Endogenous 5-HT outflow from chicken aorta by 5-HT uptake inhibitors and amphetamine derivatives

Chemoreceptor cells aggregating in clusters in the chicken thoracic aortacontain 5-hydroxytryptamine (5-HT) and have voltage-dependent ion channels and nicotinicacetylcholine receptors, which are characteristics typically associated with neurons. Theaim of the present study was to investigate the effects of 5-HT uptake inhibitors,fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives,p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HToutflow from the isolated chick thoracic aorta in vitro. 5-HT wasmeasured by using a HPLC system with electrochemical detection. The amphetaminederivatives and 5-HT uptake inhibitors caused concentration-dependent increases inendogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflowthan MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCAand CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HTinduced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca²⁺concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on theextracellular NaCl concentration. These results suggest that the 5-HT uptake system of5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristicssimilar to those of 5-HT-containing neurons in the mammalian central nervous system(CNS).