刺激大鼠下丘脑室旁核激活的中脑中央灰质神经元对躯体传入的反应

电刺激大鼠下丘脑室旁核(PVH),在同侧中脑中央灰质(CG)内寻找逆行及顺行反应单位,然后观察它们对躯体感觉刺激的反应。实验结果表明:CG 及邻近网状结构内有10%(32/318)的单位呈逆行反应。逆行传导速度平均为0.37±0.24m/s(均数±标准差);推测这种CG→PVH 投射纤维属于细有髓或无髓神经纤维。这些单位分布于 CG 的腹外侧及背外侧亚核。50%(14/28)的逆行单位对坐骨(胫)神经的强电刺激和夹尾等损伤性刺激起反应,但对触毛或低强度的神经干刺激无明显反应。以上结果表明:外周躯体感觉,特别是损伤性信息传入 PVH 时,CG 是其中枢驿站之一。电刺激 PVH 还能顺行激活7.55(24/318)、抑制0.7%(2/318)的 CG 单位。有69%(18/26)的顺行反应单位对外周躯体神经强电刺激及夹尾起反应。提示 PVH 可能通过影响 CG神经元的活动而参与中枢痛觉的整合。

RESPONSES OFMIDBRAIN CENTRAL GRAY NEURONS ACTIVATED BY HYPOTHALAMIC PARAVENTRICULAR NUCLEUS(PVH)STIMULATION TO SOMATIC AFFERENT INPUT IN RATS

Extracellular single unit recordings were made from 318 neurons within themidbrain central gray in urethane-anesthetized rats.Following electrical stimu-lation of the hypothalamic paraventricular nucleus(PVH),10% of the units incentral gray(CG)were antidromically activated,while 7.5% were orthodromicallyexcited,and 0.7% were orthodromically inhibited.Among those antidromically activated neurons,28 units were further examinedfor their responsiveness to peripheral somatic sensory stimulation.Strong electricalstimulation of contralateral sciatic and tibial nerve,and tail pinching producedexcitation in 12 and inhibition in 2 units.No significant responses to non-noxiousstimulation were observed in these units.Of the 26 orthodromically activated units,14 were excited and 4 inhibited by the sciatic nerve stimulation or tail pinching.These results support the hypothesis that CG is one of the relay stations in theafferent pathway of somatic sensory especially,noxious,information transmittingto the PVH,and that the PVH may play a role in central pain control or modu-lation via their descending influence on CG unit.