Abstract

Dopamine (DA) has been shown to play a significant role in drug reinforcement and the reinstatement of drug seeking due to priming or drug cue presentations. However, DA is suggested to play a limited role in stress-induced reinstatement, as modelled by footshock-induced reinstatement. Here the role of DA in acute food deprivation (FD)-induced reinstatement of heroin seeking, an alternative model of stress-induced reinstatement, is investigated. Rats were trained to self-administer heroin (0.05 mg/kg/infusion) for 10 days (days 1-5: 3 X 3 h sessions; days 6-10: 1 X 3 h session). Heroin-seeking behavior was extinguished by removing the drug. Following extinction, rats were tested for 48 h FD-induced reinstatement while pretreated with specific DA receptor antagonists. An attenuation of drug seeking was seen in rats given the high dose (10.0 og/kg) of the DA D 1 receptor antagonist, SCH 23390; but, not the low dose of this antagonist (5.0 og/kg) or the DA D 2 and D 3 receptor antagonists raclopride (50.0 and 100.0 og/kg) and NGB 2904 (0.1 and 5.0 mg/kg). The lack of effect for raclopride on FD-induced reinstatement was validated by demonstrating a role for this antagonist on cue-induced reinstatement of extinguished heroin seeking. These results suggest that FD-induced reinstatement may be mediated, at least in part, by the activation of the DA D 1 receptor. Moreover, since systemic injection of SCH 23390 has previously been shown to have no effect on footshock-induced reinstatement the current study suggests that DA transmission may play a differential role in footshock and FD-induced reinstatement.