Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.16.2 (PCP)
3,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Transmitters of motoneurons in the stomatogastric ganglion (STG) of Squilla were identified by analyzing the excitatory neuromuscular properties of muscles in the posterior cardiac plate (pcp) and pyloric regions. 2. Bath and iontophoretic applications of glutamate produce depolarizations in these muscles. The pharmacological experiments and desensitization of the junctional receptors elucidate the glutamatergic nature of the excitatory junctional potentials (EJPs) evoked in the constrictor and dilator muscles. The reversal potentials for the excitatory junctional current (EJC) and for the glutamate-induced current are almost the same. 3. Some types of dilator muscle show sensitivity to both glutamate and acetylcholine (ACh) exogenously applied. The pharmacological evidence and desensitization of the junctional receptors indicate the glutamatergic nature of neuromuscular junctions in these dually sensitive muscles. The reversal potentials for the EJC and for the ACh-induced current are not identical. 4. Glutamate is a candidate as an excitatory neuro-transmitter at the neuromuscular junctions which the STG motoneurons named PCP, PY, PD, LA and VC make with the identified muscles. Kainic and quisqualic acids which act on glutamate receptors are potent excitants of these muscles. Extrajunctional receptors to ACh are present in two types of the muscle innervated by LA and VC. 5. Neurotransmitters used by the STG motoneurons of stomatopods are compared to those of decapods.
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PMID:Glutamatergic motoneurons in the stomatogastric ganglion of the mantis shrimp Squilla oratoria. 135 28

Glutamate evoked contractions of the longitudinal muscle/myenteric plexus (LMMP) preparation by an action at N-methyl-D-aspartate (NMDA) receptors. Other agonists at the NMDA recognition site, but not quisquilate or kainate, also contracted the LMMP, and glutamate-evoked contractions were competitively inhibited by selective NMDA receptor antagonists. Glutamate-evoked contractions were noncompetitively inhibited by MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine moleate], phencyclidine (PCP) and other compounds that bind to the PCP receptor, which is a binding site on the NMDA channel complex. Their potencies for this effect were highly correlated with their affinities for the PCP receptor. Glycine significantly shifted the glutamate concentration-response curve to the left. Glycine site antagonists caused a glycine-sensitive, noncompetitive inhibition of glutamate-evoked contractions, and their potencies for this effect were highly correlated with their affinities for the glycine binding site of the NMDA channel complex. Mg++ and Zn++ also noncompetitively inhibited glutamate-evoked contractions. The modulatory effects of glycine, Mg++, Zn++ and PCP receptor ligands were specific to glutamate-evoked contractions. MK-801 was highly selective for inhibition of glutamate-evoked contractions; MK-801 also inhibited nicotinic responses at a 500-fold lower potency. Two novel compounds are described that bind to the PCP receptor with high affinity and selectively inhibit glutamate-evoked contractions in the LMMP.
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PMID:N-methyl-D-aspartate receptor-mediated contractions of the guinea pig ileum longitudinal muscle/myenteric plexus preparation: modulation by phencyclidine and glycine receptors. 167 35

Polyamines such as spermidine potentiate activation of the N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptor. The goal of the present study was to investigate interactions between the putative polyamine binding site and previously described sites for glutamate and glycine. Binding of the high-potency PCP receptor ligand [3H]MK-801 to well-washed rat brain membranes was used as an in vitro probe of NMDA receptor activation. Spermidine concentration-response studies were performed in the absence and presence of both glutamate and glycine, with and without D-(-)-2-amino-5-phosphonovaleric acid (D(-)-AP-5) or 7-chlorokynurenic acid (7Cl-KYN). Incubation in the presence of spermidine alone induced a 20.4-fold increase in [3H]MK-801 binding with an EC50 value of 13.3 microM. The mean concentration of spermidine which induced maximal stimulation of binding was 130 microM (n = 10, S.E.M. = 24.66, range = 25-250 microM). Glutamate (10 microM) decreased the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding to 3.4 microM. Glycine (10 microM) did not significantly alter either maximum spermidine-induced [3H]MK-801 binding or the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding. Incubation in the presence of the specific glutamate antagonist D(-)AP-5 attenuated [3H]MK-801 binding in a glutamate-reversible fashion. The competitive glycine antagonist 7Cl-KYN decreased maximum spermidine-induced [3H]MK-801 binding in a glycine-reversible fashion. In addition, 7Cl-KYN increased the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding while D(-)AP-5 was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Polyamine effects upon N-methyl-D-aspartate receptor functioning: differential alteration by glutamate and glycine site antagonists. 168 87

