Inescapable shock alters mescaline's disruption of active avoidance acquisition.

Rats were tested on a two-way avoidance acquisition with or without inescapable shock given 24 h prior to training. Mescaline given to nonshock rats disrupted acquisition in a dose-dependent fashion and tolerance developed to this disruption. Mescaline given to shock rats had no effect on acquisition even though levels of acquisition were the same for both shock and nonshock rats without drug. Moreover, subchronic treatment (5 days facilitated acquisition. These experiments demonstrate an interaction between shock, which presumably is a stressor, and mescaline. The data are consistent with the observation that when animals are exposed to presumptive stressors (e.g., shock, handling) hallucinogens can facilitate behavior, while in other situations, hallucinogens disrupt behavior.