TRANSIENT CHANGES IN FLOCCULONODULAR LOBE PROTEIN-KINASE-C EXPRESSIONDURING VESTIBULAR COMPENSATION

Protein kinase C (PKC) is a family of intracellular signal transductio n enzymes, comprising isoforms that vary in sensitivity to calcium, ar achidonic acid, and diacylglycerol. PKC isoforms alpha, gamma, and del ta are expressed by cerebellar Purkinje cells and neurons in the cereb ellar nuclei and vestibular nuclei of the Long-Evans rat. In control r ats, these PKCs are distributed symmetrically in the flocculonodular-l obe Purkinje cells. Behavioral recovery from vestibular dysfunction pr oduced by unilateral labyrinthectomy (UL) is accompanied by asymmetric expression of PKC isoforms in these regions within 6 hr after UL. The se expression changes were localized within parasagittal regions of th e floculus and nodulus. The distribution of PKC alpha, -gamma, and -de lta were identical, suggesting that they are coregulated in cerebellar Purkinje cells during this early compensatory period. The pattern of Purkinje cell PKC expression returned to the control, symmetric distri bution within 24 hr after UL. It is hypothesized that these regional c hanges in Purkinje cell PKC expression are an early intracellular sign al contributing to vestibular compensation. In particular, regulation of PKC expression may contribute to changes in the efficacy of cerebel lar synaptic plasticity during the acute post-UL period.