The beta1 isoform of phospholipase-C is exclusively present in the nucleus of several hematopoietic and non-hematopoietic cell lines and primary cells of different species. When present, it represents the key enzyme for initiating the nuclear phospholipid breakdown that is involved in the cellular response to proliferating and differentiating stimuli. We have studied the expression of this enzyme isoform in the rat cerebellar cortex. We demonstrate that phospholipase-C beta1 (PLCbeta1) is predominantly expressed in the neurons of the granular layer, while it is virtually absent in the molecular and Purkinje cell layers of rat cerebellar cortex. This pattern of expression is partially different from that of the mouse cerebellar cortex, where not only granular cells, but also Purkinje cells express PLCbeta1. The high level of synaptic inputs that converge on granular cells may imply a constantly active nuclear phospholipid metabolism that may not be strictly required for the appropriate cellular responses of the other cell types of rat cerebellar cortex.