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bioRxiv · 10.1101/440198

Local reciprocal release of GABA from dendritic spines of olfactory bulb granule cells requires local sodium channel activation and occurs on both fast and slow timescales

Lage-Rupprecht, V.·Ona Jodar, T.·Yeghiazaryan, G.·Rozsa, B.·Egger, V.
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Abstract

In the rodent olfactory bulb the smooth dendrites of the principal glutamatergic mitral cells (MCs) form reciprocal dendrodendritic synapses with large spines on GABAergic granule cells (GC), where unitary release of glutamate can trigger postsynaptic local activation of voltage-gated Na+-channels (Navs), i.e. a spine spike. Can such single MC input evoke reciprocal release? We find that unitary-like activation via two-photon uncaging of glutamate causes GC spines to release GABA both synchronously and asynchronously onto MC dendrites. This release indeed requires activation of Navs and high-voltage-activated Ca2+-channels (HVACCs), but also of NMDA receptors (NMDAR). Simulations show temporally overlapping HVACC- and NMDAR-mediated Ca2+-currents during the spine spike, and ultrastructural data prove NMDAR presence within the GABAergic presynapse. This cooperative action of presynaptic NMDARs allows to implement synapse-specific, activity-dependent lateral inhibition and thus could provide an efficient solution to combinatorial percept synthesis in a sensory system with many receptor channels.

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Lage-Rupprecht, V., Ona Jodar, T., Yeghiazaryan, G., Rozsa, B., Egger, V.. 2018-10-10. Local reciprocal release of GABA from dendritic spines of olfactory bulb granule cells requires local sodium channel activation and occurs on both fast and slow timescales. https://doi.org/10.1101/440198

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