Synthesis and pharmacological properties of novel glycine antagonists

Article abstract of DOI:10.1016/S0031-6865(99)00059-X

The NMDA receptor is an ionotropic receptor complex widely distributed in the central nervous system and its activation, particularly in hypoxic conditions such as stroke, traumatic head injury and hypoglycemia, results in a massive influx of calcium ions

Full text of DOI:10.1016/S0031-6865(99)00059-X

Ž
.
Pharmaceutica Acta Helvetiae 74 2000 239–245
www.elsevier.comrlocaterpharmactahelv
Synthesis and pharmacological properties of novel glycine antagonists
)
D. Donati , R. Di Fabio
Glaxo Wellcome, Medicines Research Centre Via A. Fleming, 4, 37100 Verona, Italy
Abstract
The NMDA receptor is an ionotropic receptor complex widely distributed in the central nervous system and its activation, particularly
in hypoxic conditions such as stroke, traumatic head injury and hypoglycemia, results in a massive influx of calcium ions into the
post-synaptic neurones, leading to cell death through the activation of several neurotoxic cascades. The NMDA receptor is a unique
ionotropic receptor complex because its activation requires the simultaneous binding of glutamate and glycine and selective antagonists at
the glycine binding site are endowed with a better side-effect profile than competitive NMDA antagonists. Then, considerable efforts have
been devoted to find potent and selective ligands, resulting in the identification of several classes of glycine antagonists. The research at
Glaxo Wellcome has been aimed at the identification of novel in vivo active glycine antagonists, and led to the synthesis and
pharmacological characterization of a number of novel, potent and systemically active compounds belonging to different chemical classes.
q 2000 Elsevier Science B.V. All rights reserved.
w
x
Keywords: NMDA; Glycine antagonists; Stroke; Indole-2-carboxylates; Benzoazepines; Pyrido 2,3-b pyrazines
1. Introduction
disability with a high health-care cost for society. Al-
though it is possible to reduce the factors of risk for stroke,
no effective neuroprotective agents, able to block the
progression of the cerebral damage, are currently available.
Therefore, neuroprotection after stroke is clearly an area of
unmet need in current medicine.
In the recent past, the role of excitatory amino acids
Ž
.
EAAs in the physiology and pathophysiology of the
central nervous system has been widely investigated and
Ž
elucidated Meldrum and Garthwaite, 1990; McCullogh,
.
1992 and since the discovery of the neurotoxic properties
In ischaemic conditions, the reduction of the oxygen-
energy supply to the cells causes a significant increase of
of glutamate, the most important excitatory neurotrans-
mitter in mammalian brain, a significant body of evidence
have associated, among others, the glutamatergic hypothe-
Ž
glutamate within the synaptic clefts Cotman et al., 1981;
.
Watchins and Evans, 1981; Choi and Rothman, 1991 .
Ž
.
sis of acute neurodegeneration with stroke Choi, 1988 .
This event is responsible for the overstimulation of the
Glutamate acts through the activation of either the
Ž
.
glutamatergic receptor Fig. 1 . In particular, the activation
of the ion channel associated with the NMDA receptor
results in a massive influx of Ca2q into the post-synaptic
neurones, leading to cell death through the activation of
Ž
.
ionotropic NMDA, AMPA and kainic acid subtypes or
Ž
the metabotropic receptors Hollman and Hwinemann,
1994 . A great attention has been concentrated on the
.
activation of NMDA receptors as a key event in triggering
excitotoxicity and therefore in studying their role in major
brain physiological and pathological conditions, such as
stroke, traumatic head injury and hypoglycemia. Stroke is
generally defined as an abrupt onset of neurological func-
tions caused by a sudden reduction of cerebral blood flow,
which is due in turn to either an ischaemic occlusion or a
haemorrhagic episode. This event is one of the leading
causes of death worldwide and the first cause of long-term
Ž
. Ž
different neurotoxic cascades excitotoxicity Di Fabio et
.
al., 1998a . Therefore, a pharmacological intervention with
competitive and non-competitive NMDA antagonists,
blocking the abnormal influx of Ca2q within the post-syn-
aptic neurones, has been suggested to have a potential
therapeutic benefit Meldrum, 1991; Collingridge and
Watkins, 1994 . The molecular structure of the NMDA
receptor is not fully elucidated yet. By analogy with other
receptor gated ion channels e.g., nicotinic receptor , it is
believed that NMDA receptor is formed Fig. 2 by the
assembly of five different subunits named NR1 and
Ž
.
