Abstract
It has been shown previously that Renshaw cells (RCs) are strongly inhibited by sensory stimuli in the cat spinal cord (Wilson et al. J. Neurophysiol. 27, 1063-1079. 1963). However, much remains unknown about the physiological and pharmacological nature of synaptic inputs from spinal reflex pathways to RCs. We performed whole cell recordings from identified RCs in the lumbar ventral horn using isolated spinal cord preparations taken from GAD67-GFP-knock-in mouse neonates (as described in Nishimaru et al. PNAS. 102, 5245-5249, 2005) and examined the evoked responses to electrical stimulation of dorsal roots (DRs). In voltage clamp recordings, electrical stimulation of ipsilateral DR (intensity 1.5-3 times of threshold) of the segment in which the RCs soma is located, evoked a short latency (<10 ms) EPSC followed by a barrage of IPSCs. The evoked response was completely blocked by bath-application of CNQX and AP5 indicating that EPSCs are mediated by ionotropic glutamate receptors and IPSCs are polysynaptically elicited in the RCs. Both PSCs persisted in the presence of mecamylamine, a nicotinic receptor antagonist, indicating that they are unlikely to have derived from motor axon collaterals. Electrical stimulation of ipsilateral DRs in caudal segments and contralateral DRs only evoked long latency (>20 ms) IPSCs. These results indicate that RC activity is differentially modulated by different sources of sensory inputs in the developing mouse spinal cord. [J Physiol Sci. 2008;58 Suppl:S197]
