Propagation of γPKC translocation along the dendrites of Purkinje cell in γPKC‐GFP transgenic mice

To elucidate spatial and temporal profiles of the protein kinase C (PKC) activation in relation to neuronal functions including synaptic plasticity, we tried to detect PKC translocation in living brain slices. We first developed brain region‐specific and inducible γPKC‐GFP transgenic mice using a tetracycline (tet)‐regulated system. In the transgenic mice, the expression of γPKC‐GFP was region‐specifically regulated by the promoter and abolished by the administration of doxycycline. Cerebellar slices from the mice were utilized for intracellular recording and fluorescence imaging of γPKC‐GFP in Purkinje cells. GFP fluorescence was uniformly distributed from soma to dendritic arbor. When mGluR agonists were applied, the intensity was transiently increased at the edge of the dendrite and concomitantly decreased in the cytoplasm, indicating that γPKC translocated to the plasma membrane. This transient change in the pattern of GFP fluorescence simultaneously occurred throughout the Purkinje cell dendrites by agonist stimulation. Translocation of γPKC‐GFP was also induced by electrical stimulation of parallel fibres. However, the event was not restricted at the distal dendrites, propagated forwardly along the dendritic tree and reached to the proximal trunk close to the soma. Time course of the propagation was slower than the electrical signal and Ca 2+ waves and faster than conveying molecules through microtubules. The present results indicate that PKC signals activated locally by parallel fibre input could propagate to the soma through dendrites in living Purkinje neurones. The findings may provide us with a new insight for understanding molecular mechanisms of the synaptic plasticity including cerebellar long‐term depression.