MEDIAL POSTERIOR HYPOTHALAMIC INPUT IS INVOLVED IN ADRENOCORTICAL ACTIVATION FOLLOWING FOREBRAIN LIMBIC STIMULATION

Previous experiments have demonstrated that posterior hypothalamic deafferentation, which involved also the medial forebrain bundle, has prevented the rise in serum corticosterone following limbic stimuli. Consequently, the effects of a small medial posterior hypothalamic deafferentation, excluding the medial forebrain bundle, on corticosterone responses following electrical stimulation of the hippocampus, amygdala, septum and reticular formation in the rat were studied. Posterior hypothalamic deafferentation did not change basal corticosterone levels but significantly inhibited the adrenocortical responses following stimulation of the above structures when compared to intact or sham-stimulated rats. Posterior hypothalamic deafferentation did not affect median eminence corticotropin releasing factor-41 content. It is concluded that a medial posterior hypothalamic input is involved in adrenocortical activation following limbic stimulation.