Precise Localization of Renshaw Cells with a New Marking Technique

Abstract

FOR some years Renshaw cells in the spinal cord have been extensively investigated. While their physiological and pharmacological properties are relatively well known, knowledge concerning their location in the spinal cord is only approximate and is mostly derived from electrophysiological observations¹ and indirect anatomical evidence². From all this work it has been concluded that Renshaw cells are located in the ventral horn medial to motoneurones. For accurate localization of these and other cells within the central nervous system, however, it is necessary to record the electrical activity with microelectrodes which have satisfactory electrical properties, and then to indicate the location of the electrode tip by making, while causing a minimum of damage to the area, a small and easily identifiable mark. A number of techniques have been used for locating the position of microelectrode tips in nervous tissue³. However, most of these techniques require special histological procedures, may be unreliable, or can only be used at the end of an experiment. While the method of Galifret and Szabo⁴ needs no special histological procedure and can be used several times in an experiment, it makes rather large marks (several hundred μ) and has not proved completely reliable. We have therefore developed a new technique for routinely making precise, easily located marks and have used this technique in localizing Renshaw cells.