dizocilpine-maleate and 2-amino-4-phosphonobutyric-acid

The thiol amino acid L-cysteine increases arterial blood pressure (ABP) when injected into the cerebrospinal fluid space in conscious rats, indicating a pressor response to centrally acting L-cysteine. A prior synaptic membrane binding assay suggests that L-cysteine has a strong affinity for the L-2-amino-4-phosphonobutyric acid (L-AP4) binding site. The central action of L-cysteine may be vial-AP4 sensitive receptors. The present study investigated cardiovascular responses to L-cysteine and L-ap4 microinjected into the autonomic area of the caudal ventrolateral medulla (CVLM) where inhibitory neurons regulate ABP via pre-sympathetic vasomotor neurons. Both the injection of L-cysteine and L-AP4 in the CVLM sites identified with L-glutamate produced the same depressor and bradycardic responses in urethane-anesthetized rats. Neither a prior antagonist microinjection of MK801 for the N-methyl-D-aspartate (NMDA) receptor nor CNQX for the non-NMDA receptor attenuated the responses to L-cysteine, but the combination of the two receptor blocking with an additional prior injection abolished the response. In contrast, either receptor blockade alone abolished the response to L-AP4, indicating distinct mechanisms between responses to L-cysteine and L-AP4 in the CVLM. The results indicate that the CVLM is a central active site for L-cysteine's cardiovascular response. Central L-cysteine's action could be independent of the L-AP4 sensitive receptors. Cardiovascular regulation may involve endogenous L-cysteine in the CVLM. Further multidisciplinary examinations are required to elaborate on L-cysteine's functional roles in the CVLM.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Aminobutyrates; Anesthetics; Animals; Arterial Pressure; Cardiovascular Agents; Cysteine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Glutamic Acid; Heart Rate; Male; Medulla Oblongata; Microinjections; Rats, Wistar; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Urethane

D-Serine, a recently identified gliotransmitter, serves as an endogenous coagonist binding to the glycine site of N-methyl-D-aspartate (NMDA) receptors. However, it is not clear whether this native ligand is able to bind to and modulate alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) receptors. In the present study, we showed that D-serine was able to concentration-dependently inhibit kainate-induced AMPA receptor-mediated current in acutely isolated hippocampal neurons. The blocking action of D-serine on AMPA receptors was characterized by a shift in concentration-response curve of kainate-induced current to the right with no change in the maximal response and independent of holding potential in the range of -80 to +60 mV. This is consistent with a model that D-serine is a competitive antagonist on AMPA receptors. In contrast, L-serine did not exert such an inhibitory action. Consistent with this observation, we found that several D-isoforms, but not L-isoforms, of endogenous and exogenous amino acids were able to block AMPA receptors. These results indicate that there is a low affinity and stereo-selective site at the agonist binding pocket of AMPA receptors for these D-amino acids. More importantly, vesicular-released endogenous D-serine from astrocytes could potentially modulate AMPA receptors in synaptic transmission in hippocampus.

Topics: Action Potentials; Amino Acids; Aminobutyrates; Animals; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Hippocampus; Kainic Acid; Molecular Structure; Neurons; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Serine; Stereoisomerism; Valine

The concentrations of glutamic and aspartic acids were measured in the dialysate obtained with vertical microdialysis probes implanted into the paraventricular nucleus of the hypothalamus of sexually potent male rats during sexual activity. Animals showed noncontact erections when put in the presence of, and copulated with, a receptive (ovarietomized oestrogen- and progesterone-primed) female rat. The concentrations of glutamic and aspartic acids in the paraventricular dialysate increased by 37 and 80%, respectively, above baseline values during exposure to the receptive female rat and by 55 and 127%, respectively, during copulation. No changes in the concentrations of glutamic and aspartic acids were detected in the paraventricular dialysate when sexually potent male rats were exposed to nonreceptive (ovariectomized not oestrogen- and progesterone-primed) female rats or when impotent male rats were used. The injection into the paraventricular nucleus of the excitatory amino acid receptor antagonist dizocilpine (5 micro g), a noncompetitive N-methyl-d-aspartic acid receptor antagonist, reduced noncontact erections and significantly impaired copulatory activity. The alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione (5 micro g) was also able to impair copulatory activity, but to a much lower extent than dizocilpine. In contrast, (+/-)-2-amino-4-phosphono-butanoic acid, a metabotropic receptor antagonist (5 micro g), was found to be ineffective. These results confirm the involvement of the paraventricular nucleus in the control of erectile function and copulatory behaviour and show that excitatory amino acid concentration increases in the paraventricular nucleus when penile erection occurs in physiological contexts.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Aminobutyrates; Analysis of Variance; Animals; Aspartic Acid; Behavior, Animal; Copulation; Dialysis; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glutamic Acid; Male; Microinjections; Paraventricular Hypothalamic Nucleus; Penile Erection; Rats; Rats, Sprague-Dawley; Reaction Time; Receptors, N-Methyl-D-Aspartate; Sexual Behavior, Animal

