Our previous study showed that chemical stimulation of the lateral hypothalamus (LH) by carbachol can produce conditioned place preference (CPP) in rats. Also, it has been indicated that orexin activates the mesolimbic dopamine projecting neurons to the nucleus accumbens (NAc) and promotes the development of reward in rodents. Therefore, in this study, we tried to determine the role of intra-accumbal D1 and D2 dopamine receptors in the development (acquisition) of reward-related behaviors induced by chemical stimulation of the LH. Eighty-eight adult male Wistar rats were unilaterally implanted by two separate cannulae into the LH and NAc. For chemical stimulation of LH, carbachol (250nmol/0.5μl saline) was microinjected once daily during 3-days conditioning phase (acquisition period) of CPP paradigm. In the next experiments, different doses of D1 receptor antagonist, SCH23390 (0.25, 1 and 4μg/0.5μl saline) or sulpiride (0.25, 1 and 4μg/0.5μl DMSO) as a D2 receptor antagonist were unilaterally microinjected into the NAc, 5min prior to LH stimulation. One-way ANOVA showed that intra-accumbal administration of SCH23390 or sulpiride can decrease the development of LH stimulation-induced CPP in the rats. However, this decrease is more effective after blockade of the D2 dopamine receptor in the NAc. It seems that the dopaminergic system in this area is involved in place preference induced by LH stimulation.
Keywords: Conditioned place preference; Dopamine receptor; Lateral hypothalamus; Nucleus accumbens; Rat; Reward.
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