Astrocytic Dagla Deletion Decreases Hedonic Feeding in Female Mice.

Introduction: Endocannabinoids and exogenous cannabinoids are potent regulators of feeding behavior and energy metabolism. Stimulating cannabinoid receptor signaling enhances appetite, particularly for energy-dense palatable foods, and promotes energy storage. To elucidate the underlying cellular mechanisms, we investigate here the potential role of astrocytic endocannabinoid 2-arachidonoylglycerol (2-AG). Astrocytes provide metabolic support for neurons and contribute to feeding regulation but the effect of astrocytic 2-AG on feeding is unknown. Materials and Methods: We generated mice lacking the 2-AG synthesizing enzyme diacylglycerol lipase alpha (Dagla) in astrocytes (GLAST-Dagla KO) and investigated hedonic feeding behavior in male and female mice. Body weight and baseline water and food intake was characterized; additionally, the mice went through milk, saccharine, and sucrose preference tests in fed and fasted states. In female mice, the estrous cycle stages were identified and plasma levels of female sex hormones were measured. Results: We found that the effects of the inducible astrocytic Dagla deletion were sex-specific. Acute milk preference was decreased in female, but not in male mice and the effect was most evident in the estrus stage of the cycle. This prompted us to investigate sex hormone profiles, which were found to be altered in GLAST-Dagla KO females. Specifically, follicle-stimulating hormone was elevated in the estrus stage, luteinizing hormone in the proestrus, and progesterone was increased in both proestrus and estrus stages of the cycle compared with controls. Conclusions: Astrocytic Dagla regulates acute hedonic appetite for palatable food in females and not in males, possibly owing to a deregulated female sex hormone profile. It is plausible that endocannabinoid production by astrocytes at least partly contributes to the greater susceptibility to overeating in females. This finding may also be important for understanding the effects of exogenous cannabinoids on sex hormone profiles.

Epidrugs in the Therapy of Central Nervous System Disorders: A Way to Drive on?

The polygenic nature of neurological and psychiatric syndromes and the significant impact of environmental factors on the underlying developmental, homeostatic, and neuroplastic mechanisms suggest that an efficient therapy for these disorders should be a complex one. Pharmacological interventions with drugs selectively influencing the epigenetic landscape (epidrugs) allow one to hit multiple targets, therefore, assumably addressing a wide spectrum of genetic and environmental mechanisms of central nervous system (CNS) disorders. The aim of this review is to understand what fundamental pathological mechanisms would be optimal to target with epidrugs in the treatment of neurological or psychiatric complications. To date, the use of histone deacetylases and DNA methyltransferase inhibitors (HDACis and DNMTis) in the clinic is focused on the treatment of neoplasms (mainly of a glial origin) and is based on the cytostatic and cytotoxic actions of these compounds. Preclinical data show that besides this activity, inhibitors of histone deacetylases, DNA methyltransferases, bromodomains, and ten-eleven translocation (TET) proteins impact the expression of neuroimmune inflammation mediators (cytokines and pro-apoptotic factors), neurotrophins (brain-derived neurotropic factor (BDNF) and nerve growth factor (NGF)), ion channels, ionotropic receptors, as well as pathoproteins (ß-amyloid, tau protein, and α-synuclein). Based on this profile of activities, epidrugs may be favorable as a treatment for neurodegenerative diseases. For the treatment of neurodevelopmental disorders, drug addiction, as well as anxiety disorders, depression, schizophrenia, and epilepsy, contemporary epidrugs still require further development concerning a tuning of pharmacological effects, reduction in toxicity, and development of efficient treatment protocols. A promising strategy to further clarify the potential targets of epidrugs as therapeutic means to cure neurological and psychiatric syndromes is the profiling of the epigenetic mechanisms, which have evolved upon actions of complex physiological lifestyle factors, such as diet and physical exercise, and which are effective in the management of neurodegenerative diseases and dementia.