Ž
.
Ž
.
)
Tel.: q0039-045-9218653; fax: q0039-045-9218196; e-mail:
Ž
NR2A-B-C-D, respectively Nakanishi, 1992; Mori and
dd8260@glaxowellcome.co.uk
0031-6865r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
Ž
.
PII: S0031-6865 99 00059-X

(
)
240
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
these results, glycine was defined as co-agonist of gluta-
mate. In other words, glutamate and glycine co-operate
together to promote the transition of the NMDA ion
Ž
channel associated from the closed to the open state Corsi
.
et al., 1996; Danysz and Parsons, 1998 .
Therefore, the glycinergic site associated to the NMDA
receptor has gained considerable interest and, during the
last decade, it was perceived as a unique target for medici-
nal chemistry in terms of potential therapeutic intervention
Ž
Iversen and Kemp, 1994; Leeson and Iversen, 1994; Di
Fig. 1. Involvement of NMDA receptors in the excitotoxic cascade.
.
Fabio et al., 1996 , since the observation that one of the
first glycine antagonists identified, the 7-chloro kynurenic
Ž
. Ž .
acid 7-Cl KA 1 depicted in Fig. 3, was endowed with a
greater therapeutic index compared to different series of
competitive and non-competitive NMDA antagonists
.
Mishina, 1995 which are encoded by separate genes and
several splice variants for each gene have been described
Danysz and Parsons, 1998 . On the basis of morphologi-
cal studies, it has been shown that NMDA receptors are
probably heteromeric assemblies of at least four subunits,
with their composition depending from the regional ex-
pression in different brain areas Danysz and Parsons,
1998 . Such a conclusion is also supported by electrophys-
iological and pharmacological studies showing that the
pharmacology of NMDA receptor ligands agonist and
Ž
.
Ž
.
Chiamulera et al., 1990 . Then, considerable efforts have
been devoted to find potent and selective ligands, resulting
in the identification of several classes of glycine antago-
Ž
.
nists e.g., tetrahydroquinolines, indoles, quinoxalines, etc.
Ž
as exemplified in Fig. 3.
.
However, despite their high in vitro affinity at the
glycine binding site, many of the aforementioned com-
pounds showed poor in vivo activity in a variety of animal
models, probably because of their insufficient brain pene-
tration Carling et al., 1993; Moore et al., 1993 . As a
result of our efforts aimed at the identification of novel in
vivo active glycine antagonists as potential antistroke
agents, a number of new templates were selected for
further exploration, and, among others, we focused our
Ž
.
antagonists is strongly influenced by the receptor compo-
sition. The pathophysiological implication of these differ-
ences is still unknown, but this remains a fascinating area
of research interest.
In addition to the molecularrstructural complexity de-
scribed above, the NMDA receptor is also characterized by
a higher level of complexity which is given by the differ-
ent regulatory sites which control its function. Among the
different binding sites present within the NMDA receptor,
a special interest has been attracted by the strychnine-in-
Ž
.
w
x
Ž . Ž
attention on pyrido 2,3-b pyrazines
Ž . Ž
Fabio et al., 1998a and benzoazepines 9 Di Fabio et al.,
7
Micheli et al.,
.
1996, 1997 indole-2-carboxylates 8 see for example, Di
Ž . Ž
.
. Ž
.
1999a Fig. 4 . The synthesis and pharmacological charac-
terization of both indoles and benzoazepines will be de-
scribed in detail in the following sections. Even though the
Ž
.
sensitive glycine site glycine receptor . The conductance
through the channel associated with the NMDA receptor is
indeed strongly influenced by the presence of glycine.
Ž
Some years ago, it has been reported Johnson and Ascher,
.
1987; Kleckner and Dingledine, 1988 that in cultured
cerebral neurones, the frequency of the opening of this ion
channel was markedly affected by the presence of glycine.
This event was so relevant that in the absence of glycine,
glutamate failed to activate the NMDA receptor. Based on
Fig. 2. Schematic representation of the NMDA receptor.
