Membrane properties of rat medial vestibular nucleus neurons in vivo

In our previous study using the whole-cell patch clamp technique combined with reverse transcription-polymerase chain reaction analysis in rat brainstem slices, we demonstrated that the classification of neurons in the medial vestibular nucleus (MVN) based on three membrane properties detected as voltage response properties to depolarizing and hyperpolarizing current pulses, namely afterhyperpolarization (AHP) profiles, firing patterns, and response patterns to hyperpolarizing current pulses, is useful for clarifying the relationship between membrane properties and cellular markers for excitatory and inhibitory neurons. These membrane properties characterized in vitro, however, have not been ascertained in vivo. To address this issue, we applied the whole-cell patch clamp recording method to in vivo preparations of young adult rats and investigated voltage responses to depolarizing and hyperpolarizing current pulses. We found three AHP profiles, three firing patterns, and three response patterns to hyperpolarizing current pulses in MVN neurons in vivo that were characterized in our previous in vitro study. The MVN neuronal populations classified on the basis of the three membrane properties in vivo were comparable to those obtained in vitro. This finding indicates that the classification of MVN neurons based on the three membrane properties is applicable to in vivo preparations.