The effects of intra-amygdaloid injections of 6-hydroxy-dopamine on avoidance responding in rats.

1 The effects of bilateral intra-amygdaloid injections of 6-hydroxydopamine (6-OHDA) on shuttle box avoidance acquisition, retention, and extinction, and passive avoidance acquisition were examined in rats. 2 Intra amygdaloid 6-OHDA injections produced catecholamine depletion in and around the amygdalae but failed to reduce striatal dopamine concentrations. 3 Conditioned avoidance acquisition was markedly inhibited in 6-OHDA-treated rats whereas retention and extinction were only slightly impaired. 4 Passive avoidance acquisition was slightly but significantly improved in rats with amygdaloid 6-OHDA lesions. 5 Treated rats showed no motor abnormalities, they were not hypoactive in a photocell activity cage and they performed as well as controls on a rotating rod. 6 It is suggested that the conditioned avoidance acquisition deficit in rats with amygdaloid 6-OHDA lesions may be related to an impairment of associative learning rather than to perceptual or motor disturbances.