Action of a chronic administration of mescaline in dynamic behavioural situations.

The modifications of the rat behaviour caused by a chronic administration of mescaline were studied in two schedules of operant conditioning. In the "periodic conditioning" test, the schedule of reinforcement was changed from a fixed ratio to a fixed interval schedule. Mescaline (4 mg/kg/day and 10 mg/kg/day) caused no modification of the ability of the rat to adapt its behaviour to the new experimental situation. In the "reversal test" the contingency for food delivery was switched from one lever, where responses were previously reinforced to the other lever where responses had no programmed consequences. A chronic administration of mescaline (4 mg/kg/day) caused a total incapacity of the rat to switch to the lever which became reinforced in the reversal trial. A chronic administration of 9 mg/kg/day of mescaline had an excitatory effect and the number of reinforced responses in the II and III reversals exceeded the unreinforced responses in a measure greater than in the controls.