An Assessment of the Addiction Potential of the Opioid Associated with Milk

¹ Department of Psychology, Rensselaer Polytechnic Institute, Troy, NY 12180-3590

Eighty-four male rats were tested to determine their preference for one 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 ß-casomorphin, a standard dose of morphine, or placebo. Subsequently, rats were tested for place preferences. No evidence emerged indicating that injections of ß-casomorphin conditioned a place preference, but evidence indicated that morphine conditioned a place preference. Consequently, systemically administered ß-casomorphin has very limited or no reinforcing properties similar to those of morphine. Ingestion of milk products containing ß-casomorphin is not likely to become the focus of an addiction.

Key Words: ßbeta;-casomorphin • conditioned place preference • addiction potential • opioids

Submitted on February 22, 1993
Accepted on October 14, 1993

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