Possible parasympathetic control of insulin secretion from the endocrine pancreas of the domestic fowl

Possible parasympathetic control of insulin secretion from chicken pancreatic islets was investigated. Electrical stimulation of the vagus nerve was utilized to increase vagal activity. Changes in plasma glucose and cerebrospinal fluid (CSF) insulin-like activity (ILA) were measured during the period of stimulation, and ultrastructural evidence of beta cell degranulation resulting from electrical stimulation was sought using the light and electron microscope. Additionally, a histochemical technique was employed in an attempt to demonstrate cholinergic nerve terminals in the pancreatic islet. It was observed that no significant change from control values occurred in plasma glucose, CSF-ILA, or ultrastructure of the beta cells during the 30-minute period of intermittent stimulation of the vagus nerve. Although neural elements were found in the connective tissue of the surrounding acinar tissue, no neural elements -were found associated with islet tissue per se. The absence of neural elements in the pancreatic islet as seen by these histological studies appears to be contradictory to earlier work indicating parasympathetic involvement in insulin secretion in the chicken.