In vitro dopamine biosynthesis in the median eminence of rat hypothalamic slices: possible involvement of a Na+-Ca2+ exchange mechanism.

Equimolar replacement of Na+ in medium with choline chloride or sucrose and experimental manipulations known to increase [Na+]i, such as ouabain addition and K+ deprivation from medium, caused a marked increase in in vitro DOPA synthesis in the median eminence of rat hypothalamic slices in a Ca2+-dependent manner. These results suggest that a Na+-Ca2+ exchange mechanism is closely involved in the regulation of dopamine biosynthesis in tuberoinfundibular neurons.