Integrated analysis of transcriptomic and proteomic alterations in mouse models of ALS/FTD identify early metabolic adaptions with similarities to mitochondrial dysfunction disorders.

OBJECTIVE: Sporadic and familial amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disease that results in loss of motor neurons and, in some patients, associates with frontotemporal dementia (FTD). Apart from the accumulation of proteinaceous deposits, emerging literature indicates that aberrant mitochondrial bioenergetics may contribute to the onset and progression of ALS/FTD. Here we sought to investigate the pathophysiological signatures of mitochondrial dysfunction associated with ALS/FTD. METHODS: By means of label-free mass spectrometry (MS) and mRNA sequencing (mRNA-seq), we report pre-symptomatic changes in the cortices of TDP-43 and FUS mutant mouse models. Using tissues from transgenic mouse models of mitochondrial diseases as a reference, we performed comparative analyses and extracted unique and common mitochondrial signatures that revealed neuroprotective compensatory mechanisms in response to early damage. RESULTS: In this regard, upregulation of both Acyl-CoA Synthetase Long-Chain Family Member 3 (ACSL3) and mitochondrial tyrosyl-tRNA synthetase 2 (YARS2) were the most representative change in pre-symptomatic ALS/FTD tissues, suggesting that fatty acid beta-oxidation and mitochondrial protein translation are mechanisms of adaptation in response to ALS/FTD pathology. CONCLUSIONS: Together, our unbiased integrative analyses unveil novel molecular components that may influence mitochondrial homeostasis in the earliest phase of ALS.

BCL7A-containing SWI/SNF/BAF complexes modulate mitochondrial bioenergetics during neural progenitor differentiation.

Mammalian SWI/SNF/BAF chromatin remodeling complexes influence cell lineage determination. While the contribution of these complexes to neural progenitor cell (NPC) proliferation and differentiation has been reported, little is known about the transcriptional profiles that determine neurogenesis or gliogenesis. Here, we report that BCL7A is a modulator of the SWI/SNF/BAF complex that stimulates the genome-wide occupancy of the ATPase subunit BRG1. We demonstrate that BCL7A is dispensable for SWI/SNF/BAF complex integrity, whereas it is essential to regulate Notch/Wnt pathway signaling and mitochondrial bioenergetics in differentiating NPCs. Pharmacological stimulation of Wnt signaling restores mitochondrial respiration and attenuates the defective neurogenic patterns observed in NPCs lacking BCL7A. Consistently, treatment with an enhancer of mitochondrial biogenesis, pioglitazone, partially restores mitochondrial respiration and stimulates neuronal differentiation of BCL7A-deficient NPCs. Using conditional BCL7A knockout mice, we reveal that BCL7A expression in NPCs and postmitotic neurons is required for neuronal plasticity and supports behavioral and cognitive performance. Together, our findings define the specific contribution of BCL7A-containing SWI/SNF/BAF complexes to mitochondria-driven NPC commitment, thereby providing a better understanding of the cell-intrinsic transcriptional processes that connect metabolism, neuronal morphogenesis, and cognitive flexibility.

AIFM1 beyond cell death: An overview of this OXPHOS-inducing factor in mitochondrial diseases.

Apoptosis-inducing factor (AIF) is a mitochondrial intermembrane space flavoprotein with diverse functions in cellular physiology. In this regard, a large number of studies have elucidated AIF's participation to chromatin condensation during cell death in development, cancer, cardiovascular and brain disorders. However, the discovery of rare AIFM1 mutations in patients has shifted the interest of biomedical researchers towards AIF's contribution to pathogenic mechanisms underlying inherited AIFM1-linked metabolic diseases. The functional characterization of AIF binding partners has rapidly advanced our understanding of AIF biology within the mitochondria and beyond its widely reported role in cell death. At the present time, it is reasonable to assume that AIF contributes to cell survival by promoting biogenesis and maintenance of the mitochondrial oxidative phosphorylation (OXPHOS) system. With this review, we aim to outline the current knowledge around the vital role of AIF by primarily focusing on currently reported human diseases that have been linked to AIFM1 deficiency.

SGPL1 stimulates VPS39 recruitment to the mitochondria in MICU1 deficient cells.

