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GTPases of the Rho family are components of signaling pathways linking extracellular signals to the control of cytoskeleton dynamics. Among these, RAC1 plays key roles during brain development, ranging from neuronal migration to neuritogenesis, synaptogenesis, and plasticity. RAC1 activity is positively and negatively controlled by guanine nucleotide exchange factors (GEFs), guanosine nucleotide dissociation inhibitors (GDIs), and GTPase-activating proteins (GAPs), but the specific role of each regulator in vivo is poorly known. ARHGAP15 is a RAC1-specific GAP expressed during development in a fraction of migrating cortical interneurons (CINs) and in the majority of adult CINs. During development, loss of ARHGAP15 causes altered directionality of the leading process of tangentially migrating CINs, along with altered morphology in vitro. Likewise, time-lapse imaging of embryonic CINs revealed a poorly coordinated directional control during radial migration, possibly due to a hyper-exploratory behavior. In the adult cortex, the observed defects lead to subtle alteration in the distribution of CALB2-, SST-, and VIP-positive interneurons. Adult Arhgap15-knock-out mice also show reduced CINs intrinsic excitability, spontaneous subclinical seizures, and increased susceptibility to the pro-epileptic drug pilocarpine. These results indicate that ARHGAP15 imposes a fine negative regulation on RAC1 that is required for morphological maturation and directional control during CIN migration, with consequences on their laminar distribution and inhibitory function.

Additional file 1: Figure S1. No difference in eEF2 phosphorylation levels in total homogenate of liver, kidney, and heart between Scn1a �� and WT mice. (A-C) Western blots and relative quantification for phosphorylated eEF2 in samples of liver (A), kidney (B) and heart (C) show no significant difference in 3, 6 and 9 months old in Scn1a �� mice compared with WT mice. All Data are presented as mean �� SEM; N = 4 per group. One-sample t-test. Figure S2. Genetic characterization and levels of phosphorylated eEF2 in WT, Scn1a �� , eEF2K���/��� and Scn1a �� eEF2K���/��� mice. (A) Representative PCR for SCN1A gene (left). WT Scn1a+/+ (WT) mice display single band of 300 bp, heterozygous Scn1a �� mice display one at 300 bp and the other ad 150 bp. Representative PCR for eEF2K gene (right). Length of the bands for WT and KO is at the same high at 1.2 kb. Two different PCR were performed for WT and KO. (B) Representative western blot and relative quantification for phosphorylated eEF2 in hippocampus and cerebral cortex of eEF2K���/���, Scn1a �� , WT (Scn1a+/+ eEF2K+/ +) and Scn1a �� eEF2K���/��� show that eEF2 phosphorylation is totally absent in eEF2K���/��� and Scn1a �� eEF2K���/��� mice. All data are presented as mean �� SEM. N = 4 per group. Statistical analysis ***p

Summary NMDA receptor (NMDAR) subunit composition plays a pivotal role in synaptic plasticity at excitatory synapses. Still, the mechanisms responsible for the synaptic retention of NMDARs following induction of plasticity need to be fully elucidated. Rabphilin3A (Rph3A) is involved in the stabilization of NMDARs at synapses through the formation of a complex with GluN2A and PSD-95. Here we used different protocols to induce synaptic plasticity in the presence or absence of agents modulating Rph3A function. The use of Forskolin/Rolipram/Picrotoxin cocktail to induce chemical LTP led to synaptic accumulation of Rph3A and formation of synaptic GluN2A/Rph3A complex. Notably, Rph3A silencing or use of peptides interfering with the GluN2A/Rph3A complex blocked LTP induction. Moreover, in vivo disruption of GluN2A/Rph3A complex led to a profound alteration of spatial memory. Overall, our results demonstrate a molecular mechanism needed for NMDAR stabilization at synapses after plasticity induction and to trigger downstream signaling events necessary for cognitive behavior., Graphical Abstract, Highlights • LTP induces trafficking of Rph3A at synapses and formation of GluN2A/Rph3A complex • Disruption of Rph3A/GluN2A complex leads to LTP impairment • Rph3A/GluN2A complex is needed for modifications of dendritic spines induced by LTP • Disruption of Rph3A/GluN2A complex leads to spatial memory impairment, Molecular Interaction; Neuroscience; Molecular Neuroscience

Recently, a potential neuroprotective effect of rimonabant, independent of the CB1 receptor interaction, has been proposed. In the present study, the role of transient receptor potential channel vanilloid subfamily member 1, named VR1, on neuroprotective effect of rimonabant, on global cerebral ischemia in gerbils, was investigated. Rimonabant (0.05-3 mg kg-1), given i.p. 5 min after recirculation, dose dependently antagonized the ischemia-induced decrease in electroencephalographic (EEG) total spectral power and restored relative frequency band distribution 7 days after ischemia. Rimonabant (0.125-0.5 mg kg-1) fully prevented ischemia-induced hyperlocomotion 1 day after ischemia and memory impairment evaluated in a passive avoidance task, 3 days after ischemia. At 7 days after ischemia, the survival of pyramidal cells, in the CA1 subfield, was respectively 91 and 96%, in the animals given rimonabant 0.25 and 0.5 mg kg-1, compared to the vehicle group. Higher doses were not protective. The protection induced by rimonabant followed a bell-shaped curve, the maximal active doses being 0.25 and 0.5 mg kg-1. Capsazepine (0.01 mg kg-1), a selective VR1 vanilloid receptor antagonist, completely reversed rimonabant-induced neuroprotective effects against EEG flattening, memory impairment and CA1 hippocampal neuronal loss. These findings suggest that VR1 vanilloid receptors are involved in rimonabant's neuroprotection even if other mechanisms can contribute to this effect.

