Infusion of a D-1 receptor agonist into the nucleus accumbens enhances cocaine-induced behavioural sensitization

THE present study was designed to evaluate the effect of dopamine (DA) D-1receptor activation in the nucleus accumbens (NAC) on the locomotor sensitizing effects of repeated intra-accumbens (intra-NAC) infusions of cocaine. Repeated infusion of cocaine (10 mu g/0.5 mu l daily for 2 days) resulted in an enhanced locomotor response to a subsequent intra-NAC and systemic (i.p.) challenging dose of the psychostimulant. Pretreatment with the selective D-l agonist SK&F82958 (1.0 mu g) markedly enhanced the sensitizing effects of both intra-NAC and systemic cocaine. The effect of SK&F82958 was completely blocked by systemic administration of the D-1antagonist SCH23390 (0.1 mg/kg, i.p.). These data give further support to the idea that activation of D-1 receptors plays an important role in the induction of locomotor sensitization and show that the NAC may, in fact, be an anatomical locus of initiation of behavioural sensitization. (C) 1998 Rapid Science Ltd.