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Changes in the firing activity of serotonergic neurons in the dorsal raphe nucleus in a rat model of Parkinson's disease

Zhang Qiaojun, Gao Rui, Liu Jian, Liu Yaping, Wang Shuang

Department of Neurology, the Second Affiliated Hospital, School of Medicine, Xi'an Jiaotong University.Xi'an 710004,Shaanxi;China

Abstract

In the present study, changes in the neuronal activity of serotonergic neurons in the dorsal raphe nucleus (DRN) and the effect of the selective 5-HT_(1A) receptor antagonist WAY-100635 in a rat model of Parkinson's disease (PD) were investigated by using extracellular single unit recording. Rat model of PD was produced by microinjection of 6-hydroxydopamine (6-OHDA) into the substantia nigra pars compacta on the right side of the brain. The results showed that the mean spontaneous firing rate of DRN serotonergic neurons in the control and 6-OHDA-lesioned rats were (1.76+0.11) spikes/s (n=24) and (2.43+0.17) spikes/s (n=21),respectively. The firing rate of serotonergic neurons in 6-OHDA-lesioned rats was significantly higher than that in the control rats (P<0.001). In the control rats, 92% (22/24) of the neurons fired regularly and 8% (2/24) fired in bursts. In rats with 6-OHDA lesions, 9%(2/21) of neurons fired regularly, 43% (9/21) exhibited irregular pattern and 48% (10/21) fired in bursts. The percentage of DRN serotonergic neurons firing in bursts was obviously higher in 6-OHDA-lesioned rats than that in the control rats (P<0.001). Local injection of WAY-100635 (3 μg in 200 nL) into the DRN significantly increased the firing rate of serotonergic neurons with no change in firing pattern in the control rats (n=19, P<0.002), but did not change the firing rate and firing pattern of serotonergic neurons in 6-OHDA-lesioned rats (n=17, P>0.05). These results suggest the dysfunction of 5-HT_(1A) receptor in 6-OHDA-lesioned rats and the involvement of the DRN in the pathophysiological mechanism of PD.

Key words: Dorsal raphe nucleus;5-HT_(1A) receptor;WAY-100635;Parkinson's disease

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Citing This Article:

Zhang Qiaojun, Gao Rui, Liu Jian, Liu Yaping, Wang Shuang. Changes in the firing activity of serotonergic neurons in the dorsal raphe nucleus in a rat model of Parkinson's disease. Acta Physiol Sin 2007; 59 (2): 183-189 (in Chinese with English abstract).