Usefulness of an animal behavioral model in studying the duration of action of LSD and the onset and duration of tolerance to LSD in the cat.

LSD elicits a number of emergent behaviors in the cat, including limb flicking, abortive grooming, investigatory and hallucinatory-like behaviors, which we have proposed as an animal behavior model for studying the actions of LSD and related hallucinogens. These emergent behaviors were used in the present study to investigate the duration of action of LSD, as well as the onset and duration of tolerance. A dose of 10 microgram/kg of LSD produced significant behavioral changes for up to 4h, while a dose or 50 microgram/kg produced changes lasting for at least 8 h. Tolerance to a test dose of 50 microgram/kg of LSD is virtually complete one day after a single 50 microgram/kg dose, and lasts for approximately 5 days. Tolerance to a test dose of 50 microgram/kh of LSD one day after a single dose of 10 microgram/kg is quite marked, and lasts for approximately 3 days. A significant tolerance to a test dose of 50 microgram/kg of LSD occurs within 2 h after a single injection of 10 microgram/kg. The limb flick was found to be the most sensitive index in all tests: it showed the longest time-course, as well as the most rapid and longest-lasting tolerance. These studies demonstrate that the LSD-induced behavioral syndrome in the cat parallels important parameters of the action of LSD in humans, and thus enhances the usefulness of the model.