Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.16.2 (PCP)
 3,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

THE NMDA receptor antagonist phencyclidine (PCP) has low micromolar affinity for the 5-HT reuptake site, but it is uncertain whether PCP blocks 5-HT reuptake when given systemically to rats in behaviourally stimulating doses. We here report for the first time that systemically administered PCP (5 mg/kg, s.c.) increases extracellular 5-HT levels in the rat medial prefrontal cortex (to 322%) and dorsal hippocampus (to 233%). Increases were found also when citalopram (1 microM) was included in the perfusion medium (to 184 and 180%, respectively). Extracellular 5-HIAA concentrations increased during both conditions, and extracellular GABA decreased in the dorsal hippocampus. It is concluded that systemic PCP treatment elevates extracellular 5-HT levels, probably through mechanisms other than a blockade of 5-HT reuptake.
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PMID:Systemic PCP treatment elevates brain extracellular 5-HT: a microdialysis study in awake rats. 980 2

NRA0160, 5 - [2- ( 4- ( 3 - fluorobenzylidene) piperidin-1-yl) ethyl] - 4 -(4-fluorophenyl) thiazole-2-carboxamide, has a high affinity for human cloned dopamine D4.2, D4.4 and D4.7 receptors, with Ki values of 0.5, 0.9 and 2.7 nM, respectively. NRA0160 is over 20,000fold more potent at the dopamine D4.2 receptor compared with the human cloned dopamine D2L receptor. NRA0160 has negligible affinity for the human cloned dopamine D3 receptor (Ki=39 nM), rat serotonin (5-HT)2A receptors (Ki=180 nM) and rat alpha1 adrenoceptor (Ki=237 nM). NRA0160 and clozapine antagonized locomotor hyperactivity induced by methamphetamine (MAP) in mice. NRA0160 and clozapine antagonized MAP-induced stereotyped behavior in mice, although their effects did not exceed 50% inhibition, even at the highest dose given. NRA0160 and clozapine significantly induced catalepsy in rats, although their effects did not exceed 50% induction even at the highest dose given. NRA0160 and clozapine significantly reversed the disruption of prepulse inhibition (PPI) in rats produced by apomorphine. NRA0160 and clozapine significantly shortened the phencyclidine (PCP)-induced prolonged swimming latency in rats in a water maze task. These findings suggest that NRA0160 may have unique antipsychotic activities without the liability of motor side effects typical of classical antipsychotics.
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PMID:A selective dopamine D4 receptor antagonist, NRA0160: a preclinical neuropharmacological profile. 1057 64

In the present study, the comparative mechanisms of action of phencyclidine (PCP) and amphetamine were addressed employing the parameter of locomotion in rats. PCP-induced locomotion (PLOC) was potently blocked by the selective serotonin (5-HT)2A vs. D2 antagonists, SR46349, MDL100,907, ritanserin and fananserin, which barely affected amphetamine-induced locomotion (ALOC). In contrast, the selective D2 vs. 5-HT2A antagonists, eticlopride, raclopride and amisulpride, preferentially inhibited ALOC vs. PLOC. The potency of these drugs and 12 multireceptorial antipsychotics in inhibiting PLOC vs. ALOC correlated significantly with affinities at 5-HT2A vs. D2 receptors, respectively. Amphetamine and PCP both dose dependently increased dialysate levels of dopamine (DA) and 5-HT in the nucleus accumbens, striatum and frontal cortex (FCX) of freely moving rats, but PCP was proportionally more effective than amphetamine in elevating levels of 5-HT vs. DA in the accumbens. Further, whereas microinjection of PCP into the accumbens elicited locomotion, its introduction into the striatum or FCX was ineffective. The action of intra-accumbens PCP, but not intra-accumbens amphetamine, was abolished by SR46349 and clozapine. Parachloroamphetamine, which depleted accumbens pools of 5-HT but not DA, likewise abolished PLOC without affecting ALOC. In contrast, intra-accumbens 6-hydroxydopamine (6-OHDA), which depleted DA but not 5-HT, abolished ALOC but only partially attenuated PLOC. In conclusion, PLOC involves (indirect) activation of accumbens-localized 5-HT2A receptors by 5-HT. PLOC is, correspondingly, more potently blocked than ALOC by antipsychotics displaying marked affinity at 5-HT2A receptors.
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PMID:Contrasting mechanisms of action and sensitivity to antipsychotics of phencyclidine versus amphetamine: importance of nucleus accumbens 5-HT2A sites for PCP-induced locomotion in the rat. 1059 69

