Chromatin remodeler Arid1a regulates subplate neuron identity and wiring of cortical connectivity.

Loss-of-function mutations in chromatin remodeler gene ARID1A are a cause of Coffin-Siris syndrome, a developmental disorder characterized by dysgenesis of corpus callosum. Here, we characterize Arid1a function during cortical development and find unexpectedly selective roles for Arid1a in subplate neurons (SPNs). SPNs, strategically positioned at the interface of cortical gray and white matter, orchestrate multiple developmental processes indispensable for neural circuit wiring. We find that pancortical deletion of Arid1a leads to extensive mistargeting of intracortical axons and agenesis of corpus callosum. Sparse Arid1a deletion, however, does not autonomously misroute callosal axons, implicating noncell-autonomous Arid1a functions in axon guidance. Supporting this possibility, the ascending axons of thalamocortical neurons, which are not autonomously affected by cortical Arid1a deletion, are also disrupted in their pathfinding into cortex and innervation of whisker barrels. Coincident with these miswiring phenotypes, which are reminiscent of subplate ablation, we unbiasedly find a selective loss of SPN gene expression following Arid1a deletion. In addition, multiple characteristics of SPNs crucial to their wiring functions, including subplate organization, subplate axon-thalamocortical axon cofasciculation ("handshake"), and extracellular matrix, are severely disrupted. To empirically test Arid1a sufficiency in subplate, we generate a cortical plate deletion of Arid1a that spares SPNs. In this model, subplate Arid1a expression is sufficient for subplate organization, subplate axon-thalamocortical axon cofasciculation, and subplate extracellular matrix. Consistent with these wiring functions, subplate Arid1a sufficiently enables normal callosum formation, thalamocortical axon targeting, and whisker barrel development. Thus, Arid1a is a multifunctional regulator of subplate-dependent guidance mechanisms essential to cortical circuit wiring.

The analysis of Period1 gene expression in vivo and in vitro using a micro PMT system.

To detect a small amount of Period1 (Per1) expression, we developed a micro-photomultiplier tube (µPMT) system which can be used both in vivo and in vitro. Using this system, we succeeded in detecting Per1 gene expression in the skin of freely moving mice over 240 times higher compared with that of the tissue contact optical sensor (TCS) as previously reported. For in vitro studies, we succeeded in detecting elevated Per1 expression by streptozotocin (STZ) treatment in the scalp hairs at an early stage of diabetes, when glucose content in the blood was still normal. In addition, we could detect elevated Per1 expression in a single whisker hair at the time of diabetes onset. These results show that our µPMT system responds to minute changes in gene expression in freely moving mice in vivo and in mice hair follicles in vitro. Furthermore, Per1 in the hair can be used for a marker of diabetic aggravation.

In vivo imaging of neural circuit formation in the neonatal mouse barrel cortex.

Higher brain function in mammals primarily relies on complex yet sophisticated neuronal circuits in the neocortex. In early developmental stages, neocortical circuits are coarse. Mostly postnatally, the circuits are reorganized to establish mature precise connectivity, in an activity-dependent manner. These connections underlie adult brain function. The rodent somatosensory cortex (barrel cortex) contains a barrel map in layer 4 (L4) and has been considered an ideal model for the study of postnatal neuronal circuit formation since the first report of barrels in 1970. Recently, two-photon microscopy has been used for analyses of neuronal circuit formation in the mammalian brain during early postnatal development. These studies have further highlighted the mouse barrel cortex as an ideal model. In particular, the unique dendritic projection pattern of barrel cortex L4 spiny stellate neurons (barrel neurons) is key for the precise one-to-one functional relationship between whiskers and barrels and thus an important target of studies. In this article, I will review the morphological aspects of postnatal development of neocortical circuits revealed by recent two-photon in vivo imaging studies of the mouse barrel cortex and other related works. The focus of this review will be on barrel neuron dendritic refinement during neonatal development.

Transcriptional Profiling of Whisker Follicles and of the Striatum in Methamphetamine Self-Administered Rats.

