Effects of chronic naltrexone treatment in rats on place preference and locomotor activation after acute administration of cocaethylene or ethanol plus cocaine

Abstract 

When cocaine and ethanol are taken together a cocaine metabolite called cocaethylene is produced. Investigators have determined that cocaine, ethanol, and cocaethylene all produce a conditioned place preference when administered intraperitoneally. On the basis of the moderate success of naltrexone at attenuating the rewarding effects of ethanol and cocaine administered independently, we examined the ability of chronic naltrexone treatment (administered by means of subcutaneous implant across 6 days) to reduce the preference and motor-stimulating effects resulting from intraperitoneal administration of cocaethylene (Experiment 1) and the co-administration of ethanol with cocaine (Experiment 2) in outbred rats. Results demonstrated naltrexone modestly reduced conditioned place preference for cocaethylene but had no effect on the locomotor stimulation resulting from cocaethylene administration. Naltrexone failed to decrease the preference for the chamber paired with co-administration of ethanol and cocaine and did not change the degree of locomotor activation produced by these drugs. These results support the suggestion that naltrexone as a pharmacotherapy to treat co-abuse of ethanol and cocaine in human beings may have limited benefits.

Keywords: CPP, Motor-stimulating effects, Co-abuse