Pharmacological study on sympathetic inhibition of the urinary bladder in dogs

The sympathetic inhibitory mechanism in dog urinary bladder studied. The bladder contractions induced by electrical stimulation of the pelvic nerve both proximal and distal to the pelvic plexus and by intraarterial administration of tetramethylammonium (TMA) were inhibited by stimulation of the hypogastric nerve and intraarterial injection of catecholamines. The inhibition by hypogastric nerve stimulation was more potent at the low frequency of pelvic nerve stimulation than at the high frequency. The inhibition of contraction induced by stimulation of the pre-plexal pelvic nerve was antagonized by phentolamine and propranolol, whereas the inhibition of contraction induced by stimulation of the post-plexal pelvic nerve and by TMA treatment were antagonized only by propranolol. It is concluded that inhibition by hypogastric nerve stimulation of bladder contraction induced by pelvic nerve stimulation is composed of two different components. One occurs at the ganglia in the pelvic plexus and is mediated by alpha-adrenoceptors. The other occurs at the post-plexal pelvic pathway, probably at the ganglia in the bladder wall or on the muscle cells, and is mediated by beta-adrenoceptors. Moreover, the alpha-adrenergic action facilitated the pelvic nerve excitation in its pathway from the ganglionic cell bodies to the muscle cells.