Distribution of locomotor-labelled neurons in the neonatal rat thoracolumbar spinal cord

Abstract

The present study was undertaken to identify thoracolumbar spinal neurons (T10-L6) active during 5-HT-induced hindlimb locomotor-like activity in the isolated intact neonatal rat spinal cord preparation in vitro. The synaptic transmission-dependent endocytosis and consequent retrograde transport of the fluorescent dye sulforhodamine 101 was used to identify activated cells. Immunohistochemical labeling of spinal cells into neurons and astrocytes suggested that cells labeled during locomotor-like activity were most likely to be neurons. We show that serious methodological errors in a similar previous study (Kjaerulff et al 1994) necessitated the present re-examination and identification of neuron active during the locomotor rhythm. We conclude that any studies which include NMDA to induce locomotion may recruit additional populations of neurons unrelated to the spinal locomotor network. We conclude that 5-HT, when applied alone, is a reliable agent for the selective labeling of neurons recruited during locomotor-like activity. (Abstract shortened by UMI.)