Cortical Circuits of Callosal GABAergic Neurons.
Anatomical studies have shown that the majority of callosal axons are glutamatergic. However, a small proportion of callosal axons are also immunoreactive for glutamic acid decarboxylase, an enzyme required for gamma-aminobutyric acid (GABA) synthesis and a specific marker for GABAergic neurons. Here, we test the hypothesis that corticocortical parvalbumin-expressing (CC-Parv) neurons connect the two hemispheres of multiple cortical areas, project through the corpus callosum, and are a functional part of the local cortical circuit. Our investigation of this hypothesis takes advantage of viral tracing and optogenetics to determine the anatomical and electrophysiological properties of CC-Parv neurons of the mouse auditory, visual, and motor cortices. We found a direct inhibitory pathway made up of parvalbumin-expressing (Parv) neurons which connects corresponding cortical areas (CC-Parv neurons → contralateral cortex). Like other Parv cortical neurons, these neurons provide local inhibition onto nearby pyramidal neurons and receive thalamocortical input. These results demonstrate a previously unknown long-range inhibitory circuit arising from a genetically defined type of GABAergic neuron that is engaged in interhemispheric communication.
Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Crystal
C
Rock
Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Hector
H
Zurita
Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Sharmon
S
Lebby
Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Charles J
CJ
Wilson
Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Alfonso Junior
AJ
Apicella
D000818:Animals; D001303:Auditory Cortex / Q000166:cytology* / Q000502:physiology; D000075402:Channelrhodopsins / Q000235:genetics / Q000378:metabolism; D003337:Corpus Callosum / Q000166:cytology*; D004558:Electric Stimulation; D005260:Female; D059330:GABAergic Neurons / Q000502:physiology*; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000502:physiology*; D062308:Optogenetics; D010320:Parvalbumins / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D014162:Transfection; D050599:Vesicular Glutamate Transport Protein 2
D000075402:Channelrhodopsins; D008164:Luminescent Proteins; D010320:Parvalbumins; D050599:Vesicular Glutamate Transport Protein 2