![]() Quantitative ultrastructural analysis of hippocampal excitatory synapses. Cell type and pathway dependence of synaptic AMPA receptor number and variability in the hippocampus. Spine motility declined with the maturation of neurons, but was not changed by the blockade or stimulation of neuronal activity. Using time-lapse imaging, the authors observed high motility of spines and filopodia in slices from different brain areas. Developmental regulation of spine motility in the mammalian central nervous system. Analysis of spine morphological plasticity in developing hippocampal pyramidal neurons. Three-dimensional organization of smooth endoplasmic reticulum in hippocampal CA1 dendrites and dendritic spines of the immature and mature rat. Synaptogenesis via dendritic filopodia in developing hippocampal area CA1. Three-dimensional structure of dendritic spines and synapses in rat hippocampus (CA1) at postnatal day 15 and adult ages: implications for the maturation of synaptic physiology and long-term potentiation. The small pyramidal neuron of the rat cerebral cortex. Transient and enduring morphological correlates of synaptic activity and efficacy change in the rat hippocampal slice. Structure, development, and plasticity of dendritic spines. Overview on the structure, composition, function, development, and plasticity of hippocampal dendritic spines. Three-dimensional analysis of the structure and composition of CA3 branched dendritic spines and their synaptic relationships with mossy fiber boutons in the rat hippocampus. Dendritic spines: cellular specializations imparting both stability and flexibility to synaptic function. For example, what is the actual function of spines in brain plasticity and behaviour? What are the intrinsic and extrinsic factors that determine the formation of spines? What is the relationship between the structural plasticity of spines, and the movements of molecules and membranes into and out of this postsynaptic compartment? Several questions remain to be answered in this nascent field. They include GTPases of the Rho/Rac/Cdc42 family, the small GTPase Ras, and a series of receptors and scaffold proteins. The cytoskeleton is crucial for their development and stability, and an expanding set of actin-binding and actin-regulatory molecules has also been implicated in these processes. ![]() The underlying molecular mechanisms of this motile behaviour, and its functional significance, are unknown.Ĭonsiderable progress has been made in identifying the molecules that control spine growth and maturation. The shape change involves a remodelling of the cytoskeleton in the spine, and actin-based protrusive activity from the spine head. Moreover, spine morphology is markedly influenced by the activity of glutamate receptors.ĭendritic spines exhibit rapid motility. In general terms, spines seem to be maintained by an 'optimal' level of synaptic activity: spine density increases when there is insufficient activity, and decreases when stimulation is excessive. Indeed, changes in spine density have been observed in response to changes in the efficacy of neurotransmission. Regulated changes in spine number might reflect mechanisms for converting transient changes in synaptic activity into long-lasting alterations. So, the filopodium–spine transition is unlikely to be a predestined process, but instead one that is reversible and regulated by factors such as synaptic activity. However, a simple developmental relationship between filopodia and spines does not seem to exist. What is the significance of dendritic spines? There is no definitive answer to this question, but the prevailing view is that their primary function is to provide a microcompartment for segregating postsynaptic chemical responses, such as elevated calcium.ĭendritic filopodia are widely believed to be the precursors of dendritic spines. In addition, most spines exhibit a single, continuous postsynaptic density (PSD), but some PSDs are discontinuous or perforated. However, spine morphology is not static spines change size and shape over variable timescales. Spines have been classified by shape as thin, stubby, mushroom- and cup-shaped. So, spines represent the main unitary postsynaptic compartment for excitatory input. Most excitatory synapses in the mature mammalian brain occur on spines. Dendritic spines are morphological specializations that protrude from the main shaft of dendrites.
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