RESUMO
BACKGROUND AND OBJECTIVES: This study was aimed to investigate the effects of 5-Hydroxytryptamine (5-HT) on the spontaneous activity of medial vestibular nuclear neurons of the rat. MATERIALS AND METHOD: Sprague-Dawley rats aged 14 to 16 days were anesthetized with ether and decapitated. After enzymatic digestion, the brainstem portion of medial vestibular nuclear neuron was obtained by micropunching. The dissociated neurons were transferred into a recording chamber mounted on an inverted microscope and spontaneous action potentials were recorded by standard patch-clamp techniques. RESULTS: The response of medial vestibular nuclear neurons to 5-HT applied in the recording chamber was not uniform. The spontaneous action potentials were increased in 10 cells, decreased in 3 cells and not altered in 2 of 15 cells. The spike width of the neurons was not affected by 5-HT. The spike frequency and resting membrane potential of these cells were increased by 5-HT. The depth of afterhyperpolarization was decreased by 5-HT. CONCLUSION: These results suggest 5-HT increases spontaneous firing of the medial vestibular nuclear neurons by altering the afterhyperpolarization.