Blockade of cue- and drug-induced reinstatement of morphine-induced conditioned place preference with intermittent sucrose intake.

Sucrose intake has been suggested to alter the expression of morphine-induced conditioned place preference (CPP). To date, the potential effects of sucrose intake on the extinction and drug-induced reinstatement of CPP have not been determined. In the present study, sucrose solution (15%) was given prior to, during, and following the acquisition of morphine-induced CPP. Place preference was subsequently assessed during expression, extinction, and morphine-induced reinstatement. The results showed that the sucrose solution given prior to place conditioning training transiently suppressed the expression of morphine CPP. Sucrose solution given during place conditioning training had no effects on the expression, extinction, and reinstatement of CPP. When the sucrose solution was given following the acquisition of morphine CPP, the extinction of morphine CPP was accelerated, and morphine-induced reinstatement was profoundly inhibited. The above results demonstrated that sucrose intake could differentially affect the expression, extinction, and reinstatement of morphine-induced CPP, depending on the interference schedules. Our findings suggest that offering non-drug rewards could be a valuable approach to maintain abstinence and preventing relapse in drug addicts.