Depression-Associated Negr1 Gene-Deficiency Induces Alterations in the Monoaminergic Neurotransmission Enhancing Time-Dependent Sensitization to Amphetamine in Male Mice.

In GWAS studies, the neural adhesion molecule encoding the neuronal growth regulator 1 (NEGR1) gene has been consistently linked with both depression and obesity. Although the linkage between NEGR1 and depression is the strongest, evidence also suggests the involvement of NEGR1 in a wide spectrum of psychiatric conditions. Here we show the expression of NEGR1 both in tyrosine- and tryptophan hydroxylase-positive cells. Negr1-/- mice show a time-dependent increase in behavioral sensitization to amphetamine associated with increased dopamine release in both the dorsal and ventral striatum. Upregulation of transcripts encoding dopamine and serotonin transporters and higher levels of several monoamines and their metabolites was evident in distinct brain areas of Negr1-/- mice. Chronic (23 days) escitalopram-induced reduction of serotonin and dopamine turnover is enhanced in Negr1-/- mice, and escitalopram rescued reduced weight of hippocampi in Negr1-/- mice. The current study is the first to show alterations in the brain monoaminergic systems in Negr1-deficient mice, suggesting that monoaminergic neural circuits contribute to both depressive and obesity-related phenotypes linked to the human NEGR1 gene.

Dynamic Changes in the Endocannabinoid System during the Aging Process: Focus on the Middle-Age Crisis.

Endocannabinoid (eCB) signaling is markedly decreased in the hippocampus (Hip) of aged mice, and the genetic deletion of the cannabinoid receptor type 1 (CB1) leads to an early onset of cognitive decline and age-related histological changes in the brain. Thus, it is hypothesized that cognitive aging is modulated by eCB signaling through CB1. In the present study, we detailed the changes in the eCB system during the aging process using different complementary techniques in mouse brains of five different age groups, ranging from adolescence to old age. Our findings indicate that the eCB system is most strongly affected in middle-aged mice (between 9 and 12 months of age) in a brain region-specific manner. We show that 2-arachidonoylglycerol (2-AG) was prominently decreased in the Hip and moderately in caudate putamen (CPu), whereas anandamide (AEA) was decreased in both CPu and medial prefrontal cortex along with cingulate cortex (mPFC+Cg), starting from 6 months until 12 months. Consistent with the changes in 2-AG, the 2-AG synthesizing enzyme diacylglycerol lipase α (DAGLα) was also prominently decreased across the sub-regions of the Hip. Interestingly, we found a transient increase in CB1 immunoreactivity across the sub-regions of the Hip at 9 months, a plausible compensation for reduced 2-AG, which ultimately decreased strongly at 12 months. Furthermore, quantitative autoradiography of CB1 revealed that [3H]CP55940 binding markedly increased in the Hip at 9 months. However, unlike the protein levels, CB1 binding density did not drop strongly at 12 months and at old age. Furthermore, [3H]CP55940 binding was significantly increased in the lateral entorhinal cortex (LEnt), starting from the middle age until the old age. Altogether, our findings clearly indicate a middle-age crisis in the eCB system, which could be a potential time window for therapeutic interventions to abrogate the course of cognitive aging.

Regulation of adult neurogenesis by the endocannabinoid-producing enzyme diacylglycerol lipase alpha (DAGLa).

