From form to function: calcium compartmentalization in dendritic spines

Dendritic spines compartmentalize calcium, and this could be their I nain f unction. We review experimental work on spine calcium dynamics. Calcium inf lux into spines is mediated by calcium channels and by NMDA and AMPA recept ors and is followed by fast diffusional equilibration within the spine head . Calcium decay kinetics are controlled by slower diffusion through the spi ne neck and by spine calcium pumps. Calcium release occurs in spines, altho ugh its role is controversial. Finally, the endogenous calcium buffers in s pines remain unknown. Thus, spines are calcium compartments because of thei r morphologies and local influx and extrusion mechanisms. These studies hig hlight the richness and heterogeneity of pathways that regulate calcium acc umulations in spines and the close relationship between the morphology and function of the spine.