During perfusions with glucose concentrations of 25 and 150 mg./100 ml., the effect of infusions of acetyl choline on glucagon and insulin release was investigated in five perfusion experiments. Acetyl choline at concentrations of 10 to 100 μM. stimulated release of glucagon both at the low glucose strength as well as at the high concentration, which in itself inhibits basal glucagon release. Glucagon was released in a monophasic pattern, resembling the release pattern found after catecholamines and contrasting with the biphasic pattern obtained after stimulation with gastrointestinal hormones and amino acids, as previously reported from our laboratory.
Acetyl choline always stimulated release of insulin in a biphasic pattern, at the high glucose concentration, while no consistent effect was obtained at the low glucose concentration. At the termination of the acetyl choline infusions, a rebound increase in insulin was observed during perfusion with both low and high glucose concentrations.
Infusion of atropine at a concentration of 25 μM. completely abolished the stimulatory effect of acetyl choline on both glucagon and insulin release.
The results suggest that the parasympathetic nervous system may play a direct role in the control mechanism of the release of the pancreatic hormones during food ingestion.