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)

Biochemical and electrophysiological studies have provided evidence that a complex comprising the N-methyl-D-aspartate (NMDA)-type excitatory amino acid (EAA) receptor and the phencyclidine (PCP) recognition site exists in mammalian brain. This complex, which has been compared to that established for the inhibitory amino acid, gamma-aminobutyric acid, and the benzodiazepine anxiolytic, diazepam, is sensitive to the effects of the divalent cation Mg2+, which has suggested the presence of a third, ion channel component. Using a radioreceptor assay for the PCP receptor, L-glutamate (L-Glu) produced a concentration-dependent increase in the binding of [3H]thienyl cyclohexylpiperazine ([3H]TCP) in well washed membranes from rat forebrain. The EAA produced a maximal increase in specific binding of 400%, with an EC50 value of 340 nM. The ability of L-Glu to enhance [3H]TCP binding was 10-fold more potent in the presence of 30 microM Mg2+, which inhibits NMDA-evoked responses in intact tissue preparations and produces a 50% increase in [3H]TCP binding on its own. Analysis of saturation curves indicated that the effect of both L-Glu and Mg2+ could be attributed to an increase in receptor affinity as well as increases in the proportion of a high affinity state of the PCP-binding site. Assessment of the effect of a number of EAAs on basal [3H]TCP binding (well washed membranes in the absence of either L-Glu or Mg2+) showed that the EAA recognition site involved in the effects of L-Glu was the NMDA subtype. Further studies examined a series of compounds thought to interact with either the NMDA or PCP components of the receptor complex under four binding conditions: basal, +Mg2+; +L-Glu; and +Mg2+/L-Glu. These results showed that dissociative anesthetics, such as dexoxadrol and PCP, as well as the novel anticonvulsant MK-801, selectively interact with the high affinity state of the PCP receptor. NMDA antagonists, such as CPP, were also found to inhibit binding to the high affinity state of the PCP receptor, although not as potently as the dissociative anesthetics. Interestingly, the NMDA antagonists did not inhibit any of the binding to the low affinity state of the receptor. The sigma ligands (+/-)-SKF 10,047 and haloperidol recognized two components of [3H]TCP binding only in the presence of L-Glu. The results of the present study are consistent with the finding that agonists of the NMDA receptor induce a high affinity state of the PCP receptor.
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PMID:Interaction of L-glutamate and magnesium with phencyclidine recognition sites in rat brain: evidence for multiple affinity states of the phencyclidine/N-methyl-D-aspartate receptor complex. 289 25

Phencyclidine (PCP) receptors were successfully solubilized from rat forebrain membranes with 1% sodium cholate. Approximately 58% of the initial protein and 20-30% of the high-affinity PCP binding sites were solubilized. The high affinity toward PCP-like drugs, the stereo-selectivity of the sites, and the sensitivity to N-methyl-D-aspartate (NMDA) receptor ligands were preserved. Binding of the potent PCP receptor ligand N-[3H][1-(2-thienyl)cyclohexyl] piperidine ([3H]TCP) to the soluble receptors was saturable (KD = 35 nM), and PCP-like drugs inhibited [3H]TCP binding in a rank order of potency close to that observed for the membrane-bound receptors; the most potent inhibitors were TCP (Ki = 31 nM) and the anticonvulsant MK-801 (Ki = 50 nM). The NMDA receptor antagonist 2-amino-5-phosphonovaleric acid inhibited binding of [3H]TCP to the soluble receptors; glutamate or NMDA diminished this inhibition in a dose-dependent manner. Taken together, the results indicate that the soluble PCP receptor preparation contains the glutamate recognition sites and may represent a single receptor complex for PCP and NMDA, as suggested by electrophysiological data. The successful solubilization of the PCP receptors in an active binding form should now facilitate their purification.
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PMID:Solubilization of rat brain phencyclidine receptors in an active binding form that is sensitive to N-methyl-D-aspartate receptor ligands. 289 2

The effects of the N-methyl-D-aspartate (NMDA) receptor antagonists, D-2-amino-5-phosphonovalerate (D-APV) and phencyclidine (PCP), were studied in vitro on epileptiform activity induced in magnesium-free solution in neurons of the basolateral amygdala of the rat, using intracellular recording techniques. Twenty to 30 min after switching to magnesium-free medium, spontaneous interictal-like events were observed in 33 out of 37 amygdala slices. The spontaneous interictal-like events consisted of an initial burst followed by a number of afterdischarges. Superfusion with D-APV, a competitive NMDA receptor antagonist, reversibly reduced the duration of the events was also reduced. The IC50, estimated from the graph of the concentration-response relationship, was approximately 10 microM which is close to the IC50 for the binding of D-AVP to the NMDA receptor in other regions of the brain. The effect of phencyclidine, a noncompetitive NMDA receptor antagonist, was similar to that of D-APV. These results suggest that activation of NMDA receptors plays an intrinsic role in the induction or propagation of epileptiform activity seen in magnesium-free solution in the neurons of the amygdala.
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PMID:Epileptiform activity induced by magnesium-free solution in slices of rat amygdala: antagonism by N-methyl-D-aspartate receptor antagonists. 290 76

