Abstract
At the 57 annual-meeting of the Federation of American Societies for Experimental Biology, an analysis of drug block by lysergic acid diethylamide (LSD), serotonin (5-HT), and gamma-aminobutyric acid (GABA) in cats was reported. Continuous intracellular monitoring of membrane changes in pyramidal, pericruciate cortex cells establishes that close arterially injected 5HT, LSD and chlorpromazine (CPZ) act in a qualitaively identical fashion, with 5HT being most active, LSD less, and CPZ very much less. in all three the concomitant changes are: reduced or stopped firing, hyperpolarization, reduced EPSPs, appearance and increase of IPSPs, and decreased conductance.Thus, CPZ appears to block by substituting at, evidently, the identical membrane site on identical but much weaker action for 5HT or LSD, demonstrating competitive inhibition in terms of critical membrane changes. CPZ local anesthesia is excluded as a factor since xylocaine, enough to reduce firing, did not reproduce the other changes. GABA membrane changes are similar except for an increased conductance. Strychnine (Strych) blocking all, is less specific and blocks GABA, presumably, largely by reducing inhibition in another contributing channel rather then ' the high conductance one. The data provide a cellular basis for a specific, competitive, and differential inhibition (CP2:), and for a less specific block (Strych)
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