Objective To study the effect of serotonergic efferent projection of the dorsal raphe nucleus(DRN)on the activity of substantia nigra pars compacta(SNc)and ventral tegmenta area(VTA)dopaminergic neurons after lesioning of the DRN by the neurotoxin 5,7-drhydroxytryptamine(5,7-DHT)in rat.Methods The changes in the firing rate and firing pattern of SNc and VTA dopaminergic neurons were observed with extracellular recording in control and the lesioned rats.Results The results showed that the mean firing rates of the fast-firing dopaminergic neurons of the SNc in control and the lesioned rats were(5.34±0.13)Hz(n=23)and(7.13±0.49)Hz(n=37),respectively.The mean firing rate of the fast-firing dopaminergic neurons of the SNc in the lesioned rats was significantly increased when compared to that of control rats(P<0.01),while the mean firing rate of the slow-firing dopaminergic neurons of the SNc did not change.The mean firing rates of dopaminergic neurons of the VTA in control and the lesioned rats were(5.27±0.38)Hz(n=35)and(3.6±0.2)Hz(n=52),respectively.Lesioning of the DRN induced a significant decrease in the mean firing rate of dopaminergic neurons of the VTA.The firing pattern of SNc and VTA dopaminergic neurons changed towards a more bursting or irrgular firing after the lesioning.Conclusion These data suggest that the serotonergic efferent projections of the DRN significantly affect the activity of SNc and VTA dopaminergic neurons. Objective To study the effect of serotonergic efferent projection of the dorsal raphe nucleus (DRN) on the activity of substantia nigra pars compacta (SNc) and ventral tegmenta area (VTA) dopaminergic neurons after lesioning of the DRN by the neurotoxin 5,7-drhydroxytryptamine (5,7-DHT) in rat. Methods The changes in the firing rate and firing pattern of SNc and VTA dopaminergic neurons were observed with extracellular recording in control and the lesioned rats. Results The results showed that the mean firing rates of the fast -firing dopaminergic neurons of the SNc in control and the lesioned rats were (5.34 ± 0.13) Hz (n = 23) and (7.13 ± 0.49) Hz (n = 37), respectively.The mean firing rate of the fast-firing dopaminergic neurons of the SNc in the lesioned rats was significantly increased when compared to that of control rats (P <0.01), while the mean firing rate of the slow-firing dopaminergic neurons of the SNc did not change. The mean firing rates of dopaminergic neurons of the VTA in control and the lesioned rats were (5.27 ± 0.38) Hz (n = 35) and (3.6 ± 0.2) Hz (n = 52), respectively. Lesioning of the DRN induced a significant decrease in the mean firing rate of dopaminergic neurons of the VTA. pattern of SNc and VTA dopaminergic neurons changed towards a more bursting or irrgular firing after the lesioning. Conclusions These data suggest that the serotonergic efferent projections of the DRN significantly affect the activity of SNc and VTA dopaminergic neurons.