Fig. 3. Classes of glycine antagonists.

(
)
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
241
Ž
years by a number of different research groups see for
example, Huettner, 1989; Salituro et al., 1990; Rowley et
.
al., 1992 following the preliminary evidence that the
substituent at the C-3 position of the indole nucleus could
modulate the affinity of these compounds for the strych-
nine-insensitive glycine binding site. However, glycine
antagonists identified within this class were devoid of
significant in vivo activity probably because of their poor
ability to penetrate the brain. Therefore, we became inter-
ested in the synthesis of novel indole-2-carboxylates ex-
hibiting the desired in vivo profile. This activity led to the
synthesis of indole-2-carboxylates substituted at the C-3
position with suitable a,b-unsaturated side chains, which
showed nanomolar affinity for the glycine binding site
coupled with both high receptor selectivity and high in
vivo potency in the NMDA-induced convulsions model in
w
x
Ž .
Fig. 4. General structures of pyrido 2,3-b pyrazines 7 , indole-2-
Ž .
Ž .
carboxylates 8 and benzoazepines 9 .
following discussion will be centered on the discovery and
characterization of novel glycine antagonists as potential
antistroke agents, it is worth mentioning that increasing
evidences support the hypothesis that the NMDA receptors
play a pivotal role in the development and maintenance of
Ž
pain hypersensitivity Woolf, 1983; Haley et al., 1990;
Woolf, 1995; Harris et al., 1996 . Following such a hy-
.
pothesis, glycine antagonists, blocking the overactivation
of the NMDA receptor and restoring the baseline level of
nociceptive transmission should be effective for the treat-
ment of the chronic pain. The identification of novel
glycine antagonists as potential and effective antihyperal-
gesic agents was therefore considered an attractive and
further objective for our project. The results obtained in
this field will however be reported and discussed in detail
Ž
.
mice i.v. an p.o. route . Among the compound initially
Ž
. Ž .
synthesized, GV150526 gavestinel 10 , currently under-
going clinical studies in man, is the most promising glycine
Ž
antagonist identified to date Di Fabio et al., 1997; Di
.
Fabio et al., 1998a . The most relevant characteristics of
GV150526 are summarized in the Table 1. The ability of
GV150526 to cross the blood–brain barrier results in a
substantial neuroprotective effect in a rat model of Middle
Ž
.
elsewhere Di Fabio et al., 1998b; Quartaroli et al., 1999 .
Ž
.
Cerebral Artery occlusion MCAo when given both pre-
Ž
.
ischaemia 70% of maximal protection at 3 mgrkg i.v.
2. Results and discussion
and post-ischaemia up to 6 h from the induction of the
cerebral damage. As shown in Fig. 5, GV150526, given 6
h after the occlusion, was able to completely stop the
damage progression.
2.1. Biological eÕaluation
Ž
.
All the new chemical entities NCEs were evaluated,
both in vitro and in vivo, according to the following
Ž .
screening cascade: a binding assay to evaluate the affin-
Ž
.
ity for the glycine site Kishimoto et al., 1981 and selec-
tivity for glutamate receptors Honore et al., 1986; Giberti
et al., 1991; Van Amsterdam et al., 1992 ; b in vitro
Ž
´
. Ž .
functional antagonism studies to evaluate potency and
Ž
. Ž .
activity Kloog et al., 1988; Ratti et al., 1990 ; c in vivo
Ž
.
Ž .
anticonvulsant activity Chiamulera et al., 1990 ; and d
the most interesting compounds in the NMDA-induced
convulsions model, were then submitted for in vivo models
Ž
.
of stroke in rats MCAo both pre- and post-ischaemia
These results support the view that the blockade of
NMDA receptor could be of therapeutic benefit, and, in
this respect, glycine antagonists appear to be extremely
effective. Furthermore, GV150526 lacks the adverse be-
havioral effects in rats observed for both competitive
NMDA antagonists and NMDA channel blockers: neither
Ž
.
Tamura et al., 1981 .
2.2. Indole-2-carboxylates
Ž .
Indole-2-carboxylates of general structure 5 represent
a class of glycine antagonists widely explored in the last
Table 1
Pharmacological profile of GV150526
Type of study
Assay
w3
Results
Notes
x
Affinity
Selectivity
H -glycine binding
PKi s8.49"0.02
No displacement at 10 mM
Rat cortical membranes
Ž
.