Methamphetamine (MA) use disorder is a chronic neuropsychiatric disease characterized by recurrent binge episodes, intervals of abstinence, and relapses to MA use. Therefore, identification of the key genes and pathways involved is important for improving the diagnosis and treatment of this disorder. In this study, high-throughput RNA sequencing was performed to find the key genes and examine the comparability of gene expression between whisker follicles and the striatum of rats following MA self-administration. A total of 253 and 87 differentially expressed genes (DEGs) were identified in whisker follicles and the striatum, respectively. Multivariate and network analyses were performed on these DEGs to find hub genes and key pathways within the constructed network. A total of 129 and 49 genes were finally selected from the DEG sets of whisker follicles and of the striatum. Statistically significant DEGs were found to belong to the classes of genes involved in nicotine addiction, cocaine addiction, and amphetamine addiction in the striatum as well as in Parkinson's, Huntington's, and Alzheimer's diseases in whisker follicles. Of note, several genes and pathways including retrograde endocannabinoid signaling and the synaptic vesicle cycle pathway were common between the two tissues. Therefore, this study provides the first data on gene expression levels in whisker follicles and in the striatum in relation to MA reward and thereby may accelerate the research on the whisker follicle as an alternative source of biomarkers for the diagnosis of MA use disorder.

Notch pathway signaling in the skin antagonizes Merkel cell development.

Merkel cells are mechanosensitive skin cells derived from the epidermal lineage whose development requires expression of the basic helix-loop-helix transcription factor Atoh1. The genes and pathways involved in regulating Merkel cell development during embryogenesis are poorly understood. Notch pathway signaling antagonizes Atoh1 expression in many developing body regions, so we hypothesized that Notch signaling might inhibit Merkel cell development. We found that conditional, constitutive overexpression of the Notch intracellular domain (NICD) in mouse epidermis significantly decreased Merkel cell numbers in whisker follicles and touch domes of hairy skin. Conversely, conditional deletion of the obligate NICD binding partner RBPj in the epidermis significantly increased Merkel cell numbers in whisker follicles, led to the development of ectopic Merkel cells outside of touch domes in hairy skin epidermis, and altered the distribution of Merkel cells in touch domes. Deletion of the downstream Notch effector gene Hes1 also significantly increased Merkel cell numbers in whisker follicles. Together, these data demonstrate that Notch signaling regulates Merkel cell production and patterning.

Optogenetic and transcriptomic interrogation of enhanced muscle function in the paralyzed mouse whisker pad.

The functional state of denervated muscle is a critical factor in the ability to restore movement after injury- or disease-related paralysis. Here we used peripheral optogenetic stimulation and transcriptome profiling in the mouse whisker system to investigate the time course of changes in neuromuscular function following complete unilateral facial nerve transection. While most skeletal muscles rapidly lose functionality after lower motor neuron denervation, optogenetic muscle stimulation of the paralyzed whisker pad revealed sustained increases in the sensitivity, velocity, and amplitude of whisker movements, and reduced fatigability, starting 48 h after denervation. RNA-seq analysis showed distinct regulation of multiple gene families in denervated whisker pad muscles compared with the atrophy-prone soleus, including prominent changes in ion channels and contractile fibers. Together, our results define the unique functional and transcriptomic landscape of denervated facial muscles and have general implications for restoring movement after neuromuscular injury or disease. NEW & NOTEWORTHY Optogenetic activation of muscle can be used to noninvasively induce movements and probe muscle function. We used this technique in mice to investigate changes in whisker movements following facial nerve transection. We found unexpectedly enhanced functional properties of whisker pad muscle following denervation, accompanied by unique transcriptomic changes. Our findings highlight the utility of the mouse whisker pad for investigating the restoration of movement after paralysis.

Nuclear localization of Meis1 in dermal papilla promotes hair matrix cell proliferation in the anagen phase of hair cycle.

The dermal papilla (DP) is a key mesenchymal compartment of hair follicles that orchestrates mesenchymal-epithelial interaction regulating hair growth cycles. In the present study, we demonstrate that a TALE-family transcription factor, Meis1, is selectively localized in the nucleus of the DP in the anagen phase of the hair cycle. By using an ex vivo organ culture of vibrissae follicles, conditional Meis1 loss causes retardation in hair growth, accompanied by defects in cell proliferation of hair matrix cells. This cell proliferation defect is partly rescued by the addition of culture supernatants derived from Meis1-sufficient but not -deficient DP cells. These findings indicate that nuclear Meis1 in DP activate genes involved in secretion of some unknown factors, which promote proliferation of hair matrix cells in the anagen phase of the hair cycle.

