Robust perisomatic GABAergic self-innervation inhibits basket cells in the human and mouse supragranular neocortex
Viktor Szegedi1Y1,Melinda Paizs1Y1, Judith Baka2, Pal Barzo3, Gabor Molnar2, Gabor Tamas2 and Karri Lamsa1
Inhibitory autapses are self-innervating synaptic connections in GABAergic interneurons in the brain. Autapses in neocortical layers have not been systematically investigated, and their function in different mammalian species and specific interneuron types is poorly known. We investigated GABAergic parvalbumin-expressing basket cells (pvBCs) in layer 2/3 (L2/3) in mice as well as in human neocortical tissue resected in deep-brain surgery. Most pvBCs showed robust GABAAR-mediated self-innervation in both species, but autapses were rare in nonfast spiking GABAergic interneurons. Light- and electron microscopy analyses revealed pvBC axons innervating their own soma and proximal dendrites. GABAergic self-inhibition conductance was similar in human and mouse pvBCs and comparable to that of synapses from pvBCs to other L2/3 neurons. Autaptic conductance prolonged somatic inhibition in pvBCs after a spike and inhibited repetitive firing. Perisomatic autaptic inhibition has evolved in pvBCs of various cortical layers and different mammalian species to control discharge of these interneurons. ACKNOWLEDGMENTS: This work was supported by the National Brain Research (Nemzeti Agykutatási) program (KL, MP, VS, JB, GM and GT), the ERC INTERIMPACT project (GT), the Hungarian Academy of Sciences (GM, GT and VS), and University of Szeged Open Access Fund (Grant number: 4373). We acknowledge Leona Mezei for technical assistance.