[Direct projection pathway between medial vestibular nucleus and vestibular efferent neurons in rats and its electrophysiological characteristics]

Objective: To confirm the direct projection pathway between the medial vestibular nucleus (MVN) and vestibular efferent (VE) neurons and explore its electrophysiological characteristics. Methods: Newborn [(9±1) day-old] male and female Wistar rats were used in the study. The postsynaptic currents of VE were recorded after stimulating neurons in MVN by the whole-cell patch clamp recording technique. The action potentials (APs) of the afferent neurons in MVN were recorded retrogradely after stimulating the area of VE neurons distribution medial to genu of facial nerve (g7), and the position and shape of the recorded neurons were determined by biocytin staining. Results: The resting membrane potentials of VE neurons located medial to g7 ranged between -70 mV and -55 mV in current clamp recordings. Excitatory postsynaptic currents (EPSCs) were recorded in the VE neurons medial to the g7 evoked by single-pulse (0.08 mA, 0.1 Hz, 100 μs) electrical stimulation of MVN. The mean values of amplitude and duration were (195.6±23.7) pA and (23.9±5.9) ms, respectively. APs were recorded in MVN after stimulating the distribution area of VE neurons. The mean amplitude of the action potentials was (62.0±4.3) mV, and the mean duration was (94.9±4.7) ms. Biocytin staining indicated that the recorded neurons located in MVN and the axons' terminals went into the area medial to g7 in which VE neurons located. Conclusions: There is a direct excitatory pathway projecting from MVN to VE neurons medial to g7. Its physiological function may be related to the feedback regulation of vestibular center to peripheral vestibular afferent signals.