The effects of representative drugs from three classes of psychotomimetic compounds (arylcyclohexylamines, benzomorphan opioids and dioxolanes) have been examined on synaptic transmission at an identified monosynaptic pathway in rat hippocampal slices. The compounds tested were phencyclidine (PCP) and ketamine, the racemate and isomers of SKF 10,047 (N-allylnormetazocine), and the isomers of dioxadrol (dexoxadrol and levoxadrol). In the absence of added magnesium ions (Mg) in the perfusion medium low frequency stimulation of the Schaffer collateral-commissural pathway evoked a burst of population spikes in the CA1 cell body region. The secondary components of this response could be abolished by the selective N-methyl-D-aspartate (NMDA) antagonist D-2-amino-5-phosphonovalerate (APV). PCP (1 microM) or ketamine (10 microM) selectively blocked the secondary components of the synaptic response. The effect of PCP was neither mimicked nor prevented by hexamethonium and atropine, phentolamine and propranolol, or clonidine and was therefore unlikely to involve cholinergic or adrenergic neurotransmitter systems. The sigma opiate, (+/-)-SKF 10,047 (10 microM) also abolished selectively the secondary components of the synaptic response. There was no apparent difference between the potency of the stereoisomers of this compound. The action of (+/-)-SKF 10,047 was not affected by either naloxone or haloperidol, indicating that this effect did not involve opioid receptors or the haloperidol-sensitive sigma site. Dexoxadrol (10 microM), but not levoxadrol (10 microM), also selectively blocked the secondary components of the synaptic response. It is concluded that these psychotomimetic agents can block an NMDA receptor-mediated component of synaptic transmission in the hippocampus and that this effect is mediated by a specific PCP/sigma site.
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PMID:Effects of phencyclidine, SKF 10,047 and related psychotomimetic agents on N-methyl-D-aspartate receptor mediated synaptic responses in rat hippocampal slices. 303 43

Memantine is an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist with therapeutic potential in dementia, spasticity and Parkinson's disease. The Ki-value of memantine at the phencyclidine (PCP) binding site of the NMDA receptor is 0.5 microM in human frontal cortex. We investigated whether concentrations of memantine in cerebrospinal fluid (CSF) and serum samples under therapeutic conditions are in the range of its Ki-value at the PCP binding site. The serum levels ranged from 0.025 to 0.529 microM with daily doses between 5 and 30 mg. CSF levels were highly correlated to serum levels and were below serum levels in each patient with a mean CSF/serum ratio of 0.52. Serum and CSF levels were correlated to the daily dose, but not to the duration of treatment. At the concentrations reported here, memantine is expected to specifically interact with the PCP binding site of the NMDA receptor.
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PMID:Cerebrospinal fluid and serum concentrations of the N-methyl-D-aspartate (NMDA) receptor antagonist memantine in man. 747 69

Since the hippocampus is likely to be a major site of phencyclidine (PCP) action, the effects of various doses of PCP (1.8, 18 or 36 nM) as well as 3.6 nM MK-801 or saline injected directly into the dentate gyrus of the hippocampus was tested for acquisition of a spatial navigation task (dry land version of a water maze) using a paradigm that assesses short term memory based on learning within a day and long term memory based on learning between days. Results indicated that relative to saline or 1.8 nM PCP injected rats, rats with 18 or 36 nM PCP or 3.6 nM MK-801 injections were impaired in acquisition of the task as measured by increased distances traveled to find the food location between days but not within days. In additional experiments 36 nM PCP or 3.6 nM MK-801 did not produce any deficits in the acquisition of an object discrimination task. It is suggested that PCP through its blocking action of the NMDA receptor in the dentate gyrus or CA1 region of the dorsal hippocampus mediates the consolidation of new spatial location information.
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PMID:Phencyclidine injections into the dorsal hippocampus disrupt long- but not short-term memory within a spatial learning task. 748 May 53

The present study was undertaken to determine the role and modulation of the PCP/NMDA receptor complex and sigma binding sites in the central nervous system of animals treated with psychostimulant agents. Repeated exposure of mice to cocaine (45 mg/kg/day; for 7 days) was associated with a progressive increase in convulsive response and lethality rate. The sensitization to the toxic effects of cocaine in mice was completely abolished by pretreatment with either the noncompetitive NMDA receptor antagonist MK-801 (0.35 mg/kg/day), or the nitric oxide synthase inhibitor Ng-nitro-L-arginine methyl ester (100 mg/kg/day). Parallel in vitro receptor binding assays indicated first, upregulation of cortical NMDA receptors labeled with [3H]CGP 39653, and second, glutamate-dependent sensitization of [3H]MK-801 binding to the PCP site in cortical membranes of the mice treated for 7 days with cocaine. Repeated exposure of rats to methamphetamine (4.0 mg/kg/day; for 10 days) resulted in a significant upregulation of the sigma-1 binding site labeled with (+)[3H]pentazocine in the frontal cortex and substantia nigra. The cocaine-related studies suggest that the PCP/NMDA receptor complex is involved in the development of sensitization to the neurotoxic effects of the drug, such as "pharmacological kindling". The methamphetamine-related studies insinuate a potential role of sigma-1 binding sites in psychostimulant-induced behavioral disorders.
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PMID:Modulation of the PCP/NMDA receptor complex and sigma binding sites by psychostimulants. 752 45

