Biochemical and pharmacological basis for the lateral hypothalamic syndrome.

The lateral hypothalamic (LH) syndrome characterized by impairment of the ability to regulate food and water intake has been reported to occur after injections of 6-hydroxydopamine (6-OHDA) into this region. In the present experiment the fluorescence histochemical technique was used to assess monoamine depletion of noradrenaline and dopamine containing neurons following intrahypothalamic injection of 6-OHDA. Results show that the intensity and area of monoamine accumulation in axons served by 6-OHDA is correlated with the severity of behavioral deficits but that actual catecholamine depletion of either the corpus striatum or the hypothalamus is unrelated to the syndrome. Possible mechanisms of action of this accumulation in producing behavioral deficits are discussed.