THE EFFECTS OF DORSAL BUNDLE INJECTIONS OF 6‐HYDROXYDOPAMINE ON AVOIDANCE RESPONDING IN RATS

Abstract

The effects of injection of 6‐hydroxydopamine (6‐OHDA) into the fibres of the dorsal noradrenergic bundle on acquisition, retention and extinction of active avoidance in rats were examined. 6‐OHDA injections severely depleted noradrenaline in all forebrain areas assayed, with the interesting exception of the septum. No significant effect on dopamine concentrations in various forebrain regions was found. Acquisition and retention of active avoidance was not altered by the lesion. Marked resistance to extinction was seen when the unconditioned stimulus (shock) was removed. A comparison with work by other authors in which both forebrain noradrenaline and dopamine were depleted suggest that the alteration in extinction seen in both studies is a noradrenergic effect, whereas the deficits in acquisition and retention found previously are dopaminergic in origin. 1978 British Pharmacological Society