Increase in IGF-1 Expression in the Injured Infraorbital Nerve and Possible Implications for Orofacial Neuropathic Pain.

Insulin-like growth factor-1 (IGF-1) is upregulated in the injured peripheral nerve bundle and controls nociceptive neuronal excitability associated with peripheral nerve injury. Here, we examined the involvement of IGF-1 signaling in orofacial neuropathic pain following infraorbital nerve injury (IONI) in rats. IONI promoted macrophage accumulation in the injured ION, as well as in the ipsilateral trigeminal ganglion (TG), and induced mechanical allodynia of the whisker pad skin together with the enhancement of neuronal activities in the subnucleus caudalis of the spinal trigeminal nucleus and in the upper cervical spinal cord. The levels of IGF-1 released by infiltrating macrophages into the injured ION and the TG were significantly increased. The IONI-induced the number of transient receptor potential vanilloid (TRPV) subfamily type 4 (TRPV4) upregulation in TRPV subfamily type 2 (TRPV2)-positive small-sized, and medium-sized TG neurons were inhibited by peripheral TRPV2 antagonism. Furthermore, the IONI-induced mechanical allodynia was suppressed by TRPV4 antagonism in the whisker pad skin. These results suggest that IGF-1 released by macrophages accumulating in the injured ION binds to TRPV2, which increases TRPV4 expression in TG neurons innervating the whisker pad skin, ultimately resulting in mechanical allodynia of the whisker pad skin.

The effect of orofacial complete Freund's adjuvant treatment on the expression of migraine-related molecules.

BACKGROUND: Migraine is a neurovascular primary headache disorder, which causes significant socioeconomic problems worldwide. The pathomechanism of disease is enigmatic, but activation of the trigeminovascular system (TS) appears to be essential during the attack. Migraine research of recent years has focused on neuropeptides, such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide 1-38 (PACAP1-38) as potential pathogenic factors and possible therapeutic offensives. The goal of present study was to investigate the simultaneous expression of CGRP and precursor of PACAP1-38 (preproPACAP) in the central region of the TS in a time-dependent manner following TS activation in rats. METHODS: The right whisker pad of rats was injected with 50 µl Complete Freund's Adjuvant (CFA) or saline. A mechanical allodynia test was performed with von Frey filaments before and after treatment. Transcardial perfusion of the animals was initiated 24, 48, 72 and 120 h after injection, followed by the dissection of the nucleus trigeminus caudalis (TNC). After preparation, the samples were stored at - 80 °C until further use. The relative optical density of CGRP and preproPACAP was analyzed by Western blot. One-way ANOVA and Kruskal-Wallis followed by Tukey post hoc test were used to evaluate the data. Regression analysis was applied to explore the correlation between neuropeptides expression and hyperalgesia. RESULTS: Orofacial CFA injection resulted in significant CGRP and preproPACAP release in the TNC 24, 48, 72 and 120 h after the treatment. The level of neuropeptides reached its maximum at 72 h after CFA injection, corresponding to the peak of facial allodynia. Negative, linear correlation was detected between the expression level of neuropeptides and value of mechanonociceptive threshold. CONCLUSION: This is the first study which suggests that the expression of CGRP and preproPACAP simultaneously increases in the central region of activated TS and it influences the formation of mechanical hyperalgesia. Our results contribute to a better understanding of migraine pathogenesis and thereby to the development of more effective therapeutic approaches.

Ectopic Atoh1 expression drives Merkel cell production in embryonic, postnatal and adult mouse epidermis.

Merkel cells are mechanosensitive skin cells whose production requires the basic helix-loop-helix transcription factor Atoh1. We induced ectopic Atoh1 expression in the skin of transgenic mice to determine whether Atoh1 was sufficient to create additional Merkel cells. In embryos, ectopic Atoh1 expression drove ectopic expression of the Merkel cell marker keratin 8 (K8) throughout the epidermis. Epidermal Atoh1 induction in adolescent mice similarly drove widespread K8 expression in glabrous skin of the paws, but in the whisker pads and body skin ectopic K8+ cells were confined to hair follicles and absent from interfollicular regions. Ectopic K8+ cells acquired several characteristics of mature Merkel cells in a time frame similar to that seen during postnatal development of normal Merkel cells. Although ectopic K8+ cell numbers decreased over time, small numbers of these cells remained in deep regions of body skin hair follicles at 3 months post-induction. In adult mice, greater numbers of ectopic K8+ cells were created by Atoh1 induction during anagen versus telogen and following disruption of Notch signaling by conditional deletion of Rbpj in the epidermis. Our data demonstrate that Atoh1 expression is sufficient to produce new Merkel cells in the epidermis, that epidermal cell competency to respond to Atoh1 varies by skin location, developmental age and hair cycle stage, and that the Notch pathway plays a key role in limiting epidermal cell competency to respond to Atoh1 expression.

