NITRIC-OXIDE, AN INTERCELLULAR MESSENGER IN CEREBELLAR SYNAPTIC PLASTICITY

Simultaneous activation of parallel and climbing fiber inputs evokes l ong-term depression (LTD) in the parallel fiber/Purkinje cell synapses . We have demonstrated that LTD requires endogenous nitric oxide (NO), which is produced locally by climbing fiber input and reaches to para llel fiber synapses by diffusion. The nature of NO as a gas of low mol ecular weight determines the character of NO-mediated intercellular co mmunication, which cannot keep the spatial information required for sy naptic plasticity. However in the case of LTD, the spatial information is maintained by Ca2+ signaling which climbing fiber input makes acti ve and is strictly confined to the Purkinje cell receiving the input. Therefore, NO-mediated information can serve for other purpose such as a global factor coding climbing fiber information in a certain area a s a whole.