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.
^Buhl EH, Han ZS, Lörinczi Z, Stezhka VV, Karnup SV, Somogyi P (April 1994). "Physiological properties of anatomically identified axo-axonic cells in the rat hippocampus". Journal of Neurophysiology. 71 (4): 1289–307. doi:10.1152/jn.1994.71.4.1289. PMID8035215.