The effects of electrical stimulation and lesion of the lateral hypothalamic area (LHA) on catecholamine (CA) secretion from the adrenal medulla were investigated in anesthetized rats. A differential secretion of epinephrine (E) and norepinephrine (NE) was observed, in which a single stimulating site could produce different effects on E and NE secretion. On the basis of change in the E secretion rate during stimulation, stimulation sites could be classified into 3 groups: group A which showed increase in E secretion (no change in NE), group B which showed decrease in E (and also decrease in NE), and group C which showed no change in E (but a decrease in NE). No relationship was observed between the sites of stimulation in the LHA and the direction of the responses. Lesions of the stimulation sites decreased CA secretion to different extent among the three groups and these differences could be predicted by the effects of stimulation at the same sites. These results suggest that the LHA has both facilitatory and inhibitory effects on the sympatho-adrenal function and that the former is predominant.
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