6-Hydroxydopamine induced catecholamine depletion and passive avoidance learning in rats.

Rats were injected with 6-hydroxydopamine either intracisternally, intraperitoneally, or both, in order to examine the effects of central vs. peripheral catecholamine depletion on a step-down passive avoidance task. All rats acquired the response at the end of the five asquisition trials but the rates of acquisition of the drug-treated groups were siginificantly different from the control group. No significant difference in the performance results were observed between groups during the extinction period. These findings failed to confirm the hypothesis that an intact central and/or peripheral catecholaminergic systems may be necessary for the acquisition and extinction of a step-down passive avoidance response. In addition, this study also showed that plasma corticosterone levels in the rats depleted of central or peripheral catecholamine did not differ significantly from each other after passive avoidance training.