OBJECTIVE: Mitochondrial "retrograde" signaling may stimulate organelle biogenesis as a compensatory adaptation to aberrant activity of the oxidative phosphorylation (OXPHOS) system. To maintain energy-consuming processes in OXPHOS deficient cells, alternative metabolic pathways are functionally coupled to the degradation, recycling and redistribution of biomolecules across distinct intracellular compartments. While transcriptional regulation of mitochondrial network expansion has been the focus of many studies, the molecular mechanisms promoting mitochondrial maintenance in energy-deprived cells remain poorly investigated. METHODS: We performed transcriptomics, quantitative proteomics and lifespan assays to identify pathways that are mechanistically linked to mitochondrial network expansion and homeostasis in Caenorhabditis elegans lacking the mitochondrial calcium uptake protein 1 (MICU-1/MICU1). To support our findings, we carried out biochemical and image analyses in mammalian cells and mouse-derived tissues. RESULTS: We report that micu-1(null) mutations impair the OXPHOS system and promote C. elegans longevity through a transcriptional program that is independent of the mitochondrial calcium uniporter MCU-1/MCU and the essential MCU regulator EMRE-1/EMRE. We identify sphingosine phosphate lyase SPL-1/SGPL1 and the ATFS-1-target HOPS complex subunit VPS-39/VPS39 as critical lifespan modulators of micu-1(null) mutant animals. Cross-species investigation indicates that SGPL1 upregulation stimulates VPS39 recruitment to the mitochondria, thereby enhancing mitochondria-lysosome contacts. Consistently, VPS39 downregulation compromises mitochondrial network maintenance and basal autophagic flux in MICU1 deficient cells. In mouse-derived muscles, we show that VPS39 recruitment to the mitochondria may represent a common signature associated with altered OXPHOS system. CONCLUSIONS: Our findings reveal a previously unrecognized SGPL1/VPS39 axis that stimulates intracellular organelle interactions and sustains autophagy and mitochondrial homeostasis in OXPHOS deficient cells.

CEST-2.2 overexpression alters lipid metabolism and extends longevity of mitochondrial mutants.

Mitochondrial dysfunction can either extend or decrease Caenorhabditis elegans lifespan, depending on whether transcriptionally regulated responses can elicit durable stress adaptation to otherwise detrimental lesions. Here, we test the hypothesis that enhanced metabolic flexibility is sufficient to circumvent bioenergetic abnormalities associated with the phenotypic threshold effect, thereby transforming short-lived mitochondrial mutants into long-lived ones. We find that CEST-2.2, a carboxylesterase mainly localizes in the intestine, may stimulate the survival of mitochondrial deficient animals. We report that genetic manipulation of cest-2.2 expression has a minor lifespan impact on wild-type nematodes, whereas its overexpression markedly extends the lifespan of complex I-deficient gas-1(fc21) mutants. We profile the transcriptome and lipidome of cest-2.2 overexpressing animals and show that CEST-2.2 stimulates lipid metabolism and fatty acid beta-oxidation, thereby enhancing mitochondrial respiratory capacity through complex II and LET-721/ETFDH, despite the inherited genetic lesion of complex I. Together, our findings unveil a metabolic pathway that, through the tissue-specific mobilization of lipid deposits, may influence the longevity of mitochondrial mutant C. elegans.

Unbiased proteomic profiling reveals the IP3R modulator AHCYL1/IRBIT as a novel interactor of microtubule-associated protein tau.

Microtubule-associated protein tau is a naturally unfolded protein that can modulate a vast array of physiological processes through direct or indirect binding with molecular partners. Aberrant tau homeostasis has been implicated in the pathogenesis of several neurodegenerative disorders, including Alzheimer's disease. In this study, we performed an unbiased high-content protein profiling assay by incubating recombinant human tau on microarrays containing thousands of human polypeptides. Among the putative tau-binding partners, we identify SAH hydrolase-like protein 1/inositol 1,4,5-trisphosphate receptor (IP3R)-binding protein (AHCYL1/IRBIT), a member of the SAH hydrolase family and a previously described modulator of IP3R activity. Using coimmunoprecipitation assays, we show that endogenous as well as overexpressed tau can physically interact with AHCYL1/IRBIT in brain tissues and cultured cells. Proximity ligation assay experiments demonstrate that tau overexpression may modify the close localization of AHCYL1/IRBIT to IP3R at the endoplasmic reticulum. Together, our experimental evidence indicates that tau interacts with AHCYL1/IRBIT and potentially modulates AHCYL1/IRBIT function.

