Glucoregulatory effects of intrahypothalamic injections of bombesin and other peptides.

The influence of neuropeptides on hypothalamic regulation of plasma glucose and pancreatic hormone secretion was studied in anesthetized rats. Neuropeptides were injected directly into the ventromedial hypothalamus (VMH) and the lateral hypothalamic area (LHA) and changes in hepatic venous plasma glucose, insulin, and glucagon concentrations were studied. Injection of bombesin into the VMH resulted in a marked and sustained hyperglycemia in the hepatic venous plasma, which was also observed after injection into the LHA. Microinjection of SRIF into the VMH or LHA caused a decrease in hepatic venous plasma glucose concentration. Injection of neurotensin into the VMH or LHA resulted in a transient release of insulin in the 10-min postinjection samples. In 30- and 60-min postinjection samples, significant increases in glucagon concentrations were observed after substance P injection into the VMH or LHA. No major difference in the plasma glucose, insulin, or glucagon concentrations was observed when VMH and LHA stimulation was compared. These data suggest that glucoregulatory neuropeptides may act on the VMH and LHA, which do not necessarily follow the currently recognized anatomical boundaries.