Pharmacologic characteristics of bladder micturition function in anesthetized mice

In the present study, we observed the effects of an α(1)-adrenoceptor agonist (phenylephrine), β-adrenoceptor agonist (isoprenaline), muscarinic cholinoceptor agonist (carbachol), and α(1)-adrenoceptor antagonist (doxazosin) on the bladder micturition function in anesthetized mice. Changes in bladder pressure in response to filling and blood pressure were recorded by using a data acquisition system. Phenylephrine (50 to 800 μg/kg) increased vesical micturition pressure in a dose-dependent manner but increased micturition basal pressure only at 800 μg/kg. Carbachol (3 to 7 μg/kg) increased the intercontraction interval and micturition time in a dose-dependent manner but increased micturition basal pressure only at 7 μg/kg. Isoprenaline (10 to 1000 μg/kg) increased micturition time and decreased vesical micturition pressure in a dose-dependent manner. Doxazosin (10 to 1000 μg/kg) did not affect bladder micturition function but dose-dependently inhibited phenylephrine-induced increases in vesical micturition pressure. Carbachol (7 μg/kg) and isoprenaline (1 mg/kg) caused a transient fall in blood pressure, whereas doxazosin (1 mg/kg) had a long-lasting hypotensive effect. The maximal decrease in systolic and mean blood pressure by carbachol did not differ from that by doxazosin and isoprenaline, respectively. Phenylephrine (800 μg/kg) transiently increased the blood pressure of anesthetized mice. These results indicate that activation of muscarinic cholinoceptors decreases voiding frequency and increases bladder capacity in anesthetized mice. Activation of α(1)-adrenoceptors mainly increases vesical micturition pressure, whereas activation of β-adrenoceptors decreases vesical micturition pressure and prolongs micturition time in anesthetized mice.