Me.iial vestibular nucleus (MVN) neurons are the primary central targets of afferent from the ipsilateral horizontal semicircular canal and their projections are involved in the reflex control of the head and eyes. MVN neurons may also be involved in the recovery of vestibular function after peripheral vestibular lesions.
In this study, the types and characteristics of voltage-dependent ion currents were investigated in acutely isolated MVN neurons of postnatal rats by means of the whole cell patch clamp techniques. Transverse slice (400 gm) of the vestibular nucleus region was sequentially treated with pronase 0.2 mg/me and thermolysin 0.2 mg/me, then single neurons were mechanically dissociated. Ionic currents were recorded from the dissociated MVN neurons selected by criteria such as size and shape of cell body. Voltage-dependent sodium currents showed that the half-maximum activation potential was -43 mV and half-maximum inactivation potential was -60 mV. And the currents were blocked totally by application of 100 nM tetrodotoxin. Two types, high and low thresholds, of voltage dependent calcium currents were recorded. High voltage gated currents were present in all investigated neurons but low ones were recorded in only a few neurons. Also, MVN neurons possess at least four types of voltage-dependent potassium currents, including the delayed rectifier current (Ix), Ca 2´-dependent
transient current (Ic), Ca 2+-dependent sustained current (IAHP) and A current (IA) which were identified by the electrical and pharmacological methods.
These results reveal that MVN neurons express a variety of voltage-dependent ionic currents with distinct physiological and pharmacological properties. This diversity could be related both with the functional synaptic characteristics and with the intrinsic physiological properties in MVN neurons.
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