Lee J W, Erskine M S
Department of Biology, Boston University, MA 02215, USA.
Neuroscience. 1996 Sep;74(1):237-49. doi: 10.1016/0306-4522(96)00103-0.
In female rats, vaginocervical stimulation induces neuroendocrine responses necessary for pregnancy as well as analgesia to a variety of noxious stimuli. In this study, Fos immunocytochemistry was used to detect vaginocervical stimulation-induced changes in the activity of spinal neurons at levels T11-S3, segments known to receive afferent input from nerves which innervate the reproductive tract. Adult ovariectomized estrogen and progesterone-treated rats were killed 1 h after receiving mating stimulation from males, which included five or 15 intromissions, mounts-without-intromission by use of either vaginal masks or genitally-anaesthetized males, or immediately after being removed from their home cages. At all spinal levels, Fos labelling was lowest in the home cage group (50 +/- 22 cells), intermediate in the groups receiving intromissions (84 +/- 8 and 118 +/- 22 cells) and highest in groups receiving mounts-without-intromission stimulation (187 +/- 21 and 218 +/- 35 cells). Significant increases above control levels following intromissive stimulation were observed at levels L6, S1 and S2. Surprisingly, both groups receiving mounts-without-intromission showed significantly higher numbers of Fos-positive cells than did the fully mated groups at all levels. Analysis of selected spinal segments by Rexed's laminae revealed that intromissive stimulation increased Fos labelling above control levels in laminae II-V and X at L6, and laminae I, II, V and X at S1; vaginocervical stimulation did not increase labelling at L1. The greater Fos responses seen in mounts-without-intromission animals than in control or intromitted animals were apparent at L1, L6 and S1 within the same laminae (II-V and X). These results suggest that stimulation of the uterine cervix initiates activity within L6-S2 neurons which receive pelvic nerve afferents and that such stimulation suppresses activity at all levels within populations of neurons normally activated by cutaneous somatic inputs received from male mounts. As antinociceptive agents are known to suppress c-fos expression, vaginocervical stimulation received during natural mating may be capable of initiating spinal and/or brain mechanisms of analgesia.
在雌性大鼠中，阴道宫颈刺激可诱导妊娠所需的神经内分泌反应以及对多种有害刺激产生镇痛作用。在本研究中，采用Fos免疫细胞化学方法检测阴道宫颈刺激引起的T11 - S3节段脊髓神经元活动变化，已知这些节段接收来自支配生殖道神经的传入输入。成年去卵巢并用雌激素和孕激素处理的大鼠在接受来自雄性的交配刺激（包括5次或15次插入、使用阴道罩或生殖器麻醉的雄性进行无插入式骑跨）1小时后处死，或在从其饲养笼中取出后立即处死。在所有脊髓节段，饲养笼组的Fos标记最低（50±22个细胞），接受插入刺激的组居中（84±8和118±22个细胞），接受无插入式骑跨刺激的组最高（187±21和218±35个细胞）。在L6、S1和S2节段观察到插入刺激后显著高于对照水平的增加。令人惊讶的是，在所有节段，接受无插入式骑跨的两组Fos阳性细胞数量均显著高于完全交配组。通过Rexed板层对选定脊髓节段的分析显示，插入刺激使L6节段的II - V层和X层以及S1节段的I层、II层、V层和X层的Fos标记高于对照水平；阴道宫颈刺激在L1节段未增加标记。在同一板层（II - V和X）内，L1、L6和S1节段接受无插入式骑跨的动物比对照或插入动物出现更大的Fos反应。这些结果表明，子宫颈刺激可启动L6 - S2神经元的活动，这些神经元接收盆神经传入，并且这种刺激可抑制通常由雄性骑跨时接收到的皮肤躯体输入激活的神经元群体在所有水平的活动。由于已知抗伤害感受剂可抑制c - fos表达，自然交配期间接受的阴道宫颈刺激可能能够启动脊髓和/或脑的镇痛机制。
