PT  - JOURNAL ARTICLE
AU  - Attila Ozsvár
AU  - Gergely Komlósi
AU  - Gáspár Oláh
AU  - Judith Baka
AU  - Gábor Molnár
AU  - Gábor Tamás
TI  - Linear summation of metabotropic postsynaptic potentials follows coactivation of neurogliaform interneurons
AID  - 10.1101/2020.12.10.418913
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.12.10.418913
4099  - http://biorxiv.org/content/early/2020/12/11/2020.12.10.418913.short
4100  - http://biorxiv.org/content/early/2020/12/11/2020.12.10.418913.full
AB  - Summation of ionotropic receptor-mediated responses is critical in neuronal computation by shaping input-output characteristics of neurons. However, arithmetics of summation for metabotropic signals are not known. We characterized the combined ionotropic and metabotropic output of neocortical neurogliaform cells (NGFCs) using electrophysiological and anatomical methods. These experiments revealed that GABA receptors are activated up to 1.8 microns from release sites and confirmed coactivation of putative NGFCs in superficial cortical layers in vivo. Triple recordings from presynaptic NGFCs converging to a postsynaptic neuron revealed sublinear summation of ionotropic GABAA responses and linear summation of metabotropic GABAB responses. Based on a model combining distances of volume transmission from release sites and distributions of all NGFC axon terminals, we postulate that 2 to 3 NGFCs provide input to a point in the neuropil. We suggest that interactions of metabotropic GABAergic responses remain linear even if most superficial layer interneurons specialized to recruit GABAB receptors are simultaneously active.Competing Interest StatementThe authors have declared no competing interest.