Phencyclidine (PCP) is known to be an inhibitor of serotonin (5-HT) uptake and to increase serotonergic activity. The development of tolerance to serotonergic stereotyped behaviors induced by repeated PCP treatment and changes of 5-HT transporters were examined. Backpedalling was significantly reduced in frequency following 14 days PCP treatment (7.5 mg/kg per day). Furthermore, repeated PCP treatment decreased the equilibrium dissociation constant (Kd) of [3H]paroxetine binding to 5-HT transporters in whole brain excluding the cerebellum without any change of maximum number of binding sites (Bmax). Single treatment with PCP failed to change binding parameters. These results indicate that repeated PCP treatment causes tolerance in serotonergic stereotyped behavior and increases affinity of 5-HT transporters for [3H]paroxetine binding. The increased affinity of 5-HT transporters could represent compensatory responses to chronic inhibition of 5-HT uptake by PCP.
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PMID:Effects of repeated phencyclidine treatment on serotonin transporter in rat brain. 1069 10

Clinical studies utilizing imaging techniques demonstrate that classical antipsychotic drugs, such as haloperidol, in clinically effective doses display around 75% dopamine (DA)-D(2) receptor occupancy in the brain. In contrast, the atypical antipsychotic drug clozapine is even more effective at only about 45% D(2)-receptor occupancy. Yet at this D(2)-receptor occupancy classical antipsychotics are not effective, raising the question of which other receptors may be involved in mediating the atypical antipsychotic profile of clozapine and other atypical antipsychotics. The present paper describes experimental work aimed at elucidating this critical question, utilizing the phencyclidine (PCP) model of schizophrenia in combination with studies of typical and atypical antipsychotics as well as various specific receptor blocking agents. Both electrophysiological methods, i.e. single cell recording from DA neurons in the ventral tegmental area (VTA), and biochemical analysis of biogenic amines such as DA following microdialysis in difference DA terminal areas in the brain, were used. In addition, behavioural measurements using the conditioned avoidance response (CAR) paradigm and assessments of locomotor activity were utilized. Experiments with functional inactivation of the medial frontal cortex (mPFC) in the rat as well as with MK-801 and other antagonists at central NMDA-receptors revealed that following systemic administration of schizophrenomimetic NMDA-receptor antagonists a profound dysregulation of the mesocorticolimbic DA system occurs, severely impairing the dynamic physiological response range of the neurons. Specifically, DA neurons which largely project to the mPFC showed a profound loss of burst firing, whereas VTA-DA neurons, which mainly project subcortically, showed an increased monotonous high-frequency firing with increased DA output from nerve terminals and concomitant behavioural activation. Significantly, drugs with a prominent 5-HT(2A)-receptor blocking action could effectively restore the burst firing mode, i.e. phasic responsivity, in mesocortically projecting DA neurons, and also potentiate the CAR suppressant effect of the selective D(2)/D(3)-receptor antagonist raclopride without increasing catalepsy scores. The selective alpha(1)-adrenoreceptor antagonist prazosin effectively suppressed both the stereotyped, high-frequency firing of subcortically projecting DA neurons following systemic MK-801 and the concomitant behavioural, i.e. locomotor, activation. In addition, the MK-801 evoked DA release in the nucleus accumbens was suppressed. A similar effect was seen also with AMPA-receptor antagonists when applied locally into the VTA and, in addition, systemic administration of chemically different AMPA-receptor antagonists caused a CAR-suppressant effect similar to both classical and atypical antipsychotic drugs. These results and other data showing a clearcut difference between typical and atypical antipsychotic drugs on DA output in the shell and core, respectively, of the nucleus accumbens, suggest that both the 5-HT(2A)- and the alpha(1)-adrenoreceptor blocking effects of a number of atypical antipsychotic drugs in all probability contribute to their antipsychotic effect. Moreover, our results indicate that AMPA-receptor antagonists may possess an atypical antipsychotic profile.
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PMID:Dysfunctional brain dopamine systems induced by psychotomimetic NMDA-receptor antagonists and the effects of antipsychotic drugs. 1071 59

