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Protein kinase C (PCK) is a family of isoforms that are implicated in subcellular signal transduction. The authors investigated the distribution of several PKC isoforms (PKC-alpha, PKC-beta, PKC-gamma, PKC-delta, and PKC-epsilon) within major cerebellar cell types as well as cerebellar projection target neurons, including Purkinje neurons, cerebellar nuclear neurons, and secondary vestibular neurons. PKC-alpha, PKC-beta, PKC-gamma, PKC-delta, and PKC-epsilon are found within the cerebellum. Of these isoforms, PKC-gamma and PKC-delta are highly expressed in Purkinje cells. PKC-gamma is expressed in all Purkinje cells, whereas the expression of PKC-delta is restricted to sagittal bands of Purkinje cells in the posterior cerebellar cortex. In the lower folia of the uvula and nodulus, Purkinje cell expression of PKC-delta is uniformly high, and the sagittal banding for PKC-delta expression is absent. Within the cerebellar nuclei, PKC-delta-immunolabeled axons terminate within the medial aspect of the caudal half of the ipsilateral interpositus nucleus. PKC delta-immunolabeled axons also terminated within the caudal medial and descending vestibular nuclei (MVN and DVN, respectively), the parasolitary nucleus (Psol), and the nucleus prepositus hypoglossi (NPH). PKC-gamma-immunolabeled axons terminated in all of the cerebellar nuclei as well as in the lateral and superior vestibular nuclei and the MVN, DVN, Psol, and NPH. The projection patterns of PKC-immunolabeled Purkinje cells were confirmed by lesion-depletion studies in which unilateral uvula-nodular lesions caused depletion of PKC-immunolabeled terminals ipsilateral to the lesion in the vestibular complex. These data identify circuitry that is unique to cerebellar-vestibular interactions.
Barmack et al. (Sat,) studied this question.