Design, synthesis and biological evaluation of new 3-[(4-aryl)piperazin- 1-yl]-1-arylpropane derivatives as potential antidepressants with a dual mode of action: Serotonin reuptake inhibition and 5-HT(1A) receptor antagonism

Article abstract of DOI:10.1016/S0014-827X(00)00050-1

It has been suggested that the combination of a selective serotonin reuptake inhibitor (SSRI) and a 5-HT(1A) receptor antagonist may facilitate the onset of the SSRIs antidepressant action. Accordingly, we describe the synthesis of a series of new 3-[(4-aryl)piperazin-1-yl]-1-arylpropane derivatives with structural modifications performed in Ar₁, Ar₂ and Z (Z is different functional groups) to obtain the sought dual activity. Compounds were evaluated for in vitro affinity at 5-HT(1A) receptors and 5-HT transporter. The antidepressant-like activity of derivatives with the higher affinity was assessed initially using the forced swimming test (FST). Compound 1-(2,4-dimethylphenyl)-3-[(2-methoxyphenyl)piperazin-1-il]-1- propanone (III.1.a) showed the best antidepressant-like activity which was further confirmed in the learned helplessness test. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0014-827X(00)00050-1

www.elsevier.nl/locate/farmac
Il Farmaco 55 (2000) 345–353
Design, synthesis and biological evaluation of new
3-[(4-aryl)piperazin-1-yl]-1-arylpropane derivatives as potential
antidepressants with a dual mode of action: serotonin reuptake
inhibition and 5-HT1A receptor antagonism
A.M. Oficialdegui a, J. Martinez a, S. Pe´rez a, B. Heras a, M. Irurzun a, J.A. Palop a,
R. Tordera b, B. Lasheras b, J. del R´ıo b, A. Monge a,*
a Department of Medicinal Chemistry, Centro de In6estigacio´n en Farmacobiolog´ıa Aplicada (CIFA), Uni6ersidad de Na6arra,
C/Irunlarrea s/n, 31080 Pamplona, Spain
b Department of Pharmacology, Uni6ersidad de Na6arra, Pamplona, Spain
Received 12 December 1999; accepted 26 April 2000
Abstract
It has been suggested that the combination of a selective serotonin reuptake inhibitor (SSRI) and a 5-HT1A receptor antagonist
may facilitate the onset of the SSRIs antidepressant action. Accordingly, we describe the synthesis of a series of new
3-[(4-aryl)piperazin-1-yl]-1-arylpropane derivatives with structural modifications performed in Ar1, Ar2 and Z (Z is different
functional groups) to obtain the sought dual activity. Compounds were evaluated for in vitro affinity at 5-HT1A receptors and
5-HT transporter. The antidepressant-like activity of derivatives with the higher affinity was assessed initially using the forced
swimming test (FST). Compound 1-(2,4-dimethylphenyl)-3-[(2-methoxyphenyl)piperazin-1-il]-1-propanone (III.1.a) showed the
best antidepressant-like activity which was further confirmed in the learned helplessness test. © 2000 Elsevier Science S.A. All
rights reserved.
Keywords: Antidepressant; 5-HT1A antagonist; 5-HT reuptake inhibitor; Arylpiperazine
might explain the slow onset of their antidepressant
effects in humans and could be involved in some of the
1. Introduction
undesired side effects, notable loss of libido [5]. There-
Abundant data support the contention of a fre-
fore, one of the still unmet therapeutic needs is the
quently reduced central serotoninergic neurotransmis-
availability of antidepressants with a more rapid onset
sion in depression. In particular, this pathological case
of action. Extensive studies on the mechanism of action
involves suboptimal activity of the post-synaptic 5-
of the SSRIs led to the discovery of the key role of
HT1A receptor subtype [1], in fact, 5-HT1A postsynaptic
somatodendritic 5-HT1A autoreceptors in a negative
agonists demonstrated efficacy in the treatment of de-
control of serotoninergic neurotransmission [6,7]. Mi-
pression disorders [2]. In addition, drugs which selec-
crodialysis studies have shown that 5-HT1A autorecep-
tively inhibit the reuptake of serotonin (SSRI) are
effective antidepressants with a low incidence of side
effects; however, their therapeutic effect is achieved
only after repeated administration [3,4]. No-selective
serotoninergic activation following SSRI treatment
tor antagonists enhance the 5-HT reuptake blocking
properties of SSRIs in terminal areas of the serotonin-
ergic system by preventing the negative feedback of
serotonin (5-HT) acting at somatodendritic 5-HT1A re-
ceptors [8–11]. In addition, pindolol, a 5-HT1A receptor
antagonist has been reported to accelerate the antide-
pressant action of SSRIs in several open and placebo-
controlled clinical trials [12–17]. These observations
prompted us to develop the synthesis of new antide
* Corresponding author. Tel.: +34-948-425 600 ext. 6343; fax:
+34-948-425 652.
