The spontaneous contractile force of muscle strips isolated from male rabbit urinary bladder dome (detrusor) and base (trigonal muscle) was dose dependently inhibited by isoproterenol, a non-specific beta-adrenoceptor agonist. The relaxant response to 10––6M isoproterenol in the detrusor muscle was completely blocked by butoxamine (10––4M), a selective beta-2-antagonist, and by propranolol (10––6M), a non-specific beta-antagonist, but not by metopronol (10––6 to 10––4M), a selective beta-1-antagonist. Relaxation of trigonal muscle induced by 10––6M isoproterenol was inhibited 30% by metoprolol (10––5M), 70% by butoxamine (10––4M), and 100% by propranolol (10––6M). Terbutaline, a selective beta-2-adrenoceptor agonist, also caused dose dependently a relaxant response in detrusor and trigonal muscle. The maximum relaxant responses to isoproterenol and terbutaline were significantly greater in detrusor than in trigonal muscle. Dobutamine, a relatively specific beta-1-adrenoceptor agonist, caused a small but significant relaxant response in trigonal, but no change in detrusor muscle. In trigonal muscle the relaxant response to dobutamine was less than that to terbutaline. Cyclic adenosine monophosphate accumulation in detrusor did not significantly increase after administration of dobutamine, but significantly increased after administration of terbutaline. On the other hand, not only terbutaline, but also dobutamine, markedly increased cyclic adenosine monophosphate accumulation in trigonal muscle. These findings are consistent with the detrusor having a greater density of beta-adrenoceptors than trigonal muscle and with the relaxant responses to beta-adrenoceptors being mediated by the beta-2-subtype in the detrusor and by both beta-1 – and beta-2-subtypes in trigonal muscle of the rabbit through cyclic adenosine monophosphate accumulation.
The functional activity of the sphincter muscle of the urethra is known to be controlled largely by the hypogastric and pudendal nerves. It remains unknown, however, whether innervation of the muscle by these peripheral nerves is ipsi- or bilateral. In an attempt to answer this question urethral closure pressure was determined simultaneously in the anterior, posterior, right and left portions of urethral wall in dogs. The pressure measurements were stereographed with the aid of a computer (stereo-UPP) and by this means the effect of unilateral section or electrical stimulation of hypogastric and pudendal nerves on the intraurethral pressure profile was analyzed. Unilateral section or electrical stimulation of the hypogastric nerve, distal to its division, produced a fall and a rise primarily in proximal intraurethral pressure, respectively, in all four directions. There was no significant difference in this response between the involved and uninvolved sides. Unilateral section of the pudendal nerve resulted in a fall primarily in distal intraurethral pressure in all four directions. No significant difference was present between the injured and noninjured sides. In contrast, electrical stimulation of the pudendal nerve distal to the point of its division caused a rise in intraurethral pressure in all four directions, with a significantly greater pressor response on the stimulated than on the nonstimulated side. These observations suggest decussating motor innervation of the urethra by the hypogastric nerves and also the possibility of the distal urethra being ipsilaterally innervated by the pudendal nerve.
A 58-year-old man with neurogenic bladder dysfunction was hospitalized with chief complaints of urinary retention and abdominal distention. He had been treated for neurogenic bladder due to cerebral infarction for 3 years. The pelvic CT scan and excretory urogram revealed an obstruction of the neck of the bladder due to an abundant stool, which was found to have resulted from adult idiopathic megacolon. A permanent colostomy with sigmoid resection was established. The postoperative urodynamic examination demonstrated improvement of micturition.
The effects of forskolin and isoproterenol on contractile force and cyclic AMP (cAMP) levels were compared in rabbit detrusor. Both forskolin and isoproterenol produced relaxation of rabbit detrusor and an increase in cAMP levels in the tissue. Although the relaxant response to forskolin was similar to that of isoproterenol, the increase in cAMP levels induced by forskolin was significantly larger than that induced by isoproterenol. These results suggest that there is a discrepancy in the relaxation responses and cAMP levels in response to forskolin and isoproterenol.forskolin ; isoproterenol ; rabbit detrusor ; relaxantion : cAMP levels Forskolin has been reported to produce relaxation in various smooth muscles and to increase cAMP levels (Dubey et al. 1981;Muller and Baer 1983). Isoproterenol also causes smooth muscle relaxation associated with an increase of cAMP (Bar 1974). The purpose of the present study is to compare the changes in cAMP levels with relaxation of rabbit urinary bladder smooth muscle induced by forskolin and isoproterenol. MATERIALS AND METHODSTen male New Zealand white rabbits weighing 2-2.5 kg were stunned and bled. Two muscle strips, 2 mm wide and 10 mm long, were dissected from each urinary bladder dome (detrusor).Measurement of contractile force. Muscle strips were mounted in a 3.0 ml bath containing modified Krebs solution bubbled with 95% 02 and 5% CO2 at 37°C. One end of the strip was attached with a 4-0 silk thread to a hook fixed at the bottom of the bath and the other end was similary attached to a Statham UC-2 force transducer. A baseline force of 1.0 g was applied and maintained during the experiment. The strip was equilibrated for 60 min prior to the administration of the drug. Drugs were added directly to the muscle bath in an amount of 0.1 ml. Effects of drugs were determined by calculating the change in peak contractile force (active force+baseline force).
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