Hippocampal GluA1 expression in Gria1 −/− mice only partially restores spatial memory performance deficits

Nonlinear super-resolution signal processing allows intracellular tracking of calcium dynamics

Objective.Traditional quantification of fluorescence signals, such asΔF/F, relies on ratiometric measures that necessitate a baseline for comparison, limiting their applicability in dynamic analyses. Our goal here is to develop a baseline-independent method for analyzing fluorescence data that fully exploits temporal dynamics to introduce a novel approach for dynamical super-resolution analysis, including in subcellular resolution.Approach.We introduce ARES (Autoregressive RESiduals), a novel method that leverages the temporal aspect of fluorescence signals. By focusing on the quantification of residuals following linear autoregression, ARES obviates the need for a predefined baseline, enabling a more nuanced analysis of signal dynamics.Main result.We delineate the foundational attributes of ARES, illustrating its capability to enhance both spatial and temporal resolution of calcium fluorescence activity beyond the conventional ratiometric measure (ΔF/F). Additionally, we demonstrate ARES's utility in elucidating intracellular calcium dynamics through the detailed observation of calcium wave propagation within a dendrite.Significance.ARES stands out as a robust and precise tool for the quantification of fluorescence signals, adept at analyzing both spontaneous and evoked calcium dynamics. Its ability to facilitate the subcellular localization of calcium signals and the spatiotemporal tracking of calcium dynamics-where traditional ratiometric measures falter-underscores its potential to revolutionize baseline-independent analyses in the field.

The ortholog of human ssDNA-binding protein SSBP3 influences neurodevelopment and autism-like behaviors in Drosophila melanogaster

1p32.3 microdeletion/duplication is implicated in many neurodevelopmental disorders-like phenotypes such as developmental delay, intellectual disability, autism, macro/microcephaly, and dysmorphic features. The 1p32.3 chromosomal region harbors several genes critical for development; however, their validation and characterization remain inadequate. One such gene is the single-stranded DNA-binding protein 3 (SSBP3) and its Drosophila melanogaster ortholog is called sequence-specific single-stranded DNA-binding protein (Ssdp). Here, we investigated consequences of Ssdp manipulations on neurodevelopment, gene expression, physiological function, and autism-associated behaviors using Drosophila models. We found that SSBP3 and Ssdp are expressed in excitatory neurons in the brain. Ssdp overexpression caused morphological alterations in Drosophila wing, mechanosensory bristles, and head. Ssdp manipulations also affected the neuropil brain volume and glial cell number in larvae and adult flies. Moreover, Ssdp overexpression led to differential changes in synaptic density in specific brain regions. We observed decreased levels of armadillo in the heads of Ssdp overexpressing flies, as well as a decrease in armadillo and wingless expression in the larval wing discs, implicating the involvement of the canonical Wnt signaling pathway in Ssdp functionality. RNA sequencing revealed perturbation of oxidative stress-related pathways in heads of Ssdp overexpressing flies. Furthermore, Ssdp overexpressing brains showed enhanced reactive oxygen species (ROS), altered neuronal mitochondrial morphology, and up-regulated fission and fusion genes. Flies with elevated levels of Ssdp exhibited heightened anxiety-like behavior, altered decisiveness, defective sensory perception and habituation, abnormal social interaction, and feeding defects, which were phenocopied in the pan-neuronal Ssdp knockdown flies, suggesting that Ssdp is dosage sensitive. Partial rescue of behavioral defects was observed upon normalization of Ssdp levels. Notably, Ssdp knockdown exclusively in adult flies did not produce behavioral and functional defects. Finally, we show that optogenetic manipulation of Ssdp-expressing neurons altered autism-associated behaviors. Collectively, our findings provide evidence that Ssdp, a dosage-sensitive gene in the 1p32.3 chromosomal region, is associated with various anatomical, physiological, and behavioral defects, which may be relevant to neurodevelopmental disorders like autism. Our study proposes SSBP3 as a critical gene in the 1p32.3 microdeletion/duplication genomic region and sheds light on the functional role of Ssdp in neurodevelopmental processes in Drosophila.