E-mail address: amonge@unav.es (A. Monge).
0014-827X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0014-827X(00)00050-1

346
A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
reported previously [21]. Other piperazines, such as
2-hydroxyphenylpiperazine and 1-naphtylpiperazine,
were also considered in an attempt to enhance the
affinity at the 5-HT1A receptor and 5-HT transporter.
All synthesized compounds were screened in rat brain
homogenates for their affinity at these two sites. The
forced swimming test was carried out subsequently in
order to study the antidepressant properties of selected
compounds. Compound III.1.a, which revealed high
effectiveness in this test, was further characterized by
means of radioligand binding studies at different cen-
tral receptors, to define its selectivity profile, and hy-
pothermic studies in rat and mice to investigate
agonist/antagonist properties at postsyanptic and presy-
naptic 5-HT1A receptors [22]. The antidepressant-like
property of this new compound was further studied in
comparison with other antidepressants, in the learned
helplessness test, a widely accepted animal model of
depression because of the behavioral analogies with
some signs of depression in humans [23].
Fig. 1.
pressants with a dual mode of action: serotonin reup-
take inhibition and 5-HT1A receptor antagonism. Previ-
ous works of our group have dealt with this strategy of
combining two chemically different structures, associ-
ated to the sought activities, in a single chemical entity
(Fig. 1): In this figure it can be observed that the
nitrogen of the g-phenoxypropylamine moiety (struc-
ture related to the SSRI [18], structure I, part A) has
been combined with an arylpiperazine ring (long chain
arylpiperazine represent one of the most important
classes of 5-HT1A receptors ligands [19], structure I,
part B). The results obtained in these previous works
[20] showed that compounds without the aromatic ring
Ar3 were endowed with the dual activity, so we synthe-
sized new compounds according to the general struc-
ture II (Fig. 1) in which Z consists in different
functional groups such as ketones or alcohols. The
structural modifications consisted in the introduction of
methyl groups on the phenyl ring Ar2 maintaining the
2-methoxyphenylpiperazine moiety. This modification
was proposed with the aim of increasing the electronic
density without altering the electronic distribution sub-
stantially. This was suggested on the basis of pharma-
cophores associated to the 5-HT reuptake inhibitors
2. Chemistry
The 3-[(4-aryl)piperazin-1-yl]-1-arylpropane deriva-
tives presented in this work (I.1–3.a; II.1–2.a; III.1–
2.a–c) were prepared according to methods reported
already as shown in Scheme 1. The synthesis of the
ketone derivatives was carried out by the condensation
of the corresponding acetophenones with the different
phenylpiperazine hydrochlorides and paraformaldehyde
in ethanol and acid medium (Mannich reaction). The
reduction of ketones with sodium borohydride in
methanol afforded the corresponding alcohols. Treat-
ment of the alcohols with sodium hydride and 4-fluoro-
trifluoromethylbenzene led to the phenolic ether (I.3.a).
All the phenylpiperazines (a and b) were available
commercially, except 1-naphtylpiperazine (c), which
was obtained by the condensation of 1-naphtylamine
Scheme 1.

A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
347
with bis-chloroethylamine in basic medium (Scheme 2).
Yields and the physical and spectroscopic properties of
the compounds are reported in Tables 1 and 2.
900 instrument. The mass spectra were recorded on a
Hewlett–Packard 5988-A instrument at 70 eV.
2.1.1. Synthesis of 1-aryl-3-(4-arylpiperazin-1-yl)-
propan-1-one (I.1.a, II.1.a, III.1.a–c)
2.1. Experimental
A mixture of the appropriated substituted acetophe-
nones (30 mmol), arylpiperazine hydrochloride (30
mmol) and concentrated hydrochloric acid in absolute
ethanol (40 ml) was refluxed. Paraformaldehyde (90
mmol) was added in four equal portions over a period
of 40 min. The reaction mixture was refluxed for an-
other 8 h, cooled and poured onto crushed ice. The
separated solid was filtered and recrystallized from
isopropanol (I.1.a, II.1.a, III.1.a, III.1.c). For the isola-
tion of compound III.1.b, a solution of sodium hydrox-
ide (10%) was added to the reaction mixture until basic
pH was reached. It was then extracted with ethyl
acetate (3×20 ml), washed with brine (3×10 ml) and
dried (anhydrous sodium sulfate). The solvent was re-
moved under reduced pressure. The impure oil was
purified by flash chromatography (SP, silica gel), elut-
ing with n-hexane–ethyl acetate 60:40 (v/v).