Microglia jointly degrade fibrillar alpha-synuclein cargo by distribution through tunneling nanotubes.

Microglia are the CNS resident immune cells that react to misfolded proteins through pattern recognition receptor ligation and activation of inflammatory pathways. Here, we studied how microglia handle and cope with α-synuclein (α-syn) fibrils and their clearance. We found that microglia exposed to α-syn establish a cellular network through the formation of F-actin-dependent intercellular connections, which transfer α-syn from overloaded microglia to neighboring naive microglia where the α-syn cargo got rapidly and effectively degraded. Lowering the α-syn burden attenuated the inflammatory profile of microglia and improved their survival. This degradation strategy was compromised in cells carrying the LRRK2 G2019S mutation. We confirmed the intercellular transfer of α-syn assemblies in microglia using organotypic slice cultures, 2-photon microscopy, and neuropathology of patients. Together, these data identify a mechanism by which microglia create an "on-demand" functional network in order to improve pathogenic α-syn clearance.

Alopecia in Harlequin mutant mice is associated with reduced AIF protein levels and expression of retroviral elements.

We investigated the contribution of apoptosis-inducing factor (AIF), a key regulator of mitochondrial biogenesis, in supporting hair growth. We report that pelage abnormalities developed during hair follicle (HF) morphogenesis in Harlequin (Hq) mutant mice. Fragility of the hair cortex was associated with decreased expression of genes encoding structural hair proteins, though key transcriptional regulators of HF development were expressed at normal levels. Notably, Aifm1 (R200 del) knockin males and Aifm1(R200 del)/Hq females showed minor hair defects, despite substantially reduced AIF levels. Furthermore, we cloned the integrated ecotropic provirus of the Aifm1Hq allele. We found that its overexpression in wild-type keratinocyte cell lines led to down-regulation of HF-specific Krt84 and Krtap3-3 genes without altering Aifm1 or epidermal Krt5 expression. Together, our findings imply that pelage paucity in Hq mutant mice is mechanistically linked to severe AIF deficiency and is associated with the expression of retroviral elements that might potentially influence the transcriptional regulation of structural hair proteins.

Comparative analysis of CI- and CIV-containing respiratory supercomplexes at single-cell resolution.

Mitochondria sustain the energy demand of the cell. The composition and functional state of the mitochondrial oxidative phosphorylation system are informative indicators of organelle bioenergetic capacity. Here, we describe a highly sensitive and reproducible method for a single-cell quantification of mitochondrial CI- and CIV-containing respiratory supercomplexes (CI∗CIV-SCs) as an alternative means of assessing mitochondrial respiratory chain integrity. We apply a proximity ligation assay (PLA) and stain CI∗CIV-SCs in fixed human and mouse brains, tumorigenic cells, induced pluripotent stem cells (iPSCs) and iPSC-derived neural precursor cells (NPCs), and neurons. Spatial visualization of CI∗CIV-SCs enables the detection of mitochondrial lesions in various experimental models, including complex tissues undergoing degenerative processes. We report that comparative assessments of CI∗CIV-SCs facilitate the quantitative profiling of even subtle mitochondrial variations by overcoming the confounding effects that mixed cell populations have on other measurements. Together, our PLA-based analysis of CI∗CIV-SCs is a sensitive and complementary technique for detecting cell-type-specific mitochondrial perturbations in fixed materials.

Loss of Ryanodine Receptor 2 impairs neuronal activity-dependent remodeling of dendritic spines and triggers compensatory neuronal hyperexcitability.

Dendritic spines are postsynaptic domains that shape structural and functional properties of neurons. Upon neuronal activity, Ca2+ transients trigger signaling cascades that determine the plastic remodeling of dendritic spines, which modulate learning and memory. Here, we study in mice the role of the intracellular Ca2+ channel Ryanodine Receptor 2 (RyR2) in synaptic plasticity and memory formation. We demonstrate that loss of RyR2 in pyramidal neurons of the hippocampus impairs maintenance and activity-evoked structural plasticity of dendritic spines during memory acquisition. Furthermore, post-developmental deletion of RyR2 causes loss of excitatory synapses, dendritic sparsification, overcompensatory excitability, network hyperactivity and disruption of spatially tuned place cells. Altogether, our data underpin RyR2 as a link between spine remodeling, circuitry dysfunction and memory acquisition, which closely resemble pathological mechanisms observed in neurodegenerative disorders.