Mechanical transmission at spine synapses: Short-term potentiation and working memory

Do dendritic spines, which comprise the postsynaptic component of most excitatory synapses, exist only for their structural dynamics, receptor trafficking, and chemical and electrical compartmentation? The answer is no. Simultaneous investigation of both spine and presynaptic terminals has recently revealed a novel feature of spine synapses. Spine enlargement pushes the presynaptic terminals with muscle-like force and augments the evoked glutamate release for up to 20 min. We now summarize the evidence that such mechanical transmission shares critical features in common with short-term potentiation (STP) and may represent the cellular basis of short-term and working memory. Thus, spine synapses produce the force of learning to leave structural traces for both short and long-term memories.

Disrupting the nNOS/NOS1AP interaction in the medial prefrontal cortex impairs social recognition and spatial working memory in mice

The neuronal isoform of nitric oxide synthase (nNOS) and its interacting protein NOS1AP have been linked to several mental disorders including schizophrenia and depression. An increase in the interaction between nNOS and NOS1AP in the frontal cortex has been suggested to contribute to the emergence of these disorders. Here we aimed to uncover whether disruption of their interactions in the frontal cortex leads to mental disorder endophenotypes. Targeting the medial prefrontal cortex (mPFC), we stereotaxically injected wild-type C57BL/6J mice with recombinant adeno-associated virus (rAAV) expressing either full-length NOS1AP, the nNOS binding region of NOS1AP (i.e. NOS1AP_396-503), or the nNOS amino-terminus (i.e. nNOS_1-133), which was shown to disrupt the interaction of endogenous nNOS with PSD-95. We tested these mice in a comprehensive behavioural battery, assessing different endophenotypes related to mental disorders. We found no differences in anxiety-related and exploratory behaviours. Likewise, social interaction was comparable in all groups. However, social recognition was impaired in NOS1AP and NOS1AP_396-503 mice. These mice, as well as mice overexpressing nNOS_1-133 also displayed impaired spatial working memory (SWM) capacity, while spatial reference memory (SRM) remained intact. Finally, mice overexpressing NOS1AP and nNOS_1-133, but not NOS1AP_396-503, failed to habituate to the startling pulses in an acoustic startle response (ASR) paradigm, though we found no difference in overall startle intensity or prepulse inhibition (PPI) of the ASR. Our findings indicate a distinct role of NOS1AP/nNOS/PSD-95 interactions in the mPFC to contribute to specific endophenotypic changes observed in different mental disorders.

Unraveling the mysteries of dendritic spine dynamics: Five key principles shaping memory and cognition

Recent research extends our understanding of brain processes beyond just action potentials and chemical transmissions within neural circuits, emphasizing the mechanical forces generated by excitatory synapses on dendritic spines to modulate presynaptic function. From in vivo and in vitro studies, we outline five central principles of synaptic mechanics in brain function: P1: Stability - Underpinning the integral relationship between the structure and function of the spine synapses. P2: Extrinsic dynamics - Highlighting synapse-selective structural plasticity which plays a crucial role in Hebbian associative learning, distinct from pathway-selective long-term potentiation (LTP) and depression (LTD). P3: Neuromodulation - Analyzing the role of G-protein-coupled receptors, particularly dopamine receptors, in time-sensitive modulation of associative learning frameworks such as Pavlovian classical conditioning and Thorndike's reinforcement learning (RL). P4: Instability - Addressing the intrinsic dynamics crucial to memory management during continual learning, spotlighting their role in "spine dysgenesis" associated with mental disorders. P5: Mechanics - Exploring how synaptic mechanics influence both sides of synapses to establish structural traces of short- and long-term memory, thereby aiding the integration of mental functions. We also delve into the historical background and foresee impending challenges.

