Food restriction enhances peak corticosterone levels, cocaine-induced locomotor activity, and DeltaFosB expression in the nucleus accumbens of the rat.

Chronic stress has been known to potentiate addictive behaviours in both human addicts and experimental animals. In the present study, chronic mild food restriction was used as a stressor to investigate its effect on the locomotor simulant effects of cocaine as well as FosB expression in the nucleus accumbens and caudate putamen. Chronic mild food restriction enhanced the locomotor response to the first cocaine injection, such that chronically food restricted animals showed a significant increase in activity upon an initial administration of 15 mg/kg of cocaine, an effect which only became apparent in control animals after repeated injections. Food restriction also increased expression of the 35-37 kDa isoforms of DeltaFosB compared to free-fed rats. DeltaFosB proteins have been previously implicated in the rewarding effects of drugs of abuse and therefore their upregulation by the prolonged stress of food restriction suggests a possible mechanism for the enhancement of addictive behaviours by stress.