Melting points (°C) were determined using a Mettler
FP82+FP80 apparatus and are uncorrected. Infrared
spectra were recorded on a Perkin–Elmer 1600 series
FTIR apparatus, using potassium bromide pellets for
solid products and sodium chloride plates for oil prod-
ucts; the frequencies are expressed in cm−1. The 1H
NMR spectra were obtained with a Brucker AC-200E
(200 MHz) instrument, using tetramethylsilane as the
internal reference, at a concentration of ca. 0.1 g/ml
and with chloroform–CDCl3 as solvents; the chemical
shifts are reported in parts per million (ppm) of te-
tramethylsilane in l units, and the J values are given in
hertz (Hz). Elemental analyses were obtained from
vacuum-dried samples (over phosphorus pentoxide at
3–4 mmHg, 24 h, at ca. 80–100°C) with a Leco CHN-
2.1.2. Synthesis of 1-aryl-3-(4-arylpiperazin-1-yl)-
propan-1-ol (I.2.a, II.2.a, III.2.a–b)
An excess of sodium borohydride was added to a
well-stirred solution or suspension of the corresponding
1-substituted-3-(1-piperazinyl)-1-propanone (3 mmol)
in methanol, over a period of 15 min at 0°C. The
stirring was continued for another 4–8 h. The reaction
mixture was poured onto water. It was then extracted
with ethyl acetate (3×20 ml), washed with water (3×
10 ml), and dried (anhydrous sodium sulfate). The
solvent was removed under reduced pressure. The
product obtained was further purified by recrystalliza-
tion or by flash chromatography (SP, silica gel) eluting
with n-hexane–ethyl acetate 50:50 (v/v) as detailed in
Table 1.
Scheme 2.
Table 1
Formula and physical constants of synthesized compounds
a
Compound
Formula
M.p. Yield b
(°C) (%)
Purification
method c
I.1.a
C21H26N2O2·
HCl
21H28N2O2
160 44
A
I.2.a
I.3.a
II.1.a
C
106 45
88 23
199 36
B
C
A
C28H31F3N2O2
C21H26N2O2·
HCl
2.1.3. Synthesis of 3-[4-(2-methoxyphenyl)piperazin-
1-yl]-1-(4-methylphenyl)-1-(4-trifluoromethylphenoxy)-
propane (I.3.a)
II.2.a
III.1.a
C21H28N2O2
C22H28N2O2·
HCl
C22H30N2O2
C21H26N2O2
C21H28N2O2
C25H28N2O·
HCl
102 21
157 60
B
A
3-[4-(2-Methoxyphenyl)piperazin-1-yl]-1-(4-methyl-
phenyl)propan-1-ol (2.5 mmol) was dissolved in N,N-
dimethylacetamide (15 ml) and heated to 75°C. Sodium
hydride (2.5 mmol) was then added and the reaction
mixture was maintained at 75°C for 2 h to allow the
formation of the salt. After this period of time, 1-
fluoro-4-trifluoromethylbenzene was added (2.5 mmol)
and the resulting mixture was heated at 110°C for 4 h.
The reaction mixture was poured onto crushed ice. It
was then extracted with diethyl ether (4×10 ml),
washed with brine (3×10 ml) and dried (anhydrous
sodium sulfate). The solvent was removed under re-
III.2.a
III.1.b
III.2.b
III.1.c
88 40
157 46
149 32
240 25
C
C
C
A
a All new compounds were analyzed for C, H, N, which were
within 0.4% of the theoretical values.
b Value of the final transformation is expressed.
c Purification method of the final form: A, recrystallized from
isopropanol; B, recrystallized from hexane–isopropanol; C, column
chromatography (SP, silica gel; MP, n-hexane–ethyl acetate 50:50
(v/v)).

348
A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
Table 2
1H NMR (CDCl3) spectra and IR absorption of the 3-[(4-aryl)piperazin-1-yl]-1-phenyl derivatives
Compound 1H NMR (CDCl3) l values
IR absorption
in KBr (cm−1
)
I.1.a
(free base): 2.33 (s, 3H, CH3); 2.75–2.77 (m, 4H, N1(CH2)2); 2.92 (t, 2H, N1CH2); 3.03–3.19 (m, 4H,
N4(CH2)2); 3.23 (t, 2H, CH2ꢀCO); 6.78 (d, 1H, o-OCH3ꢀPh, H6, J=7.2 Hz); 6.83–6.98 (m, 3H,
o-OCH3ꢀPh, H3+H4+H5); 7.19 (d, 2H, p-CH3ꢀPh, H3+H5, J=8.0 Hz); 7.81 (d, 2H, p-CH3ꢀPh, H2+H6,
J=7.8 Hz).
2931, 1675, 756
I.2.a
I.3.a
1.83–1.90 (m, 2H, CH2CH); 2.34 (s, 3H, CH3); 2.65–2.83 (m, 6H, CH2N1(CH2)2); 3.07–3.19 (m, 4H,
N4(CH2)2); 3.86 (s, 3H, OCH3); 4.93 (t, 1H, CH, J=5.6 Hz); 6.84–7.01 (m, 4H, o-OCH3ꢀPh); 7.15 (d, 2H,
p-CH3ꢀPh, H3+H5, J=8.0 Hz); 7.28 (d, 2H, p-CH3ꢀPh, H2+H6, J=8.0 Hz).
