The ability of morphine, leu-enkephalin and β-endorphin to antagonize the binding of 3H-spiroperidol to bovine anterior pituitary membranes was studied. All three drugs were virtually inactive despite their ability to stimulate prolactin secretion in vivo and the reported ability of morphine to antagonize the inhibitory effect of dopamine on prolactin release from rat hemi-pituitaries. These results suggest that opiates do not produce their direct effect on prolactin secreation at the pituitary level through an effect on the 3H-spiroperidol binding site. The opiates may antagonize the effect of dopamine at a component of the dopamine receptor which is independent of the 3H-spiroperidol binding site, or the opiates may stimulate prolactin secretion by an effect on the lactotrophes which is independent of dopamine.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)