STOCHASTIC MODELING OF INOSITOL-1,4,5-TRISPHOSPHATE RECEPTORS IN PURKINJE CELL SPINE

Transient rises in cytosolic calcium concentration play a crucial role in initiating long-term depression (LTD) of synapticactivity. Calciumrelease fromendoplasmicretic- ulum is particularly important in LTD. In Purkinje cells, thereleaseis mediatedbyinositol-1,4,5-trisphosphate(IP3) receptors (IP3Rs) that are highly expressed in dendritic spines. The small volume of spine and the small num- ber of molecules involved increase stochasticity in bio- chemicalprocesses. We studiedthe effectsofstochasticity by comparing stochastic and deterministic simulations for two different IP3R models. We found a significant differ- ence between the responses when using small initial con- centration of calcium or IP3. Deterministic simulations of IP3R activation do not produce realistic results under all conditions.