Altered caudate nucleus field potentials following sustained stimulation to different substantia nigra regions

Evoked potential recording techniques were used as a physiological tool for electrode placement into the substantia nigra pars compacta (SNpc). It was found that when the recording electrodes were implanted at the level of the caudate nucleus (CN), typical patterns were obtained only when the stimulation electrode was located in the SNpc. When the stimulation electrode was fixed in the SNpc and four electrodes were simultaneously used to record depth profile from the caudate nucleus and the septum, the typical responses following stimulation were obtained only when electrodes were within the CN head. High frequency stimulation of the SNpc, which is known to alter dopamine content within the CN, caused a reversible diminution of responses in CN for 5-10 min. This observation was discussed in terms of terminal transmitter depletion.