2.11–2.35 (m, 1H, CHaCH); 1.25–2.35 (m, 4H, CHbCH, CH3); 2.60–2.74 (m, 6H, CH2N1(CH2)2); 3.08–3.18
(m, 4H, N4(CH2)2); 3.85 (s, 3H, OCH3); 5.28 (dd, 1H, CH, J=7.8 Hz, J%=5.0 Hz); 6.57 (d, 2H, p-CF3ꢀPh,
H2+H6); 6.80–7.00 (m, 4H, o-OCH3ꢀPh); 7.13 (d, 2H, p-CH3ꢀPh; H3+H5, J=8.0 Hz); 7.22–7.44 (m, 4H,
p-CH3ꢀPh, H2+H6, p-CF3ꢀPh, H3+H5).
3410, 820
1327, 1243, 838
II.1.a
II.2.a
III.1.a
(Free base): 2.43 (s, 3H, CH3); 2.62–2.64 (m, 4H, N1(CH2)2); 2.76–2.83 (m, 2H, N1CH2); 3.01–3.10 (m, 6H,
CH2ꢀCO, N4(CH2)2); 3.78 (s, 3H, OCH3); 6.76–6.92 (m, 4H, o-OCH3ꢀPh); 7.15–7.33 (m, 3H, o-CH3ꢀPh,
H3+H4+H5); 7.57 (d, 1H, o-CH3ꢀPh, H6, J=7.3 Hz).
2937, 1685, 735
3310, 1237, 745
1.82–1.85 (m, 2H, CH2CH); 2.32 (s, 3H, CH3); 2.70–2.75 (m, 6H, CH2N1(CH2)2); 3.11–3.23 (m, 4H,
N4(CH2)2); 3.87 (s, 3H, OCH3); 5.16 (t, 1H, CH, J= 5.0 Hz); 6.88–6.95 (m, 4H, o-OCH3ꢀPh) 7.12–7.16 (m,
3H, o-CH3ꢀPh, H3+H4+H5); 7.55–7.63 (m, 1H, o-CH3ꢀPh, H6).
(Free base): 2.27 (s, 3H, CH3); 2.41 (s, 3H, CH3); 2.62(t, 4H, N1(CH2)2); 2.79 (t, 2H, N1CH2, J=7.1 Hz);
3.03–3.10 (m, 6H, N4(CH2)2, CH2ꢀCO); 3.78 (s, 3H, OCH3); 6.78 (d, 1H, o-OCH3ꢀPh, H6, J=7.4 Hz);
6.83–7.00 (m, 5H, o-OCH3ꢀPh, H3+H4+H5, o,p-diCH3ꢀPh, H3+H5); 7.53 (d, 1H, o,p-diCH3ꢀPh, H6,
J=8.4 Hz).
2926, 1689,
1242
III.2.a
1.80–1.82 (m, 2H, CH2CH); 2.27 (s, 3H, CH3); 2.29 (s, 3H, CH3); 2.66–2.83 (m, 6H, CH2N1(CH2)2);
3.05–3.21 (m, 4H, N4(CH2)2); 3.85 (s, 3H, OCH3); 5.11 (t, 1H, CH, J=5.6 Hz); 6.62 (b s, 1H, OH);
6.83–6.99 (m, 4H, o-OCH3ꢀPh) 7.00–7.06 (m, 2H, o,p-diCH3ꢀPh, H3+H5); 7.45 (d, 1H, o,p-diCH3ꢀPh, H6,
J=7.9 Hz).
3252, 1240, 747
III.1.b
III.2.b
III.1.c
2.35 (s, 3H, CH3); 2.50 (s, 3H, CH3); 2.61–2.69 (m, 4H, N4(CH2)2); 2.82–2.90 (m, 6H, N1(CH2)3); 3.09–3.16 3373, 1679, 751
(m, 2H, CH2–CO); 6.81–6.95 (m, 4H, o-OHꢀPh); 7.04–7.17 (m, 2H, o,p-diCH3ꢀPh, H3+H5); 7.58–7.62 (m,
1H, o,p-diCH3ꢀPh, H6).
1.78–1.86 (m, 2H, CH2CH); 2.27 (s, 3H, CH3); 2.29 (s, 3H, CH3); 2.60–2.85 (m, 6H, CH2N1(CH2)2);
2.88–2.99 (m, 4H, N4(CH2)2); 5.12 (t, 1H, CH, J=5.5 Hz); 6.82–7.18 (m, 6H, o-OHꢀPh, o,p-diCH3ꢀPh,
H3+H5);) 7.44 (d, 1H, o,p-diCH3ꢀPh, H6).