Distinct contributions of GluA1-containing AMPA receptors of different hippocampal subfields to salience processing, memory and impulse control

Schizophrenia is associated with a broad range of severe and currently pharmacoresistant cognitive deficits. Prior evidence suggests that hypofunction of AMPA-type glutamate receptors (AMPARs) containing the subunit GLUA1, encoded by GRIA1, might be causally related to impairments of selective attention and memory in this disorder, at least in some patients. In order to clarify the roles of GluA1 in distinct cell populations, we investigated behavioural consequences of selective Gria1-knockout in excitatory neurons of subdivisions of the prefrontal cortex and the hippocampus, assessing sustained attention, impulsivity, cognitive flexibility, anxiety, sociability, hyperactivity, and various forms of short-term memory in mice. We found that virally induced reduction of GluA1 across multiple hippocampal subfields impaired spatial working memory. Transgene-mediated ablation of GluA1 from excitatory cells of CA2 impaired short-term memory for conspecifics and objects. Gria1 knockout in CA3 pyramidal cells caused mild impairments of object-related and spatial short-term memory, but appeared to partially increase social interaction and sustained attention and to reduce motor impulsivity. Our data suggest that reduced hippocampal GluA1 expression-as seen in some patients with schizophrenia-may be a central cause particularly for several short-term memory deficits. However, as impulse control and sustained attention actually appeared to improve with GluA1 ablation in CA3, strategies of enhancement of AMPAR signalling likely require a fine balance to be therapeutically effective across the broad symptom spectrum of schizophrenia.

Hippocampal overexpression of NOS1AP promotes endophenotypes related to mental disorders

BACKGROUND

Nitric oxide synthase 1 adaptor protein (NOS1AP; previously named CAPON) is linked to the glutamatergic postsynaptic density through interaction with neuronal nitric oxide synthase (nNOS). NOS1AP and its interaction with nNOS have been associated with several mental disorders. Despite the high levels of NOS1AP expression in the hippocampus and the relevance of this brain region in glutamatergic signalling as well as mental disorders, a potential role of hippocampal NOS1AP in the pathophysiology of these disorders has not been investigated yet.

METHODS

To uncover the function of NOS1AP in hippocampus, we made use of recombinant adeno-associated viruses to overexpress murine full-length NOS1AP or the NOS1AP carboxyterminus in the hippocampus of mice. We investigated these mice for changes in gene expression, neuronal morphology, and relevant behavioural phenotypes.

FINDINGS

We found that hippocampal overexpression of NOS1AP markedly increased the interaction of nNOS with PSD-95, reduced dendritic spine density, and changed dendritic spine morphology at CA1 synapses. At the behavioural level, we observed an impairment in social memory and decreased spatial working memory capacity.

INTERPRETATION

Our data provide a mechanistic explanation for a highly selective and specific contribution of hippocampal NOS1AP and its interaction with the glutamatergic postsynaptic density to cross-disorder pathophysiology. Our findings allude to therapeutic relevance due to the druggability of this molecule.

FUNDING

This study was funded in part by the DFG, the BMBF, the Academy of Finland, the NIH, the Japanese Society of Clinical Neuropsychopharmacology, the Ministry of Education of the Russian Federation, and the European Community.

Cathinone: An alkaloid of Catha edulis (Khat) exacerbated hyperglycemia in diabetes-induced rats

Cathinone, the main bioactive alkaloid of Catha edulis (khat), slightly increased the blood sugar levels of healthy animals, while its effect on blood sugar levels of diabetic animals has not yet been reported. This study investigated the in vitro inhibition of cathinone on α-amylase and α-glucosidase as well as its in vivo glycemic effects in diabetes-induced rats. Rats were fed on a high fat diet for five weeks, which then intraperitoneally injected with streptozotocin (30 mg/kg). Diabetic rats were distributed randomly into diabetic control (DC, n = 5), 10 mg/kg glibenclamide-treated group (DG, n = 5), and 1.6 mg/kg cathinone-treated group (CAD, n = 5). Additional healthy untreated rats (n = 5) served as a nondiabetic negative control group. Throughout the experiment, fasting blood sugar (FBS), caloric intake and body weight were recorded weekly. By the 28th day of treatment, rats were euthanized to obtain blood samples and pancreases. The results demonstrated that cathinone exerted a significantly less potent in vitro inhibition than α-acarbose against α-amylase and α-glucosidase. As compared to diabetic control group, cathinone significantly increased FBS of diabetic rats, while insulin levels of diabetic rats significantly decreased. In conclusion, cathinone was unable to induce a substantial in vitro inhibition on α-amylase and α-glucosidase, while it exacerbated the hyperglycemia of diabetes-induced rats.

