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

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