Activation of hypothalamic beta-endorphin pools by reward induced by highly palatable food.
Experiments were performed to find biochemical evidence of an activation of endogenous opiate peptides in the brain by incentive reward. A method used to estimate specific in vivo opiate binding in rats using the labelled opiate agonist, 3H-etorphine, indicated a considerable reduction in opiate binding exclusively in the hypothalamus of non-deprived animals given a highly palatable food to eat for 20 min. Radioimmunoassay of the hypothalamus of rats under similar conditions found a pronounced drop in the concentration of beta-endorphin, but not in dynorphin, in the hypothalamus, indicating a release and breakdown of beta-endorphin. Therefore, the reduction in opiate binding in the hypothalamus may at least be partially explained by an occupation of opiate receptors by beta-endorphin, causing a reduced availability of receptors to etorphine. A possible role of hypothalamic beta-endorphin in the facilitation of reward pathways in the brain is discussed.
D000818:Animals; D004326:Drinking; D004399:Dynorphins; D004435:Eating; D004723:Endorphins / Q000378:metabolism*; D005048:Etorphine / Q000378:metabolism; D007031:Hypothalamus / Q000502:physiology*; D008297:Male; D009042:Motivation / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism; D012201:Reward; D013649:Taste / Q000502:physiology*; D001615:beta-Endorphin
D004723:Endorphins; D011957:Receptors, Opioid; D005048:Etorphine; D001615:beta-Endorphin; D004399:Dynorphins