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)

Although barbiturates are often effective as therapeutic agents in several types of brain ischemia, there is no consensus as to their mechanisms of action. Exactly why other intravenous anesthetics such as ketamine are not effective therapies in brain ischemia is not known. Structural analogs of ketamine such as phencyclidine (PCP) not only exert potent hallucinogenic properties and are widely abused drugs, but often result in hypertensive encephalopathies and death. In view of the paucity of information on the cerebral circulatory actions of barbiturates, ketamine and PCP (and analogs), in-vivo (microcirculatory) and in-vitro studies were undertaken. Barbiturates, in anesthetic concentrations (e.g., 10(-5) to 10(-4) M), were found to exert direct vasodilator actions on cerebral arterial smooth muscle; these relaxant actions appear to be related to inhibition of calcium ion (Ca2+) influx in cerebral vessels. The latter may be important in the salutory actions of barbiturates in brain ischemia, head trauma and cerebrovasospasm. Unlike barbiturates, ketamine was found to exert spasmogenic actions on cerebral arteries, which may aid in explaining the inability of this anesthetic to be of therapeutic value in brain ischemia. PCP and its analogs, as well as other hallucinogenic molecules (e.g., LSD, mescaline) produced spasms in cerebral arterioles, venules and arteries in concentrations which mimic their hallucinogenic potencies. Distinct PCP-like receptors which subserve contraction appear to exist on large as well as microscopic cerebral blood vessels. Spasms induced by PCP, its analogs and ketamine can be readily reversed or prevented completely by calcium channel blockers. The latter agents could be quite useful, clinically, in prevention of cerebral infarction, hypertension and fatality associated with PCP (and analogs) intoxication.
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PMID:Effects of barbiturates, phencyclidine, ketamine and analogs on cerebral circulation and cerebrovascular muscle. 640 Apr 29

Phencyclidine (PCP) is a popular illicit drug often misrepresented as some other hallucinogenic substance and distributed in widely varying dosage forms and strengths. Users of hallucinogenic drugs may present with unintentional PCP overdoses. Toxicological laboratory analyses are essential to establish the diagnosis. In nine admitted overdose patients, the consciousness level ranged from alert to comatose on presentation, and all showed a prolonged recovery phase with agitation and toxic psychosis. Severe behavior disorder, paranoid ideation, and amnesia for the entire period of in-hospital stay are characteristic. In very high dose patients, shallow respiratory excursions and periods of apnoea and cyanosis coincided with generalized extensor spasm and spasm of neck muscles. Excessive bronchial secretions, gross ataxia, opisthotonic posturing, and grimacing occur. PCP toxic psychosis should be considered in drug-abusing patients presenting with schizophrenic-like symptoms, psychosis, or other bizarre behavior, whether or not they admit to taking PCP.
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PMID:Phencyclidine ingestion: drug abuse and psychosis. 728 52