3230, 753
(Free base): 2.27 (s, 3H, CH3); 2.44 (s, 3H, CH3); 2.59–2.78 (m, 4H, N1(CH2)2); 2.84 (t, 2H, N1CH2ꢀ,
J=7.2 Hz); 3.06–3.13 (m, 6H, N4(CH2)2, CH2ꢀCO); 6.98–7.01 (m, 3H, o,p-diCH3ꢀPh, H3+H5, naph, H2);
7.27–7.56 (m, 4H, naph, H3+H4+H6+H7); 7.71—7.76 (m, 1H, naph, H5); 8.08–8.13 (m, 1H, naph, H8).
2968, 1681
duced pressure. The impure oil was purified by flash
chromatography (SP, silica gel), eluting with light
petroleum–ethyl acetate 1:1 (v/v).
used, the source of tissue and the corresponding refer-
ence are indicated. Displacement curves were analyzed
with the receptor fit competition LUNDON program and
IC50 values, concentration required to inhibit specific
binding by 50%, were calculated. Inhibition constants
(Ki) were obtained according to the equation of Cheng
and Prussoff Ki=IC50/(1+[L]/[Kd]) ([L], ligand con-
centration; [Kd], dissociation constant). Ki values were
determined from at least three competition binding
experiments.
3. Pharmacology
3.1. Animals
Male Swiss mice (23–28 g) housed in groups of ten
and male Wistar rats (180–220 g) housed in groups of
five, were used. Animals were kept in conditions of
constant temperature (2291°C) controlled lighting on
a 12-h light/dark cycle and free access to food and
water.
3.3. OH-DPAT induced hypothermia in rat and mice
These studies were performed as described previously
[22]. Body temperature was measured with a lubricated
digital thermometer probe (pb0331, Panlab, Barcelona)
inserted to a depth of 2 or 4 cm into the rectum of the
mice and rats, respectively. Temperature was recorded
at 15, 30 and 60 min for mice and 30, 60 and 90 min for
3.2. Radioligand binding experiments
Binding studies to different receptors were performed
as summarized in Table 3, in which the radioligand

A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
349
the rats, after injection of 8-OH-DPAT or other com-
pound. To study the antagonism to 8-OH-DPAT-in-
duced hypothermia, test compounds or vehicle (control)
were administered i.p. 30 min before the injection of
8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT)
(0.5 mg/kg s.c.). The results were expressed as change in
body temperature (Dt) with respect to basal body tem-
perature. The obtained data were analyzed by Anova
and Dunnett’s test.
(Coulbourn Instruments, USA). Each rat was then
exposed to inescapable electric foot shocks (1.1 mA, 10
s) every 30 s during 30 min.
3.4.2.2. Conditioned a6oidance training. Animals were
placed individually into a shuttle-box (Letica Instru-
ments, Spain) consisting of two compartments of the
same size separated by a door. Shocks delivered
through the grid floor were terminated as soon as the
animal entered into the other compartment. The assay
consisted in 30 stimulus-shock trials of 8 s with a 30 s
resting period between each trial. During the first 5 s of
each trial, a light and a sound were on (conditioned
stimulus). If the animal did not cross, within this period
to the other compartment, a shock (1 mA, 3 s maximal
duration) was delivered. Avoidance sessions were per-
formed during 3 consecutive days and the number of
escape failures and of inter-trial crossings were
recorded.
Animals received either saline or treatment through-
out the 4-day period. On day 1, the drug was given 6 h
after the exposure to the inescapable shocks and days
2–4, the drug was administered twice a day, 30 min
before shuttle-box exposure and 6 h after. On each day
of avoidance testing, differences between control and
treated rats were evaluated by the Mann–Whitney U-
test.
3.4. Antidepressant acti6ity
3.4.1. Forced swimming test [34]
Mice were placed individually for 6 min into glass
cylinders (height 24 cm, diameter 13 cm) containing 14
cm of water, maintained at 22–23°C. This procedure
was repeated for 2 consecutive days. On the second day
the animals were treated 30 min before water-immer-
sion and the duration of immobility was recorded the
second day during the last 4 min of the 6 min testing
period. A mouse was considered to be immobile when it
floated in an upright position, and made only small
movements to keep its head above water. The tricyclic
antidepressant amitriptyline was used as a reference
compound.
3.4.2. Learned helplessness test
The test was performed as described previously [35]
with minor modifications. Experimental conditions
were as follows.
4. Results and discussion
3.4.2.1. Helpless induction. On day 1, rats were placed
individually in an operant conditioning chamber with a
grid floor connected to a scrambled shock generator
We have synthesized a number of structural ana-
logues
of
3-[(4-aryl)piperazin-1-yl]-1-arylpropane
derivatives. Their affinities at both, the 5-HT1A recep-
tors and the 5-HT transporter are shown in Table 4.