Growth rate and stable carbon and nitrogen isotope trophic discrimination factors of lion and leopard whiskers.

RATIONALE: Stable isotope analysis (SIA) of whiskers has been used to identify temporal feeding habits, intra-population diet variation, as well as individual dietary specialisation of marine and terrestrial carnivores. However, the potential of the method to disclose such dietary information for large wild felids is hampered by lack of information on species-specific whisker growth rates, whisker growth patterns and whisker-diet trophic discrimination factors (TDFs). METHODS: Whisker growth rates and growth patterns were measured for four lions (Panthera leo) and one leopard (Panthera pardus) held at the National Zoological Gardens, Pretoria, South Africa. Actively growing whiskers of the felids were 'marked' four times over 185 days using 13 C-depleted, C3 -based giraffe (Giraffa camelopardalis) meat. The periods with low δ13 C values, identified following serial sectioning of the regrown whiskers at 1 mm intervals and isotopic analysis, were then correlated to specific giraffe meat feeding bouts and hence growth periods. δ13 C and δ15 N whisker-diet TDFs were estimated for five lions whose diet remained consistent over multiple years. RESULTS: The whisker growth rates of three lionesses and the leopard were similar (mean = 0.65 mm day-1 ), despite species, sex and age differences. There was a decrease in whisker growth rate over time, suggesting a non-linear whisker growth pattern. However, linear and non-linear growth simulations showed slight differences between the two growth patterns for the proximal ~50 mm of whiskers. δ13 C and δ15 N lion whisker-diet TDFs were also similar amongst individuals (mean = 2.7 ± 0.12 ‰ for δ13 C values and 2.5 ± 0.08 ‰ for δ15 N values), irrespective of age and sex. CONCLUSIONS: The whisker growth rate and δ13 C and δ15 N lion whisker-diet TDFs obtained in this study can be applied in future studies to assign dietary information contained in analysed felid whiskers to the correct time period and improve deductions of prey species consumed by wild felids.

Molecularly Defined Subplate Neurons Project Both to Thalamocortical Recipient Layers and Thalamus.

In mammals, subplate neurons (SPNs) are among the first generated cortical neurons. While most SPNs exist only transiently during development, a number of SPNs persist among adult Layer 6b (L6b). During development, SPNs receive thalamic and intra-cortical input, and primarily project to Layer 4 (L4). SPNs are critical for the anatomical and functional development of thalamocortical connections and also pioneer corticothalamic projections. Since SPNs are heterogeneous, SPN subpopulations might serve different roles. Here, we investigate the connectivity of one subpopulation, complexin-3 (Cplx3)-positive SPNs (Cplx3-SPNs), in mouse whisker somatosensory (barrel) cortex (S1). We find that many Cplx3-SPNs survive into adulthood and become a subpopulation of L6b. Cplx3-SPNs axons project to thalamorecipient layers, that is, L4, 5a, and 1. The L4 projections are biased towards the septal regions between barrels in the second postnatal week. Thus, S1 Cplx3-SPN targets co-localize with the eventual projections of the medial posterior thalamic nucleus (POm). In addition to their cortical targets, Cplx3-SPNs also extend long-range axons to several thalamic nuclei, including POm. Thus, Cplx3-SPN/L6b neurons are associated with paralemniscal pathways and can potentially directly link thalamocortical and corticothalamic circuits. This suggests an additional key role for SPNs in the establishment and maintenance of thalamocortical processing.

Barrels XXX meeting report: Barrels in Baltimore.

The Barrels meeting annually brings together researchers focused on the rodent whisker to cortical barrel system prior to the Society for Neuroscience meeting. The 2017 meeting focused on the classification of cortical interneurons, the role interneurons have in shaping brain dynamics, and finally on the circuitry underlying oral sensations. The meeting highlighted the latest advancements in this rapidly advancing field.

