EFFECT OF MORPHINE OR ALCOHOL TREATMENT ON THE BIOSYNTHESIS OF β-ENDORPHIN BY THE NEUROINTERMEDIATE LOBE

Rats were rendered tolerant to either morphine or alcohol, by 21 day drug treatment. Morphine treatment induced a decrease in the degree of incorporation of (3H)-phenylalanine into pro-opiomelanocortin (POMC), β-lipotropin (β-LPH) and β-endorphin (β-EP) associated with a decrease in the content of β-endorphin like immunoreactivity (β-EPLI) in the neurointermediate lobe (NIL) extract and in the incubation medium. Alcohol induced an increase in the degree of incorporation of (3H)-phenylalanine into POMC, β-LPH and β-EP and an increase in the β-EPLI content in the incubation medium but not in the NIL extract. These results indicate an effect of chronic morphine and alcohol treatment on the biosynthesis and release of β-EP by the rat NIL.