Synaptic effects of xenon on NMDA receptor-mediated response in rat spinal neuron

To investigate the precise mechanism of xenon (Xe), pharmacologically isolated AMPA/KA and NMDA receptor-mediated spontaneous (s) and evoked (e) excitatory postsynaptic currents (s/eEPSC_AMPA/KA and s/eEPSC_NMDA) were recorded from mechanically isolated single spinal sacral dorsal commissural nucleus (SDCN) neurons attached with glutamatergic nerve endings (boutons) using conventional whole-cell patch-clamp technique. We analysed kinetic properties of both s/eEPSC_AMPA/KA and s/eEPSC_NMDA by focal single- and/or paired-pulse electrical stimulation to compare them. The s/eEPSC_NMDA showed smaller amplitude, slower rise time, and slower 1/e decay time constant (τ_Decay) than those of s/eEPSC_AMPA/KA. We previously examined how Xe modulates s/eEPSC_AMPA/KA, therefore, examined the effects on s/eEPSC_NMDA in the present study. Xe decreased the frequency and amplitude of sEPSC_NMDA, and decreased the amplitude but increased the failure rate and paired-pulse ratio of eEPSC_NMDA without affecting their τ_Decay. It was concluded that Xe might suppress NMDA receptor-mediated synaptic transmission via both presynaptic and postsynaptic mechanisms.