Developmental electrophysiological changes in mouse mesencephalic trigeminal neurons

This study examined the postnatal maturation of electrophysiological properties in mesencephalic trigeminal (MesV) neurons, focusing on firing patterns, intrinsic membrane properties, membrane resonance, and inward‑rectifying currents. MesV neurons exhibited phasic, tonic, and stuttering firing modes, with phasic firing predominant at P7 and an increased proportion of tonic firing at P14 and P21, indicating progressive diversification of discharge behaviors during postnatal development. Resting membrane potential and spike threshold remained stable, whereas input resistance decreased and membrane charging kinetics changed, consistent with neuronal growth and reduced excitability. Membrane resonance matured with development, characterized by a decline in impedance and a marked increase in resonance frequency by P21, suggesting enhanced frequency selectivity. Inward rectification was also strengthened, as evidenced by faster sag responses, increased inward‑rectifying current density, depolarizing shifts in half‑maximal activation, and faster activation kinetics. Together, these findings demonstrate coordinated maturation of passive and active membrane properties in MesV neurons, supporting improved regulation of firing and integration of membrane inputs during postnatal development.