Out-of-register axons control output

Abstract

Neuroscience A neuron integrates synaptic inputs and fires action potentials from its axon initial segment (AIS), a specialized membrane region on neuronal axons that also forms synapses with other axons. Stimulating neurons chronically can cause the AIS to move distally along the axon, but do its associated synapses move with it? To find out, Wefelmeyer et al. used optogenetics and imaging to show that in the rat hippocampus, synapses of chandelier interneurons on pyramidal neurons do not move with the AIS. Nor is there a change in the number of synapses or their architecture. Computational modeling revealed that neurons with distal AIS and proximal synapses have weaker and delayed action potentials. Such AIS plasticity may be a homeostatic mechanism for neurons to avoid becoming overexcited. Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1502902112 (2015).