Effect of 5-HT receptor and adrenoceptor antagonists on micturition in conscious cats.

Micturition was induced in awake cats by infusing saline into the bladder at a physiological filling rate. Methysergide, a serotonergic antagonist given intrathecally, decreased the volume at which micturition occurred. Phentolamine, a non-specific alpha-adrenoceptor antagonist, also decreased volume threshold. Prazosin, an alpha 1-adrenoceptor antagonist, was without effect on micturition. These results imply that 5-HT receptors and alpha 2-adrenoceptors may be inhibitory to micturition at a spinal level.