Catecholamine secretion from the rabbit adrenal gland is not modulated by a mechanism involving beta-adrenoceptors.

The possibility that catecholamine secretion from the rabbit adrenal gland is subject to modulation by a mechanism involving beta-adrenoceptors was investigated in an isolated perfused preparation of the gland. The adrenal catecholamine stores were radiolabelled with 3H-adrenaline and subsequently efflux of radioactivity was elicited by stimulation of an attached branch of the splanchnic nerve. The efflux of radioactivity evoked by nerve stimulation (1 min at 5 Hz) was not altered by isoprenaline (0.1 microM), metroprolol (0.1 microM) or (+/-)-propranolol (1 microM). Stimulation-induced efflux was reduced in the presence of a higher concentration of (+/-)-propranolol (10 microM); however, it was also reduced by (+)-propranolol (10 microM). These findings do not support the existence in the rabbit adrenal gland of a mechanism involving beta-adrenoceptors through which catecholamine secretion may be modulated.