Gajewski J, Downie J W, Awad S A
J Urol. 1984 Aug;132(2):403-9. doi: 10.1016/s0022-5347(17)49637-6.
The present study was done to test the hypothesis that alpha-adrenoceptor blocking drugs (phentolamine and prazosin) could interfere with somatic control of the external sphincter through an action in the central nervous system. Stimulation of the hypogastric nerve in the chloralose-anesthetized cat caused a urethral constriction which could be antagonized by alpha-receptor blockers. However, the constriction produced by stimulation of the S1 or S2 ventral root was completely resistant to alpha blockade. The drugs therefore had the expected action against sympathetic stimulation of the urethra but had no peripheral effect on the somatic component. The central effect of these drugs was investigated by recording urethral perfusion pressure responses, or compound action potentials on the central cut end of the pudendal nerve, evoked by stimulation of the contralateral pudendal or pelvic nerve. The urethral constriction produced by stimulation of the central cut end of 1 pudendal nerve was antagonized by both prazosin and phentolamine. Action potentials evoked on the pudendal nerve by stimulation of the central cut end of the contralateral pudendal or pelvic nerve were substantially inhibited by prazosin. Phentolamine produced a more variable blockade of the pudendal-pudendal reflex. The results strongly indicate that these alpha-adrenoceptor antagonists and especially prazosin can influence pudendal nerve-dependent urethral responses through a central nervous system action and not through a peripheral mechanism.
α-肾上腺素能受体阻断药物（酚妥拉明和哌唑嗪）可通过作用于中枢神经系统来干扰外括约肌的躯体控制。在氯醛糖麻醉的猫身上，刺激腹下神经会引起尿道收缩，而α受体阻断剂可对抗这种收缩。然而，刺激S1或S2腹侧神经根所产生的收缩对α阻断完全具有抗性。因此，这些药物对尿道的交感神经刺激具有预期的作用，但对躯体成分没有外周效应。通过记录由对侧阴部神经或盆神经刺激诱发的尿道灌注压反应或阴部神经中枢切断端的复合动作电位，来研究这些药物的中枢效应。刺激一条阴部神经的中枢切断端所产生的尿道收缩，可被哌唑嗪和酚妥拉明两者拮抗。刺激对侧阴部神经或盆神经的中枢切断端在阴部神经上诱发的动作电位，被哌唑嗪显著抑制。酚妥拉明对阴部-阴部反射的阻断作用更具变异性。结果强烈表明，这些α-肾上腺素能拮抗剂，尤其是哌唑嗪，可通过中枢神经系统作用而非外周机制来影响阴部神经依赖性尿道反应。