The endocannabinoid system modulates adult hippocampal neurogenesis by promoting the proliferation and survival of neural stem and progenitor cells (NSPCs). This is demonstrated by the disruption of adult neurogenesis under two experimental conditions: (1) NSPC-specific deletion of cannabinoid receptors and (2) constitutive deletion of the enzyme diacylglycerol lipase alpha (DAGLa) which produces the endocannabinoid 2-arachidonoylglycerol (2-AG). However, the specific cell types producing 2-AG relevant to neurogenesis remain unknown. Here we sought to identify the cellular source of endocannabinoids in the subgranular zone of the dentate gyrus (DG) in hippocampus, an important neurogenic niche. For this purpose, we used two complementary Cre-deleter mouse strains to delete Dagla either in neurons, or in astroglia and NSPCs. Surprisingly, neurogenesis was not altered in mice bearing a deletion of Dagla in neurons (Syn-Dagla KO), although neurons are the main source for the endocannabinoids in the brain. In contrast, a specific inducible deletion of Dagla in NPSCs and astrocytes (GLAST-CreERT2-Dagla KO) resulted in a strongly impaired neurogenesis with a 50% decrease in proliferation of newborn cells. These results identify Dagla in NSPCs in the DG or in astrocytes as a prominent regulator of adult hippocampal neurogenesis. We also show a reduction of Daglb expression in GLAST-CreERT2-Dagla KO mice, which may have contributed to the neurogenesis phenotype.

Brain Expression, Physiological Regulation and Role in Motivation and Associative Learning of Peroxisome Proliferator-activated Receptor γ.

Like other members of the superfamily of nuclear receptors, the peroxisome proliferator-activated receptor γ (PPARγ), is a ligand-activated transcription factor known for its insulin-sensitizing actions in the periphery. Despite only sparse evidence for PPARγ in the CNS, many reports suggest direct PPARγ-mediated actions in the brain. This study aimed to (i) map PPARγ expression in rodent brain areas, involved in the regulation of cognitive, motivational, and emotional functions, (ii) examine the regulation of central PPARγ by physiological variables (age, sex, obesity); (iii) chemotypically identify PPARγ-expressing cells in the frontal cortex (FC) and hippocampus (HP); (iv) study whether activation of PPARγ by pioglitazone (Pio) in FC and HP cells can induce target gene expression; and (v) demonstrate the impact of activated PPARγ on learning behavior and motivation. Immunoreactive PPARγ was detectable in specific sub-nuclei/subfields of the FC, HP, nucleus accumbens, amygdala, hypothalamus, thalamus, and granular layers of the cerebellum. PPARγ protein levels were upregulated during aging and in high fat diet-induced obesity. PPARγ mRNA expression was upregulated in the amygdala of females (but not males) that were made obese. Neural precursor cells, mature neurons, and astrocytes in primary FC and HP cultures were shown to express PPARγ. Pioglitazone dose-dependently upregulated PPARγ target genes in manner that was specific to the origin (FC or HP) of the cultures. Lastly, administration of Pio impaired motivation and associative learning. Collectively, we provide evidence for the presence of regulatable PPARγ in the brain and demonstrate their participation the regulation of key behaviors.

High-Fat Diet Induces Pre-Diabetes and Distinct Sex-Specific Metabolic Alterations in Negr1-Deficient Mice.

In the large GWAS studies, NEGR1 gene has been one of the most significant gene loci for body mass phenotype. The purpose of the current study was to clarify the role of NEGR1 in the maintenance of systemic metabolism, including glucose homeostasis, by using both male and female Negr1-/- mice receiving a standard or high fat diet (HFD). We found that 6 weeks of HFD leads to higher levels of blood glucose in Negr1-/- mice. In the glucose tolerance test, HFD induced phenotype difference only in male mice; Negr1-/- male mice displayed altered glucose tolerance, accompanied with upregulation of circulatory branched-chain amino acids (BCAA). The general metabolomic profile indicates that Negr1-/- mice are biased towards glyconeogenesis, fatty acid synthesis, and higher protein catabolism, all of which are amplified by HFD. Negr1 deficiency appears to induce alterations in the efficiency of energy storage; reduced food intake could be an attempt to compensate for the metabolic challenge present in the Negr1-/- males, particularly during the HFD exposure. Our results suggest that the presence of functional Negr1 allows male mice to consume more HFD and prevents the development of glucose intolerance, liver steatosis, and excessive weight gain.

Cannabinoid receptor 1 signalling modulates stress susceptibility and microglial responses to chronic social defeat stress.

