Resumen:
elease of alpha-MSH from male rat hypothalamic slices was studied using
a sensitive bioassay (1-2 pg). Addition of 60 mM KCl to superfusion
medium resulted in a twofold increase in alpha-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-NH2
(PLG, or MIF-1); 0.04 microgram to 1 microgram PLG inhibited the
alpha-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 alpha-MSH release from the
slices. Contrarily, DA did not modify either spontaneous or potassium-
induced alpha-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 alpha-MSH
release in the pituitary. This suggests differences in the regulation