Properties of nicotinic receptors underlying Renshaw cell excitation by alpha-motor neurons in neonatal rat spinal cord.

We used anatomical and physiological approaches to characterize nicotinic receptors (AChRs) on Renshaw cells of the neonatal rat spinal cord. Confocal imaging of Renshaw cells, identified by their characteristic pattern of gephyrin immunoreactivity, revealed that these neurons are immuno-positive for the alpha4 and beta2 AChR subunits but not for the alpha7 subunit. We used whole cell recording in spinal cord slices to characterize synaptic transmission from alpha-motor neurons to Renshaw cells, which could be identified pharmacologically by the sensitivity of transmission to d-tubocurarine. alpha-Motor neuron-to-Renshaw cell synapses were blocked by 10 microM dihydro-beta-erythroidine (dHbetaE), but not 50 nM methyllycaconitine (MLA), a selective alpha7 antagonist. These findings support a role for alpha4beta2-like AChRs, but not alpha7 AChRs, in rapid excitatory transmission between alpha-motor neurons and Renshaw cells in rat spinal cord.