraspinally
mediated analgesic effect of antidepressant drugs. Pol. J.
Pharmacol., 52, 93-99 (2000).
˘
lu-
Erkara, S. H., Sagratini, G., Ricciutelli, M., Vittori, S., and
Maggi, F., New antidepressant drug candidate: Hypericum
montbretti extract. Nat. Prod. Res., 25, 1469-1472 (2011).
Chapleo, C. B., Myers, M., Myers, P. L., Saville, J. F., Smith,
A. C., Stillings, M. R., Tulloch, I. F., Walter, D. S., and
Welbourn, A. P., Substituted 1,3,4-thiadiazoles with anti-
convulsant activity. 1. Hydrazines. J. Med. Chem., 29,
Lima, L. M. and Barreiro, E. J., Bioisosterism: A useful strat-
egy for molecular modification and drug design. Curr.
Med. Chem., 12, 23-49 (2005).
Özdemir, A., Turan-Zitouni, G., Kaplancikli, Z. A., and
Tunall, Y., Synthesis and biological activities of new hydra-
zide derivatives. J. Enzym. Inhib. Med. Chem., 24, 825-
831 (2009).
2
273-2280 (1986).
Pandey, A., Dewangan, D., Verma, S., Mishra, A., and Dubey,
R. D., Synthesis of Schiff bases of 2-amino-5-aryl-1,3,4-
thiadiazole and its analgesic, anti-inflammatory, anti-
bacterial and anti-tubercular activity. Int. J. ChemTech
Res., 3, 178-184 (2011).
Patani, G. A. and LaVoie, E. J., Bioisosterism: A rational
approach in drug design. Chem. Rev., 96, 3147-3176 (1996).
Pattanayak, P., Sharma R., and Sahoo, P. K., Synthesis and
evaluation of 2-amino-5-sulfanyl-1,3,4-thiadiazoles as anti-
depressant, anxiolytic, and anticonvulsant agents. Med.
Chem. Res., 18, 351-361 (2009).
Pavin, N. F., Donato, F., Cibin, F. W., Jesse, C. R., Schneider,
P. H., de Salles, H. D., Soares, L. D., Alves, D., and
Savegnago, L., Antinociceptive and anti-hypernociceptive
effects of Se-phenyl thiazolidine-4-carboselenoate in mice.
Eur. J. Pharmacol., 668, 169-176 (2011).
Ragavendran, J. V., Sriram, D., Patel, S. K., Reddy, I. V.,
Bharathwajan, N., Stables, J., and Yogeeswari, P., Design
and synthesis of anticonvulsants from a combined phth-
alimide-GABA-anilide and hydrazone pharmacophore.
Eur. J. Med. Chem., 42, 146-151 (2007).
Chufán, E. E., Pedregosa, J. C., Baldini, O. N., and Bruno-
Blanch, L., Anticonvulsant activity of analogues of aceta-
zolamide. Farmaco, 54, 834-841 (1999).
Ciapetti, P. and Giethlen, B., Molecular variations based on
isosteric replacements, In Wermuth, C. M. (Ed.). The Prac-
tice of Medicinal Chemistry. Academic Press, Burlington,
pp. 290-342, (2008).
Clerici, F. and Pocar, D., Synthesis of 2-Amino-5-sulfanyl-
1
,3,4-thiadiazole derivatives and evaluation of their
antidepressant and anxiolytic activity. J. Med. Chem., 44,
31-936 (2001).
9
Cryan, J. F., Markou, A., and Lucki, I., Assessing antide-
pressant activity in rodents: recent developments and
future needs. Trends Pharmacol. Sci., 23, 238-245 (2002).
D’Amour, F. E. and Smith, D. L., A method for determining
loss of pain sensation. J. Pharmacol. Exp. Ther., 72, 74-79
(1941).
Despaigne, A. A. R., Vieira, L. F., Mendes, I. C., da Costa, F. B.,
Spezialib, N. L., and Beraldo, H., Organotin(IV) complexes
with 2-acetylpyridine benzoyl hydrazones: antimicrobial
activity. J. Braz. Chem. Soc., 21, 1247-1257 (2010).
Dharmshaktu, P., Tayal, V., and Kalra, B. S., Efficacy of
antidepressants as analgesics: A review. J. Clin. Pharma-
col., 52, 6-17 (2012).
Ergenç, N., Günay, N. S., and Demirdamar, R., Synthesis and
antidepressant evaluation of new 3-phenyl-5-sulfonami-
doindole derivatives. Eur. J. Med. Chem., 33, 143-148
Rajak, H., Deshmukh, R., Aggarwal, N., Kashaw, S., Kharya,
M. D., and Mishra, P., Synthesis of novel 2,5-disubstitut-
ed 1,3,4-thiadiazoles for their potential anticonvulsant
activity: pharmacophoric model studies. Arch. Pharm.
(Weinheim), 342, 453-461 (2009).
Rollas, S. and Küçükgüzel, S
hydrazone derivatives. Molecules, 12, 1910-1939 (2007).
Salgin-Göksen, U., Gökhan-Kelekçi, N., Göktas, O., Köysal, Y.,
Kiliç, E., Isik, S., Aktay, G., and Ozalp, M., 1-Acylthiosemi-
¸
. G., Biological activities of
(1998).