Glutamate activates high (40-50 pS) and low (5-15 pS) conductance cationic channels in outside-out patches excised from cultured cortical and cerebellar granule neurons of neonatal rats. In these neurons, the excitatory amino acid N-methyl-D-aspartic acid (NMDA) activates mainly high conductance channels. Phencyclidine (PCP) at 2 microM selectively reduces the number of NMDA-activated channel openings, at 20 microM it reduces the channel open-time. Glycine increases the opening frequency of high conductance NMDA-activated channels. This action is counteracted by PCP. This inhibition by PCP can be eliminated by reversing the polarity of the membrane patch. However, the effect of glycine is voltage independent. These results imply different sites of action for these two modulators.
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PMID:Phencyclidine and glycine modulate NMDA-activated high conductance cationic channels by acting at different sites. 245 Nov 95

In vivo microdialysis was used to study the effects of systemically administered phencyclidine (PCP, 10 mg/kg) on the extracellular levels of dopamine, dihydroxyphenylacetate (DOPAC), homovanillate (HVA), 5-hydroxy-indolacetate (5-HIAA), gamma-aminobutyrate (GABA), glutamate, and aspartate in the rat dorsolateral striatum. In order to demarcate the effects of anesthesia, tissue trauma and gliosis, the effect of PCP was studied in both anesthetized rats with long and short probe implantation periods and in conscious rats with a long probe implantation period. PCP significantly increased the extracellular levels of dopamine in all experimental groups, though the post-implantation interval and anesthesia modulated the degree of increase. PCP increased 5-HIAA levels in both conscious and anesthetized rats after a long post-implantation period and HVA only in anesthetized rats after a long post-implantation period. Glutamate, aspartate, and DOPAC were not affected by PCP challenge but our study indicated for the first time that systemic PCP elevates extracellular GABA in conscious rats.
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PMID:Systemic phencyclidine administration is associated with increased dopamine, GABA, and 5-HIAA levels in the dorsolateral striatum of conscious rats: an in vivo microdialysis study. 753 16

The physiological model for glutamate receptor mediated excitotoxicity entails elevation of intraneuronal calcium levels. Excessive activation of the NMDA receptor leads to excitotoxicity by prolonged calcium influx via its calcium channel. The purpose of this research was to examine the mechanism of non-NMDA glutamate receptor mediated excitotoxicity. Mammalian AMPA receptors do not show significant calcium conductance. However, some kainate receptors show significant calcium conductance. The hypothesis of this research states that non-NMDA glutamate agonists (quisqualate (5 microliters of 2 mg/ml i.c.v.), AMPA (4 microliters of 1 mg/ml i.c.v.), and kainate (15 mg/kg i.p.)) produce significant heat shock gene, hsp70, induction via glutamate release with subsequent opening of the NMDA receptor calcium channel. PCP (phencyclidine) and ketamine are noncompetitive blockers of the NMDA calcium channel. They act to prevent significant NMDA receptor excitotoxicity. PCP (20 mg/kg i.p.) and ketamine (60 mg/kg i.p.) both diminished quisqualate and AMPA hsp70 induction in the CA1, CA2, CA3 areas of the hippocampus, in the polymorph area of the dentate gyrus, and in the parietal neocortex. PCP significantly (P < 0.05) diminished kainate hsp70 induction only in the CA1 area and the neocortex. Ketamine failed to reduce kainate hsp70 induction. AMPA receptors appear to result in excitotoxic damage via glutamate release. Glutamate opens NMDA receptor calcium channels which increases intraneuronal calcium levels. Kainate receptors probably mediate excitotoxicity via direct calcium conductance with glutamate release being important in the CA1 area and neocortex.
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PMID:PCP and ketamine inhibit non-NMDA glutamate receptor mediated hsp70 induction. 886 85

Glutamate-containing neuronal terminals are ubiquitous in the central nervous system and their functional importance in mental activity is considerable. Therefore, the involvement of this neurotransmitter in the pathology of schizophrenia is being studied. Biochemical evidence has suggested that glutamatergic transmission may be regionally reduced in schizophrenia, although this evidence has never been completely consistent nor fully replicable. More striking has been the behavioral effects in humans of the antiglutamatergic drugs phencyclidine (PCP) and its congener ketamine. By historical report, PCP produces a 'schizophrenia-like' psychosis in normal humans and aggravates the psychosis in schizophrenics. More recently, ketamine has been shown to produce a mild psychotomimetic effect in normal volunteers, which has some schizophrenia-like features. We have studied the effects of ketamine in schizophrenic patients. Here, ketamine intensified each patient's specific underlying psychosis, an effect not blocked by haloperidol. Moreover, ketamine selectively increased cerebral blood flow (CBF) in the anterior cingulate cortex and reduced CBF in hippocampus and lingual gyrus. These data may be pertinent to the subject's psychosis exacerbation, especially because both cingulate and hippocampus have been previously implicated in schizophrenic psychosis. In addition, ketamine produced a distinctive dynamic time-course of regional CBF changes in different anatomic regions, with immediate (5-10 min) changes in cingulate, but somewhat more delayed changes (20-40 min) in the thalamus and cerebellum. Our immediate early gene (IEG) time-course data with c-fos and zif268 in rats following PCP suggest that a single dose of this antiglutamatergic compound can have an effect in some brain areas which lasts beyond 48 h, an effect which is distinct by IEG and by region. Together, these data suggest that glutamate-mediated neurotransmission has a strong influence in schizophrenia, although the specifics of this involvement have yet to be articulated.
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PMID:Glutamate pharmacology and the treatment of schizophrenia: current status and future directions. 886 63

