Sympathetic activity of internal urethral spincter. In empty and partially filled bladder.

The sympathetic activity was investigated by recording the fall of internal sphincter pressure produced by a dose of phentolamine (Regitine) which completely abolished all alpha adrenergic sympathetic activity. It was found that when the bladder was empty, the mean fall of internal sphincter pressure was 7.1 cm, water; but when the bladder was partially filled, the mean fall was 17.6 cm. water. After use of reserpine, which creates a "pharmacologic sympathectomy," no sympathetic activity was demonstrated.