¸
¸
Gabra, B. H. and Sirois, P., Beneficial effect of chronic treat-
ment with the selective bradykinin B1 receptor antagoni-
sts, R-715 and R-954, in attenuating streptozotocin-diabe-
tic thermal hyperalgesia in mice. Peptides, 24, 1131-1139
¸
carbazides, 1,2,4-triazole-5(4H)-thiones, 1,3,4-thiadiazoles
and hydrazones containing 5-methyl-2-benzoxazolinones:
synthesis, analgesic-anti-inflammatory and antimicrobial
activities. Bioorg. Med. Chem., 15, 5738-5751 (2007).
Sharma, R., Misra, G. P., Sainy, J., and Chaturvedi, S. C.,
Synthesis and biological evaluation of 2-amino-5-sulfanyl-
1,3,4-thiadiazole derivatives as antidepressant, anxioly-
tics and anticonvulsant agents. Med. Chem. Res., 20, 245-
253 (2011).
Siddiqui, N., Ahuja, P., Ahsan, W., Pandeya, S. N., and
Shamsher Alam, M., Thiadiazoles: Progress report on
biological activities. J. Chem. Pharm. Res., 1, 19-30 (2009).
Silva, G. A., Costa, L. M., Brito, F. C., Miranda, A. L., Barreiro,
E. J., and Fraga, C. A., New class of potent antinociceptive
and antiplatelet 10H-phenothiazine-1-acylhydrazone deri-
vatives. Bioorg. Med. Chem., 12, 3149-3158 (2004).
(2003).
Kaplancikli, Z. A., Turan-Zitouni, G., Ozdemir, A., Can, O.,
and Chevallet, P., Synthesis and antinociceptive activities
of some pyrazoline derivatives. Eur. J. Med. Chem., 44,
2606-2610 (2009).
Kaplancikli, Z. A., Ozdemir, A., Turan-Zitouni, G., Altintop,
M. D., and Can, O. D., New pyrazoline derivatives and their
antidepressant activity. Eur. J. Med. Chem., 45, 4383-
4
387 (2010).
Kidwai, M. and Kumar, P., Microwave-induced syntheses of
-(substituted aryl)-3-[(5-methyl-1,3,4-thiadiazol-2-ylsulfan-
6
yl)methyl]-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles. J. Chem.
Res. Synop., 5, 254-255 (1996).

Effect of Thiadiazole Derivatives on CNS of Mice
669
Silverman, R. B., The organic chemistry of drug design and
drug action. Elsevier Academic Press, Burlington, pp. 53-
Waterbeemd, H. and Mannhold, R., Lipophilicity descriptors
for structure-property correlation studies: Overview of
experimental and theoretical methods and a benchmark
of log P calculations, In: Mannhold, R., Kubinyi, H., and
Timmerman, H. (Series Eds.), Pliska, V., Testa, B.,
Waterbeemd, H. (Vol. Eds.). Lipophilicity in Drug Action
and Toxicology. VCH Publishers, New York, pp. 401-418,
(1996).
Watson, C. P., Gilron, I., Sawynok, J., and Lynch, M. E.,
Nontricyclic antidepressant analgesics and pain: are
serotonin norepinephrine reuptake inhibitors (SNRIs)
any better? Pain, 152, 2206-2210 (2011).
Wong, C. H., Day, P., Yarmush, J., Wu, W., and Zbuzek, U.
K., Nifedipine induced analgesic after epidural injections
in rats. Anesth. Anal., 79, 303-306 (1994).
Woolfre, H. G. and MacDonald, A. D., The evaluation of the
analgesic action of pethidine hydrochloride (Demerol). J.
Pharmacol. Exp. Ther., 80, 300-307 (1944).
62, (2004).
Steru, L., Chermat, R., Thierry, B., and Simon, P., The tail
suspension test: a new method for screening antidepres-
sants in mice. Psychopharmacol. (Berl), 85, 367-370 (1985).
Stillings, M. R., Welbourn, A. P., and Walter, D. S., Substi-
tuted 1,3,4-thiadiazoles with anticonvulsant activity. 2.
aminoalkyl derivatives. J. Med. Chem., 29, 2280-2284
(1986).
Takeda, H., Tsuji, M., and Matsumiya, T., Changes in head-
dipping behavior in the hole-board test reflect the anxio-
genic and/or anxiolytic state in mice. Eur. J. Pharmacol.,
350, 21-29 (1998).
Tanaka, M. and Telegdy, G., Involvement of adrenergic and
serotonergic receptors in antidepressant-like effect of
Urocortin 3 in a modified forced swimming test in mice.
Brain Res. Bull., 77, 301-305 (2008).
Varvaresou, A., Siatra-Papastaikoudi, T., Tsotinis, A.,
Tsantili-Kakoulidou, A., and Vamvakides, A., Synthesis,
lipophilicity and biological evaluation of indole-containing
Yusuf, M., Khan, R. A., and Ahmed, B., Syntheses and anti-
depressant activity of 5-amino-1,3,4-thiadiazole-2-thiol
imines and thiobenzyl derivatives. Bioorg. Med. Chem.,
16, 8029-8034 (2008).
derivatives of 1,3,4-thiadiazole and 1,2,4-triazole. Farmaco
,
53, 320-326 (1998).