Phencyclidine (PCP) induces a psychotic state closely resembling schizophrenia in normal individuals. PCP and related agents induce their unique behavioral effects by blocking neurotransmission mediated at N-methyl-D-aspartate (NMDA)-type glutamate receptors, indicating that dysfunction of NMDA receptor-mediated neurotransmission may play a crucial role in the pathophysiology of schizophrenia. NMDA receptors are activated by the amino acids glutamate and glycine, working at independent binding sites. Glutamate cannot be administered exogenously because of excitotoxicity. In contrast, glycine administered exogenously may potentiate NMDA receptor-mediated neurotransmission in vivo following peripheral administration. In rodents, glycine is effective in elevating brain glycine levels and reversing PCP-induced hyperactivity at doses of 0.8 g/kg and above. Three studies have now been completed utilizing moderate to high (0.4-0.8 g/kg/day) doses of glycine, added to neuroleptics, for the treatment of schizophrenia. Across studies, 15 to 30 percent improvement in negative symptoms was observed with no corresponding worsening of positive symptoms. Although preliminary, these studies indicate that dietary supplementation with glycine or treatment with other glycinergic agents may be effective in the treatment of schizophrenia.
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PMID:Glycinergic augmentation of NMDA receptor-mediated neurotransmission in the treatment of schizophrenia. 899 96

Glutamate stimulation of N-methyl-D-aspartate (NMDA) receptors results in release of nitric oxide which may mediate the effects of NMDA receptor stimulation and/or may result in feedback inhibition of the presynaptic neuron. Results of a previous study showed that nitric oxide synthase (NOS) inhibitors blocked dizocilpine-induced behavior in mice. In the present study, NOS inhibitors were tested in combination with phencyclidine (PCP), a drug which typically dose-dependently disrupts prepulse inhibition of the acoustic startle response in rats. Alone, NOS inhibitors and promoters do not affect prepulse inhibition; however, when tested in combination with PCP, the NOS inhibitors, L-NOARG, 7-nitroindazole and arcaine--but not the NR2B-selective polyamine site NMDA antagonist, eliprodil--attenuated PCP-induced disruption of prepulse inhibition of the acoustic startle response. These effects are similar to those produced by many atypical antipsychotics and suggests that this class of drugs should be investigated further for their potential utility as antipsychotics and as treatments for PCP abuse.
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PMID:Nitric oxide synthase inhibitors attenuate phencyclidine-induced disruption of prepulse inhibition. 960 80

Schizophrenia-mimicking compounds such as phencyclidine (PCP) and MK801 are antagonists at the N-methyl-D-aspartate (NMDA) receptor and produce the whole spectrum of positive, negative, and cognitive symptoms. This is one of the most important pillars of the hypoglutamatergic hypothesis of schizophrenia. Since the synthesis of glutamate and GABA in neurons is closely connected to astrocyte metabolism, the study of astrocytic function is essential in this context. Dizocilpine-maleate (MK801) (0.5 mg/kg) was injected into rats every day for 6 days. The last dose was given together with [1-(13)C]glucose and [1,2-(13)C]acetate. Extracts from frontal, retrosplenial, and cingulate cortices (CRFC) and temporal lobes were examined by (13)C nuclear magnetic resonance spectroscopy, high pressure liquid chromatography, and light microscopy. In CRFC, significant increases in the levels of glutamate, glutathione, and taurine were seen, whereas amounts and turnover of noradrenaline, dopamine, and serotonin were unchanged. Glutamate and glutamine, derived from [1,2-(13)C]acetate and thus astrocytes, were significantly decreased in CRFC as compared to controls. Labeling from [1-(13)C]glucose and thus mostly neuronal metabolism was affected in the same brain region with decreased labeling of glutamate and GABA. The present model mimics the increased glutamate/glutamine activity found in drug-naive patients with first episode schizophrenia. Moreover, the decreased labeling indicates the transition to lower glutamatergic function seen in chronic schizophrenia patients. The disturbance in astrocytic function and the glutamine-glutamate-GABA cycle are of significant importance and might add to the malfunction of the cortico-striato-thalamo-cortical loop caused by NDMA receptor blockade.
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PMID:Glial-neuronal interactions are impaired in the schizophrenia model of repeated MK801 exposure. 1639 97


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