With a single exception, all of the analogues displayed
better affinity for the 5-HT1A receptor than for the
5-HT transporter. The best results of affinity at 5-HT1A
receptors were obtained by the insertion of the methyl
group in position 2 (compounds II.1.a. and II.2.a).
However, the best dual activity was obtained with the
2,4-dimethyl derivatives. Receptor binding studies indi-
cated that compound III.1.a exhibited the higher
affinity for both the 5-HT transporter (Ki=415 nM)
and 5-HT1A receptors (42 nM), however it was approx-
imately 20 times weaker than that showed by fluoxetine
(Ki=21 nM) and by 8-OH-DPAT (Ki=2 nM), respec-
tively. The incorporation of the third ring provoked a
loss of both activities, probably caused by the excess of
volume associated to these ethers (compound I.3.a).
These results are in accordance with our previous stud-
ies [20]. The change of 2-methoxyphenylpiperazine by
other piperazines such as 2-hydroxyphenyl and 1-
naphtylpiperazine, reduced 5-HT1A receptor binding
affinity, although the enhancement of the binding
Table 3
Radioligand binding studies and references a
Receptor
5-HT
transporter
5-HT1A
receptor
5-HT1D
receptor
3H-Ligand
Tissue
References
[24]
3H-paroxetina
Rat frontal
cortex
3H-8-OH-DPAT Rat frontal
cortex
[25]
3H-5-HT
Bovine caudate [26]
5-HT2 receptor 3H-ketanserine Rat frontal
cortex
[27]
[28]
5-HT3 receptor 3H-BRL
Rat frontal
cortex
D2 receptor
a1 receptor
a2 receptor
b receptor
M receptor
3H-spiroperidol Rat striatum
[29]
[30]
[31]
[32]
[33]
3H-prazosin
3H-clonidina
3H-DHA
Rat cortex
Rat cortex
Rat cortex
Rat cortex
3H-QNB
a Abbreviations:
3H-8-OH-DPAT,
8-hydroxy-2-(di-n-propy-
lamino)tetraline; 3H-BRL, 3H-BRL 43694; 3H-DHA, 3H-dihydroal-
prenolol; 3H-QNB, 3H-quinuclidinylbenzylate.

350
A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
Table 4
Structure and binding affinity (Ki, nM) at 5-HT1A receptors and 5-HT transporter
Compound
Ar2
Z
Ar1
5-HT1A receptor
5-HT transporter
(Ki) a
(ui) a
I.1.a
I.2.a
I.3.a
II.1.a
II.2.a
III.1.a
III.2.a
III.1.b
III.2.b
III.1.c
4-CH3-phenyl
4-CH3-phenyl
4-CH3-phenyl
2-CH3-phenyl
CꢁO
2-OCH3-phenyl
2-OCH3-phenyl
2-OCH3-phenyl
2-OCH3-phenyl
2-OCH3-phenyl
2-OCH3-phenyl
2-OCH3-phenyl
2-OH-phenyl
100911
4095.4
\5000
2592.3
21.591.5
4293.5
9098.2
115910
11099
\5000
\5000
CHOH
CHOC6H5CF3
CꢁO
CHOH
CꢁO
CHOH
CꢁO
CHOH
CꢁO
50009125
50009120
8009110
415950
20009105
1800995
17009110
195913
2-CH3-phenyl
2,4-di-CH3-phenyl
2,4-di-CH3-phenyl
2,4-di-CH3-phenyl
2,4-di-CH3-phenyl
2,4-di-CH3-phenyl
2-OH-phenyl
1-Naphtyl
500923
a Results are the mean 9SEM of three experiments except for the Ki values \5.000 nM which were the mean of two separate experiments.
affinity to the 5-HT transporter caused by the introduc-
tion of the 1-naphtylpiperazine should be highlighted
(III.1.c).
to the interplay between a1-adrenoceptor and 5-HT1A
(auto)receptor mechanisms in the control of 5-HT re-
lease in the rat forebrain. Thus it is predictable low
implication of the adrenergic component in the phar-
macology of compound III.1.a after its systemic admin-
istration. On the other hand, there is good evidence
that the better safety profile of SSRIs over tricyclic
antidepressants (TCAs) is due partially to a lack of
anticholinergic and cardiovascular side effects, which
are derived from the inhibition of muscarinic and a1
adrenergic receptors, respectively [41,42]. We can sug-
gest that III.1.a may show, like SSRIs, a better safety
profile than TCAs.
