The role of the autonomic nervous system in the control of pancreatic endocrine responses to milk ingestion in the calf.

Abstract

1. Pancreatic endocrine responses to ingestion of milk have been investigated in conscious unweaned calves, 3-5 weeks after birth. Passage of gastric content from abomasum to small intestine was prevented by means of a cannula placed in the duodenum adjacent to the pylorus and food was witheld for at least 22 h in order to deplete liver glycogen. 2. Under these conditions ingestion of milk was followed by a prompt rise in the concentrations of pancreatic glucagon, PP and gastrin in the arterial plasma but the usual rises in plasma glucose and insulin concentration were absent. 3. Evidence was obtained to show that absorption of glucose from the small intestine occurs sufficiently rapidly to account for the initial rise in plasma glucose concentration after feeding in normal animals. However, the rise in plasma glucagon concentration was sufficient to contribute to alimentary hyperglycaemia by promoting hepatic glycogenolysis in calves with abundant liver glycogen. 4. None of the neuroendocrine responses to ingestion of milk was affected by prior section of the splanchnic nerves whereas each was blocked by atropine (0.2 mg/kg), showing that all depend upon muscarinic, parasympathetic rather than sympathetic activity, in the absence of extraneous stress.