Dendriittispineet

Dendriittispineet (dendritic spines) are small membranous protrusions that extend from neuronal dendrites. In the mature brain they typically host the postsynaptic component of most excitatory synapses, primarily glutamatergic contacts. Each spine contains postsynaptic receptors, signaling apparatus, and a specialized cytoskeleton that supports its morphology and biochemical compartmentalization.

Structure and diversity: The spine consists of a bulbous head connected to the dendrite by a narrow neck. Spines show diverse shapes and sizes, including mushroom, thin, stubby, and filopodial forms, and can transition between shapes as networks remodel. The spine head houses postsynaptic densities enriched in glutamate receptors (AMPA, NMDA variants) and scaffolding proteins. The spine neck can restrict diffusion of ions and molecules, creating a biochemical microdomain. In some spines a spine apparatus, an extension of smooth endoplasmic reticulum, is present.

Plasticity and function: Dendritic spines are dynamic; their formation, elimination, and remodeling are closely tied to synaptic plasticity and learning. Increases in synaptic strength (LTP) are often accompanied by spine enlargement or spine formation, while LTD can cause shrinkage or spine loss. Calcium influx through NMDA receptors and downstream signaling regulate actin remodeling via small GTPases (Rac1, Cdc42, RhoA) and actin-regulating proteins (Arp2/3, cofilin). Spine remodeling helps compartmentalize signaling and protect synaptic changes from diffusion.

Development and clinical relevance: Dendritic spines emerge and mature postnatally, with density and morphology influenced by neural activity and experience. Abnormal spine dynamics or density have been associated with neurodevelopmental and neurodegenerative disorders, including autism spectrum disorders and Alzheimer's disease, as well as aging. Researchers study spines using imaging methods such as two-photon microscopy and electron microscopy, as well as biochemical and genetic approaches.