Neuropharmacological characterization of insulin-sensitive CNS glucoregulator

Regional insulinization of the central nervous system (CNS) through the carotid artery causes an immediate decrease of the systemic blood sugar level in rats under light barbiturate anesthesia. Cervical vagotomy or intraperitoneal or intravenous atropine pretreatment results in partial inhibition of the systemic hypoglycemic response that follows intracarotid insulin injection. Intraperitoneal, intravenous, or intracarotid pretreatment with phentolamine or propranolol or intracarotid pretreatment with epinephrine had no effect on this centrally induced hypoglycemia. Intracarotid atropine injection immediately prior to intracarotid insulin injection completely abolished the systemic hypoglycemic response. Pretreatment with neostigmine administered intravenously prevented the inhibitory effect of intracarotid atropine on the hypoglycemic response that followed intracarotid insulin injection. It is consluded that the insulin-sensitive glucoregulator center of the CNS is under cholinergic influence, or its efferent pathways have a centrally located cholinergic synapsis.