Tanaka J, Arnold A P
Department of Psychology, University of California, Los Angeles 900024-1563.
Exp Brain Res. 1993;96(1):117-24. doi: 10.1007/BF00230445.
Recent anatomical evidence suggests that descending projections from the lateral vestibular nucleus (LVe) and gigantocellular reticular nucleus (Gi) innervate areas of the lumbar spinal cord near the spinal nucleus of the bulbocavernosus (SNB). To confirm this finding electrophysiologically, we recorded and mapped averaged field potentials within the lumbar spinal cord of male rats in response to electrical stimulation of the LVe or Gi and compared these with the location of averaged field potentials evoked at the same levels by stimulation of SNB axons in the bulbocavernosus (BC) nerve. Stimulation of the LVe or the Gi produced negative field potentials that were largest at sites 200-450 microns dorsolateral to SNB somata. In an attempt to verify that this region innervates SNB motoneurons, the BC motor nerve volley was recorded in response to microstimulation at various depths within the spinal cord. Stimulation of sites dorsolateral and lateral to the SNB somata elicited volleys in the BC nerve that had two components. The onset latency of the earlier component was similar to the antidromic latency of SNB motoneurons to BC nerve stimulation, and the threshold for eliciting this component was lowest at sites in the electrode track near SNB somata. Thus, the earlier component may be evoked by direct stimulation of the SNB motoneurons. The threshold for evoking the later component was lowest at the sites 230-380 microns dorsolateral to SNB somata, suggesting that this component involves activation of other neurons. These results indicate that the LVe and Gi may modulate the activity of SNB motoneurons through interneurons located in a region several hundred microns away from SNB somata.
近期的解剖学证据表明，来自外侧前庭核（LVe）和巨细胞网状核（Gi）的下行投射支配球海绵体肌核（SNB）附近的腰脊髓区域。为了从电生理角度证实这一发现，我们记录并绘制了雄性大鼠腰脊髓内的平均场电位，以响应LVe或Gi的电刺激，并将其与球海绵体肌（BC）神经中SNB轴突刺激在相同水平诱发的平均场电位位置进行比较。刺激LVe或Gi产生负性场电位，在SNB神经元胞体背外侧200 - 450微米处的位点最大。为了验证该区域支配SNB运动神经元，记录了BC运动神经冲动以响应脊髓内不同深度的微刺激。刺激SNB神经元胞体背外侧和外侧的位点会在BC神经中诱发具有两个成分的冲动。较早成分的起始潜伏期与SNB运动神经元对BC神经刺激的逆向潜伏期相似，并且诱发该成分的阈值在靠近SNB神经元胞体的电极轨迹位点处最低。因此，较早成分可能是由SNB运动神经元的直接刺激诱发的。诱发较晚成分的阈值在SNB神经元胞体背外侧230 - 380微米处的位点最低，表明该成分涉及其他神经元的激活。这些结果表明，LVe和Gi可能通过位于距SNB神经元胞体数百微米区域内的中间神经元来调节SNB运动神经元的活动。
