Characteristics of the neuroendocrine responses to stimulation of the splanchnic nerves in bursts in the conscious calf

Abstract

Neuroendocrine responses to splanchnic nerve stimulation in bursts (at 40 Hz for 1 s at 10 s intervals for 10 min) have been investigated in conscious adrenalectomized calves, 3-6 weeks after birth, in the presence of various pharmacological blocking agents. Preganglionic blockade with hexamethonium abolished all the neuroendocrine responses that were monitored. Pre-treatment with phentolamine significantly reduced, but failed to eliminate, the release of both pancreatic glucagon and pancreatic polypeptide. In the presence of phentolamine splanchnic nerve stimulation produced a massive rise in arterial plasma insulin concentration. None of these pancreatic neuroendocrine responses was significantly affected by additional pre-treatment with propranolol. The rise in mean plasma insulin concentration which occurred in calves pre-treated with both phentolamine and propranolol was significantly reduced by atropine. Release of bombesin-like immunoreactivity (BLI) was unaffected by total post-ganglionic adrenergic and cholinergic blockade. The results indicate that pancreatic endocrine responses to splanchnic nerve stimulation may be attributable, at least in part, to release of BLI in this species.