PMID: 6400429Apr 1, 1984Paper

Effects of barbiturates, phencyclidine, ketamine and analogs on cerebral circulation and cerebrovascular muscle

Microcirculation, Endothelium, and Lymphatics
B T Altura, B M Altura

Abstract

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 an...Continue Reading

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