Pacheco P, Martinez-Gomez M, Whipple B, Beyer C, Komisaruk B R
Departamento de Fisiologia, Instituto de Investigaciones Biomedicas, UNAM, Mexico.
Brain Res. 1989 Jun 19;490(1):85-94. doi: 10.1016/0006-8993(89)90433-2.
The efferent innervation of the pelvic and pudendal nerves was characterized in this study by identifying the muscles activated by electrical stimulation of the nerves distal to the point at which they bifurcate from the L6-S1 trunk. Pelvic nerve electrical stimulation produced EMG-monitored contraction of the ipsilateral ilio- and pubococcygeus muscles, which was abolished by cutting one ('muscular') branch of the bifurcated nerve. (This 'muscular' branch receives proprioceptive input activated by tail displacement, whereas the other, 'viscero-cutaneous' branch receives sensory innervation from the midline perineal region.) Pudendal nerve electrical stimulation produced contraction of the coccygeus, external anal sphincter, and ischiocavernosus muscles. Movements of the orifice and wall of the vagina were directly visualized during electrical stimulation of the two nerves. Intravaginal pressure measured by balloon was increased by pelvic nerve stimulation and decreased by pudendal nerve stimulation. Reflexive contraction of the ilio- en pubococcygeus muscles was produced by mechanostimulation of the perineum, clitoral sheath and distal vagina. This response was abolished by gentle cervical mechanostimulation. One implication of this finding is that passage of the fetuses through the cervix during parturition may relax the ilio- and pubococcygeus muscles, thereby facilitating delivery.
在本研究中，通过识别在盆神经和阴部神经从L6 - S1干分叉点远端进行电刺激时所激活的肌肉，对其传出神经支配进行了表征。盆神经电刺激产生了同侧髂尾肌和耻骨尾骨肌的肌电图监测收缩，切断分叉神经的一个（“肌肉”）分支后这种收缩消失。（这个“肌肉”分支接收由尾部移位激活的本体感觉输入，而另一个“内脏 - 皮肤”分支接收来自会阴中线区域的感觉神经支配。）阴部神经电刺激产生了尾骨肌、肛门外括约肌和坐骨海绵体肌的收缩。在对这两条神经进行电刺激期间，直接观察到了阴道开口和壁的运动。通过球囊测量的阴道内压力在盆神经刺激时升高，在阴部神经刺激时降低。对会阴、阴蒂包皮和阴道远端进行机械刺激会产生髂尾肌和耻骨尾骨肌的反射性收缩。这种反应在轻柔的宫颈机械刺激后消失。这一发现的一个意义在于，分娩过程中胎儿通过宫颈可能会使髂尾肌和耻骨尾骨肌放松，从而有助于分娩。
