Serotonin uptake via plasma membrane monoamine transporter during myocardial ischemia-reperfusion in the rat heart in vivo.

Serotonin (5-HT) accumulates in the heart during myocardial ischemia and induces deleterious effects on the cardiomyocytes through receptor-dependent and monoamine oxidase-dependent pathways. We aimed to clarify the involvement of extra-neuronal monoamine transporters in the clearance of 5-HT during ischemia and reperfusion in the heart. Using a microdialysis technique in the anesthetized Wistar rat heart, we monitored myocardial interstitial 5-HT and 5-hydroxyindole acetic acid (5-HIAA) concentration by means of electro-chemical detection coupled with high-performance liquid chromatography (HPLC-ECD). Effects of inhibitors of the plasma membrane monoamine transporter (PMAT) and the organic cation transporter 3 (OCT3) (decynium-22 and corticosterone) on the 5-HT and 5-HIAA concentrations during baseline, coronary occlusion, and reperfusion were investigated. Basal dialysate 5-HT concentration were increased by local administration of decynium-22, but not by corticosterone. Addition of fluoxetine, a serotonin transporter (SERT) inhibitor further increased the 5-HT concentration upon during administration of decynium-22. Decynium-22 elevated the background level of 5-HT during coronary occlusion and maintained 5-HT concentration at a high level during reperfusion. Production of 5-HIAA in the early reperfusion was significantly suppressed by decynium-22. These results indicate that PMAT and SERT independently regulate basal level of interstitial 5-HT, and PMAT plays a more important role in the clearance of 5-HT during reperfusion. These data suggest the involvement of PMAT in the monoamine oxidase-dependent deleterious pathway in the heart.