Fukuda H, Koga T
Department of Physiology, Kawasaki Medical School, Kurashiki, Japan.
Exp Brain Res. 1991;83(2):303-16. doi: 10.1007/BF00231154.
Inhibition of the micturition, defecation and rhythmic straining reflexes by midbrain stimulation was compared with the inhibition of the jaw-opening reflex caused by tooth pulp stimulation in decerebrate dogs. All of the reflexes were inhibited by stimulation of the dorsal and ventral periaqueductal gray, dorsal raphe nucleus and central tegmental field with similar threshold intensities. After a hemisection of the spinal cord at the C2 segment, the midbrain stimulation still suppressed the micturition reflex as well as field potential changes which were evoked by stimulation of the pelvic nerve and recorded from the lateral funiculus just caudal to the hemisection, but did not influence the discharges of the vesical branch of the pelvic nerve which were elicited by stimulation of the lateral funiculus just rostral to the hemisection. The results suggest that stimulation of the neural elements in the 4 midbrain areas depresses the ascending activities from vesical and colorectal afferents of the pelvic nerve at the spinal level, and consequently inhibits the pelvic nerve reflexes. Systemic methysergide suppressed midbrain inhibition of the jaw-opening reflex, but did not affect the midbrain inhibition of the pelvic nerve reflexes. Systemic naloxone did not influence midbrain inhibition of the pelvic nerve reflexes or the jaw-opening reflex, but enhanced the micturition and rhythmic straining reflexes. Possible roles of the midbrain inhibition of the pelvic nerve reflexes are discussed.
在去大脑的狗中，比较了中脑刺激对排尿、排便和节律性用力反射的抑制作用与牙髓刺激对张口反射的抑制作用。通过刺激中脑导水管周围灰质背侧和腹侧、中缝背核和被盖中央区，以相似的阈值强度抑制所有这些反射。在脊髓C2节段进行半横断后，中脑刺激仍能抑制排尿反射以及由盆神经刺激诱发并在半横断尾侧的外侧索记录到的场电位变化，但不影响由半横断头侧的外侧索刺激所引起的盆神经膀胱支的放电。结果表明，刺激4个中脑区域的神经元可抑制脊髓水平盆神经膀胱和结肠传入神经的上行活动，从而抑制盆神经反射。全身应用麦角新碱可抑制中脑对张口反射的抑制作用，但不影响中脑对盆神经反射的抑制作用。全身应用纳洛酮不影响中脑对盆神经反射或张口反射的抑制作用，但增强了排尿和节律性用力反射。文中讨论了中脑对盆神经反射抑制作用的可能机制。
