OBJECTIVETo study the membrane properties of rat medial vestibular nucleus (MVN) neurons and their firing responses to simulated input signals of peripheral vestibular system, and to discuss how the intrinsic membrane properties contribute to physiologic functions in central vestibular system.

METHODSBy using infrared differential interference contrast technique, whole-cell recordings were made from rat MVN neurons under direct observation. On the basis of their averaged action potential shapes, the MVN neurons were classified. Linear and non-linear currents were put into the neurons to simulate the input signals of peripheral vestibular system. The differences of intrinsic membrane properties and firing response dynamics were observed between two types.

RESULTSThe discharge activities were recorded in MVN neurons, which remained in low Ca2+-high Mg2+ artificial cerebrospinal fluid (ACSF). Neurons are classified as type A (33%) characterized by a single deep after-hyperpolarization (AHP) and A-like rectification, or type B (63%) characterized by double AHP, and another two neurons with all or none of the characters. The passive membrane properties were not significantly different between type A and type B neurons, while part of active membrane properties was significantly different. Both type A and B neurons well responded to simulated current inputs, but disparities existed in response range and firing dynamics.

CONCLUSIONSThe discharge activities of MVN neurons were initiated by their intrinsic membrane properties. Most MVN neurons were classified as type A and B, while several showed unrepresentative firing properties. Linear and nonlinear inputs evoked a heterogeneous range of firing responses. The differences of response range and firing dynamics between neurons may determine their different physiological functions.