Stimulation of mouse vibrissal follicle growth by recombinant human fibroblast growth factor 20.

OBJECTIVES: To explore potential effects of recombinant human fibroblast growth factor 20 (rhFGF20) in the growth of cultured mouse vibrissal follicles. RESULTS: The growth of cultured mouse vibrissal follicles was significantly induced by rhFGF20 in a dose dependent pattern in the in vitro vibrissal follicle organ culture model. However, too high concentration of rhFGF20 could inhibit the growth of vibrissal follicles. We further demonstrated that rhFGF20 stimulated the proliferation of hair matrix cells and activated Wnt/ß-catenin signaling pathway. CONCLUSIONS: The rhFGF20 might be a potential therapeutic agent to treat hair loss disorders.

Whisker experience-dependent mGluR signaling maintains synaptic strength in the mouse adolescent cortex.

Sensory experience-dependent plasticity in the somatosensory cortex is a fundamental mechanism of adaptation to the changing environment not only early in the development but also in adolescence and adulthood. Although the mechanisms underlying experience-dependent plasticity during early development have been well documented, the corresponding understanding in the mature cortex is less complete. Here, we investigated the mechanism underlying whisker deprivation-induced synaptic plasticity in the barrel cortex in adolescent mice. Layer 4 (L4) to L2/3 excitatory synapses play a crucial role for whisker experience-dependent plasticity in rodent barrel cortex and whisker deprivation is known to depress synaptic strength at L4-L2/3 synapses in adolescent and adult animals. We found that whisker deprivation for 5 days or longer decreased the presynaptic glutamate release probability at L4-L2/3 synapses in the barrel cortex in adolescent mice. This whisker deprivation-induced depression was restored by daily administration of a positive allosteric modulator of the type 5 metabotropic glutamate receptor (mGluR5). On the other hand, the administration of mGluR5 antagonists reproduced the effect of whisker deprivation in whisker-intact mice. Furthermore, chronic and selective suppression of inositol 1,4,5-trisphosphate (IP3 ) signaling in postsynaptic L2/3 neurons decreased the presynaptic release probability at L4-L2/3 synapses. These findings represent a previously unidentified mechanism of cortical plasticity, namely that whisker experience-dependent mGluR5-IP3 signaling in the postsynaptic neurons maintains presynaptic function in the adolescent barrel cortex.

Lrp4 and Wise interplay controls the formation and patterning of mammary and other skin appendage placodes by modulating Wnt signaling.

The future site of skin appendage development is marked by a placode during embryogenesis. Although Wnt/ß-catenin signaling is known to be essential for skin appendage development, it is unclear which cellular processes are controlled by the signaling and how the precise level of the signaling activity is achieved during placode formation. We have investigated roles for Lrp4 and its potential ligand Wise (Sostdc1) in mammary and other skin appendage placodes. Lrp4 mutant mice displayed a delay in placode initiation and changes in distribution and number of mammary precursor cells leading to abnormal morphology, number and position of mammary placodes. These Lrp4 mammary defects, as well as limb defects, were associated with elevated Wnt/ß-catenin signaling and were rescued by reducing the dose of the Wnt co-receptor genes Lrp5 and Lrp6, or by inactivating the gene encoding ß-catenin. Wise-null mice phenocopied a subset of the Lrp4 mammary defects and Wise overexpression reduced the number of mammary precursor cells. Genetic epistasis analyses suggest that Wise requires Lrp4 to exert its function and that, together, they have a role in limiting mammary fate, but Lrp4 has an early Wise-independent role in facilitating placode formation. Lrp4 and Wise mutants also share defects in vibrissa and hair follicle development, suggesting that the roles played by Lrp4 and Wise are common to skin appendages. Our study presents genetic evidence for interplay between Lrp4 and Wise in inhibiting Wnt/ß-catenin signaling and provides an insight into how modulation of Wnt/ß-catenin signaling controls cellular processes important for skin placode formation.

Tenascin-C and tenascin-W in whisker follicle stem cell niches: possible roles in regulating stem cell proliferation and migration.