Multi-omics identify xanthine as a pro-survival metabolite for nematodes with mitochondrial dysfunction.

Aberrant mitochondrial function contributes to the pathogenesis of various metabolic and chronic disorders. Inhibition of insulin/IGF-1 signaling (IIS) represents a promising avenue for the treatment of mitochondrial diseases, although many of the molecular mechanisms underlying this beneficial effect remain elusive. Using an unbiased multi-omics approach, we report here that IIS inhibition reduces protein synthesis and favors catabolism in mitochondrial deficient Caenorhabditis elegans We unveil that the lifespan extension does not occur through the restoration of mitochondrial respiration, but as a consequence of an ATP-saving metabolic rewiring that is associated with an evolutionarily conserved phosphoproteome landscape. Furthermore, we identify xanthine accumulation as a prominent downstream metabolic output of IIS inhibition. We provide evidence that supplementation of FDA-approved xanthine derivatives is sufficient to promote fitness and survival of nematodes carrying mitochondrial lesions. Together, our data describe previously unknown molecular components of a metabolic network that can extend the lifespan of short-lived mitochondrial mutant animals.

A disease-associated Aifm1 variant induces severe myopathy in knockin mice.

OBJECTIVE: Mutations in the AIFM1 gene have been identified in recessive X-linked mitochondrial diseases. Functional and molecular consequences of these pathogenic AIFM1 mutations have been poorly studied in vivo. METHODS/RESULTS: Here we provide evidence that the disease-associated apoptosis-inducing factor (AIF) deletion arginine 201 (R200 in rodents) causes pathology in knockin mice. Within a few months, posttranslational loss of the mutant AIF protein induces severe myopathy associated with a lower number of cytochrome c oxidase-positive muscle fibers. At a later stage, Aifm1 (R200 del) knockin mice manifest peripheral neuropathy, but they do not show neurodegenerative processes in the cerebellum, as observed in age-matched hypomorphic Harlequin (Hq) mutant mice. Quantitative proteomic and biochemical data highlight common molecular signatures of mitochondrial diseases, including aberrant folate-driven one-carbon metabolism and sustained Akt/mTOR signaling. CONCLUSION: Our findings indicate metabolic defects and distinct tissue-specific vulnerability due to a disease-causing AIFM1 mutation, with many pathological hallmarks that resemble those seen in patients.

The SWI/SNF subunit Bcl7a contributes to motor coordination and Purkinje cell function.

Chromatin remodelers have emerged as prominent regulators of epigenetic processes and potential drivers of various human pathologies. The multi-subunit chromatin-remodeling SWI/SNF complex determines gene expression programs and, consequently, contributes to the differentiation, maturation and plasticity of neurons. Here, we investigate the elusive biological function of Bcl7a and Bcl7b, two newly identified subunits of the SWI/SNF complex that are highly expressed throughout the brain. We generated ubiquitous and neuron-specific Bcl7a and Bcl7b single and double knockout mice. We provide evidence that Bcl7b is dispensable for animal survival as well as behavioral plasticity. Conversely, ubiquitous Bcl7a knockout results in perinatal lethality, while genetic deletion of Bcl7a in postmitotic neurons elicits motor abnormalities and affects dendritic branching of Purkinje cells, with no obvious synergistic relationship with Bcl7b. Collectively, our findings reveal novel insights into the cellular processes linked to BCL7-containing SWI/SNF complexes and their unrecognized roles in the brain.

5-HT2A and mGlu2/3 receptor interactions: on their relevance to cognitive function and psychosis.

Serotonin [5-hydroxytryptamine (5-HT)] and glutamate have both been implicated in the pathophysiology of neuropsychiatric disorders but also in the mechanism of antipsychotic and hallucinogenic drug actions. Furthermore, close antagonistic interactions between 5-HT2A and metabotropic glutamate (mGlu)2/3 receptors have been established over the last decades on the basis of numerous electrophysiological, biochemical, and behavioral studies. Besides synaptic mechanisms, more recent findings suggested that heterodimeric 5-HT2A-mGlu2 receptor complexes in the prefrontal cortex may account for the functional crosstalk between these two receptor subtypes. In this review, we focus on in-vitro and in-vivo studies documenting the important relationship between 5-HT2A and mGlu2/3 receptors, with relevance to both normal behavioral function and psychosis.

