Neuropeptide Y applied in vitro can block the phase shifts induced by light in vivo

The effect of high frequency stimulation (HFS) of the subthalamic nucleus (STN) on the spontaneous activity of substantia nigra pars compacta (SNc) dopaminergic neurons was investigated in normal rats and in rats with globus pallidus (GP) lesions. In normal rats, the spontaneous activity of SNc neurons did not significantly differ from that of rats with GP lesions (4.2+/-2.2 versus 4.4+/-2.6 spikes/s). STN-HFS induced an increase of firing rate in the majority of tested cells in normal (76%) and GP-lesioned rats (73%) with an after-effect of 34.4+/-3.4 and 33.2+/-3.1 s, respectively. These results demonstrate that STN-HFS influences the activity of the SNc dopaminergic neurons by increasing their firing rate and that this increase of activity is independent of the globus pallidus.