Paraventricular hypothalamic adrenoceptors and energy metabolism in exercising rats

The role of adrenoceptors in the paraventricular nucleus (PVN) in the exercise-induced changes in plasma norepinephrine (NE), epinephrine (E), corticosterone, free fatty acids (FFA), and blood glucose was investigated in rats. Exercise consisted of strenuous swimming against a countercurrent for 15 min. Before, during, and after swimming, blood samples were withdrawn through a permanent heart catheter for determination of E, NE, corticosterone, FFA, and glucose, In control rats receiving artificial cerebrospinal fluid through permanent bilateral cannulas into the PVN, the levels of all blood components increased during exercise. Infusion of the alpha-adrenoceptor antagonist phentolamine into the PVN completely reduced the exercise-induced increases in blood glucose and plasma corticosterone concentrations. Plasma NE, E, and FFA were not affected. Infusion of the beta-adrenoceptor antagonist timolol into the PVN reduced blood glucose and plasma NE concentrations. Plasma E, corticosterone, and FFA remained unchanged. It is concluded that alpha- and beta-adrenergic receptors in the PVN are involved in the central nervous regulation of blood glucose levels during exercise, partly by influencing sympathetic outflow. alpha-Adrenoceptors in the PVN play an important role in the release of corticosterone during exercise.