Maternal lipopolysaccharide treatment differentially affects 5-HT(2A) and mGlu2/3 receptor function in the adult male and female rat offspring.

Maternal infection during pregnancy increases the risk for the offspring to develop schizophrenia. However, it is still not fully understood which biochemical mechanisms are responsible for the emergence of neuropsychiatric symptoms following prenatal immune activation. The serotonin (5-hydroxytryptamine, 5-HT) and glutamate system have prominently been associated with the schizophrenia pathophysiology but also with the mechanism of antipsychotic drug actions. Here, we investigated the behavioral and cellular response to 5-HT2A and metabotropic glutamate (mGlu)2/3 receptor stimulation in male and female offspring born to lipopolysaccharide (LPS)-treated mothers. Additionally, we assessed protein expression levels of prefrontal 5-HT2A and mGlu2 receptors. Prenatally LPS-exposed male and female offspring showed locomotor hyperactivity and increased head-twitch behavior in response to the 5-HT2A receptor agonist DOI. In LPS-exposed male offspring, the mGlu2/3 receptor agonist LY379268 failed to reduce DOI-induced prepulse inhibition deficits. In LPS-males, the behavioral changes were further accompanied by enhanced DOI-induced c-Fos protein expression and an up-regulation of prefrontal 5-HT2A receptors. No changes in either 5-HT2A or mGlu2 receptor protein levels were found in female offspring. Our data support the hypothesis of an involvement of maternal infection during pregnancy contributing, at least partially, to the pathology of schizophrenia. Identifying biochemical alterations that parallel the behavioral deficits may help to improve therapeutic strategies in the treatment of this mental illness. Since most studies in rodents almost exclusively include male subjects, our data further contribute to elucidating possible gender differences in the effects of prenatal infection on 5-HT2A and mGlu2/3 receptor function.

Prenatal LPS-exposure--a neurodevelopmental rat model of schizophrenia--differentially affects cognitive functions, myelination and parvalbumin expression in male and female offspring.

Maternal infection during pregnancy increases the risk for the offspring to develop schizophrenia. Gender differences can be seen in various features of the illness and sex steroid hormones (e.g. estrogen) have strongly been implicated in the disease pathology. In the present study, we evaluated sex differences in the effects of prenatal exposure to a bacterial endotoxin (lipopolysaccharide, LPS) in rats. Pregnant dams received LPS-injections (100 µg/kg) at gestational day 15 and 16. The offspring was then tested for prepulse inhibition (PPI), locomotor activity, anxiety-like behavior and object recognition memory at various developmental time points. At postnatal day (PD) 33 and 60, prenatally LPS-exposed rats showed locomotor hyperactivity which was similar in male and female offspring. Moreover, prenatal LPS-treatment caused PPI deficits in pubertal (PD45) and adult (PD90) males while PPI impairments were found only at PD45 in prenatally LPS-treated females. Following prenatal LPS-administration, recognition memory for objects was impaired in both sexes with males being more severely affected. Additionally, we assessed prenatal infection-induced alterations of parvalbumin (Parv) expression and myelin fiber density. Male offspring born to LPS-challenged mothers showed decreased myelination in cortical and limbic brain regions as well as reduced numbers of Parv-expressing cells in the medial prefrontal cortex (mPFC), hippocampus and entorhinal cortex. In contrast, LPS-exposed female rats showed only a modest decrease in myelination and Parv immunoreactivity. Collectively, our data indicate that some of the prenatal immune activation effects are sex dependent and further strengthen the importance of taking into account gender differences in animal models of schizophrenia.

DOI-induced deficits in prepulse inhibition in Wistar rats are reversed by mGlu2/3 receptor stimulation.

Prepulse inhibition (PPI) of the acoustic startle response (ASR) provides a measure of sensorimotor gating mechanisms that are impaired in schizophrenia patients. Interactions of the serotonin (5-hydroxytryptamine, 5-HT) and glutamatergic systems, especially via the 5-HT(2A) receptor subtype, have been implicated in the regulation of PPI. The present study investigated the involvement of interactions between 5-HT(2A) and metabotropic glutamate (mGlu)2/3 receptors in modulating PPI in Wistar and Lister Hooded rats. Systemic administration of the 5-HT(2A/2C) receptor agonist DOI ((+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropan hydrochloride; 3mg/kg) reduced PPI and ASR magnitude in Wistar but not in Lister Hooded rats. In Wistar rats, pre-treatment with the mGlu2/3 receptor agonist LY379268 (1mg/kg) attenuated the DOI-induced disruption of PPI as well as the DOI-elicited reductions of ASR magnitude. LY379268 itself did not alter PPI in both strains and only slightly increased ASR magnitudes in Wistar rats. Taken together, these findings support the notion of functionally antagonistic interactions between 5-HT(2A) and mGlu2/3 which might be involved in regulating sensorimotor gating mechanisms. Additionally, the data suggest that stimulation of mGlu2/3 receptors may be useful to ameliorate sensorimotor gating deficits resulting from an overstimulation of 5-HT(2A) receptors.

