The modulatory effect of the hypothalamus on glucagon and insulin secretion in the rat.

Rats were provided both with brain cannulas, to permit infusion in the ventromedial and lateral hypothalamic areas (resp. VMH and LH), and with two heart catheters. In this way infusions of fluids and withdrawal of blood could be done in unanesthetized free moving animals. Infusion of norepinephrine (NE) in the VMH elicited glucagon release during the whole period of NE infusion whereas insulin levels did not change. This glucagon release could not be suppressed by alpha- and beta-receptor blockade but it was suppressed by hexamethonium, a blocking agent of signal transmission in peripheral ganglia of the autonomic nervous system. On the other hand, infusion of NE in the LH elicited insulin release during the whole period of NE infusion whereas glucagon levels remained unchanged. It is argued that [1] the sympathetic nervous system is involved in glucagon release, [2] no alpha- and beta-receptor mechanisms are involved during this glucagon release, [3] the parasympathetic nervous system is involved in insulin release during noradrenergic LH stimulation.