RT-PCR demonstrated that ionotropic (iGluR NR1) and metabotropic (mGluR Group III) glutamate receptors are expressed in rodent lymphocytes. Flow cytometry showed that activation of iGluR NR1 by N-methyl-D-aspartate (NMDA) increased intracellular free calcium and reactive oxygen species (ROS) levels and activated caspase-3. The latter effect was attenuated by the NMDA antagonist, 5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801), by the antioxidant N-acetylcysteine and by cyclosporin A. Treatment with L-2-amino-4-phosphonobutyric acid (L-AP4), an mGluR Group III agonist, increased lymphocyte ROS levels but to a lower extent than did NMDA. Activation of lymphocytes with both NMDA and L-AP4 caused a synergistic increase in ROS levels and induced necrotic cellular death without elevating the caspase-3 activation observed in the presence of NMDA alone. These results show that lymphocyte iGluR NR1 and mGluR Group III receptors may be involved in controlling rodent lymphocyte functions and longevity as they regulate events in cell proliferation, maturation, and death.

Topics: Aminobutyrates; Animals; Calcium; Caspase 3; Caspases; Dizocilpine Maleate; Enzyme Activation; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Lymphocyte Activation; Lymphocytes; Mice; Molecular Sequence Data; N-Methylaspartate; Rabbits; Rats; Rats, Wistar; Reactive Oxygen Species; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate

Both postsynaptic density and presynaptic active zone are structural matrix containing scaffolding proteins that are involved in the organization of the synapse. Little is known about the functional role of these proteins in the signaling of presynaptic receptors. Here we show that the interaction of the presynaptic metabotropic glutamate (mGlu) receptor subtype, mGlu7a, with the postsynaptic density-95 disc-large zona occludens 1 (PDZ) domain-containing protein, PICK1, is required for specific inhibition of P/Q-type Ca(2+) channels, in cultured cerebellar granule neurons. Furthermore, we show that activation of the presynaptic mGlu7a receptor inhibits synaptic transmission and this effect also requires the presence of PICK1. These results indicate that the scaffolding protein, PICK1, plays an essential role in the control of synaptic transmission by the mGlu7a receptor complex.

Topics: Aminobutyrates; Animals; Calcium Channel Blockers; Calcium Channels, P-Type; Calcium Channels, Q-Type; Carrier Proteins; Cell Cycle Proteins; Cells, Cultured; Cerebellum; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Humans; Mice; Mice, Knockout; Neurons; Nuclear Proteins; Oligonucleotides, Antisense; omega-Agatoxin IVA; omega-Conotoxin GVIA; Patch-Clamp Techniques; Receptors, Metabotropic Glutamate; Synaptic Transmission; Synaptophysin

Two antagonists of metabotropic glutamate receptors, L-AP4 and MCPG, were tested in a one-trial passive avoidance task in the chick to investigate whether these receptor subtypes play a role in learning and memory. Drugs were injected i.c. L-AP4 produced amnestic effects when injected pre- or post-training. When injected pretraining, amnesia onset was observed after 1 h post-training. D-AP4 had no effect on memory formation. MCPG in comparison had no effect when injected post-training. When injected pretraining, the onset of amnesia was dose-dependent, ranging from 2 to 1 h post-training. When injecting MCPG along with the mGluR agonist ACPD, no amnestic effect was visible. ACPD on its own had no effect at the dose used.

