Fukuda H, Koga T
Department of Physiology, Kawasaki Medical School, Kurashiki, Japan.
Jpn J Physiol. 1991;41(3):493-511. doi: 10.2170/jjphysiol.41.493.
To clarify the cortical portion of dogs which corresponds to the portion to perform voluntary straining in human, the posterior sigmoid gyrus of anesthetized dogs was systematically stimulated. When reflex-straining was elicited at constant intervals (10-20 s) by stimulation of pelvic afferents, extra-straining (cortical straining) intervening between reflex-straining was elicited after a latent period (0.2-1.0 s) by pulse train stimulation of a focal portion in the trunk area of the motor cortex (M1). Cortical straining reset cycles of reflex-straining. The minimum threshold intensity was observed in the fifth or sixth layer of the focal portion. No difference was recognized between the firing patterns exhibited during cortical and reflex-straining by the phrenic and rectus abdominis muscle nerves, and by the nerves innervating the glottis adductors and external urethral sphincter. Pulse train stimulation of the focal portion, however, interrupted reflex-straining when it was applied during reflex-straining. Pulse train stimulation of the focal portion also elicited burst firings in the phrenic and abdominal muscle nerves after short latencies (20 and 12 ms). The short-latency bursts disappeared after severance of the medulla pyramis ipsilateral to the stimulated focal portion, but cortical straining induced by stimulation of the same cortical site persisted. Stimulation of the focal portion still elicited straining after severance of the ipsilateral hypothalamus, but not after severance of the cerebral peduncle at the midbrain level. However, the cortical stimulation intensified to about three times occasionally induced straining after severance of the peduncle. From these results, it may be concluded that stimulation of the focal portion in the trunk motor area induces straining through the cerebral peduncle, midbrain tegmentum, and pontine straining reflex center.
为了明确犬类中与人类进行自主排尿时相对应的皮质部分，对麻醉犬的后乙状结肠回进行了系统刺激。当通过刺激盆腔传入神经以恒定间隔（10 - 20秒）引发反射性排尿时，在运动皮层（M1）躯干区域的局部部分进行脉冲串刺激，经过潜伏期（0.2 - 1.0秒）后，在反射性排尿之间会引发额外排尿（皮质性排尿）。皮质性排尿会重置反射性排尿的周期。在局部部分的第五或第六层观察到最小阈值强度。膈神经和腹直肌神经以及支配声门内收肌和尿道外括约肌的神经在皮质性排尿和反射性排尿期间所表现出的放电模式之间没有差异。然而，在反射性排尿期间施加对局部部分的脉冲串刺激会中断反射性排尿。对局部部分的脉冲串刺激还会在短潜伏期（20和12毫秒）后在膈神经和腹部肌肉神经中引发爆发性放电。在切断受刺激局部部分同侧的延髓锥体后，短潜伏期爆发消失，但由相同皮质部位刺激诱导的皮质性排尿仍然存在。切断同侧下丘脑后，刺激局部部分仍会引发排尿，但在中脑水平切断脑桥后则不会。然而，在切断脑桥后，偶尔将皮质刺激强度增强到约三倍会诱导排尿。从这些结果可以得出结论，刺激躯干运动区域的局部部分会通过脑桥、中脑被盖和脑桥排尿反射中枢诱导排尿。
