Central action of glucagon in rat hypothalamus

The effects of electrophoretically applied glucagon on neuronal activity in the rat lateral hypothalamic area (LHA), dorsomedial hypothalamic nucleus (DMH), and ventromedial hypothalamic nucleus (VMH) were examined. In the LHA glucagon significantly suppressed the activity of glucose-sensitive neurons compared with its effect on non-glucose-sensitive neurons. This inhibitory effect of glucagon on LHA neurons was blocked by ouabain. Intracellular recordings from LHA neurons revealed that glucagon hyperpolarized the cell membrane without a significant change in the input membrane resistance. Intra-arterial injection of glucagon suppressed the activity of some neurons that were suppressed by electrophoretically applied glucagon. Similarly, glucagon suppressed the activity of significant numbers of DMH and VMH neurons with doses higher than those that affected LHA glucose-sensitive neurons. Cortical neurons were unaffected by glucagon. The data suggest that blood-borne glucagon could suppress the activity of LHA glucose-sensitive neurons and, in addition, might contribute to the control of metabolism and the termination of feeding behavior.