Pre-treatment with the mGlu2/3 receptor agonist LY379268 attenuates DOI-induced impulsive responding and regional c-Fos protein expression.

RATIONALE: Overactivation of serotonin (5-hydroxytryptamine, 5-HT)(2A) receptors causes impulsivity and attentional deficits. Since 5-HT(2A) receptors are known to entertain antagonistic interactions with metabotropic glutamate (mGlu)2/3 receptors, this interaction may provide an alternative target for a novel class of antipsychotics. OBJECTIVES/METHODS: The study characterizes interactions between 5-HT(2A) and mGlu2/3 receptors implicated in impulse control. Hooded Lister rats were trained in a 5-choice serial reaction time task (5-CSRTT) and treated with the 5-HT(2A/2C) receptor agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropan hydrochloride (DOI, 0.1 mg/kg) and the mGlu2/3 receptor agonist LY379268 (1 mg/kg). In addition, associated drug-induced changes in neuronal activity were assessed via c-Fos immunoreactivity (Fos IR), and co-localization of c-Fos and GABAergic markers was detected using double immunofluorescence labeling. RESULTS: Systemic DOI caused impulsive overresponding that was attenuated in animals pre-treated with LY379268. LY379268 itself had no significant effect on the rats' performance in the 5-CSRTT. DOI enhanced Fos IR within fronto-cortical and limbic brain structures, and this effect was blocked by LY379268 pre-treatment. Double immunofluorescence labeling showed a specific co-localization of DOI-elicited Fos IR with GABAergic (GAD(67)-positive) cells lacking the calcium-binding protein parvalbumin while LY379268 increased Fos IR in GABAergic and non-GABAergic cells. CONCLUSION: Our results suggest that impulsivity is possibly due to a primary increase in Glu transmission mediated via 5-HT(2A) receptor activation. Thus, mGlu2/3 receptor agonists might have some potential for treating motor impulsivity-related impairments while their cognitive enhancing effects were not confirmed in this study.

Impulsive behaviour in rats induced by intracortical DOI infusions is antagonized by co-administration of an mGlu2/3 receptor agonist.

The orbitofrontal cortex (OFC) and the medial prefrontal cortex (mPFC) modulate impulsive behaviours. Serotonin [5-hydroxytryptamine (5-HT)] 2A receptors have also been implicated in impulsivity and govern antagonistic interactions with metabotropic glutamate (mGlu)2/3 receptors. This study examined the interactions between 5-HT2A and mGlu2/3 receptors in the OFC and mPFC with relevance to impulsive choice and impulsive action. Impulsive choice was assessed in Lister Hooded rats, trained in a delay-discounting T-maze task, after bilateral intra-OFC infusions of the 5-HT2A/C receptor agonist DOI [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropan hydrochloride; 5 µg/0.5 µl] and the mGlu2/3 receptor agonist LY379268 (1 µg/0.5 µl). Impulsive action was assessed in a second group of rats trained in a five-choice serial reaction time task (5-CSRTT) and receiving bilateral intra-mPFC infusions of DOI (5 µg/0.5 µl) and LY379268 (1 µg/0.5 µl). Intra-OFC DOI increased impulsive choice, which was not seen when DOI was co-administered with LY379268. LY379268 itself had no effect on choice behaviour. Intra-mPFC DOI caused impulsive over-responding in the 5-CSRTT that was attenuated when DOI and LY379268 were co-injected. Local mPFC-infusions of LY379268 had no effect on 5-CSRTT performance. This study suggests a differential involvement of OFC and mPFC 5-HT2A receptors in impulsive choice and impulsive action. Moreover, compounds acting at mGlu2/3 receptors might have the potential to improve impulsivity-related impairments.