Continuous measurement of the effect of a depressing drug upon the organism

A method and apparatus are described for continuously recording, quantitatively, the effect of a depressing drug throughout a long experimental session. The procedure consists of recording the intensity of stimulus necessary to elicit a reflex response of constant extent. The right hind foot flexion reflex of the dog was used, and a d.c. electric shock, 0.2 seconds in duration, was the stimulus. Normal animals showed an essentially unchanged reflex to a constant stimulus over a 2-hour period. Dogs given intraperitoneal injections of nembutal showed a marked reduction in sensitivity, varying from a 250% increase in d.c. voltage 10-20 minutes after injection, to 50% increase, one hour after injection. "Individual differences . . . were much reduced under nembutal. This is probably because of the relatively greater influence of the drug upon the cerebral cortex and basal ganglia than upon the lower nerve centers."