axodendritic

Axodendritic describes a synaptic arrangement in which the presynaptic axon terminal forms a chemical synapse with the dendrite of another neuron. It is one of the principal synapse types in the central nervous system, alongside axosomatic and axoaxonal contacts. In axodendritic synapses, neurotransmitter release from the presynaptic bouton crosses the synaptic cleft and binds to receptors on the dendritic membrane. Contacts may occur on dendritic shafts or on dendritic spines; spines provide isolated postsynaptic compartments that support rapid signaling and synaptic plasticity.

Most axodendritic synapses are excitatory and glutamatergic, involving AMPA and NMDA receptors on the postsynaptic side. Inhibitory axodendritic synapses do occur, typically using GABA, and can modulate the local excitability of the dendrite and the integration of synaptic inputs.

Morphology and function: the presynaptic bouton contains synaptic vesicles and an active zone; the postsynaptic density aligns with receptor clusters. Activity at these synapses underlies synaptic integration, the generation of postsynaptic potentials, and forms the substrate for synaptic plasticity such as long-term potentiation and long-term depression, especially at spine synapses.

Clinical relevance: alterations in axodendritic synapses and dendritic spines have been associated with neurodevelopmental and neurodegenerative disorders, reflecting their role in neural circuitry and cognitive function.