The release of endogenous dopamine from rat striatum during incubation in vitro

In this study the conditions for quantitative estimation of the spontaneous and KCl-stimulated release of endogenous dopamine from rat striatum during in vitro incubation have been investigated. KCl concentrations of 15-35 mM produced increasing stimulation of dopamine release during 20 min of incubation in vitro, while KCl concentrations of 45 and 60 mM produced no further significant increase in release. In the presence of 4.7 or 20 mM KCl, dopamine release was linear throughout a 20 min period of incubation; in the presence of 25 or 60 mM KCl, however, dopamine release was not linear, reaching a maximum within 8 min of incubation. Three structurally unrelated inhibitors of monoamine uptake were shown to enhance the net spontaneous release of endogenous dopamine at low concentrations, but to inhibit release at high concentrations. The ethanol-induced enhancement of striatal dopamine release was used to demonstrate the importance of an appropriate concentration of an amine uptake inhibitor in the incubation media. It is concluded that the incubation of rat striatal tissues in vitro, coupled with amine analysis by high performance liquid chromatography with electrochemical detection, constitutes an effective technique for the quantitative estimation of endogenous dopamine release, providing appropriate concentrations of a reuptake inhibitor and a monoamine oxidase inhibitor are included in the incubation media. Where rates of KCl-stimulated amine release with time are to be determined, however, a low concentration of KCl must be used, or the tissues must be subjected to incubation for short periods of time.