POST-STIMULATION EXCITABILITY OF DIENCEPHALIC SELF-STIMULATION NEURONS

We used the double-pulse technique with moveable electrodes to estimat e the refractory periods of self-stimulation neurons within the rat's dorsal diencephalon and surrounding areas. Refractory period estimates varied substantially depending on the site of stimulation. For some s ites, recovery from refractoriness was noted at post-stimulation inter vals as short as 0.5 ms, an estimate similar to that reported for the MFB axis and the dorsal raphe and periaqueductal grey. The longest rec overy intervals were similar to those reported for the prefrontal cort ex, caudate, and substantia nigra. Step-like recovery (believed to ind icate the presence of neural populations with non overlapping refracto ry periods) was also noted in several sites. The large range of recove ry intervals found in the present study may suggest that the diencepha lon plays an integrative role for rewarding signals arriving from vari ous brain areas.