Properties of Nicotinic Receptors Underlying Renshaw Cell Excitation by α-Motor Neurons in Neonatal Rat Spinal Cord

Abstract

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 α4 and β2 AChR subunits but not for the α7 subunit. We used whole cell recording in spinal cord slices to characterize synaptic transmission from α-motor neurons to Renshaw cells, which could be identified pharmacologically by the sensitivity of transmission to d-tubocurarine. α-Motor neuron-to-Renshaw cell synapses were blocked by 10 μM dihydro-β-erythroidine (dHβE), but not 50 nM methyllycaconitine (MLA), a selective α7 antagonist. These findings support a role for α4β2-like AChRs, but not α7 AChRs, in rapid excitatory transmission between α-motor neurons and Renshaw cells in rat spinal cord.