Effect of serotonin and its antagonists on bladder detrusor function

: In anesthetized dogs, intravenous administration of serotonin causes biphasic contraction of the urinary bladder followed by relaxation. The m-antagonist of serotonin, morphine inhibits the first phase of contraction but does not affect the second phase and relaxation. The T-antagonist tipindole exerts no effect on the serotonin-induced contraction and relaxation of the detrusor. The D-antagonists, LSD-25, dihydroergotamine, droperidol and cyproheptadine produce no effect on the first phase of contraction but inhibit the second one and successive relaxation of the urinary bladder detrusor. In addition to D-antagonists of serotonin, the relaxation of the detrusor is also suppressed by inderal and guanethidine which indicates the participation of the sympathetic component in the effect realization. The serotonin-induced relaxation of the detrusor is not suppressed by benzohexonium.