Sodium Channel-Dependent and -Independent Mechanisms Underlying Axonal Afterdepolarization at Mouse Hippocampal Mossy Fibers

ENeuro
Shunsuke Ohura, Haruyuki Kamiya

Abstract

Action potentials propagating along axons are often followed by prolonged afterdepolarization (ADP) lasting for several tens of milliseconds. Axonal ADP is thought to be an important factor in modulating the fidelity of spike propagation during repetitive firings. However, the mechanism as well as the functional significance of axonal ADP remain unclear, partly due to inaccessibility to small structures of axon for direct electrophysiological recordings. Here, we examined the ionic and electrical mechanisms underlying axonal ADP using whole-bouton recording from mossy fiber terminals in mice hippocampal slices. ADP following axonal action potentials was strongly enhanced by focal application of veratridine, an inhibitor of Na+ channel inactivation. In contrast, tetrodotoxin (TTX) partly suppressed ADP, suggesting that a Na+ channel-dependent component is involved in axonal ADP. The remaining TTX-resistant Na+ channel-independent component represents slow capacitive discharge reflecting the shape and electrical properties of the axonal membrane. We also addressed the functional impact of axonal ADP on presynaptic function. In paired-pulse stimuli, we found that axonal ADP minimally affected the peak height of subsequent action p...Continue Reading

Citations

Aug 21, 2020·Journal of Neurophysiology·James Weifu Lee
Sep 27, 2019·Frontiers in Cellular Neuroscience·Haruyuki Kamiya
May 30, 2019·Frontiers in Cellular Neuroscience·Haruyuki Kamiya

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