Coordinated developmental recruitment of latent fast spiking interneurons in layer IV barrel cortex.
Feedforward inhibitory GABAergic transmission is critical for mature cortical circuit function; in the neonate, however, GABA is depolarizing and believed to have a different role. Here we show that the GABAA receptor-mediated conductance is depolarizing in excitatory (stellate) cells in neonatal (postnatal day [P]3-5) layer IV barrel cortex, but GABAergic transmission at this age is not engaged by thalamocortical input in the feedforward circuit and has no detectable circuit function. However, recruitment occurs at P6-7 as a result of coordinated increases in thalamic drive to fast-spiking interneurons, fast-spiking interneuron-stellate cell connectivity and hyperpolarization of the GABAA receptor-mediated response. Thus, GABAergic circuits are not engaged by thalamocortical input in the neonate, but are poised for a remarkably coordinated development of feedforward inhibition at the end of the first postnatal week, which has profound effects on circuit function at this critical time in development.
Daw
Michael I
MI
Medical Research Council Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, Bristol BS8 1TD, UK.
Ashby
Michael C
MC
Isaac
John T R
JT
D000200:Action Potentials / Q000502:physiology*; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001640:Bicuculline / Q000494:pharmacology; D002540:Cerebral Cortex / Q000166:cytology*; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018756:GABA Antagonists / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000254:growth & development*; D018408:Patch-Clamp Techniques / Q000379:methods; D013788:Thalamus / Q000033:anatomy & histology / Q000502:physiology*
D018756:GABA Antagonists; D049452:Green Fluorescent Proteins; D001640:Bicuculline