Effects of Reduced Central and Peripheral Catecholamines on Avoidance Learning

Abstract

Adult male Sprague-Dawley rats were randomly divided into 3 groups of 10. Using an independent-groups design the 6-hydroxydopamine animals received intraventricular and IP injections of the drug. The sham drug rats received intraventricular and IP injections of a vehicle solution while the control subjects were not injected. When administered either centrally or peripherally, 6-hydroxydopamine specifically and extensively depletes catecholamine levels. All rats were consequently given 30 trials per day over a 5-day period on a one-way active avoidance jump task. Using latency of response and number of avoidance responses as criteria, drug-induced depletion of central and peripheral catecholamines significantly retarded and in half the rats totally inhibited the acquisition of the one-way avoidance response. The results were discussed in relation to recent empirical findings on reduced catecholamine levels and avoidance behavior. Theoretically the results were interpreted as supporting Mowrer's two-factor learning theory and in conflict with DiGiusto and King's hypothesis about “difficulty of task.”