In vitro Purkinje cell electrical behavior related to tissular environment

Cerebellar explants from newborn rats and kittens were cultivated in Maximow assemblies. The spontaneous electrical activity of Purkinje cells was recorded simultaneously by means of 3 extracellular micropipettes. These were placed near to cell bodies which appeared in the same microscopic field. Identification of these neurons was performed by intracellular staining with Procion Yellow. Mature Purkinje cells which had been deprived of their extracerebellar afferent connections tend to fire in grouped discharges (bursts). No correlation was ever observed between the firing pattern of a Purkinje cell and that of its neighbors. Purkinje cells which grew in connection with extracerebellar nuclei showed comparable burst discharges. In these explants synchronization of the burst pattern was obvious from the statistical analysis of the simultaneous recordings. Discharges in bursts were not observed in immature Purkinje cells from young cultures, from cells situated in peripheral thin areas of older explants or from cells grown with an antimitotic (MAM). These cells showed a rather regular frequency of discharge. Synchronized slow waves occurred in cerebellar which grew in the presence of MAM. These "inhibitory" waves accompanied the arrest of cell activity and may have analogues in vitro. The observed differences in the spontaneous firing of these neurons were discussed on the basis of different synaptic organizations of the explants.