Topics: Aminobutyrates; Amnesia; Animals; Avoidance Learning; Benzoates; Chickens; Cycloleucine; Cyclopropanes; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Glycine; Injections, Intraperitoneal; Injections, Intraventricular; Male; Motor Activity; Phosphoserine; Receptors, Metabotropic Glutamate

The pharmacological specificity of the mGluR1 alpha subtype of the metabotropic glutamate receptor (mGluR) was examined in a cloned baby hamster kidney cell line (BHK-ts13) measuring [3H]glutamate binding and inositol phosphate (PI) hydrolysis. PI-hydrolysis was maximally stimulated by quisqualate (1112 +/- 105% of basal), glutamate (1061 +/- 70% of basal), ibotenate (1097 +/- 115% of basal) and beta-N-methylamino-L-alanine (BMAA) (1010 +/- 104% of basal). In contrast, the maximal stimulation of PI-hydrolysis by (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (t-ACPD) was only 673 +/- 78% of the basal level. The relative order of potency was quisqualate > glutamate > ibotenate > t-ACPD > BMAA. Agonist-stimulated PI-hydrolysis was attenuated (25 +/- 4% inhibition) by L-2-amino-3-phosphonopropionic acid and partially blocked (44 +/- 7%) by pertussis toxin treatment. Saturation binding studies with [3H]glutamate on membranes prepared from BHK-ts13 cells expressing the mGluR1 alpha subtype showed that glutamate binds to a single affinity state of this receptor with a limited capacity (Kd = 296 nM, Bmax = 0.8 pmol/mg protein). In competition experiments, [3H]glutamate was displaced by quisqualate, glutamate, ibotenate, t-ACPD and BMAA with a rank order of potency similar to that found for stimulation of PI-hydrolysis.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Amino Acids, Diamino; Aminobutyrates; Animals; Binding, Competitive; Cell Line; Cell Membrane; Clone Cells; Cricetinae; Cyanobacteria Toxins; Dizocilpine Maleate; Glutamates; Glutamic Acid; Ibotenic Acid; Inositol Phosphates; Kidney; Kinetics; Neurotoxins; Pertussis Toxin; Quinoxalines; Quisqualic Acid; Receptors, Glutamate; Recombinant Proteins; Transfection; Virulence Factors, Bordetella

The effect of excitatory amino acid receptor antagonists, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5, 10-imine hydrogen maleate ((+)-MK-801), (+/-)-3-(2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and (+/-)-2-amino-4-phosphonobutanoic acid (AP-4), on penile erection and yawning induced by subcutaneous apomorphine (80 micrograms/kg), intracerebroventricular (i.c.v.) oxytocin (30 ng) and adrenocorticotropin (ACTH)-(1-24) (10 micrograms) was studied in male rats. Intraperitoneal (0.1-0.4 mg/kg) and i.c.v. (10-50 micrograms) (+)-MK-801 prevented dose dependently the penile erection and yawning induced by the three drugs. The (+)-MK-801 effect coincided with the appearance of head weaving, body rolling, hyperlocomotion and ataxia. Haloperidol (0.5 mg/kg i.p.) antagonized the prevention by (+)-MK-801 of oxytocin responses. Penile erection but not yawning was also prevented by high, but not low doses of CPP and CNQX, which impaired motor performance, AP-4 was ineffective at all doses tested. The above compounds were ineffective when injected into the paraventricular nucleus of the hypothalamus, the brain area where apomorphine and oxytocin act to induce penile erection and yawning. The results suggest that excitatory amino acid transmission is not involved in the expression of penile erection and yawning induced by the above compounds.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Adrenocorticotropic Hormone; Aminobutyrates; Animals; Apomorphine; Dizocilpine Maleate; Dose-Response Relationship, Drug; Injections, Intraperitoneal; Injections, Intraventricular; Injections, Subcutaneous; Male; Oxytocin; Penile Erection; Piperazines; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, Amino Acid; Yawning

