Measurement of 5-hydroxytryptamine release in the rat medial vestibular nucleus using in vivo microdialysis

The function of the 5-hydroxytryptamine (5-HT) system in the medial vestibular nucleus (MVN) was evaluated using KCl-evoked 5-HT release assessed by in vivo microdialysis. The release of 5-HT in the MVN was increased by the local application of KCl (100 mM) in a calcium-dependent manner. Likewise, perfusion of a 5-HT reuptake blocking agent, clomipramine (1 microM), increased extracellular levels of 5-HT in the MVN. Finally, pretreatment with the selective 5-HT(1A) agonist, 8-hydroxy-2-(di-N-propylamino) tetralin (1 mg/kg, intraperitoneally), attenuated the KCl-evoked 5-HT release. These findings suggest that 5-HT stored in vesicles is released from nerve terminals in the MVN. In addition, its regulation may be mediated by control of somatodendritic 5-HT(1A) receptor activation.