Possible involvement of the cholinergic system in hormonal secretion by the perfused pancreas from ventromedial-hypothalamic lesioned rats.

Total arginine-induced secretion of insulin, glucagon and somatostatin was studied during a 20 min period in isolated perfused pancreases from control and non-hyperphagic ventromedial hypothalamic (VMH) lesioned rats. Compared to controls pancreases from VMH-lesioned rats secreted more insulin (82 +/- 13 ng vs 36 +/- 9 ng) and more glucagon (130 +/- 23 ng vs 73 +/- 14 ng) but less somatostatin (0.58 +/- 0.18 ng vs 1.12 +/- 0.14 ng). These abnormalities were restored to normal by perfusion with atropine (25 mumol/l). Pancreases of both groups were perfused with the cholinergic agonist methacholine (100 mumol/l). Again pancreases from VMH-lesioned rats secreted more insulin (157 +/- 19 ng vs 33 +/- 6 ng) and more glucagon (95 +/- 13 ng vs 57 +/- 9 ng) but less somatostatin (0.80 +/- 0.15 ng vs 1.30 +/- 0.18 ng). These results support the concept that, in pancreases isolated from VMH-lesioned rats increased "cholinergic activity" may prevail via increased release of endogenous acetylcholine from islet-postsynaptic ganglion cells together with increased numbers of muscarinic receptors on postsynaptic ganglion cells as well as on endocrine cells.