Genetic manipulations of AMPA glutamate receptors in hippocampal synaptic plasticity

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are the principal mediators of fast excitatory synaptic transmission and they are required for various forms of synaptic plasticity, including long-term potentiation (LTP) and depression (LTD), which are key mechanisms of learning and memory. AMPARs are tetrameric complexes assembled from four subunits (GluA1-4), however, the lack of subunit-specific pharmacological tools has made the assessment of individual subunits difficult. The application of genetic techniques, particularly gene targeting, allows for precise manipulation and dissection of each subunit in the regulation of neuronal function and behaviour. In this review, we summarize studies using various mouse models with genetically altered AMPARs and focus on their roles in basal synaptic transmission, LTP, and LTD at the hippocampal CA1 synapse. These studies provide strong evidence that there are multiple forms of LTP and LTD at this synapse which can be induced by various induction protocols, and they are differentially regulated by different AMPAR subunits and domains. We conclude that it is necessary to delineate the mechanism of each of these forms of plasticity and their contribution to memory and brain disorders.

Effect of Etazolate upon Cuprizone-induced Demyelination In Vivo: Behavioral and Myelin Gene Analysis

Demyelination is a well-known pathological process in CNS disorders such as multiple sclerosis (MS). It provokes progressive axonal degeneration and functional impairments and no efficient therapy is presently available to combat such insults. Recently, we have shown that etazolate, a pyrazolopyridine compound and an α-secretase activator, was able to promote myelin protection and remyelination after cuprizone (CPZ)-induced acute demyelination in C57Bl/6 mice. In continuation of this work, here we have further investigated the effects of etazolate treatment after acute cuprizone-induced demyelination at the molecular level (expression of myelin genes Plp, Mbp and Mag and inflammatory markers Il-1β, Tnf-α) and at the functional level (locomotor and spatial memory skills) in vivo. To this end, we have employed two protocols which consists of administering etazolate (10 mg/kg/d) for a period of 2 weeks either during (Protocol #1) or after (Protocol #2) 5-weeks of CPZ-induced demyelination. At the molecular level, we observed that CPZ intoxication altered inflammatory and myelin gene expression and it was not restored with either of the etazolate treatment protocols. At the functional level, the locomotor activity was impaired after 3-weeks of CPZ intoxication (Protocol #1) and our data indicates a modest but beneficial effect of etazolate treatment. Spatial memory evaluated was not affected either by CPZ intake or etazolate treatment in both protocols. Altogether, this study shows that the beneficial effect of etazolate upon demyelination does not occur at the gene expression level at the time points studied. Furthermore, our results also highlight the difficulty in revealing functional sequelae following CPZ intoxication.

Genetic and metabolic links between the murine microbiome and memory

BACKGROUND

Recent evidence has linked the gut microbiome to host behavior via the gut-brain axis [1-3]; however, the underlying mechanisms remain unexplored. Here, we determined the links between host genetics, the gut microbiome and memory using the genetically defined Collaborative Cross (CC) mouse cohort, complemented with microbiome and metabolomic analyses in conventional and germ-free (GF) mice.

RESULTS

A genome-wide association analysis (GWAS) identified 715 of 76,080 single-nucleotide polymorphisms (SNPs) that were significantly associated with short-term memory using the passive avoidance model. The identified SNPs were enriched in genes known to be involved in learning and memory functions. By 16S rRNA gene sequencing of the gut microbial community in the same CC cohort, we identified specific microorganisms that were significantly correlated with longer latencies in our retention test, including a positive correlation with Lactobacillus. Inoculation of GF mice with individual species of Lactobacillus (L. reuteri F275, L. plantarum BDGP2 or L. brevis BDGP6) resulted in significantly improved memory compared to uninoculated or E. coli DH10B inoculated controls. Untargeted metabolomics analysis revealed significantly higher levels of several metabolites, including lactate, in the stools of Lactobacillus-colonized mice, when compared to GF control mice. Moreover, we demonstrate that dietary lactate treatment alone boosted memory in conventional mice. Mechanistically, we show that both inoculation with Lactobacillus or lactate treatment significantly increased the levels of the neurotransmitter, gamma-aminobutyric acid (GABA), in the hippocampus of the mice.

