Razook Joel C, Chandler Margaret J, Foreman Robert D
Department of Physiology, University of Oklahoma Health Sciences Center, P.O. Box 26901, Oklahoma City, OK 73190 USA.
Pain. 1995 Oct;63(1):117-125. doi: 10.1016/0304-3959(95)00026-O.
Effects of electrical stimulation of the ipsilateral phrenic nerve above the heart were determined on cells in the C1-C2 spinal cord segments of 27 rats anesthetized with pentobarbital. Forty-five cells that responded to this stimulus were included in this study. These cells then were examined at the same stimulus parameters for effects of stimulating the ipsilateral phrenic nerve below the heart, the contralateral phrenic nerve above the heart, and/or the left (ipsilateral) cervical vagus nerve. Ipsilateral phrenic nerve stimulation below the heart had no effect on 20 of 20 cells tested. Seven of 16 cells tested for effects of contralateral phrenic nerve stimulation above the heart were excited and activity of 9 cells was unaffected. Activity changes and activation latencies were not significantly different in the 7 cells excited by both ipsilateral and contralateral phrenic nerve stimulation. Thirty-seven of 45 cells excited by ipsilateral phrenic nerve stimulation also were excited by stimulation of the left cervical (ipsilateral) vagus nerve. The mean increase in cell activity was significantly greater following vagal nerve stimulation compared to phrenic nerve stimulation, and mean activation latency was significantly longer for vagal stimulation. Excitatory receptive somatic fields were classified for 35 cells. Somatic field locations for most cells (80%) included the ipsilateral neck and jaw. Activity of 26 cells was increased by both noxious pinch and brushing the hair, activity of 6 cells was increased only by noxious pinch, and activity of 3 cells was increased only by brushing the hair. Results of this study indicate that there are afferent fibers in the phrenic nerve above the heart, but not below the heart, that excite cells in the C1-C2 segments of the spinal cord. Most cells also were excited by noxious stimuli applied to their somatic receptive fields. Thus, the phrenic nerve may provide a pathway for referral of pain to the neck and jaw from thoracic structures.
在27只戊巴比妥麻醉的大鼠的C1 - C2脊髓节段的细胞上，测定了心脏上方同侧膈神经电刺激的效应。本研究纳入了45个对该刺激有反应的细胞。然后在相同的刺激参数下，检测这些细胞对心脏下方同侧膈神经、心脏上方对侧膈神经和/或左侧（同侧）颈迷走神经刺激的反应。心脏下方同侧膈神经刺激对20个受试细胞中的20个没有影响。在检测心脏上方对侧膈神经刺激效应的16个细胞中，7个细胞被兴奋，9个细胞的活动未受影响。同侧和对侧膈神经刺激均兴奋的7个细胞中，活动变化和激活潜伏期无显著差异。同侧膈神经刺激兴奋的45个细胞中，37个细胞也被左侧颈（同侧）迷走神经刺激所兴奋。与膈神经刺激相比，迷走神经刺激后细胞活动的平均增加显著更大，迷走神经刺激的平均激活潜伏期显著更长。对35个细胞的兴奋性感受躯体野进行了分类。大多数细胞（80%）的躯体野位置包括同侧颈部和下颌。26个细胞的活动因有害捏压和刷毛而增加，6个细胞的活动仅因有害捏压而增加，3个细胞的活动仅因刷毛而增加。本研究结果表明，心脏上方的膈神经存在传入纤维，而心脏下方的膈神经不存在，这些传入纤维可兴奋脊髓C1 - C2节段的细胞。大多数细胞也被施加于其躯体感受野的有害刺激所兴奋。因此，膈神经可能为从胸部结构向颈部和下颌传递疼痛提供一条途径。
