Meal-stimulated increased concentrations of beta-endorphin in the hypothalamus of Zucker obese and lean rats

Increased opiate peptide concentrations in brain and plasma have been associated with increased feeding. The role of beta-endorphin in the control of food intake and obesity was examined by measuring concentrations in hypothalamus, pituitary and plasma of hungry (6-hr fasted) and satiated (5 min after a meal) Zucker obese and lean rats. beta-Endorphin concentrations (1) in satiated vs. hungry rats were increased in the VMH (90 vs. 79 pg/mg tissue, p less than 0.05) and decreased in the supraoptic nucleus (65 vs. 78 pg/mg tissue, p less than 0.05), (2) in obese vs. lean rats were decreased in the VMH (79 vs. 90 pg/mg tissue, p less than 0.05) and (3) in female vs. male rats were increased in the anterior hypothalamus (123 vs. 59 pg/mg tissue, p less than 0.01) and VMH (90 vs. 79 pg/mg tissue, p less than 0.05). Analysis of a phenotype by feeding condition interaction revealed that obese but not lean rats had higher beta-endorphin concentrations in the satiated vs. hunger condition. However, plasma beta-endorphin concentrations did not differ with feeding condition, phenotype or sex. Intermediate and posterior but not anterior pituitary beta-endorphin concentrations were lower in obese than lean rats. Thus, there is some evidence for a relationship between beta-endorphin concentration and feeding in the hypothalamus, but beta-endorphin concentrations in plasma do not appear to be influenced by feeding condition or obesity.