Rhythmic discharges in the perfused isolated brainstem preparation of adult guinea pig.

An isolated brainstem preparation of adult guinea pig was used for an in vitro electrophysiological study of rhythmic neuronal discharge patterns. More than half of the spontaneously active neurons (40/71) exhibited a rhythmic discharge. Rhythmic discharges were recorded dorsally in the nucleus tractus solitarius and ventrally in the ambiguus and paragigantocellular reticular nuclei. Three types of rhythmic patterns of discharge were identified in these areas: repetitive single discharge, repetitive bursting discharge and spontaneous periodic discharge. No rhythmic patterns were recorded in other explored parts of the brainstem. Comparison of these data with those from brainstem slices shows that spontaneous periodic discharges may require extended networks within the brainstem.