MODULATION OF PLASMA-GLUCOSE BY THE MEDIAL PREOPTIC AREA IN FREELY MOVING RATS

The effect of norepinephrine (NE) injection into the medial preoptic a rea (MPOA) on plasma glucose was studied in freely moving male rats. T he rats were implanted with chronic jugular catheters for blood sampli ng and with unilateral intracerebral cannulas placed just above the MP OA. Blood samples were taken immediately before and 5, 10, 15, and 30 min after NE injection. As early as 5 min after NE injection, plasma g lucose levels rose rapidly, reaching a peak at 15 min poststimulus. Th e hyperglycemic response to NE injection into the MPOA was dose-relate d within the range of doses tested (10, 20, and 40 nmol). Previous adm inistration of phentolamine (50 nmol), but not propranolol (100 nmol), into the MPOA blocked the hyperglycemic response to NE injection into the MPOA. The increase of plasma glucose induced by NE into the MPOA and the blockade of the hyperglycemic response to NE by phentolamine s uggest the involvement of an alpha-adrenergic mechanism in MPOA-mediat ed hyperglycemia. On the basis of these and previous results, we propo se that MPOA alpha-adrenergic synapses relay impulses activating the s ympathetic outflow expressed by neurally mediated hyperglycemia. Copyr ight (C) 1997 Elsevier Science Inc.