DOPAMINE REGULATES CANINE PLASMA β-ENDORPHIN-IMMUNOREACTIVITY LEVELS

Abstract
Intravenous administration of the dopamine antagonists domperidone and metoclopramide elevates canine plasma β-endorphin immunoreactivity. Pretreatment with dopamine, but not dexamethasone, inhibits this effect. Sephadex G-50 chromatography shows that this response is due to β-endorphin-like peptides, not β-lipotropin. These findings indicate that pituitary β-endorphin secretion is tonically inhibited by dopamine and suggest that the intermediate lobe is the source of this secretion.