Pancreatic Response to Mild Non–Insulin-Induced Hypoglycemia Does Not Involve Extrinsic Neural Input

Abstract

Mild non–insulin-induced hypoglycemia achieved by administration of a glycogen phosphorylase inhibitor results in increased glucagon and decreased insulin secretion in conscious dogs. Our aim was to determine whether the response of the endocrine pancreas to this mild hypoglycemia can occur in the absence of neural input to the pancreas. Seven dogs underwent surgical pancreatic denervation (PDN [study group]), and seven dogs underwent sham denervation (control [CON] group). Each study consisted of a 100-min equilibration period, a 40-min control period, and a 180-min test period. At the start of the test period, Bay R3401 (10 mg/kg), a glycogen phosphorylase inhibitor, was administered orally. Arterial plasma glucose (mmol/l) fell to a similar minimum in CON (5.0 ± 0.1) and PDN (4.9 ± 0.3). Arterial plasma insulin also fell to similar minima in both groups (CON, 20 ± 6 pmol/l; PDN, 14 ± 5 pmol/l). Arterial plasma glucagon rose to a similar maximum in CON (73 ± 8 ng/l) and PDN (72 ± 9 ng/l). Insulin and glucagon secretion data support these plasma hormone results, and there were no significant differences in the responses in CON and PDN for any parameter. Pancreatic norepinephrine content in PDN was only 4% of that in CON, confirming successful sympathetic denervation. Pancreatic polypeptide levels tended to increase in CON and decrease in PDN in response to mild hypoglycemia, indicative of parasympathetic denervation. It thus can be concluded that the responses of α- and β-cells to mild non–insulin-induced hypoglycemia can occur in the absence of extrinsic neural input.