Behavioral effects of LSD in the cat: proposal of an animal behavior model for studying the actions of hallucinogenic drugs.

In the course of examining the complete dose-response relationship for the behavioral effects of LSD in the cat, we discovered that, in addition to large increases in investigatory and hallucinatory-like responses, two behaviors, not previously reported, are emitted with a high probability under LSD. Beginning from a baseline of essentially zero in saline-treated animals, limb flicks and abortive grooming increase in frequency in direct relation to the dose of LSD administered (2.5, 10, 25 and 50 microgram/kg i.p.) and then decrease at higher doses (100 and 200 microgram/kg). Limb flicks are a species-specific behavior seen in normal cats almost exclusively in response to the presence of a foreign substance, such as water, on the hindpaw or forepaw. In abortive grooming, the cat orients to the body surfaces as if to groom but does not emit the consummatory grooming response (bite, lick or scratch), or emits the response in midair. These behaviors can serve as an animal behavior model for the actions of LSD and related hallucinogens in humans. The specificity of these behavioral changes is indicated by the fact that they are never seen in response to other classes of psychoactive drugs such as D-amphetamine, atropine, caffeine, and cholorpheniramine. They are, however, elicited by compounds such as psilocybin which are structurally and functionally related to LSD. The validity of the model is based on evidence indicating that it is: specific to hallucinogens, dose dependent, observed in a dose range effective in humans, parallels the major parameters of the actions of LSD in humans (see following paper), sensitive, robust, reliable, quantifiable and easy to score.