Further pharmacological studies were performed
with III.1.a, the most interesting compound in this
series. In the forced swimming test (Table 5), III.1.a
presented the best result, exhibiting antidepressant-like
activity over a wide dose range (0.1–10 mg/kg). In
contrast, the SSRI fluoxetine showed only anti-immo-
bility effects at the high dose of 30 mg/kg, in keeping
with previous data [36]. There is a good evidence that
5-HT1A receptor agonists are active in the forced swim-
ming test at lower doses than SSRIs indicating that the
stimulation of 5-HT1A receptors appears to be impor-
tant in reducing immobility time [36]. Further studies
showed that the 5-HT1A receptors mediating increased
mobility are located postsynaptically [37]. We suggest
that the mechanism mediating antidepressant activity
by III.1.a in the forced swimming test is related to an
agonist activity to postsynaptic 5-HT1A receptors, how-
ever we do not discharge a possible influence also of the
inhibition of 5-HT uptake.
Body temperature measurements revealed that III.1.a
(5 mg/kg i.p.) antagonized 8-OH-DPAT-induced hy-
pothermia in rats and more weakly in mice suggesting
some antagonistic properties of both post and presy-
naptic 5-HT1A receptors, respectively (Tables 7 and 8).
Table 5
Effects of II.2.a and III.1.a and antidepressants on immobility time in
the forced swimming test a
In terms of selectivity (Table 6), III.1.a also exhibited
an interesting biochemical profile, since it was devoid of
affinity at other 5-HT receptor subtypes. Compound
III.1.a exhibited no affinity for muscarinic receptors
(Ki\5.000 nM) but showed certain affinity for a1
adrenoceptors (Ki=80 nM) although 160 times weaker
than the reference compound prazosin. Microdialysis
studies with compounds that exhibit a dual activity to
a1 adrenoceptors and 5-HT1A receptors have shown
that the excitation mediated by the a1-adrenoceptor is
outweighed by simultaneous activation of the latter-5-
HT1A receptors [38–40]. These studies have shown that
the receptor 5-HT1A is the most important with regard
Treatment
Immobility time (s)
Vehicle 0.1
Amitriptyline 128.2916.8 123.1914.7 130.5915.6
1
10
19.390.1 c
Fluoxetine
II.2.a
III.1.a
166.999.2 175.0911.6 160.1912.3 131.5912.6
164.1913.3 177.0913.6 109.6914.2 b 157.0919.6
107.9919.5 38.0910.9 c 22.698.1 c
28.4910.2 c
a Fluoxetine 30 mg/kg i.p. reduced significantly (PB0.01) immobil-
ity time to 32.8913.5. Values are means 9SEM of ten mice.
Compounds were administered i.p. 30 min before the test.
b PB0.05.
c PB0.01 versus vehicle (Student’s t-test).

A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
351
Table 6
The results obtained in the learned helplessness test
(Table 9) appeared to confirm the antidepressant prop-
erties of III.1.a shown previously in the forced swim-
ming test. The effect of two typical SSRIs fluoxetine
and paroxetine, were also investigated in test and in
close analogy to the results obtained in the FST, they
were active at higher doses than this new compound.
We can conclude that compound III.1.a exhibits the
higher affinity for both the 5-HT1A receptors and the
5-HT transporter with a more marked activity at 5-
HT1A receptors. Furthermore III.1.a has antidepres-
sant-like properties in two widely accepted animal
models of depression and it exhibits activity at lower
doses than typical SSRIs. Mechanism mediating antide-
pressant activity by III.1.a in the forced swimming and
in the learned helplessness test should be related to an
agonist activity to postsynaptic 5-HT1A receptors with a
possible influence of the inhibition of 5-HT uptake. The
work presented have served well in focusing our atten-
tion on this class of molecules (3-[(4-aryl)piperazin-1-
Affinity (Ki, nM) of III.1.a at 5-HT receptor subtypes, dopamine D2
receptors, adrenoceptors (a1, a2 and b) and muscarinic receptors a
Receptor
Standard
displacer
Ligand
reference
III.1.a
5-HT1D
5-HT2
5-HT3
Dopamine D2
Adrenoceptor a1
Adrenoceptor a2
Adrenoceptor b
Muscarinic
Sumatriptan
Ketanserine
BRL 43694
Haloperidol
Prazosin
Clonidine
DHA
Atropine
1291.9
0.790.09
0.390.01
1.591.2
0.590.01
890.1
660956
48709212
\5.000
120910
8098.3
13009157
\5.000
\5.000
3.590.3
2.590.1
a The values represent the mean 9SEM from three independent
experiments.
It can not be discarded, however, that at the high dose
of 5 mg/kg, partial 5-HT1A agonist properties or an-
other non-specific actions of the compound could be
involved.
