Abstract
Release of α-MSH from male rat hypothalamic slices was studied using a sensitive bioassay (1–2 pg). Addition of 60 mM KC1 to superfusion medium resulted in a twofold increase in α-MSH release compared to spontaneous release. Both spontaneous and potassium- induced release were inhibited in a dose-response manner by the tripeptide Pro-Leu-Gly-NH 2 (PLG, or MIF-1); 0.04 μg to 1 μg PLG inhibited the α-MSH release but the lowest dose demonstrated a greater inhibitory effect; high concentrations of PLG, on the other hand, did not modify either spontaneous or potassium-evoked α-MSH release from the slices. Contrarily, DA did not modify either spontaneous or potassium- induced α-MSH release at any of the doses tested. These findings demonstrate that the inhibitory behavior of PLG and DA in the central nervous system (CNS) differs from their behavior towards α-MSH release in the pituitary. This suggests differences in the regulation of α-MSH release from the pituitary and the CNS.
Published Version
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