In mature rat brain, PLC beta 3 mRNA was detected weakly only in the pituitary gland and the cerebellar Purkinje and granule cells whereas PLC beta 4 mRNA was expressed intensely in the olfactory mitral cells, thalamic nuclei, medial habenula, pituitary gland and cerebellar Purkinje and granule cells. The beta 4 mRNA was also detected discretely in large neurons of presumably cholinergic nature, scattered rather evenly throughout the caudate putamen and diagonal band, although no significant expression was seen in the medium spiny neurons in the caudate putamen, and the hippocampal pyramidal cells and dentate granule cells. PLC gamma 2 mRNA was localized only in the Purkinje and granule cells in the vermal portions of lobules IX and X of the cerebellum, and in the adenohypophysis.