Figure 1.

Slice orientation and physiology of SNr neurons. A, Parasagittal slices were taken at 15° from the midline. Dotted line shows the approximate location of the slice. B, Compound photomicrograph showing the position of the electrodes for striatal stimulation (electrode tips visible) and pallidal stimulation. Also shown is the location of the recording electrode in the SNr (patch electrode is faintly visible). Scale bar, 1 mm. C, A typical action potential recorded from the GABAergic neurons of the SNr and the dopaminergic neurons of the SNc. D, Spike width and tonic spiking frequency plotted against each other showing the distinctive firing patterns of two classes of nigral neurons. All neurons with a GABAergic phenotype were recorded randomly from the SNr. Dopaminergic neurons could only be recorded when pipettes were positioned in the SNc.