Delta Sleep Inducing Peptide Inhibits Somatostatin Release via a Dopaminergic Mechanism1

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Abstract
Delta sleep inducing peptide (DSIP) has been localized in the rat hypothalamus. The effect of DSIP on somatostatin (SRIF) release from the median eminence of the hypothalamus was evaluated in male and female rats in an in vitro incubation system. DSIP inhibited SRIF release in a dose-dependent manner. The median eminences from females were less sensitive to the inhibitory action of DSIP than those of males; however, in both sexes the maximum effect was observed at a concentration of 10–8M DSIP. This effect was blocked by addition of pimozide at a concentration of 10–6M. Pimozide alone had no effect on SRIF release. These findings lead to the conclusion that DSIP inhibits SRIF release via a dopaminergic mechanism.