Effects of sympathetic nerve stimulation in the presence of specific adrenergic antagonists on Na, K, and Cl transport in perfused rat submandibular duct.

The role of beta 1- and beta 2-adrenoceptors in the modification of Na, K, and Cl transport in submandibular main duct of rat perfused with bicarbonate saline solution was studied with direct sympathetic nerve stimulation (4 V, 5 ms, 20 Hz) in the presence of specific adrenergic antagonists. Nerve stimulation in the presence of phenoxybenzamine (3 mg/kg b. wt., i.p.) and butoxamine (3 mg/kg b. w.t., i.p.) enhanced Na (44%) and Cl (35%) absorption but inhibited K (24%) secretion. On the other hand, the nerve-evoked response in the presence of phenoxybenzamine and metoprolol (3 mg/kg b. wt., i.p.) decreased K (19%) secretion without any changes in Na and Cl absorption. Therefore, the data suggest that beta 1- and beta 2-adrenoceptors may be present in the duct cells and activation of these receptors can modify electrolyte transport. Furthermore, prior administration of phenoxybenzamine, butoxamine, and metoprolol suppressed the effects of sympathetic nerve stimulation on transductal fluxes of Na, K and Cl; this indicates that the dosages of antagonists used were sufficiently high to block a nerve-evoked response.