ACTIN MATRIX OF DENDRITIC SPINES, SYNAPTIC PLASTICITY, AND LONG-TERM POTENTIATION

This chapter describes the composition of the spine cytoplasm along with the synaptic activity generated by the spine. Dendritic spines are appendage-like outgrowths of dendrites. They contain an enlarged terminal part (the spine head) and a slender stalk connecting the head with the parent dendrite. A small protrusion emanating from the spine head into the axon terminal contacting the dendritic spine is termed as “spinule.” Dendritic spines are endowed with a considerable degree of plasticity because they are readily modified by stimulation and changes in the environment. Synaptic plasticity is considered one of the most important properties of the brain as it allows for adaptive changes in the brain in response to past events and experiences. The spine apparatus (SA) consists of parallel membranous sacs that alternate with plates of dense material, which are contacted by dendritic microtubules during development. The SA membranous sacs are in continuity with the smooth endoplasmic reticulum (SER) of the parent dendrite. The absence of cytoplasmic organelles from the spine allows for a full use of the actin cytomatrix, which is particularly dense. Out of the entire neuron, the dendritic spines contain the highest density of actin filaments, which are arranged in such a way as to determine the characteristic shape of the spine. © 1992 Elsevier Science Publishers, B.V.