Objective To investigate changes in the firing activities of nucleus accumbens (NAc)neurons and their response to 5-HT7 receptor stimulation in a rat model of Parkinson’s disease (PD).Methods The firing activities and response of NAc neurons to 5-HT7 receptor agonist in PD rats were recorded by in vivo electroneurophysiology and neuropharmacology and then were compared with those in the sham group.Results The mean firing rate of NAc neurons was (5.46 ±0.88)Hz in the sham rats and (3.77 ±0.48)Hz in the PD rats. The firing rate of NAc neurons increased significantly compared with that in the sham rats (P <0.05).In PD rats, 65% of NAc neurons fired in bursts and 35% fired irregularly.However,in the sham rats,57.5% of NAc neurons fired in bursts and 42.5% fired irregularly.There was no significant difference in the firing pattern of NAc neurons between the PD and sham rats (P >0.05 ).Systemic administration of 5-HT7 receptor agonist AS1 9 increased the firing rate of NAc neurons in the sham and PD rats.This excitation was significant at a high dose of 1 60 μg/kg for NAc neurons in the sham rats (P <0.05).However,the excitation produced by AS1 9 was significant at a high dose of 80 μg/kg in PD rats (P <0.05).The cumulative dose-produced excitation in the PD rats was lower than that in the sham rats.The effects induced by AS1 9 were reversed by the 5-HT7 receptor antagonist SB269970 in both groups.Conclusion The reinforced firing activity of NAc neurons might be mediated by 5-HT7 receptor in the neurons of PD rats.