The stimulus-induced release of unmetabolized 5-hydroxytryptamine from superfused rat brain synaptosomes

A number of existing techniques have been modified to produce an improved technique for examining the depolarization-induced release of unmetabolized 5-hydroxytryptamine (5-HT) from drug-free superfused synaptosomes. Synaptosomes which have been pre-loaded with [3H]5-HT are set up in perfusion chambers and continuously perfused with medium. Serial samples of effluent perfusate are collected on ice and the released 5-HT and 5-hydroxy-indole acetic acid (5-HIAA) are separated by ion exchange chromatography. The technique provides reproducible Ca2+-dependent responses to K+ depolarization in the absence of monoamineoxidase inhibition and free from the interference of re-uptake. The advantages of the use of the system in examining transmitter release and its modulation is discussed.