The effects of neurotensin on the release of endogenous dopamine (DA) from rat striatal slices were investigated. DA was extracted by the aluminium adsorption method and assayed electrochemically by high-performance liquid chromatography. Neurotensin (2-100 microM) potentiated the potassium-induced release of striatal endogenous DA in a concentration-dependent manner. This neurotensin-induced release of DA was completely abolished in calcium-free medium containing EGTA 1 mM. The presence of tetrodotoxin 2 microM did not alter the effect of neurotensin 10 microM. On the other hand, neurotensin did not affect the uptake of [3H]DA into the striatal slices. In additional experiments, we confirmed that the KCl-induced release of DA in the nucleus accumbens was also potentiated b neurotensin. These results suggest that neurotensin has a direct effect on the central DA nerve terminals and releases DA in a Ca2+-dependent manner.