1. Capsaicin, the irritant principle of hot peppers, is a vanilloid agonist known to activate the transient receptor potential channel vanilloid subfamily member 1 (VR1), recently reported to be involved in neurodegeneration. The present study investigated the role of VR1 in a model of global cerebral ischemia in gerbils. 2. Over the dose range tested, capsaicin (0.01, 0.025, 0.05, 0.2 and 0.6 mg kg(-1)), given 5 min after recirculation, dose-dependently antagonized the ischemia-induced electroencephalographic total spectral power decrease and restored relative frequency band distribution evaluated 7 days after ischemia. 3. Capsaicin, at all tested doses, fully prevented ischemia-induced hyperlocomotion evaluated 1 day after ischemia. 4. Capsaicin dose-dependently antagonized ischemia-induced memory impairment evaluated in a passive avoidance task, 3 days after ischemia. 5. Capsaicin showed a dose-dependent hypothermic effect evaluated for 2 h after recirculation. 6. At 7 days after ischemia, a progressive survival of pyramidal cells in the CA1 subfield in capsaicin-treated gerbils, with a maximum of 80%, at a dose of 0.2 mg kg(-1), was obtained. 7. The selective VR1 antagonist, capsazepine (0.01 mg kg(-1)), reversed capsaicin-induced protective effects, in a competitive manner. 8. These results suggest that the neuroprotective effect of capsaicin may be attributable, at least in part, to VR1 desensitization and provide a valuable target for development of interventional pharmacological strategies.

Synaptosomal-associated protein of 25 kDa (SNAP-25) is a protein that participates in the regulation of synaptic vesicle exocytosis through the formation of the soluble NSF attachment protein receptor complex and modulates voltage-gated calcium channels activity. The Snap25 gene has been associated with schizophrenia, attention deficit hyperactivity disorder, and bipolar disorder, and lower levels of SNAP-25 have been described in patients with schizophrenia. We used SNAP-25 heterozygous (SNAP-25+/−) mice to investigate at which extent the reduction of the protein levels affects neuronal network function and mouse behavior. As interactions of genotype with the specific laboratory conditions may impact behavioral results, the study was performed through a multilaboratory study in which behavioral tests were replicated in at least 2 of 3 distinct European laboratories. Reductions of SNAP-25 levels were associated with a moderate hyperactivity, which disappeared in the adult animals, and with impaired associative learning and memory. Electroencephalographic recordings revealed the occurrence of frequent spikes, suggesting a diffuse network hyperexcitability. Consistently, SNAP-25+/− mice displayed higher susceptibility to kainate-induced seizures, paralleled by degeneration of hilar neurons. Notably, both EEG profile and cognitive defects were improved by antiepileptic drugs. These results indicate that reduction of SNAP-25 expression is associated to generation of epileptiform discharges and cognitive dysfunctions, which can be effectively treated by antiepileptic drugs., Cerebral Cortex, 24 (2), ISSN:1047-3211, ISSN:1460-2199

Smoking cessation induces a withdrawal syndrome associated with anxiety, depression, and impaired neurocognitive functions, but much less is known about the withdrawal of e-cigarettes (e-CIG). We investigated in Balb/c mice the behavioural and neurochemical effects of withdrawal for up to 90 days after seven weeks' intermittent exposure to e-CIG vapour or cigarette smoke (CIG). The withdrawal of e-CIG and CIG induced early behavioural alterations such as spatial memory deficits (spatial object recognition task), increased anxiety (elevated plus maze test) and compulsive-like behaviour (marble burying test) that persisted for 60-90 days. Notably, attention-related (virtual object recognition task) and depression-like behaviours (tail suspension and sucrose preference tests) appeared only 15-30 days after withdrawal and persisted for as long as up to 90 days. At hippocampal level, the withdrawal-induced changes in the levels of AMPA receptor GluA1 and GluA2/3 subunits, PSD 95 protein, corticotropin-releasing factor (Crf) and Crf receptor 1 (CrfR1) mRNA were biphasic: AMPA receptor subunit and PSD95 protein levels initially remained unchanged and decreased after 60-90 days, whereas Crf/CrfR1 mRNA levels initially increased and then markedly decreased after 60 days. These late reductions correlated with the behavioural impairments, particularly the appearance of depression-like behaviours. Our findings show that major behavioural and neurochemical alterations persist or even first appear late after the withdrawal of chronic CIG smoke or e-CIG vapour exposure, and underline importance of conducting similar studies of humans, including e-CIG vapers.

Alterations in the balance of inhibitory and excitatory synaptic transmission have been implicated in the pathogenesis of neurological disorders such as epilepsy. Eukaryotic elongation factor 2 kinase (eEF2K) is a highly regulated, ubiquitous kinase involved in the control of protein translation. Here, we show that eEF2K activity negatively regulates GABAergic synaptic transmission. Indeed, loss of eEF2K increases GABAergic synaptic transmission by upregulating the presynaptic protein Synapsin 2b and α5-containing GABAA receptors and thus interferes with the excitation/inhibition balance. This cellular phenotype is accompanied by an increased resistance to epilepsy and an impairment of only a specific hippocampal-dependent fear conditioning. From a clinical perspective, our results identify eEF2K as a potential novel target for antiepileptic drugs, since pharmacological and genetic inhibition of eEF2K can revert the epileptic phenotype in a mouse model of human epilepsy.