Receptogram 40 brain receptors
Ž .
Reversed by glycine agonist D-serine
Systemic activity NMDA induced convulsion in mice, i.v. ED50 s0.06 mgrkg
MCAo model Rat, i.v. ED50 s0.8 mgrkg pre-ischaemia
ED50 s3.0 mgrkg post-ischaemia Single fully protective dose given 6 h after occlusion

(
)
242
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
Fig. 5. Neuroprotective effect of GV150526A after post-ischaemia admin-
Ž
.
istration 6 h .
Scheme 1. Synthesis of substituted indole-2-carboxylates.
Ž
.
ataxic effects rotarod nor impairment of performance
Ž
.
passive avoidance were observed in mice up to a dose of
30 mgrkg administered i.v. 500-fold the ED50 observed
in inhibition of NMDA-induced convulsions , confirming
Ž
The aforementioned indoles and their analogues can be
.
Ž
prepared according to different reported methods Di Fabio
the wider therapeutic window observed with glycine antag-
et al., 1997, 1999b; Giacobbe et al., 1999 and references
cited therein , and in particular, following the general
synthetic route described in Scheme 1 Di Fabio et al.,
1999b and references cited therein . The key intermediate
12 , which is now available in large-scale as previously
described Di Fabio et al., 1997 was transformed into the
amido derivative 14 by using different methods of activa-
tion of the carboxyl group. The best results were obtained
Ž
onists Di Fabio et al., 1997; Di Fabio et al., 1998a and
.
.
references cited therein . These results also confirm the
Ž
view that our indole 2-carboxylate template could be use-
ful to generate novel and effective compounds, strengthen-
ing the need of continuing the chemical exploration of
.
Ž
.
Ž
.
Ž
.
such a class Di Fabio et al., 1998a . This further chemical
exploration allowed identification of a number of ana-
Ž
.
Ž
.
logues of GV150526, and among them, GV228869 11
exhibited high in vitro affinity to the glycine binding site
via the formation of the corresponding 2-pyridyl thioester
13 by using a stoichiometric amount of 2,2 -dipyridyldi-
X
Ž
.
Ž
.
Table 2 and promising physico-chemical and pharmaco-
Ž
.
sulphide and triphenylphosphine. In general, 13 is stable
enough to be purified by classical chromatographic proce-
dures; then, it can be reacted with the proper arylamines to
Ž
.
logical profile Di Fabio et al., 1999b . In particular, it was
found to be effective in blocking NMDA induced convul-
sions and it showed a significantly better neuroprotective
activity in the MCAo model with respect to GV150526
when given post-ischaemia up to 6 h after occlusion of the
middle cerebral artery.
Ž
. Ž
give the amides 14 the same products can be also
obtained by a ‘‘one-pot’’ procedure, without the isolation
of 13 . The amides 14 can then be transformed into the
final indole-2-carboxylates 15 in fairly good overall yields
by removal of the various protecting groups according to
standard methods.
Ž
..
Ž .
Ž
.
2.3. Benzoazepines
To discover novel non-indole classes of glycine antago-
nists as potential back-up to GV150526A, new templates
were designed by receptor mapping techniques based on
Ž
the pharmacophore model of the glycine binding site Di
Table 2
Summary of the pharmacological profile of GV228869 compared to GV150526
Type of study
GV150526
GV228869
2 nM
Affinity Ki
3 nM
Ž
.
.
Ž
.
.
Receptor selectivity IC50
NMDA-induced convulsions ED50
MCAo model pre-ischaemia rat, i.v.
Max. protection
)10 mM 70 receptors
)10 mM 70 receptors
Ž
Ž
0.06 mgrkg mice, i.v.
ED50 s0.8 mgrkg
70% at 3 mgrkg i.v.
0.07 mgrkg mice, i.v.
ED50 s0.2 mgrkg
70% at 3 mgrkg i.v.
Ž
.

(
)
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
243
Table 4
Summary of the pharmacological profile of GV224029 compared to
GV150526
Type of study
GV150526
GV224029
Affinity Ki
3 nM
32 nM
Receptor
)10 mM
)10 mM
Ž
.