Phencyclidine (PCP) acts on a variety of neurotransmitter systems--cholinergic, catechoaminergic, indoleaminergic, and peptidergic--but the dose at which it produces its psychotomimetic effects is lower than the concentration at which it affects these systems. At low doses, PCP interacts primarily with a binding site located within the ionophore associated with the NMDA receptor complex--binding to this site has been used as a biochemical marker for NMDA channel activity. PCP/NMDA receptor-channel complex has been shown to play an important role in brain development but little is known of the neurochemical effects following postnatal administration of NMDA antagonists in rats. In the present study, rats were treated with PCP from Day 5 until Day 15 after birth and binding to the PCP receptor was measured on postnatal Day 21 using [3H]MK-801; MK-801 is a more potent and specific ligand at the PCP receptor than PCP itself. Postnatal PCP administration produced specific alterations in PCP receptor binding in 21-day-old rat forebrain. There was a reduction in the high affinity component of [3H]MK-801 binding under baseline binding conditions. In the presence of both L-glutamate and glycine, [3H]MK-801 binding in PCP-treated rats increased significantly compared to baseline but did not differ from saline-treated controls. These findings suggest that chronic PCP administration in developing rats alter NMDA channel functioning which could have long-term neurobehavioral consequences.
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PMID:PCP/NMDA receptor-channel complex and brain development. 752 46

A series of novel N-methyl-D-aspartate antagonists acting at the phencyclidine site has been identified. Compound 2 has a Ki = 8 +/- 1 nM (vs [3H]thienylcyclidine, [3H]TCP) as a mixture of enantiomers. Resolution and further testing indicate that (-)-2, Ki = 4 +/- 0.7 nM, is a potent and selective TCP site ligand with neuroprotective activity in cultured neurons in the presence of excitotoxic concentrations of NMDA (IC50 = 26 nM). Compound (-)-2 is > 1000-fold selective for the TCP site vs a panel of receptor types including opiate, adrenergic, serotonergic, dopamine, adenosine, dihydropyridine, and benzodiazepine and displays increased selectivity for the activated (open) NMDA receptor-ion channel complex vs PCP and MK801 as measured by patch recordings in cultured, voltage-clamped neurons. Highly enhanced "open-channel" selectivity leads to tentative classification of these ligands as uncompetitive vs NMDA. Ligands with these characteristics may enable deconvolution of the pharmacologic effects associated with typical noncompetitive NMDA antagonists. We report here on the identification, synthesis, and activity of compounds of this structural class.
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PMID:Identification, synthesis, and characterization of a unique class of N-methyl-D-aspartate antagonists. The 6,11-ethanobenzo[b]quinolizinium cation. 752 82

To investigate the modulatory effects of sigma ligands on the N-methyl-D-aspartate (NMDA) receptor-ion channel complex in vivo, we examined the intact cell binding of 3H-N-[1-(2-thienyl)cyclohexyl]piperidine (3H-TCP) to cultured neuronal cells prepared from fetal rat telencephalon. The 3H-TCP binding was saturable, reversible, and inhibited by a selective NMDA receptor antagonist, D-amino-5-phosphonovaleric acid. MII-limolar Mg2+ inhibited 3H-TCP binding both in the absence and presence of L-glutamate. 5-Methyl-10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine maleate (MK801) inhibited 3H-TCP intact cell binding in a competitive manner, while haloperidol inhibited it in a noncompetitive manner. The effect of the test drugs to inhibit 3H-TCP intact cell binding was in the order of dextromethorphan, haloperidol > (+/-)MK 801 > (+)pentazocine > (-)pentazocine > DTG > PCP > (+)-N-allylnormetazocine [(+)SKF 10047] > (+)3-(3-hydroxyphenyl)-N- (1-propyl)piperidine [(+)3-PPP] > (-)SKF 10047 > (-)3-PPP. The IC50 values of the six sigma ligands for 3H-TCP binding were closely correlated with the Ki values of the corresponding drugs for DTG site 1 in the guinea pig brain reported by Rothman et al. (1991). These findings suggest that the sigma ligand indirectly modulates the NMDA receptor ion channel complex, presumably through sigma 1 sites in vivo as well as in vitro.
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PMID:Sigma ligands indirectly modulate the NMDA receptor-ion channel complex on intact neuronal cells via sigma 1 site. 752 31


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