Excitatory effects of 5-hydroxytryptamine on the medial vestibular nuclear neuron via the 5-HT2 receptor.

This study was designed to investigate the mechanisms of action of the 5-HT 2 receptor on the spontaneous electrical activity and potassium currents of the rat medial vestibular nuclear neurons using whole-cell patch clamp recordings. The spike width of spontaneous action potential was not affected by 5-a-methylhydroxytryptamine. The spike frequency and resting membrane potential was increased by 5-α-methylhydroxytryptamine. The amplitude of afterhyperpolarization was decreased by 5-α-methylhydroxytryptamine. The peak current of the potassium currents of the neuron treated with 5-a-methylhydroxytryptamine was decreased. After blockade of calcium-dependent potassium currents, 5-α-methylhydroxytryptamine did not inhibit potassium currents. These results suggest 5-α-methylhydroxytryptamine increases spontaneous firing of the medial vestibular nuclear neurons by inhibiting calcium dependent potassium currents.