Ž
.
selectivity IC50
NMDA-induced
convulsions ED50
70 receptors
0.06 mgrkg
70 receptors
0.07 mgrkg
Fig. 6. Benzoazepine derivatives.
Ž
.
Ž
.
mice, i.v.
mice, i.v.
MCAo model
Pre-ischaemia
ED50 s0.8 mgrkg
ED50 s3 mgrkg
ED50 s0.6 mgrkg
ED50 s2.5 mgrkg
.
Fabio et al., 1997 and references cited therein . Among
others, a novel series of benzoazepine derivatives of gen-
Ž
.
rat, i.v.
Post-ischaemia
Ž
.
Ž
.
rat, i.v.
eral structure 16 , bearing the same a,b-unsaturated side
Ž
.
chain as GV150526 at the position C-5 Fig. 6 and
different substituent at C-3 was proposed. A number of
different compounds was then prepared and evaluated and
Ž
.
results are reported in Table 3 Di Fabio et al., 1999a .
As expected, the unsubstituted derivative was devoid of
any in vitro activity, while the most active compound of
such a series was the 3-carboxylic derivative GV224029
required to avoid the double bond isomerization during
.
Ž .
deprotections in the last steps . When the malonamide 21
was reacted with 3-bromo-N-phenylacrylamide under basic
Ž
.
conditions, we obtained the open intermediate 22 which
Ž
.
Ž
.
Table 3, entry 3 . Also, 3-carboxyamides entries 4 and 5
Ž
was then cyclized, in the presence of palladium tetrakis tri-
phenylphosphine to give the protected benzoazepine 23 .
have shown an interesting affinity, comparable to
GV224029. The last one was further characterized from a
pharmacological point of view and results are reported in
Table 4 below. In particular, it is worth underlying that in
spite of its 10-fold lower affinity for the glycine binding
site, GV224029 exhibited a similar neuroprotective activity
with respect to GV150526 in the MCAo test both pre- and
post-ischaemia. The synthesis of benzoazepine derivatives
was performed following different synthetic routes, accord-
ing to the nature of the substituent at C-3. For the sake of
simplicity, only the synthesis of the C-3 carboxylic deriva-
.
Ž .
The final removal of both the N-1 and C-3 carboxylic
Ž
.
protecting groups was smoothly accomplished treating 23
first with anisole in H2 SO4rTFA and then with base to
Ž
.
give the final compound GV224029 24 .
Ž
.
tives GV224029 is reported Scheme 2 . Thus, 4-chloro-
Ž
.
2-nitro-iodobenzene 18 was obtained via Sandmeyer re-
action from 4-chloro-2-nitroaniline 17 , then reduced to
the corresponding aniline derivative 19 in high yield
using Fe in AcOHrEtOH. Reaction with p-methoxyben-
zyl chloride and sodium iodide in DMF, gave the protected
Ž
.
Ž
.
Ž
.
aniline 20 , which was reacted with methyl malonylchlo-
Ž
.
ride to give the amide 21 in high yield after proper
deprotection and esterification with t-butyl alcohol the
Ž
protection as t-butyl ester in place of the methyl ester was
Table 3
Affinity of benzoazepine derivatives for the strychnine-insensitive bind-
ing site
a
Ž
.
Entry
R
Ki nM
1
2
H
OH
)105
1288
32
39
72
916
339
Ž
.
3 GV224029
COOH
CONH2
CONHPh
COOCH3
CN
4
5
6
7
aw3
x
H -glycine displacement.
Scheme 2. Synthesis of GV224029.

(
)
244
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
glutamate as a neurotransmitter. Adv. Biochem. Biopharmacol. 27,
1–27.
3. Conclusions
Danysz, W., Parsons, C.G., 1998. Glycine and NMDA receptors—
physiological significance and possible therapeutic applications. Phar-
macol. Rev. 50, 597–664.
Di Fabio, R., Gaviraghi, G., Reggiani, A., 1996. Strychnine-insensitive
glycine binding site and the NMDA receptor. La Chimica e l’Industria
78, 283–289.
