Naloxone Decreases Centrally Induced Hyperglycemia in Dogs: Evidence for an Opioid Role in Glucose Homeostasis

Intracerebroventricular (ICV) instillation of morphine and β-endorphin causes centrally induced hyperglycemia. Locally active, endogenous opioids in the central nervous system may, therefore, also be involved in the elevation of blood sugar. This possibility was tested by examining the glucoregulatory response to central glucoprivation induced by ICV administration of 2-deoxy-D-glucose (2DG) in dogs. Administration of 2DG resulted in a rise in plasma glucose and immunoreactive glucagon (IRG) of 108 ± 19 mg/dl and 70 ± 20 pg/ml, respectively. These changes were attenuated by the simultaneous central infusion of the opiate antagonist naloxone: plasma glucose levels increased by 77 ± 14 mg/dl and IRG by 43 3 pg/ml, both significantly different from the effect of 2DG alone (P < 0.05–0.01). These findings suggest that opiate receptors participate in the counterregulatory response to central glucoprivation. They also provide a mechanism by which endogenous opioid peptides may play a role in the central regulation of glucose homeostasis.