Feeding behavior after hypothalamic 6-hydroxydopamine injections.

6-Hydroxydopamine (6-OHDA) injection into the rat hypothalamus produces profound changes in eating behavior and body weight gain. Willis and Smith have demonstrated an anorexic effect of lateral hypothalamic (LH) 6-OHDA, which they correlate with local catecholamine release from degenerating axons just behind the lesion. Work from our own laboratory has recently demonstrated that 6-OHDA injection into the medial paraventricular nucleus (PVN) has an initial effect of stimulating daily food intake and body weight gain. It is suggested that this phenomenon, consistent with reports of enhanced eating with PVN injection of norepinephrine (NE), is due to 6-OHDA-induced release of endogenous NE. Subsequently, PVN 6-OHDA causes hypophagia and reduced body weight. Although histochemical and biochemical analyses reveal a 60-90% decrease in PVN norepinephrine and dopamine after 6-OHDA treatment, a close association between the precise degree of catecholamine loss and magnitude of behavioral response could not be detected.