Table 7
Time-dependent effects of 8-OH-DPAT (0.5 mg/kg, s.c.), (−)pindolol (10 mg/kg, s.c.) and compound III.1.a on rectal temperature and on
8-OH-DPAT-induced hypothermia in the rat a
Treatment
Dose (mg/kg/day)
Change in body temperature (°C)
30 min
60 min
90 min
Saline
−0.4090.11
−2.0790.31 b
−0.490.21
−0.4590.09
−0.4890.10
−2.7090.25
−0.6290.32**
−2.8390.36
−0.9590.09**
−0.3590.02
−1.7090.15 b
−0.390.15
−0.4590.10
−0.4090.11
−1.9090.18
−0.7190.12**
−2.0190.27
−0.6790.14**
−0.6090.08
−1.3290.21 b
−0.590.11
−0.7690.15
−0.7290.19
−1.5290.17
−0.7890.15**
−1.4790.35
−0.5790.06*
8-OH-DPAT
(−)Pindolol
III.1.a
0.5
10
0.5
5
Saline/8-OH-DPAT
(−)Pindolol/8-OH-DPAT
III.1.a/8-OH-DPAT
–/0.5
10/0.5
0.5/0.5
5/0.5
a Body temperature was measured immediately before each drug injection and 30, 60 and 90 min later. Values are means 9SEM.
b PB0.01 versus saline group. *PB0.05; **PB0.01 versus 8-OH-DPAT group (one-way ANOVA followed by Dunnett’s test).
Table 8
Time dependent effects of 8-OH-DPAT (0.5 mg/kg, s.c.), (−)pindolol (10 mg/kg, i.p.) and compound III.1.a on rectal temperature and on
8-OH-DPAT induced hypothermia in the mouse a
Treatment
Dose (mg/kg/day)
Change in body temperature (°C)
15 min
30 min
60 min
Saline
–
0.5
10
0.5
−0.5590.09
−3.3390.28 b
−0.690.21
−0.4090.08
−0.7890.09
−2.6190.35
−0.7190.21**
−2.9390.38
−2.5390.32
−0.6790.12
−3.5090.50 b
−0.890.15
−0.7090.10
−0.7790.16
−2.3690.40
−0.9590.15**
−2.3090.47
−1.4790.21*
−0.7890.11
−2.3190.36 b
−0.490.11
−0.9690.15
−0.9190.16
−1.4790.20
−0.3590.09**
−1.5790.43
−1.2790.14
8-OH-DPAT
(−)Pindolol
III.1.a
5
Saline/8-OH-DPAT
(−)Pindolol/8-OH-DPAT
III.1.a/8-OH-DPAT
–/0.5
10/0.5
0.5/0.5
5/0.5
a Body temperature was measured immediately before each drug injection and 15, 30 and 60 min later. Values are means 9SEM.
b PB0.01 versus saline group. *PB0.05; **PB0.01 versus 8-OH-DPAT group (one-way ANOVA followed by Dunnett’s test).

352
A.M. Oficialdegui et al. / Il Farmaco 55 (2000) 345–353
Table 9
Acknowledgements
Effect of compound III.1.a and selected antidepressants on helpless
behavior a
The authors are grateful to the Government of
Navarra for the predoctoral grant for Ana Oficialdegui
and to laboratories VITA-INVEST for the financial
support. We also thank Sandra Lizaso and Maria
Espelosin for skilful technical assistance.
Treatment
Dose
(mg/kg)
Number of escape failures
SB1
SB2
SB3
Vehicle
–
10
30
10
1
15.792.1
9.093.0
13.091.0
3.391.4 b
8.392.2 b
11.293.0
3.391.7 c
4.090.8 b
3.090.9 b
3.491.4 b
10.792.3
1.291.0 c
3.291.0 b
2.290.6 b
2.891.6 b
Amitriptyline
Fluoxetine
Paroxetine
III.1.a
References
a Data are the means 9SEM of escape failures in each of the three
consecutive shuttle-box sessions (SB 1–3). III.1.a was injected (i.p.) on
4 consecutive days, i.e. 6 h after inescapable shocks on day 1 and then
twice a day (30 min before shuttle-box sessions and 6 h after).
b PB0.05.
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5. Elemental analyses
Compound
I.1.a
Calc.: C, 67.28; H, 7.20; N, 7.47
Found: C, 67.02; H, 7.46; N,
7.43%
Compound
I.2.a
Calc.: C, 74.11; H, 8.23; N, 8.23
Found: C, 74.04; H, 8.55; N,
8.27%
Compound
I.3.a
Calc.: C, 69.42; H, 6.40; N, 5.78
Found: C, 69.15; H, 6.54; N,
5.73%
Compound
II.1.a
Calc.: C, 67.28; H, 7.21; N, 7.47
Found: C, 66.88; H, 7.30; N,
7.40%
Compound
II.2.a
Calc.: C, 74.11; H, 8.23; N, 8.23
Found: C, 74.33; H, 8.59; N,
8.08%
Compound
III.1.a
Calc.: C, 67.95; H, 7.40; N, 7.20
Found: C, 68.10; H, 7.85; N,
7.29%
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Found: C, 74.76; H, 8.92; N,
7.89%
Compound
III.1.b
Calc.: C, 74.56; H, 7.69; N, 8.28
Found: C, 74.27; H, 7.88; N,
8.01%
Compound
III.2.b
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