RENSHAW ELEMENTS: LOCALIZATION AND ACETYLCHOLINESTERASE CONTENT

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Abstract
Fine microelectrodes filled with molar potassium acetate solution and saturated with fast green FCF dye have been used to record from and localize Renshaw elements in L7 of the cat spinal cord. Renshaw elements were identified electrophysiologically by their multiple spike responses to ventral root stimulation. Intracellularly recorded responses were obtained from 10 cells. After the recording procedures had been completed, dye was passed into the cell by applying a current through the electrode. Frozen sections were cut at 10 µ and stained for cholinesterases by the standard copper thiocholine method. Renshaw elements were found to be of extremely small size, apparently devoid of dendrites and in close proximity to motoneurons. Varying concentrations of acetylcholinesterase were found in the Renshaw elements. The distribution of these structures in the ventral horn of the spinal cord was more extensive than has been previously described. The question of their identification as interneurons or as the boutons of axon collaterals is discussed.