Abstract
The contributions of P- and R-type Ca 2+ channels on glycinergic nerve endings (boutons) projecting to the rat spinal sacral commissural nucleus (SDCN) neurons are not understood. Thus, we investigated the functional role of P- and R-type Ca 2+ channels by measuring the inhibitory postsynaptic currents (eIPSCs) evoked from individual nerve endings (boutons) by focal electrical stimulation. The current amplitude and failure rate (Rf) of glycinergic eIPSCs varied directly with changes in [Ca 2+] o. Low concentration of ω-Aga IVA (P-type selective antagonist) suppressed eIPSCs as much as high concentration (both P- and Q-type selective) indicating little contribution of Q-type Ca 2+ channels. Antagonism of R-type Ca 2+ channels with SNX-482 and Ni 2+ greatly decreased the current amplitude and increased failure rate (Rf) of glycinergic eIPSCs. Overall, our results suggest that the dominant control of glycine release depends on Ca 2+ entry through P- and R-type Ca 2+ channels that ubiquitously populate spinal glycine release sites.
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