DENDRITIC SPINES FOR NEUROPROTECTION - A HYPOTHESIS

Ever since their first description in neurons, dendritic spines could be visualized only in fixed tissue, using high-power light and electro n microscopy. Recent studies have been able to measure the free intrac ellular Ca2+ concentration ([Ca2+](i)) in dendritic spines of live neu rons, and the results suggest that the spine is an independent cellula r Ca2+ compartment, Other recent observations have indicated that the density of spines on dendrites changes in a dynamic fashion depending on ongoing neuronal activity. Together, these findings have led to the proposal that the dendritic spine is not only a storage device for lo ng-term memory but perhaps a means for isolating the cell from the har mful consequences of synaptically evoked surges in [Ca2+](i). In other words, the dendritic spine is a neuroprotectant. This hypothesis has specific testable implications, including relating cell activity to sp ine density.