Topographic analysis of AChE-positive Renshaw elements: a light- and electronmicroscopic histochemical study on the morphological basis of recurrent inhibition.

Light and electron microscopic structures of Renshaw elements as the morphological basis of the recurrent inhibition were studied by means of the histochemical localization of AChE. Renshaw elements were identified as periodically repeating bulbous dendritic dilatations of AChE-negative interneurons, equipped with numerous AChE-positive motoneuronal axon collaterals. Cumulative patterns obtained by analyzing consecutive sections from segment L5 of the cat spinal cord show that the area of the most frequent occurrence of Renshaw elements nearly coincides with the dendritic arborization of the 3. type interneuron described by MATSUSHITA. The role of the Renshaw elements in recurrent inhibition is supported by the fact that they occur in largest number in those areas of the ventral horn where the Renshaw inhibition can be elicited electrophysiologically.