Long-term sensory deprivation selectively rearranges functional inhibitory circuits in mouse barrel cortex

Abstract

Long-term whisker removal alters the balance of excitation and inhibition in rodent barrel cortex, yet little is known about the contributions of individual cells and synapses in this process. We studied synaptic inhibition in four major types of neurons in live tangential slices that isolate layer 4 in the posteromedial barrel subfield. Voltage-clamp recordings of layer 4 neurons reveal that fast decay of synaptic inhibition requires ␣1-containing GABAA receptors. After 7 weeks of deprivation, we found that GABA A-receptor-mediated inhibitory postsynaptic currents (IPSCs) in the inhibitory lowthreshold-spiking (LTS) cell recorded in deprived barrels exhibited faster decay kinetics and larger amplitudes in whisker-deprived barrels than those in nondeprived barrels in age-matched controls. This was not observed in other cell types. Additionally, IPSCs recorded in LTS cells from deprived barrels show a marked increase in zolpidem sensitivity. To determine if the faster IPSC decay in LTS cells from deprived barrels indicates an increase in ␣1 subunit functionality, we deprived ␣1(H101R) mutant mice with zolpidem-insensitive ␣1-containing GABA A receptors. In these mice and matched wild-type controls, IPSC decay kinetics in LTS cells were faster after whisker removal; however, the deprivation-induced sensitivity to zolpidem was reduced in ␣1(H101R) mice. These data illustrate a change of synaptic inhibition in LTS cells via an increase in ␣1-subunit-mediated function. Because ␣1 subunits are commonly associated with circuitspecific plasticity in sensory cortex, this switch in LTS cell synaptic inhibition may signal necessary circuit changes required for plastic adjustments in sensory-deprived cortex.interneurons ͉ networks ͉ plasticity S ynaptic inhibition is involved in sensory processing at the very first stage of cortical integration in layer 4 of the rodent primary somatosensory (barrel) cortex (1). Both feedforward and feedback inhibition from local circuit inhibitory neurons regulates the integration of thalamic and intracortical inputs (2, 3). Inhibitory neurons are distinguished from each other by action potential firing properties, morphology, and biochemical expression (4, 5). Cortical inhibitory neurons are largely separated into two functional circuits that are thought to carry out two intertwined yet separate functions in sensory processing (6). Fast-spiking (FS) cells are either basket cells or chandelier cells and express parvalbumin (4). They are readily activated by thalamic afferents and are the primary mediator of thalamocortical feedforward inhibition, and recurrent synaptic inhibition onto FS cells is very fast (6, 7). Low-threshold-spiking (LTS) cells express varying combinations of somatostatin, vasoactive intestinal peptide, and cholecystokinin (4), are weakly activated by thalamic afferents, and contribute to intracortical inhibitory transmission, and recurrent synaptic inhibition onto LTS cells decays slowly (7,8).In cortex and other regions, an emerging feature in brain networks is the ''G...

α4* Nicotinic Acetylcholine Receptors Modulate Experience-Based Cortical Depression in the Adult Mouse Somatosensory Cortex

“…There have been several recent studies showing that certain GABAergic neurons in layer 4 are very sensitive to changes in whisker experience (Jiao et al, 2006;Lee et al, 2007;P. Li et al, 2009).…”

Comparative posthearing development of inhibitory inputs to the lateral superior olive in gerbils and mice

“…Experiments in the auditory brain stem and the barrel cortex support the idea that sensory deprivation can influence IPSC kinetics. However, this change can go both ways, either accelerating or slowing IPSCs (Leao et al 2004;Li et al 2009), and is, in some cases, paralleled by a change in the ␣-subunit composition of the glycine receptor (Li et al 2009). Nevertheless, some of the above-discussed factors most likely also contribute to this effect.…”

Conductive Hearing Loss Has Long-Lasting Structural and Molecular Effects on Presynaptic and Postsynaptic Structures of Auditory Nerve Synapses in the Cochlear Nucleus

“…Previous studies have revealed changes in synaptic morphology and transmission after monocular deprivation or eyelid suture (Maffei et al, 2004;Hofer et al, 2009;Coleman et al, 2010), whisker removal or mechanical whisker manipulation (Allen et al, 2003;Bender et al, 2006;Li et al, 2009), sensorineural hearing loss in congenitally deaf animal models (Redd et al, 2000;Oleskevich and Walmsley, 2002;Lee et al, 2003;Ryugo et al, 2005), cochlear ablations (Gulley et al, 1977;Suneja et al, 1998;Asako et al, 2005;Rubio, 2006), or age-related hearing loss Manis, 2005, 2006). More recently, it has become clear that other forms of hearing impairment associated with conductive hearing loss can also alter synaptic transmission in central auditory regions (Xu et al, 2007(Xu et al, , 2010.…”