CONCLUSION

Together, this study provides new evidence for a link between Lactobacillus and memory and our results open possible new avenues for treating memory impairment disorders using specific gut microbial inoculants and/or metabolites. Video Abstract.

Distinct Genetic Signatures of Cortical and Subcortical Regions Associated with Human Memory

Despite the discovery of gene variants linked to memory performance, understanding the genetic basis of adult human memory remains a challenge. Here, we devised an unsupervised framework that relies on spatial correlations between human transcriptome data and functional neuroimaging maps to uncover the genetic signatures of memory in functionally-defined cortical and subcortical memory regions.

Despite the discovery of gene variants linked to memory performance, understanding the genetic basis of adult human memory remains a challenge. Here, we devised an unsupervised framework that relies on spatial correlations between human transcriptome data and functional neuroimaging maps to uncover the genetic signatures of memory in functionally-defined cortical and subcortical memory regions. Results were validated with animal literature and showed that our framework is highly effective in identifying memory-related processes and genes compared to a control cognitive function. Genes preferentially expressed in cortical memory regions are linked to memory-related processes such as immune and epigenetic regulation. Genes expressed in subcortical memory regions are associated with neurogenesis and glial cell differentiation. Genes expressed in both cortical and subcortical memory areas are involved in the regulation of transcription, synaptic plasticity, and glutamate receptor signaling. Furthermore, distinct memory-associated genes such as PRKCD and CDK5 are linked to cortical and subcortical regions, respectively. Thus, cortical and subcortical memory regions exhibit distinct genetic signatures that potentially reflect functional differences in health and disease, and nominates gene candidates for future experimental investigations.

Real-time contextual feedback for close-loop control of navigation

OBJECTIVE

Close-loop control of brain and behavior will benefit from real-time detection of behavioral events to enable low-latency communication with peripheral devices. In animal experiments, this is typically achieved by using sparsely distributed (embedded) sensors that detect animal presence in select regions of interest. High-speed cameras provide high-density sampling across large arenas, capturing the richness of animal behavior, however, the image processing bottleneck prohibits real-time feedback in the context of rapidly evolving behaviors.

APPROACH

Here we developed an open-source software, named PolyTouch, to track animal behavior in large arenas and provide rapid close-loop feedback in ~5.7 ms, ie. average latency from the detection of an event to analog stimulus delivery, e.g. auditory tone, TTL pulse, when tracking a single body. This stand-alone software is written in JAVA. The included wrapper for MATLAB provides experimental flexibility for data acquisition, analysis and visualization.

MAIN RESULTS

As a proof-of-principle application we deployed the PolyTouch for place awareness training. A user-defined portion of the arena was used as a virtual target; visit (or approach) to the target triggered auditory feedback. We show that mice develop awareness to virtual spaces, tend to stay shorter and move faster when they reside in the virtual target zone if their visits are coupled to relatively high stimulus intensity (⩾49 dB). Thus, close-loop presentation of perceived aversive feedback is sufficient to condition mice to avoid virtual targets within the span of a single session (~20 min).

SIGNIFICANCE

Neuromodulation techniques now allow control of neural activity in a cell-type specific manner in spiking resolution. Using animal behavior to drive closed-loop control of neural activity would help to address the neural basis of behavioral state and environmental context-dependent information processing in the brain.

The role of glutamate receptors in attention-deficit/hyperactivity disorder: From physiology to disease

Attention-deficit hyperactivity disorder (ADHD) is the most common psychiatric disorder in children and adolescents, which is characterized by behavioral problems such as attention deficit, hyperactivity, and impulsivity. As the receptors of the major excitatory neurotransmitter in the mammalian central nervous system (CNS), glutamate receptors (GluRs) are strongly linked to normal brain functioning and pathological processes. Extensive investigations have been made about the structure, function, and regulation of GluR family, describing evidences that support the disruption of these mechanisms in mental disorders, including ADHD. In this review, we briefly described the family and function of GluRs in the CNS, and discussed what is recently known about the role of GluRs in ADHD, that including GluR genes, animal models, and the treatment, which would help us further elucidate the etiology of ADHD.