Di Fabio, R., Capelli, A.M., Conti, N., Cugola, A., Donati, D., Feriani,
A., Gastaldi, P., Gaviraghi, G., Hewkin, C.T., Micheli, F., Missio, A.,
Mugnaini, M., Pecunioso, A., Quaglia, A.M., Ratti, E., Rossi, L.,
Tedesco, G., Trist, D.G., Reggiani, A., 1997. Substituted indole-2-
carboxylates as in vivo potent antagonists acting at the strychnine-in-
sensitive glycine binding site. J. Med. Chem. 40, 841–850.
Di Fabio, R., Cugola, A., Donati, D., Feriani, A., Gaviraghi, G., Ratti, E.,
Trist, D.G., Reggiani, A., 1998a. Identification and pharmacological
characterization of GV150526, a novel glycine antagonist as a potent
neuroprotective agent. Drugs Future 23, 61–69.
Di Fabio, R., Corsi, M., Donati, D., Gaviraghi, G., Quartaroli, M., Ratti,
E., Reggiani, A., Trist, D.G., 1998. Glycine antagonists as potent
analgesic compounds, XVth EFMC International Symposium on
Medicinal Chemistry. Book of Abstract, D3.
Di Fabio, R., Antolini, M., Bertani, B., Conti, N., Feriani, A., Messeri,
T., Missio, A., Pasquarello, A., Pentassuglia, G., Quaglia, A.M.,
Reggiani, A., Sabbatini, F.M., 1999. SAR and neuroprotective activ-
ity of a novel class of glycine antagonists. Book of Abstracts 217th
ACS National Meeting, Anaheim, USA, no. 278.
Di Fabio, R., Barnaby, R.J., Conti, N., De Magistris, E., Feriani, A.,
Provera, S., Sabbatini, F.M., Reggiani, A., Rovatti, L., 1999b. Substi-
tuted analogues of GV150526 as potent glycine binding site antago-
nists in animal models of cerebral ischaemia. J. Med. Chem. 42, in
press.
Giacobbe, S., Di Fabio, R., Baraldi, D., Cugola, A., Donati, D., 1999.
Synthesis of substituted indole-2-carboxylates: versatile introduction
of a carbamoyl moiety at the C-position. Synth. Commun. 29, 3125–
3135.
In spite of great efforts by many research groups, there
are still no effective drugs available to treat stroke in
humans. Among the number of different approaches that
are currently under investigation, the search for novel and
effective antagonists at the strychnine-insensitive binding
site remains probably the most exciting in the field of
neuroprotection. Our search in this context has provided
new and further evidences of the validity of such an
approach and the discovery of new templates has repre-
sented a clear step forward. The synthesis and pharmaco-
logical characterization of novel indole-2-carboxylates
bearing a suitable a,b-unsaturated side chain at position
C-3 led to the identification of a number of potent, selec-
tive and systemically active glycine antagonists and a
Ž
.
member of this class, GV150526 gavestinel is currently
in phase III clinical trials. In this respect, the importance of
the a,b-unsaturated side chain in the interaction with the
glycine binding site has been recently supported with the
synthesis and the pharmacological characterization of pyr-
role-2-carboxylic acids bearing the same side chain as
Ž
GV150526 and analogues Tarzia et al., 1998; Tarzia et
.
al., 1999 . At the same time, the identification of novel
antagonists belonging to the benzoazepine series has al-
lowed us to further elaborate the existing pharmacophoric
model concerning the interaction with the glycine binding
site and GV224029 represents a valid prototype for a
further progression of the relevant studies.
Giberti, A., Ratti, E., Gaviraghi, G., van Amsterdam, F.Th.M., 1991.
w3
x
Binding of DL
- H -a-amino-3-hydroxy-5-methyl-isoxazole-4-pro-
Acknowledgements
Ž
.
pionic acid AMPA to rat cortex membranes reveals two sites or
Ž .
affinity states. J. Recept. Res. 11 5 , 727–741.
I wish to thank all my colleagues who gave a strong
enthusiastic contribution to the very important results re-
ported above; their names are reported in the references
below.
Haley, J.E., Sullivam, A.F., Dickenson, A.H., 1990. Evidence for spinal
N-methy-D-aspartate receptor involvement in prolonged chemical no-
ciception in the rat. Brain Res. 518, 218–226.
Harris, J.A., Corsi, M., Quartaroli, M., Arban, R., Bentivoglio, M., 1996.
Up-regulation of spinal glutamate receptors in chronic pain. Neuro-
science 74, 7–12.
