STUDIES ON THE DOPAMINE-DEPENDENT MODULATION OF AMINO ACID-GATED CURRENTS IN CONE HORIZONTAL CELLS OF THE PERCH (PERCA-FLUVIATILIS)

The whole-cell patch-clamp technique was employed to record membrane c urrents from isolated horizontal cells in culture. Concentration-respo nse relationships for currents induced by L-glutamate, kainate and qui squalate were measured. Preincubation with dopamine changed the parame ters of the concentration-response curves in a particular way for each agonist. The maximum currents induced by glutamate increased by 50-10 0% and the EC50-values were slightly shifted to higher values. The inc rease of kainate-induced maximum currents after dopamine incubation di d not exceed 30% but the EC50-values were clearly shifted to lower con centrations. Quisqualate-induced maximum currents were not enhanced by dopamine preincubation but the EC50-values were shifted to lower conc entrations. The dopamine-dependent modulation was affected by removel of magnesium and preincubation with concanavalin A and aniracetam. The concentration-response relation and the time-course of the dopamine e ffect on glutamate-induced currents is described.