Mutagenicity and genotoxicity effects of Verbena officinalis leaves extract in Sprague-Dawley Rats

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally, Verbena officinalis L. has been used for reproductive and gynaecological purposes. However, the mutagenicity and genotoxicity of V. officinalis have not been extensively investigated.

AIM OF THE STUDY

To assess the in vitro mutagenicity and in vivo genotoxicity of aqueous extract of V. officinalis leaves using a modified Ames test and rat bone marrow micronucleus assay according to OECD guidelines.

MATERIALS AND METHODS

In vitro Ames test was carried out using different strains of Salmonella (TA97a, TA98, TA100, and TA1535) and Escherichia coli WP2 uvrA (pKM101) in the presence or absence of metabolic activation (S9 mixture). For micronucleus experiment, male and female Sprague-Dawley rats (n = 6/group) were received a single oral daily dose of 500, 1000, and 2000 mg/kg of V. officinalis extract for three days. Negative and positive control rats were received distilled water or a single intraperitoneal injection of 50 mg/kg of cyclophosphamide, respectively. Following dissection, femurs were collected and bone marrow cells were stained with May-Grünwald-Giemsa solution for micronucleus assessment.

RESULTS

Ames test results demonstrated that 5, 2.5, 1.25 and 0.625 mg/ml of V. officinalis extract induced a significant mutagenic effect against TA100 and TA98 strains (with and without metabolic activation). Findings of the animal study showed there were no significant increase in the micronucleated polychromatic erythrocytes (MNPE) and no significant alterations in the polychromatic erythrocytes (PCE) to normochromatic erythrocytes (NCE) ratio of treated rats as compared with their negative control. Meanwhile, significantly increased in the MNPEs was seen in the cyclophosphamide-treated group only.

CONCLUSION

Aqueous extract of V. officinalis has mutagenic effect against TA98 and TA100 strains as demonstrated by Ames test, however, there is no in vivo clastogenic and myelotoxic effect on bone marrow micronucleus of rats indicating that the benefits of using V. officinalis in traditional practice should outweigh risks.

Hippocampal-prefrontal coherence mediates working memory and selective attention at distinct frequency bands and provides a causal link between schizophrenia and its risk gene GRIA1

Increased fronto-temporal theta coherence and failure of its stimulus-specific modulation have been reported in schizophrenia, but the psychological correlates and underlying neural mechanisms remain elusive. Mice lacking the putative schizophrenia risk gene GRIA1 (Gria1^-/-), which encodes GLUA1, show strongly impaired spatial working memory and elevated selective attention owing to a deficit in stimulus-specific short-term habituation. A failure of short-term habituation has been suggested to cause an aberrant assignment of salience and thereby psychosis in schizophrenia. We recorded hippocampal-prefrontal coherence while assessing spatial working memory and short-term habituation in these animals, wildtype (WT) controls, and Gria1^-/- mice in which GLUA1 expression was restored in hippocampal subfields CA2 and CA3. We found that beta (20-30 Hz) and low-gamma (30-48 Hz) frequency coherence could predict working memory performance, whereas-surprisingly-theta (6-12 Hz) coherence was unrelated to performance and largely unaffected by genotype in this task. In contrast, in novel environments, theta coherence specifically tracked exploration-related attention in WT mice, but was strongly elevated and unmodulated in Gria1-knockouts, thereby correlating with impaired short-term habituation. Strikingly, reintroduction of GLUA1 selectively into CA2/CA3 restored abnormal short-term habituation, theta coherence, and hippocampal and prefrontal theta oscillations. Although local oscillations and coherence in other frequency bands (beta, gamma), and theta-gamma cross-frequency coupling also showed dependence on GLUA1, none of them correlated with short-term habituation. Therefore, sustained elevation of hippocampal-prefrontal theta coherence may underlie a failure in regulating novelty-related selective attention leading to aberrant salience, and thereby represents a mechanistic link between GRIA1 and schizophrenia.

