Induction of cerebellar long-term depression requires activation of calcineurin in Purkinje cells.
Cerebellar long-term depression (LTD) is an activity-dependent depression of synaptic transmission from parallel fibers to Purkinje cells underlying certain forms of motor learning. LTD is induced by the conjunctive stimulation of parallel fibers and climbing fibers, both of which supply excitatory inputs to Purkinje cells. The conjunctive stimulation induces a large increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in Purkinje cells. Although the increase in [Ca(2+)](i) is essential for LTD induction, the downstream signal transduction mechanism remains elusive. In this study, we show that LTD induction requires the activation of the Ca(2+)/calmodulin-dependent protein phosphatase 2B calcineurin. In acute cerebellar slices of mice, the LTD amplitude was significantly reduced in the presence of calcineurin inhibitors (cyclosporin A or FK506), whereas the basic electrophysiological properties of the parallel fiber-Purkinje cell synaptic transmission remained constant. Furthermore, a calcineurin autoinhibitory peptide perfused into Purkinje cells completely blocked LTD induction. On the other hand, microcystin LR, an inhibitor of protein phosphatase 1 and 2A, did not affect the induction of LTD. These results indicate that calcineurin activation is essential for LTD induction downstream of the conjunctive-stimulation-induced Ca(2+) signal in Purkinje cells.
Fujiwara
Akiko
A
Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Kakizawa
Sho
S
Iino
Masamitsu
M
D000818:Animals; D000831:Animals, Newborn; D019703:Calcineurin / Q000378:metabolism*; D002531:Cerebellum / Q000166:cytology*; D016572:Cyclosporine / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D054645:Protein Phosphatase 1; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D016559:Tacrolimus / Q000494:pharmacology; D013997:Time Factors
D004791:Enzyme Inhibitors; D016572:Cyclosporine; D019703:Calcineurin; D054645:Protein Phosphatase 1; D016559:Tacrolimus