Experimental Alterations of Endorphin Levels in Rat Pituitary

Abstract

Endorphin (END) levels in rat pituitary were assessed with the opiate receptor binding assay. Procedures reported to alter hormone secretion from END-rich intermediate or anterior lobes were examined for their effect on END content. Lesions of the paraventricular nucleus (PVN) had no significant effect on END content. Ingestion of 2% NaCl reduced END levels in a significant majority of the animals. Suckling, a natural physiological stimulus, significantly elevated neurointermediate lobe END. Footshock and immobilization each evoked 40--50% reductions in anterior lobe END content. Pituitary ENDs are thus affected by many of the same stimuli that also promote release of a number of peptide hormones derived from the same biosynthetic precursor. However, separate mechanisms likely exist for control of secretion of these peptides from anterior and neurointermediate lobe.