Serotonergic control of synaptic transmission in rat medial vestibular nucleus

Abstract

To address the role of serotonergic projections from dorsal raphe nucleus to the medial vestibular nucleus (MV), whole-cell patchclamp was employed to investigate the serotonergic modulation of spontaneous synaptic transmission within the MV of rats. Perfusion of serotonin (5-hydroxytryptamine, 5-HT) to brainstem slices robustly facilitated both spontaneous inhibitory postsynaptic currents (sIPSCs) and spontaneous excitatory postsynaptic currents (sEPSCs) in a subgroup of MV neurons. That this enhancement effect of 5-HT on sIPSCs and sEPSCs were both abolished with tetrodotoxin indicates that 5-HT acts on its receptor that expressed in the presynaptic neurons. Using different receptor antagonists, we further identified that GABAA and glycine receptors took part in the enhancement effect on sIPSCs whereas AMPA receptor was involved in sEPSCs. This 5-HT-induced effect on both sIPSCs and sEPSCs could be mimicked with application of 5-HT2 receptor agonist but was blocked with 5-HT2A receptor antagonist. Our results therefore indicate that within the MV, 5-HT2A receptors expressed on presynaptic neurons function to facilitate both inhibitory and excitatory transmission that allows the potentiation of targeted synapses.