Critical role of postsynaptic calcium in cerebellar long-term depression

It has been proposed that postsynaptic Ca2+ is required for induction of cerebellar long-term depression (LTD). However, whether a depolarization independent increase in Ca2+ is sufficient for LTD induction remains to be determined. We used nitr-5, a photolabile Ca2+ chelator, to address this issue. Photolysis of nitr-5 together with glutamate application, but neither photolysis of nitr-5 alone nor glutamate application alone induced LTD. When two independent glutamate pipettes were aimed at different dendrites of the same Purkinje neurone, LTD induction was confined to the site at which glutamate and photolysis of nitr-5 were applied. These results indicate that activation of glutamate receptors together with intracellular Ca2+ increase without depolarization is sufficient to induce LTD in cultured Purkinje neurones.