Axo-axonic synapse
Type of synapse / From Wikipedia, the free encyclopedia
An axo-axonic synapse is a type of synapse, formed by one neuron projecting its axon terminals onto another neuron's axon.[1]
Axo-axonic synapses have been found and described more recently than the other more familiar types of synapses, such as axo-dendritic synapses and axo-somatic synapses. The spatio-temporal properties of neurons get altered by the type of synapse formed between neurons. Unlike the other types, the axo-axonic synapse does not contribute towards triggering an action potential in the postsynaptic neuron. Instead, it affects the probability of neurotransmitter release in the response to any action potential passing through the axon of the postsynaptic neuron.[2] Thus, axo-axonic synapses appear to be very important for the brain in achieving a specialized neural computation.
Axo-axonic synapses are found throughout the central nervous system, including in the hippocampus, cerebral cortex and striatum in mammals;[3][4][5] in the neuro-muscular junctions in crustaceans;[6][7] and in the visual circuitry in dipterans.[8] Axo-axonic synapses can induce either inhibitory or excitatory effects in the postsynaptic neuron.[6][7][9] A classic example of the role of axo-axonic synapses is causing inhibitory effects on motoneurons in the spinal-somatic reflex arc. This phenomenon is known as presynaptic-inhibition.[10][11]