大鼠脊髓后角内甲啡肽标记及非标记结构与C纤维间关系的免疫电镜研究

向大鼠蛛网膜下腔注射辣椒素导致一级传入纤维中的Ｃ纤维变性后，用免疫电镜技术在大鼠脊髓后角浅层内观察到：（１）大量含甲啡肽的轴突终末与未标记树突（或棘）形成对称性（少数为非对称性）突触；（２）含甲啡肽的轴突终未与变性终末共同会聚于同一甲啡肽阴性树突；（３）少量含甲啡肽轴突终末与变性终末间形成轴－轴突触或接触；（４）变性终末与含甲啡肽的树突形成非对称性轴－树突触；（５）甲啡肽阴性轴突终末与变性终末会聚于同一未标记树突并与变性终末间形成轴－轴突触或接触．以上结果表明，在脊髓后角内，脑啡肽除主要以突触后抑制方式调节Ｃ纤维传入外，也可通过轴－轴突触或接触对Ｃ纤维传入进行突触前抑制；非甲啡肽能神经元也能对Ｃ纤维传入进行突出后又突触前抑制．此外，Ｃ纤维在脊髓后角内可通过兴奋性轴－树突触直接影响甲啡肽能中间神经元的活性．

AN IMMUNOELECTRON MICROSCOPIC STUDY ON THE RELATIONS OF MET-ENKEPHALIN LABELLED AND UNLABELLED ELEMENTS TO C FIBER IN THE DORSAL HORN OF THE RAT SPINAL CORD

The probe into the relations Of met-enkephalin (MEK)-containing elements to C fibers of primary afferents in the superficial layers of the spinal cord, an immunoelectron microscopic study was cartted out on the rats whose C fibers were degenerated with capsaicin injected intrathecally. under electron microscope, the following connections were found: (1)a number ofMEK-containing axonic terminals establishing symmetric axo-dendritic or spiny synapses with unlabelled dendtites orspines ; (2)MEK terminals converging on single unlabelled dendrites with degenerated terminals ; (3)a few of MEK labelledaxonic terminals forming axo-axonic syuspses or contacts with degenerated terminals ; (4)degenerated terminals synapsingwith MEK-containing dendrites asymmetrically; (5)unlabelled axonic terminals converging on single unlabelled dendriteswith degenerated terminals and synapsing or contacting with degenerated terminals. The above results indicated that, in thesuperficial layers of spinal cord, enkephalin modulates the input of C fiber not only in postsynaptic inhibition but also inpresynaptic inhibition via axo-axonic synapse and/or contact, and that some non-MEK-containing elements have the similareffects on C fiber. Additionally, the existence of asymmetric axo-dendritic synapse between degenerated terminal and MEKlabelled dendrite revealed that C fiber may directly activate enkephalinergic interneuron in the spinal dorsal horn.