Stimulus secretion coupling in vitro: a rapid perfusion apparatus for monitoring efflux of transmitter substances from tissue samples.

An apparatus for monitoring efflux rates of specific substances from cellular preparations is described. Tissue samples (homogenates, subcellular fractions, small tissue slices, cell suspensions etc.) are placed on a filter, perfused with several different media sequentially and aliquots of the perfusate collected at intervals of 5 sec. Under maximum perfusion rates, the changeover in perfusion media is completed in less than 1 sec, produces no detectable disturbance of the sample and allows only minimal mixing of the different media. The apparatus has been used successfully to study stimulus secretion coupling during release of the neurotransmitter ¹⁴C]γ-aminobutyric acid from synaptosomes.