A quantifiable behavioral correlate of psychotogen and tranquilizer actions.

A representative psychotogen, lysergic acid diethylamide (LSD-25), in doses small enough to be devoid of gross effects, increases response latency in rats to a tone indicating the availability of water reward; this effect is greatly reduced by prophylactic administration of a representative phenothiazine tranquilizer, chlorpromazine (CPZ), in doses that per se do not affect performance. The nature of the chlorpromazine action and its competition with lysergic acid diethylamide is revealed by the effects of chlorpromazine in larger doses.