The role of central dopaminergic systems in the behavioral effects of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH

Abstract

In the present study the role of the central dopaminergic systems in the behavioral action of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH was investigated. The heptapeptide inhibited the extinction of active avoidance behavior if the treatment was performed intracerebroventricularly (icv) in a dose of 1 μg, but was ineffective in a dose of 0.1 μg. If the peptide was injected into the nucleus accumbens septi (NAS) in a dose of 1 μg, 0.1 μg or 0.01 μg it inhibited the extinction, but in the latter dose its effect was only a short one. H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH in a dose of 1 μg, 10 μg or 20 μg (icv) did not influence the turning activity of unilateral substantia nigra (USN)-lesioned animals. These results suggest that the NAS plays an important role in the behavioral action of H-Phe-Ile-Tyr-His-Ser-Tyr-Lys-OH and the heptapeptide has no direct dopamine receptor stimulatory or dopamine-releasing effect in the striatum.