ABSTRACT
Objective: To study the changes in neuronal activity of the zone incerta (ZI) following the unilateral lesion of the nigrostriatal pathway. Methods: Electrophysiological recordings of ZI neurons were made in normal rats and in two groups of rats at different time intervals after injection of 6-hydrodopamine (6-OHDA) into the pars compacta of substantia nigra by extracellular recording in vivo. Results: The results showed a significant increase in the mean firing rate of ZI during the second and fourth weeks after 6-OHDA lesion [n = 32, (3.6±2) Hz, Plt;0.001; n = 35, (9.3±6.6) Hz, P<0.001, respectively] compared to that of normal rats [n = 39, (9.2±5.2) Hz]. However, no significant change was observed between two groups of 6-OHDA-lesioned rats. With regard to firing pattern, 7.7% (3/39) of ZI neurons discharged regularly, 82.1% (32/39) irregularly and 10.3% (4/39) in bursts in normal rats. During the second week after 6-OHDA lesion, the regular, irregular and bursting firing neurons recorded in the ZI were 9.4% (3/32), 59.4% (19/32) and 31.3% (10/32), and during fourth week, the regular, irregular and bursting firing neurons were 14.3% (5/35) , 57.1% (20/35) and 28.6% (10/35), respectively. The firing pattern of the neurons in the three different groups did not change significantly. Conclusion: These results suggest that the firing rate of ZI neurons in 6-OHDA-lesioned rats is increased significantly, which may contribute to the pathophysiology of Parkinson's disease.
ABSTRACT
Objective To study the changes in neuronal activity of the zone incerta (ZI) following the unilateral lesion of the nigrostriatal pathway. Methods Eiectrophysiological recordings of ZI neurons were made in normal rats and in two groups of rats at different time intervals after injection of 6-hydrodopamine (6-OHDA) into the pars compacta of snbstantia nigra by extracellular recording in vivo. Results The results showed a significant increase in the mean firing rate of ZI during the second and fourth weeks after 6-OHDA lesion [-n=32, (3.6±2. 2)Hz, P<0.001; n=35, (9.3±6.6)Hz, P<0. 001, respectively] compared to that of normal rats [n=39, (9.2±5.2)Hz]. However, no significant change was observed between two groups of 6-OHDA-lesioned rats. With regard to firing pattern, 7.7%(3/39) of ZI neurons discharged regularly, 82.1% (32/39) irregularly and 10. 3% (4/39) in bursts in normal rats. During the second week after 6-OHDA lesion, the regular, irregular and bursting firing neurons recorded in the ZI were 9.4% (3/32), 59. 4% (19/32) and 31.3% (10/32), and during fourth week, the regular, irregular and bursting firing neurons were 14.3% (5/35), 57.1% (20/35) and 28. 6% (10/35), respectively. The firing pattern of the neurons in the three different groups did not change significantly. Conclusion These results suggest that the firing rate of ZI neurons in 6-OHDA-lesioned rats is increased significantly, which may contribute to the pathophysiology of Parkinson's disease.
ABSTRACT
Objective To study the effect of serotonergic efferent projection of the dorsal rophe nucleus (DRN) on the activity of substantia nigro 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 rot. Methods The changes in the firing rote and firing pattern of SNc and VTA dopaminergic neurons were observed with extrocellular recording in control and the lesioned rats. Results The results showed that the mean firing rotes of the fast-firing dopaminergic neurons of the SNc in control and the lesioned rots were (5.34±0. 13 ) Hz (n = 23 ) and ( 7.13±0. 49 ) Hz (n=37), respectively. The mean firing rote of the fast-firing dopaminergic neurons of the SNc in the lesioned rats was significantly increased when compared to that of control rots (P<0.01), while the mean firing rote of the slow-firing dopaminergic neurons of the SNc did not change. The mean firing rotes of dopaminergic neurons of the VTA in control and the lesioned rots 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 rote 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. Conlusion These data suggest that the serotonergic efferent projections of the DRN significantly affect the activity of SNe and VTA dopaminergic neurons.