Neurotensin-induced release of endogenous noradrenaline from rat hypothalamic slices.

Effects of neurotensin on the release of endogenous noradrenaline (NA) from rat hypothalamic slices were investigated. NA was extracted by the aluminum adsorption method, and assayed electrochemically by high-performance liquid chromatography. Neurotensin (30-300 microM) enhanced the release of NA, in a dose dependent manner. Neurotensin 2 and 10 microM, doses without effect on the spontaneous release of NA, potentiated the potassium-induced release of this amine. Neurotensin 100 microM repetitively added to tbe medium at 40 min intervals induced a consistent and reproducible increase in the release of NA. This neurotensin-induced release of NA was completely abolished in calcium free medium containing EGTA 1 mM. The presence of tetrodotoxin 2 microM did not alter the effect of neurotensin 100 microM. These results of in vitro investigations suggest that neurotensin has a direct effect on NA nerve terminals in the hypothalamus and releases NA, in a Ca++-dependent manner.