Drugs such as PCP and MK-801 can cause psychotic reactions in humans by antagonizing NMDA receptors. This action is ultimately toxic to certain cortical neurons and may be one mechanism underlying neurodegenerative diseases, including schizophrenia. It has been reported that hallucinogens such as LSD, DOM, and DOI can block the neurotoxic effects of NMDA antagonists, possibly by activating inhibitory 5-HT2A receptors on GABAergic interneurons that normally inhibit glutamatergic projections to the retrosplenial and cingulate cortexes. The purpose of this experiment was to determine the extent to which similar drugs might also alter the behavioral effects of one NMDA antagonist, PCP. Rats were trained to discriminate this compound (2.5 mg/kg) from saline and were then given a series of antagonist tests. It was found that LSD (0.32 mg/kg) and DOM (4.0 mg/kg) blocked the PCP cue completely; DMT (8.0 mg/kg) and a structural congener of LSD, lisuride (LHM; 0.4 mg/kg), blocked the effects of PCP partially. The 5-HT/DA antagonists spiperone and ritanserin had no effect on the PCP cue. These data suggest that LSD, DOM, and, less effectively, DMT and LHM can block the behavioral as well as the neurotoxic effects of NMDA antagonists most likely through agonist actions at 5-HT2 receptors.
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PMID:Antagonism of a PCP drug discrimination by hallucinogens and related drugs. 1078 61

To develop an animal model for negative symptoms, in particular avolition, of schizophrenia, the effect of phencyclidine (PCP) on immobility (regarded as avolition) in the forced swimming test was investigated in mice, since PCP produces negative symptoms in humans. Unlike single, repeated treatment with PCP prolonged the immobility time in the forced swimming test 24 h after the final injection compared with saline treatment. The enhancing effect of PCP on the immobility persisted for 21 d after the withdrawal of the drug. Atypical antipsychotics attenuated the enhancing effect of PCP on the immobility. Since these attenuating effects were antagonized by a serotonin-S2 receptor agonist, (+/-)-2,5-dimethoxy-4-iodamphetamine (DOI), the effects may be mediated via serotonin-S2 receptors. In contrast with atypical antipsychotics, typical antipsychotics, antidepressants and anxiolytics had no effect. No functional changes in post-synaptic serotonin-S2 receptors were observed in PCP-treated mice following the forced swimming test. Serotonin utilization in the prefrontal cortex was increased, but dopamine utilization was decreased in PCP-treated mice showing the enhancement of immobility. The enhancing effect of PCP was significantly attenuated by D-cycloserine, an agonist for glycine binding site of N-methyl-D-aspartate (NMDA) receptor ionophore complex. Decreases of NMDA receptor function or of the cortical glutamate and glycine levels were observed in PCP-treated mice showing the enhancement of immobility. These results suggest that the enhancing effect of PCP on immobility is mediated by the imbalance of the cortical serotonergic, dopaminergic and glutamatergic systems and could be used as an animal model for negative symptoms of schizophrenia.
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PMID:[Neuropsychopharmacological study on an animal model for negative symptom of schizophrenia induced by repeated phencyclidine treatment]. 1094 17

Administration of the non-competitive NMDA receptor antagonists phencyclidine (PCP) (0.6-5 mg/kg s.c.) and MK-801 (0.1-0.8 mg/kg s.c. ) dose-dependently increased locomotor activity in the rat. Pre-treatment of rats with SB 221284 (0.1-1 mg/kg, i.p.) a 5-HT(2C/2B) receptor antagonist or SB 242084 (1 mg/kg, i.p.) a selective 5-HT(2C) receptor antagonist, doses shown to block mCPP induced hypolocomotion, significantly enhanced the hyperactivity induced by PCP or MK-801. Neither compound altered locomotor activity when administered alone. Furthermore, systemic administration of PCP (5 mg/kg s.c.) increased nucleus accumbens dopamine efflux in the rat to a maximum of approximately 220% of basal, 40-60 min after administration. Pre-treatment with the 5-HT(2C/2B) receptor antagonist SB 221284 (1 mg/kg, i.p.) and the 5-HT(2C) receptor antagonist SB 242084 (1 mg/kg i.p.) failed to affect nucleus accumbens dopamine efflux per se but significantly enhanced the magnitude and duration of the increase induced by PCP. However, the time course of the neurochemical and behavioural effects were qualitatively and quantitatively different, suggesting the potential involvement of other neurotransmitter pathways. Nevertheless, the present results provide behavioural and neurochemical evidence which demonstrate that, in the absence of effects per se, blockade of 5-HT(2C) receptors enhanced the activation of mesolimbic dopamine neuronal function by the non-competitive NMDA receptor antagonists PCP and MK-801.
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PMID:Activation of mesolimbic dopamine function by phencyclidine is enhanced by 5-HT(2C/2B) receptor antagonists: neurochemical and behavioural studies. 1097 15