Attenuation of Novelty-Induced Hyperactivity of Gria1-/- Mice by Cannabidiol and Hippocampal Inhibitory Chemogenetics

Gene-targeted mice with deficient AMPA receptor GluA1 subunits (Gria1-/- mice) show robust hyperlocomotion in a novel environment, suggesting them to constitute a model for hyperactivity disorders such as mania, schizophrenia and attention deficit hyperactivity disorder. This behavioral alteration has been associated with increased neuronal activation in the hippocampus, and it can be attenuated by chronic treatment with antimanic drugs, such as lithium, valproic acid, and lamotrigine. Now we found that systemic cannabidiol strongly blunted the hyperactivity and the hippocampal c-Fos expression of the Gria1-/- mice, while not affecting the wild-type littermate controls. Acute bilateral intra-dorsal hippocampal infusion of cannabidiol partially blocked the hyperactivity of the Gria1-/- mice, but had no effect on wild-types. The activation of the inhibitory DREADD receptor hM4Gi in the dorsal hippocampus by clozapine-N-oxide robustly inhibited the hyperactivity of the Gria1-/- mice, but had no effect on the locomotion of wild-type mice. Our results show that enhanced neuronal excitability in the hippocampus is associated with pronounced novelty-induced hyperactivity of GluA1 subunit-deficient mice. When this enhanced response of hippocampal neurons to novel stimuli is specifically reduced in the hippocampus by pharmacological treatment or by chemogenetic inhibition, Gria1-/- mice recover from behavioral hyperactivity, suggesting a hippocampal dysfunction in hyperactive behaviors that can be treated with cannabidiol.

Neocortical Microdissection at Columnar and Laminar Resolution for Molecular Interrogation

The heterogeneous organization of the mammalian neocortex poses a challenge for elucidating the molecular mechanisms underlying its physiological processes. Although high-throughput molecular methods are increasingly deployed in neuroscience, their anatomical specificity is often lacking. In this unit, we introduce a targeted microdissection technique that enables extraction of high-quality RNA and proteins at high anatomical resolution from acutely prepared brain slices. We exemplify its utility by isolating single cortical columns and laminae from the mouse primary somatosensory (barrel) cortex. Tissues can be isolated from living slices in minutes, and the extracted RNA and protein are of sufficient quantity and quality to be used for RNA sequencing and mass spectrometry. This technique will help to increase the anatomical specificity of molecular studies of the neocortex, and the brain in general, as it is applicable to any brain structure that can be identified using optical landmarks in living slices. © 2018 by John Wiley & Sons, Inc.

Effect of Catha edulis (khat) on pancreatic functions in streptozotocin-induced diabetes in male Sprague-Dawley rats

People consume Catha edulis (khat) for its euphoric effect, and type 1 diabetics have claimed that khat could reduce elevated levels of blood sugar. However, khat has been suggested to provoke diabetes mellitus through destruction of pancreatic β-cells. This study investigated the effect of an ethanolic khat extract on pancreatic functions in type 1 diabetes (T1DM)-induced male Sprague-Dawley rats and to assess its in vitro cytotoxicity in rat pancreatic β-cells (RIN-14B). T1DM was induced in a total of 20 rats with a single intraperitoneal injection of 75 mg/kg of streptozotocin. The rats were distributed into four groups (n=5): the diabetic control, 8 IU insulin-treated, 200 mg/kg khat-treated, and 400 mg/kg khat-treated groups. Another 5 rats were included as a nondiabetic control. Body weight, fasting blood sugar, and caloric intake were recorded weekly. Four weeks after treatment, the rats were sacrificed, and blood was collected for insulin, lipid profile, total protein, amylase, and lipase analysis, while pancreases were harvested for histopathology. In vitro, khat exerted moderate cytotoxicity against RIN-14B cells after 24 and 48 h but demonstrated greater inhibition against RIN-14B cells after 72 h. Neither 200 mg/kg nor 400 mg/kg of khat produced any significant reduction in blood sugar; however, 200 mg/kg khat extract provoked more destruction of pancreatic β-cells as compared with the diabetic control. Ultimately, neither 200 mg/kg nor 400 mg/kg of khat extract could produce a hypoglycemic effect in T1DM-induced rats. However, 200 mg/kg of khat caused greater destruction of pancreatic β-cells, implying that khat may cause a direct cytotoxic effect on pancreatic β-cells in vitro.