Goshgarian H G, Roubal P J
Exp Neurol. 1986 Jun;92(3):624-38. doi: 10.1016/0014-4886(86)90304-3.
Previous studies from this laboratory have localized and morphologically characterized phrenic motor neurons in the rat spinal cord at light and electron microscopic levels. The present investigation used a modification of the TMB method for the retrograde transport of horseradish peroxidase (HRP) to describe at light microscope levels the origin and distribution of phrenic primary afferent axons in the adult rat spinal cord. Dry HRP crystals were applied to the central stump of the transected phrenic nerve in the neck to label spinal ganglion cell bodies and thus determine the levels of origin of afferent axons in the phrenic nerve. Camera lucida drawings were then made from serial sections through the appropriate spinal cord levels to determine the specific distribution of transganglionically labeled phrenic central axonal processes within the spinal cord. HRP-labeled phrenic primary neurons were observed in the C3 to C7 spinal ganglia. The camera lucida studies indicated that the transganglionically labeled central processes of phrenic primary afferent axons distributed into the dorsal horn at the C4 and C5 levels of the spinal cord. Furthermore, central processes distributing to C5 were more numerous than those that distributed to C4. Afferent axons were never seen in the dorsal horn at C3, C6, or C7. As spinal ganglion cells were labeled at C3 above and C6 and C7 below, it follows that central processes of phrenic afferent fibers descend and ascend in the dorsal columns of the spinal cord before distributing into the dorsal horn. Specifically, the labeled primary afferent axons and their collateral branches were found in the fasciculus cuneatus, and in laminae I, II, III, and IV of the dorsomedial aspect of the dorsal horn. The function of these central axonal processes is unknown, but based on a comparison of our morphologic data with previous physiological and anatomical studies, we suggest that phrenic afferent fibers may arise from proprioceptors (muscle spindles and Golgi tendon organs), nociceptors, or rapidly adapting mechanoreceptors (Pacinian corpuscles) within the diaphragm.
本实验室之前的研究已在光学显微镜和电子显微镜水平对大鼠脊髓中的膈运动神经元进行了定位并描述了其形态特征。本研究采用改良的TMB方法进行辣根过氧化物酶（HRP）逆行运输，在光学显微镜水平描述成年大鼠脊髓中膈初级传入轴突的起源和分布。将干燥的HRP晶体应用于颈部横断膈神经的中枢残端，以标记脊髓神经节细胞体，从而确定膈神经传入轴突的起源水平。然后通过适当脊髓节段的连续切片制作明视绘图，以确定经神经节标记的膈中枢轴突在脊髓内的具体分布。在C3至C7脊髓神经节中观察到HRP标记的膈初级神经元。明视绘图研究表明，膈初级传入轴突经神经节标记的中枢突分布于脊髓C4和C5节段背角。此外，分布至C5的中枢突比分布至C4的更多。在C3、C6或C7背角未见传入轴突。由于C3以上及C6和C7以下的脊髓神经节细胞被标记，因此膈传入纤维的中枢突在分布至背角之前在脊髓背柱中下行和上行。具体而言，在楔束以及背角背内侧的I、II、III和IV层中发现了标记的初级传入轴突及其侧支。这些中枢轴突的功能尚不清楚，但根据我们的形态学数据与之前的生理学和解剖学研究比较，我们认为膈传入纤维可能起源于膈肌内本体感受器（肌梭和高尔基腱器官）、伤害感受器或快速适应机械感受器（环层小体）。
