AN ASSESSMENT OF THE ADDICTION POTENTIAL OF THE OPIOID ASSOCIATED WITH MILK

Eighty-four male rats were tested to determine their preference for on e of two distinctive places in an experimental space. After an initial determination of place preference, rats were assigned to six groups. They were then subjected to procedures to condition a place preference using doses of beta-casomorphin, a standard dose of morphine, or plac ebo. Subsequently, rats were tested for place preferences. No evidence emerged indicating that injections of beta-casomorphin conditioned a place preference, but evidence indicated that morphine conditioned a p lace preference. Consequently, systemically administered beta-casomorp hin has very limited or no reinforcing properties similar to those of morphine. Ingestion of milk products containing beta-casomorphin is no t likely to become the focus of an addiction.