骶髓排尿反射机制的形态学基础——HRP标记、溃变和免疫组化法的光、电镜研究

THE MORPHOLOGICAL BASIS OF THE SPINAL MICTURITION REFLEX

本文应用溃变、HRP标记和免疫组化相结合的方法,在电镜下观察了SPN区外周初级传入终末与节前神经元间的突触联系形式。证明生理状态下,两者之间存在直接突触联系。并进一步探讨了与节前神经元形成直接突触联系的初级传入终末的来源和性质。为解释反射性排尿形成机制的“脱抑制释放学说”提供了超微结构水平的形态学依据。

The clinical and electrophysiological studies have shown that transection of the spinal cord above the level of the sacral parasympathetic nucleus (SPN) makes the micturition reflex reorganized. The reorganization implies that the spinal-brain stem-spinal micturition reflex through the pontine micturition center in the animal with intact neuraxis is replaced by the spinal reflex through the sacral parasympathetic pathways. The latter reflex is characterized by direct efferent response to the information from peripheral afferent. The sacral parasympathetic nucleus is the basic centre of the reflex. However, the mechanism of this reorganization is unanswered in the past. The hypothesis that the 'spinal reflex is unmasked' was proposed by de Great with his collaborators in order to explain the mechanism. But because of the lack of morphological, especially the ultrastructural evidence their explanation was limited to the imagination. In order to investigate the morphological basis for the 'hypothesis', the authors of the present paper combine the HRP tracing technique with immunocytochemical studies and degeneration method at the light and electron microscopic level and start the study with examining whether direct synaptic connection between the primary afferent terminal and the parasympathetic neuron exists or not. The findings and clue that we have got, are shown follow:1. Combining the degeneration technique with HRP tracing method at the electron microscopic level, we have observed the direct synaptic connection between the primary afferent terminals and the SPN neurons And then, the evidence that the visceral afferent terminals also give synaptic connection with the dendrites of SPN neurons has been got from the electron microscopic observation using HRP transganglionic and retrograde tracing methods. The synapses are always axo-dendritic and located in the dorsal area of SPN. These results provide basic morphological evidence for the 'hypothesis'.2. By combining the HRP tracing technique with immunocytochemical method, it has been shown that a part of the primary afferent terminals, which form synaptie connection with the SPN neurons are characterized by CGRP-like immunoreactivity.3. A lot of axo-axonie synaptie structures are observed in the SPN area and the postsynaptic elements are always the primary afferent terminals, which implies the existence of presynaptic modulation influence. There are also the triadic structures, axon (normal)-axon(primary afferent terminals)-dendrite(HRP labelled or unlabelled)synaptie structures in the SPN area. These results provide further morphologic support for the 'hypothesis'. The character and origin of the presynaptic element of the axo-axoa synapse will be studied after.