Repeated treatment with phencyclidine (PCP) prolonged the immobility time in a forced swimming test, compared with saline treatment, this behavioral change being regarded as avolition which is one of the negative symptoms of schizophrenia. In the present study, we investigated an involvement of serotonergic (5-HTergic) and dopaminergic systems in PCP-induced enhancement of immobility in mice, since an alteration in 5-HTergic and dopaminergic systems has been hypothesized in schizophrenia. The enhancing effect of PCP on the immobility in a forced swimming test was attenuated by clozapine, risperidone and olanzapine, which have serotonin (5-HT) and dopamine receptor antagonistic properties. These attenuating effects were significantly antagonized by a 5-HT(2) receptor agonist, (+/-)-2,5-dimethoxy-4-iodamphetamine (DOI) without affecting the immobility itself. (-)Sulpiride at a low dose and methylphenidate reversed the PCP-induced enhancement of immobility whereas pimozide, chlorpromazine and levomepromazine had no effect. There was no difference in the frequency of DOI-induced head twitches, which are mediated via 5-HT(2) receptors, between PCP- and saline-treated mice following the forced swimming test, indicating no functional changes in post-synaptic 5-HT(2) receptors. 5-HT utilization in the prefrontal cortex was increased, but dopamine utilization was decreased in mice showing PCP-induced enhancement of immobility. These results suggest that the enhanced effect of PCP on the immobility is mediated by imbalance of 5-HTergic and dopaminergic systems in the prefrontal cortex and could be used as a model of the negative symptoms of schizophrenia.
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PMID:Repeated phencyclidine treatment induces negative symptom-like behavior in forced swimming test in mice: imbalance of prefrontal serotonergic and dopaminergic functions. 1098 64

Phencyclidine (PCP) administration in rats acutely in high doses or chronically in lower doses causes neurotoxicity characterized by neuronal vacuolization and apoptotic neuronal death, respectively. The purpose of this study was to determine whether drugs that previously had been reported to prevent either type of neurotoxicity were also able to prevent locomotor sensitization following chronic PCP administration. PCP (5 or 20 mg/kg) was administered once a day for 5 days following drug pretreatment. After withdrawal, rats were challenged with 3.2 mg/kg PCP and locomotor activity was assessed. Haloperidol and clozapine significantly attenuated sensitization elicited by PCP (20 mg/kg). The D(1)-like antagonist SCH23390 was much less effective than clozapine, showing a marginal inhibition. Risperidone, a D(2)/serotonin (5-HT(2)) antagonist, also resulted in a marginal attenuation of 15%. Ketanserin, a 5-HT(2) antagonist, had no effect. Atropine retarded sensitization by 35% and (+)-sulpiride caused a 50% reduction. The AMPA/kainate antagonist, 6,7-dinitroquinoxaline-2,3-dione, had no effect, but barbital sodium reduced sensitization by 54%. These data suggest that gamma-aminobutyric acid A, D(2), and muscarinic receptors play a major role in the complex pathway underlying sensitization to PCP, whereas D(1), 5-HT(2) and AMPA receptors have little or no relevance in the behavioral sensitization produced by 20 mg/kg PCP. In a model using 5 mg/kg PCP, the effects of sulpiride and SCH23390 replicated those observed with 20 mg/kg PCP and further showed that acute locomotor activation is not a strict requirement for the development of sensitization. These data argue that there is overlap, but nonidentity, between the mechanisms underlying PCP-induced sensitization and neurotoxicity.
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PMID:Pharmacological characterization of locomotor sensitization induced by chronic phencyclidine administration. 1118 23


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