Hollman, M., Hwinemann, S., 1994. Cloned glutamate receptors. Annu.
Rev. Neurosci. 17, 31–108.
References
Honore, T., Drejer, J., Nielsen, M., 1986. Calcium discriminates two
´
w3
x
Carling, R.W., Leeson, P.D., Moseley, A.M., Smith, J.D., Saywell, K.,
Tricklebank, M.D., Kemp, J.A., Marshall, J.R., Foster, A.C., Grim-
wood, S., 1993. Anticonvulsant activity of glycine-site NMDA antag-
onists: 2. Trans 2-carboxy-4-substituted tetrahydroquinolines. Bioorg.
Med. Chem. Lett. 3, 65–70.
H -kainite binding sites with different molecular targets sizes in rat
cortex. Neurosci. Lett. 65, 47–52.
Huettner, J.E., 1989. Indole-2-carboxylic acid: a competitive antagonist
of potentiation by glycine at the NMDA receptor. Science 243,
1611–1613.
Chiamulera, C., Costa, S., Reggiani, A., 1990. Effect of NMDA and
strychnine-insensitive glycine site antagonists on NMDA-mediated
convulsions and learning. Psychopharmacology 102, 551.
Choi, D.W., 1988. Neuron 1, 623.
Choi, D.W., Rothman, S.M., 1991. The role of glutamate neurotoxicity in
hypoxic–ischemic neuronal death. Annu. Rev. Pharmacol. Toxicol.
31, 171–182.
Iversen, L.L., Kemp, J.A., 1994. Noncompetitive NMDA antagonists as
Ž
.
drug. In: Collingridge, G.L., Watkins, J.C. Eds. , The NMDA Recep-
tor, 2nd edn. IRL Press, Oxford, pp. 469–486.
Johnson, J.W., Ascher, P., 1987. Glycine potentiates the NMDA receptor
reponse in cultured brain mouse neurones. Nature 325, 529–531.
Kishimoto, H., Simon, J.R., Aprison, M.H., 1981. Determination of the
equilibrium dissociation constant at a number of glycine binding site
in several areas of the rat central nervous system, using a Na-indepen-
dent system. J. Neurochem. 37, 1015–1024.
Collingridge, G.L., Watkins, J.C., 1994. The NMDA Receptor, 2nd edn.
IRL Press, Oxford.
Corsi, M., Fina, P., Trist, D.G., 1996. Co-agonism in drug receptor
activation: illustrated by the NMDA receptor. Trends Pharmacol. Sci.
17, 220–222.
Kleckner, N.W., Dingledine, R., 1988. Requirements for glycine in
activation of NMDA receptors expressed in xenopus oocytes. Science
241, 835–837.
Cotman, C.W., Foster, A.C., Lanthorn, T.H., 1981. An overview of
Kloog, Y., Haring, R., Sokolovsky, M., 1988. Kinetic characterization of

(
)
D. Donati, R. Di FabiorPharmaceutica Acta HelÕetiae 74 2000 239–245
245
the phenylcyclidine-N-methyl-
D
-aspartate receptor interaction: evi-
Ratti, E., Tacconi, S., Graziani, F., Gaviraghi, G., 1990. Requirement of
the glycine for the glutamate activity at the NMDA receptor site. Eur.
J. Pharmacol. 183, 1665.
Rowley, M., Leeson, P.D., Grimwood, S., Foster, A., Saywell, K., 1992.
2-Carboxy-indolines and indoles as potential glycinerNMDA antago-
nists: effect of five-membered ring conformation of affinity. Bioorg.
Med. Chem. Lett. 2, 1627–1630.
dence for steric blockade of the channel. Biochemistry 27, 843–848.
Leeson, P.D., Iversen, L.L., 1994. The glycine site on the NMDA
receptor: structure–activity relationships and therapeutic potential. J.
Med. Chem. 37, 4053–4067.
McCullogh, J., 1992. Excitatory amino acid antagonists and their poten-
tial for the treatment of ischemic brain damage in man. Br. J. Clin.
Pharmacol. 34, 106–114.
