Naltrexone-induced Reduction of Ethanol Preference in Drosophila melanogaster

Alcoholism, also called alcohol dependence or alcohol addiction, is a complex disorder characterized by persistent and intense alcohol-seeking, resulting in a loss of control over drinking, compulsion to drink and the development of tolerance and dependence. Alcohol consumption enhances the endogenous opioid activity. Several animal studies conducted in rats evidenced a role of opioid system in mediating alcoholism (1). Naltrexone is an opiate antagonist currently used for the treatment of alcoholism and opioid dependence in humans and it is believed to block opiate receptors which may be involved in the addictive processes. The aim of this work is to determine whether the DM model can be used for screening for the treatment of alcoholism. The well-established CAFE assay (2) was used to measure DM preference for ethanol containing food over normal food. Flies are fed through capillary tubes loaded with liquid food or liquid food + 15%ethanol. The food consumption by the flies is quantified by measuring the lowering of the meniscus on the capillary tubes.

Our results confirmed that flies previously exposed to ethanol develop a preference for alcohol containing food. The drug Naltrexone was able to reverse the preference for ethanol and produced a repulsion of ethanol containing food.

Our findings confirm that Drosophila is a useful model to study ethanol induced behavioural changes and also demonstrate that the preference assay can be used to screen compounds such as naltrexone that can be used clinically for the treatment of addiction. It would be of interest to further investigate the nature of the opiate system in Drosophila as it could be possible that Naltrexone is operating in the flies through a different mechanism that could also be present in mammals.

(1) Hubbell CL et al. (1986). Alcohol 3 1: 39-54.

(2) William W et al. (2007). Proc Natl Acad Sci U S A 104(20): 8253–8256.