The effects of depolarizing agents and neuropeptides on dopamine release from striatal synaptosomes

Synaptosomes (isolated nerve endings) from rat corpus striatum responded to several depolarizing agents by releasing dopamine. Among these agents were KCl, glutamic acid, ouabain, and veratrine. Substance P hexapeptide (SP6) also caused dopamine release, but the magnitude of this effect was small and variable. A number of other neuropeptides (cholecystokinin 1–8, des‐Tyr‐γ‐endorphin, Leu 5 ‐β‐endorphin and substance P) did not alter dopamine release. SP6‐induced dopamine release may result from substance P receptor‐induced depolarization; however, the lack of robustness of the response in this preparation makes it unsuitable for studying agonists and antagonists of substance P.