Dopaminergic inhibition of alpha-melanocyte-stimulating hormone release from superfused slices of the rat hypothalamus.

The dopamine agonist apomorphine (10(-6) M) significantly reduced the 50 mM K+-stimulated, Ca2+-dependent release of immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) from superfused slices of rat hypothalamus but did not alter baseline peptide release. Flupenthixol (10(-6) M), a dopamine receptor antagonist, significantly increased both basal and 50 mM K+-stimulated alpha-MSH release, possibly via blockade of inhibition caused by endogenous dopamine release. The latter increases were Ca2+-dependent and were inhibited by 10(-6) M apomorphine.