A detailed pharmacological characterization of the quisqualate (QA) receptor coupled to phospholipase C (Qp) was performed in striatal neurons. The experiments were carried out in the presence of the ionotropic antagonists MK-801 (1 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (30 microM), concentrations that block N-methyl-D-aspartate (NMDA) or alpha-amino-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in these cells. QA, ibotenate and trans-1-aminocyclopentyl-1,3-dicarboxylate (ACPD) evoked dose-dependent inositol phosphate formations with EC50 values of 0.3, 6.7 and 29 microM, respectively. QA and ibotenate had the same maximal effect (295.7 +/- 17.9% of basal, n = 6) whereas the efficacy of ACPD was somewhat lower (70.2 +/- 8.9% of the maximal quisqualate effect, n = 4). The QA-, ibotenate- and ACPD-induced maximal effects were not additive, and the inositol phosphate formations induced by high concentrations of L-aspartate (L-ASP), AMPA, kainate (KA) and domoate (DO) (100 microM or higher) were also not additive. The inositol phosphate responses induced by all these agonists were totally blocked by the phorbol ester phorbol 12,13-dibutyrate (PdBu), but not by atropine or prazosin suggesting that all these substances were able to stimulate the Qp excitatory amino acid receptor in striatal neurons. Of the excitatory amino acid receptor antagonists tested, only D,L-2-amino-3-phosphonopropionate (D,L-AP3) inhibited QA-induced InsP formation in a competitive manner (mean pKi = 4.45 +/- 0.43, n = 4). However, this drug was also a partial agonist of the Qp receptor since it stimulated the inositol phosphate formation. We found that D,L-AP3 also inhibited NMDA-induced calcium increase, in a competitive manner (mean pIC50 = 4.34 +/- 0.22, n = 8, and mean pKi = 3.7 +/- 0.11, n = 5). The Qp excitatory amino acid receptor in striatal neurons therefore closely resembles Qp receptors with high potency for agonists as described in striatal and retinal slices and synaptoneurosomes, and has several pharmacological differences compared to the Qp receptors which have low potency for agonists described in hippocampal and cortical slices, cerebellar granule cells, astrocytes and rat brain mRNA-injected oocytes.

Topics: 2-Aminoadipic Acid; 6-Cyano-7-nitroquinoxaline-2,3-dione; Alanine; Aminobutyrates; Animals; Cells, Cultured; Corpus Striatum; Dizocilpine Maleate; Fura-2; Ibotenic Acid; Inositol Phosphates; Kainic Acid; Mice; Neurons; Phorbol 12,13-Dibutyrate; Phosphoserine; Quinoxalines; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Type C Phospholipases

Rat pups exhibit transient "developmental dyskinesias," such as tremor and myoclonus, that are analogous to motor immaturities of the human neonate. Myoclonic jerks in the neonatal rat may reflect a developmental imbalance of excitatory and inhibitory neurotransmission. To test this hypothesis, spontaneous myoclonic jerks of naive rat pups (n = 200) were characterized behaviorally and pharmacologically. The frequency of myoclonus was high (154 +/- 14 jerks/30 min) in the first week. The distribution of jerks included limbs (47%) (27% in forelimbs and 20% in hindlimbs), tail (30%), trunk (12%), and head (11%). Myoclonus constituted the predominant neonatal adventitious movement (81%). Myoclonic jerks were variable in intensity, focal and multi-focal more often than generalized, and occurred when nonrespiratory movements were infrequent or absent, suggesting sleep. Myoclonic frequency significantly diminished after the second week; therefore, drug effects were studied in the first 7 days. Systemic injection of the novel noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 blocked neonatal myoclonus in a dose-dependent manner (ID50 = 0.67 mg/kg; r = 0.93). The nonselective excitatory amino acid (EAA) receptor antagonist kynurenic acid was ineffective. The EAA antagonist AP4 (1 and 10 mg/kg) also reduced myoclonic jerks, but other drugs, such as the selective glycine antagonist Iso-THAO (1 and 10 mg/kg), strychnine (0.5 mg/kg), clonazepam, and diazepam (1 mg/kg), were ineffective blockers. The putative agonists quisqualic acid (1-50 mg/kg) and NMDA (1-10 mg/kg) altered myoclonus only at behaviorally toxic doses. These data suggest that EAA receptors participate in developmental myoclonus of the neonatal rat and that development myoclonus may be a useful quantitative model of functional maturity of excitatory/inhibitory synapses. The efficacy of MK-801 also should be evaluated in drug- and lesion-induced myoclonus. Recognition of the high frequency and state dependence of spontaneous myoclonic jerks in neonatal rats may be important to neonatal antiepileptic drug studies.

Topics: Aminobutyrates; Analysis of Variance; Animals; Animals, Newborn; Anticonvulsants; Clonazepam; Diazepam; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Isoxazoles; Kynurenic Acid; Male; Myoclonus; N-Methylaspartate; Quisqualic Acid; Rats; Receptors, N-Methyl-D-Aspartate; Strychnine