Salituro, F.G., Harrison, B.L., Baron, B.M., Nyce, P.M., Stewart, K.T.,
McDonald, I.A., 1990. Indole derivatives: antagonists of the stych-
Meldrum, B., 1991. Excitatory amino acid antagonists. Blackwell, Ox-
ford.
nine-insensitive glycine receptor associated with the N-methyl-D-
Meldrum, B., Garthwaite, J., 1990. Excitatory amino acid neurotoxicity
and neurodegenerative diseases. Trends Pharmacol. 11, 379–387.
Micheli, F., Cugola, A., Donati, D., Guarneri, M., Missio, A., Pecunioso,
A., Reggiani, A., Tarzia, G., Zanirato, V., 1996. Synthesis and
aspartate receptor complex. J. Med. Chem. 33, 2944–2946.
Tamura, A., Graham, D.I., McCullogh, J., Teasdale, G.M., 1981. Focal
cerebral ischaemia in rat: 1. Description of techniques and early
neuropathological consequences. J. Cereb. Blood Flow Metab. 1,
53–60.
Tarzia, G., Balsamini, C., Bedini, A., Diamantini, G., Spadoni, G.,
Tontini, A., Di Fabio, R., Feriani, A., Reggiani, A., Tedesco, G.,
w
x
w
biological evaluation of pyrido 2,3-b pyrazines and pyrido 2,3-
x
b pyrazine-N-oxide as selective glycine antagonists. Bioorg. Med.
Chem. Lett. 6, 2749–2754.
Ž
.
Ž
Ž
.
.
Micheli, F., Cugola, A., Donati, D., Missio, A., Pecunioso, A., Reggiani,
Valigi, R., 1998. E -3- 2- N-Phenylcarbamoyl vinyl pyrrole-2-
carboxylic acid derivatives: a novel class of glycine antagonists. J.
Med. Chem. 41, 808–820.
w
x
A., Tarzia, G., 1997. 2,3-Dihydro-6,7-dichloro-pyrido 2,3-b pyrazine-
8-oxide as selective glycine antagonist with in vivo activity. Bioorg.
Med. Chem. 5, 2129–2132.
Tarzia, G., Balsamini, C., Bedini, A., Diamantini, G., Spadoni, G.,
Ž
.
Moore, K.W., Leeson, P.D., Carling, R.W., Tricklebank, M.D., Singh, L.,
1993. Anticonvulsant activity of glycine-site NMDA antagonists: 1.
2-Carboxyl prodrugs of 5,7-dichlorokynurenic acid. Bioorg. Med.
Chem. Lett. 3, 61–64.
Tontini, A., Di Fabio, R., Donati, D., 1999. 3- 2-Carbamoylvinyl -
4,5-dimethylpyrrole-2-carboxylic acids as ligands at the NMDA
glycine-binding site: a study on the 2-carbamoylvinyl chain modifica-
tion. Il Farmaco 54, 101–111.
Mori, H., Mishina, M., 1995. Structure and function of the NMDA
receptor channel. Neuropharmacology 34, 1219–1237.
Nakanishi, S., 1992. Molecular diversity of glutamate receptors and
implications for brain function. Science 258, 597–603.
Van Amsterdam, F.Th.M., Giberti, A., Mugnaini, M., Ratti, E., 1992.
wŽ
.
x
3- q -2-Carboxypiperazin-4-yl propyl-1-phosphonic acid recognizes
two N-methyl- -aspartate binding sites in rat cerebral cortex mem-
D
branes. J. Neurochem. 59, 1850–1855.
Quartaroli, M., Carignani, C., Dal Forno, G., Mugnaini, M., Ugolini, A.,
Arban, R., Bettelini, L., Maraia, G., Belardetti, F., Reggiani, A., Trist,
D.G., Ratti, E., Di Fabio, R., Corsi, M., 1999. Potent antihyperalgesic
activity without tolerance produced by glycine site antagonist of
Watchins, J.C., Evans, R.H., 1981. Excitatory amino acids transmitters.
Annu. Rev. Pharmacol. Toxicol. 21, 165–204.
Woolf, C.J., 1983. Evidence for a central component of post-injury
hypersensitivity. Nature 306, 686–688.
N-methyl-
290, 158–169.
D
-aspartate receptor GV196771A. J. Pharmacol. Exp. Ther.
Woolf, C.J., 1995. An overview of the mechanism of hyperalgesia. Pulm.
Pharmacol. 8, 161–167.