OBJECTIVETo establish the visual patch clamp whole-cell recording technique and study the properties and functional significance of muscarinic receptor-mediated currents in rat medial vestibular nucleus neurons (MVNn).

METHODSBrain slices containing the MVN were prepared from fifteen Wistar rats. By combining infrared differential interference contrast (IR-DIC) technique and CCD-Camera system with visual patch clamp whole-cell recording technique, twenty healthy neurons were located and muscarinic receptor-mediated currents in rat MVNn were observed and analyzed.

RESULTSVisual patch clamp technique can be used to make direct localization and to make sure of active neuron. In MVNn, a comparison of the current-voltage relationships before and during the application of muscarine, which revealed an increase in the slope of the I-V curve and the reversal potential for this response lay at (-88.4 +/- 4.9) mV (x +/- s), indicates that the activation of muscarinic cholinergic receptors leads to a decrease in potassium current. The test in the voltage sensitivity of the muscarine-induced response, which showed that the effect had a linear current-voltage relationship and reversed at (-86.7 +/- 3.5) mV, indicates that the potassium current blocked by muscarine corresponds to the voltage-insensitive leak potassium current.

CONCLUSIONSVisual patch clamp technique, which was considered better than blind patch clamp technique, can improve the success of sealing process. By the analysis of muscarinic receptor-mediated currents, the data provide support that muscarinic cholinergic mechanisms play a prominent role in the modulation of the excitability of MVNn and also offer a new idea for the efficacy of anticholinergic drugs.