Activation of axonal receptors by GABA spillover increases somatic firing

Jason R. Pugh, Craig Jahr

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Abstract

Axons can be depolarized by ionotropic receptors and transmit subthreshold depolarizations to the soma by passive electrical spread. This raises the possibility that axons and axonal receptors can participate in integration and firing in neurons. Previously, we have shown that exogenous GABA depolarizes cerebellar granule cell axons through local activation of GABAA receptors (GABAARs) and the soma through electrotonic spread of the axonal potential resulting in increased firing. We show here that excitability of granule cells is also increased by release of endogenous GABA from molecular layer interneurons (MLIs) and spillover activation of parallel fiber GABAARs in mice and rats. Changes in granule cell excitability were assessed by excitability testing after activation of MLIs with channelrhodopsin or electrical stimulation in the molecular layer. In granule cells lacking an axon, excitability was not changed, suggesting that axonal receptors are required. To determine the distance over which subthreshold potentials may spread, we estimated the effective axonal electrical length constant (520μm) by excitability testing and focal uncaging of RuBi-GABA on the axon at varying distances from the soma. These data suggest that GABAAR-mediated axonal potentials can participate in integration and firing of cerebellar granule cells.

Original languageEnglish (US)
Pages (from-to)16924-16929
Number of pages6
JournalJournal of Neuroscience
Volume33
Issue number43
DOIs
Publication statusPublished - 2013

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ASJC Scopus subject areas

  • Neuroscience(all)

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