The whisker follicle has CD34-positive stem cells that migrate from their niche near the bulge along the glassy membrane to the whisker bulb, where they participate in the formation of the whisker shaft. Using immunohistochemistry, we found the glycoprotein tenascin-C in the fibrous capsule of mouse whisker follicles, along the glassy membrane and in the trabecular region surrounding keratin-15-negative, CD34-positive stem cells. The related glycoprotein tenascin-W is found in the CD34-positive stem cell niche, in nearby trabeculae and along the glassy membrane. Tenascin-W is also found in the neural stem cell niche of nearby hair follicles. The formation of stress fibers and focal adhesion complexes in CD34-positive whisker-derived stem cells cultured on fibronectin was inhibited by both tenascin-C and tenascin-W, which is consistent with a role for these glycoproteins in promoting the migration of these cells from the niche to the whisker bulb. Tenascin-C, but not tenascin-W, increased the proliferation of whisker follicle stem cells in vitro. Thus, the CD34-positive whisker follicle stem cell niche contains both tenascin-C and tenascin-W, and these glycoproteins might play a role in directing the migration and proliferation of these stem cells.

Analysis of dermal papilla cell interactome using STRING database to profile the ex vivo hair growth inhibition effect of a vinca alkaloid drug, colchicine.

Dermal papillae (DPs) control the formation of hair shafts. In clinical settings, colchicine (CLC) induces patients' hair shedding. Compared to the control, the ex vivo hair fiber elongation of organ cultured vibrissa hair follicles (HFs) declined significantly after seven days of CLC treatment. The cultured DP cells (DPCs) were used as the experimental model to study the influence of CLC on the protein dynamics of DPs. CLC could alter the morphology and down-regulate the expression of alkaline phosphatase (ALP), the marker of DPC activity, and induce IκBα phosphorylation of DPCs. The proteomic results showed that CLC modulated the expression patterns (fold>2) of 24 identified proteins, seven down-regulated and 17 up-regulated. Most of these proteins were presumably associated with protein turnover, metabolism, structure and signal transduction. Protein-protein interactions (PPI) among these proteins, established by Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database, revealed that they participate in protein metabolic process, translation, and energy production. Furthermore, ubiquitin C (UbC) was predicted to be the controlling hub, suggesting the involvement of ubiquitin-proteasome system in modulating the pathogenic effect of CLC on DPC.

The gephyrin scaffold modulates cortical layer 2/3 pyramidal neuron responsiveness to single whisker stimulation.

Gephyrin is the main scaffolding protein at inhibitory postsynaptic sites, and its clusters are the signaling hubs where several molecular pathways converge. Post-translational modifications (PTMs) of gephyrin alter GABAA receptor clustering at the synapse, but it is unclear how this affects neuronal activity at the circuit level. We assessed the contribution of gephyrin PTMs to microcircuit activity in the mouse barrel cortex by slice electrophysiology and in vivo two-photon calcium imaging of layer 2/3 (L2/3) pyramidal cells during single-whisker stimulation. Our results suggest that, depending on the type of gephyrin PTM, the neuronal activities of L2/3 pyramidal neurons can be differentially modulated, leading to changes in the size of the neuronal population responding to the single-whisker stimulation. Furthermore, we show that gephyrin PTMs have their preference for selecting synaptic GABAA receptor subunits. Our results identify an important role of gephyrin and GABAergic postsynaptic sites for cortical microcircuit function during sensory stimulation.

Cortical astrocyte N-methyl-D-aspartate receptors influence whisker barrel activity and sensory discrimination in mice.

Astrocytes express ionotropic receptors, including N-methyl-D-aspartate receptors (NMDARs). However, the contribution of NMDARs to astrocyte-neuron interactions, particularly in vivo, has not been elucidated. Here we show that a knockdown approach to selectively reduce NMDARs in mouse cortical astrocytes decreases astrocyte Ca2+ transients evoked by sensory stimulation. Astrocyte NMDAR knockdown also impairs nearby neuronal circuits by elevating spontaneous neuron activity and limiting neuronal recruitment, synchronization, and adaptation during sensory stimulation. Furthermore, this compromises the optimal processing of sensory information since the sensory acuity of the mice is reduced during a whisker-dependent tactile discrimination task. Lastly, we rescue the effects of astrocyte NMDAR knockdown on neurons and improve the tactile acuity of the animal by supplying exogenous ATP. Overall, our findings show that astrocytes can respond to nearby neuronal activity via their NMDAR, and that these receptors are an important component for purinergic signaling that regulate astrocyte-neuron interactions and cortical sensory discrimination in vivo.