Influence of peptides on (3)H-dopamine release from superfused rat striatal slices

The effects of nine neuropeptides on the uptake and release of (3)H-dopamine (DA) were studied in slices of rat striatum. Superfusion of preloaded slices at room temperature gave a steady release of (3)H-DA after 30 min. Repetitive depolarisation with 20 mM K(+) evoked pronounced, calcium-dependent releases of (3)H-DA which declined exponentially. Substance P (SP), neurotensin and somatostatin all actively released (3)H-DA, whilst cholecystokinin octapeptide (CCK), luteinising hormone releasing hormone (LHRH), thyrotrophin releasing hormone (TRH), adrenocorticotrophin (ACTH), vasopressin and oxytocin were without effect on spontaneous (3)H-DA efflux. The effects of the peptides on K(+)-induced (3)H-DA overflow were more varied; neurotensin, TRH and ACTH had no effect, whereas CCK, somatostatin and LHRH potentiated and SP, vasopressin and oxytocin attenuated (3)H-DA release. None of the peptides altered the uptake of (3)H-DA at the concentrations which modified its release (0.1-10 ?M). It is suggested that modulating DA release may be fundamental to the central actions of these substances in the intact animal.