Involvement of 5-HT3 receptors in the nucleus accumbens in the potentiation of cocaine-induced behaviours in the rat

Abstract

1. The present study investigated the central effects of the selective serotonin reuptake inhibitor (SSRI) fluoxetine and the role of 5-hydroxytryptamine3 (5-HT3) receptors in the core of the nucleus accumbens (NAc) on cocaine-induced behavioural changes in rats. 2. The 5-HT3 receptor antagonist ondansetron (1 or 10 ng) was microinjected bilaterally into the core of the NAc 60 min prior to peripheral cocaine (15 mg kg-1, i.p.) administration followed by the assessment of locomotor activity, rearing activity and head bobs. Both doses of ondansetron attenuated cocaine's stimulatory effect on behaviours. 3. Fluoxetine (0.05 or 5 μg) microinjected bilaterally into the core of the NAc 30 min before peripheral administration of cocaine produced dose-dependent biphasic effects on cocaine-induced behaviours. Intra-NAc administration of 0.05 μg fluoxetine resulted in a potentiation of cocaine-induced behaviours, while the higher dose of the SSRI (5 μg) attenuated the stimulant effect of cocaine on behaviours. 4. To investigate a possible involvement of 5-HT3 receptors in fluoxetine's facilitatory action, ondansetron (10 ng) was microinjected 30 min prior to fluoxetine (0.05 μg), which resulted in a significant attenuation of the facilitatory effect of fluoxetine on cocaine-induced behaviours. 5. Thus, 5-HT3 receptors in the core of the NAc appear to mediate stimulatory effects on cocaine-induced locomotor activity, rears and head bobs, whereas the attenuation of cocaine-induced behaviours by fluoxetine at the higher dose, suggests the involvement of a different 5-HT receptor subtype.