Effects of delta9-tetrahydrocannabinol on active avoidance acquisition and passive avoidance retention in rats with amygdaloid lesions.

Delta9-Tetrahydrocannabinol was administered to rats with basolateral amygdaloid lesions, control rats, and normal rats in doses of 0.75, 1.5, and 3.0 mg/kg i.v. They were trained in a one-session two-way active avoidance task. Delta9-Tetrahydrocannabinol increased the percentage of avoidance and the intertrial crossing rates in all groups, regardless of lesion treatment. Rats with basolateral amygdaloid lesions were not different from controls on any measure. In a second experiment, delta9-tetrahydrocannabinol was administered to rats with basolateral amygdaloid lesions and control rats in doses of 0.75 and 3.0 mg/kg 24 h after learning of a one-trial passive avoidance task, and retention was measured. No differences were found as a function of drug treatment or lesion condition. It was concluded that the basolateral amygdala is not a necessary condition for the action of delta9-tetrahydrocannabinol on active avoidance acquisition, that the drug has no effect on passive avoidance retention, and the basolateral amygdala is not necessary for two-way active avoidance acquisition or passive avoidance retention. Active avoidance results are discussed in terms of a possible relationship between delta9-tetrahydrocannabinol, ACTH, and avoidance learning.