Effects of acute opiate-peptide administration on pro-opiomelanocortin cells of the intermediate lobe of the rat pituitary

Abstract

The effects of acute injections of synthetic opiate peptides into the lateral cerebral ventricle of young adult male rats on cells of the intermediate lobe of the pituitary were studied. Met-enkephalin (100/micrograms) injected into anesthetized rats, or 20 micrograms beta-endorphin administered via a previously implanted cannula to unanesthetized animals, will lead to cell degranulation and often to expanded Golgi zones and prominent regions of rough endoplasmic reticulum in secretory cells when tissue is fixed 45--60 min after peptide administration. Treatment of animals with the opiate antagonist naloxone hydrochloride prior to enkephalin injection appeared to prevent the cellular changes elicited with peptide alone. Observations suggest that opiate peptides administered to the cerebrospinal fluid may stimulate release of pro-opiomelanocortin-peptide from pituitary cells.

Roles of α-neurexins in synapse stabilization and Ca²⁺-dependent endocrine secretion

“…This may be explained by the ability of endocrine cells to undergo rapid structural changes depending on the state of their secretory activity. For example, treatment with dopaminergic drugs, stress and other conditions which affect peptide secretion from melanotrophs were reported to cause considerable alterations of melanotroph morphology in rodents (Back and Rechardt 1985;Chronwall et al 1988;Moriarty et al 1975;Saland 1978;Saland et al 1982;Santolaya and Ciocca 1981).…”