Psychosocial stress is one of the main environmental factors contributing to the development of psychiatric disorders. In humans and rodents, chronic stress is associated with elevated inflammatory responses, indicated by increased numbers of circulating myeloid cells and activation of microglia, the brain-resident immune cells. The endocannabinoid system (ECS) regulates neuronal and endocrine stress responses via the cannabinoid receptor 1 (CB1). CB1-deficient mice (Cnr1-/-) are highly sensitive to stress, but if this involves altered inflammatory responses is not known. To test this, we exposed Cnr1+/+ and Cnr1-/- mice to chronic social defeat stress (CSDS). Cnr1-/- mice were extremely sensitive to a standard protocol of CSDS, indicated by an increased mortality rate. Therefore, a mild CSDS protocol was established, which still induced a behavioural phenotype in susceptible Cnr1-/- mice. These mice also showed altered glucocorticoid levels after mild CSDS, suggesting dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Mild CSDS induced weak myelopoiesis in the periphery, but no recruitment of myeloid cells to the brain. In contrast, mild CSDS altered microglial activation marker expression and morphology in Cnr1-/- mice. These microglial changes correlated with the severity of the behavioural phenotype. Furthermore, microglia of Cnr1-/- mice showed increased expression of Fkbp5, an important regulator of glucocorticoid signalling. Overall, the results confirm that CB1 signalling protects the organism from the physical and emotional harm of social stress and implicate endocannabinoid-mediated modulation of microglia in the development of stress-related pathologies.

Diacylglycerol lipase alpha in astrocytes is involved in maternal care and affective behaviors.

Genetic deletion of cannabinoid CB1 receptors or diacylglycerol lipase alpha (DAGLa), the main enzyme involved in the synthesis of the endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG), produced profound phenotypes in animal models of depression-related behaviors. Furthermore, clinical studies have shown that antagonists of CB1 can increase the incidence and severity of major depressive episodes. However, the underlying pathomechanisms are largely unknown. In this study, we have focused on the possible involvement of astrocytes. Using the highly sensitive RNAscope technology, we show for the first time that a subpopulation of astrocytes in the adult mouse brain expresses Dagla, albeit at low levels. Targeted lipidomics revealed that astrocytic DAGLa only accounts for a minor percentage of the steady-state brain 2-AG levels and other arachidonic acid derived lipids like prostaglandins. Nevertheless, the deletion of Dagla in adult mouse astrocytes had profound behavioral consequences with significantly increased depressive-like behavioral responses and striking effects on maternal behavior, corresponding with increased levels of serum progesterone and estradiol. Our findings therefore indicate that lipids from the DAGLa metabolic axis in astrocytes play a key regulatory role in affective behaviors.

Expression and impact of Lsamp neural adhesion molecule in the serotonergic neurotransmission system.

Limbic system associated membrane protein (Lsamp) is a neural adhesion protein which has been recently found to be differentially expressed between serotonergic neuron subtypes. We have previously shown elevated serotonin (5-HT) turnover rate in Lsamp-deficient mice. The purpose of the current study was to elucidate the role of Lsamp in serotonergic neurotransmission. Chronic (18 days) administration of serotonin reuptake inhibitor (SSRI) escitalopram (10 mg/kg) significantly increased general activity in wild-type mice in the open field and protected exploration in Lsamp-/- mice in the elevated-plus maze. An important psychopathology-related endophenotype, elevated 5-HT turnover in the brain of Lsamp-deficient mice, was reproduced in the saline group. Escitalopram restored the elevated 5-HT turnover of Lsamp-deficient mice to a level comparable with their wild-type littermates, suggesting that high 5-HT turnover in mutants is mediated by the increased activity of serotonin transporter (SERT protein encoded by Slc6a4 gene). The baseline level of Slc6a4 transcript was not changed in Lsamp-deficient mice, however, our immunohistochemical analysis showed partial co-expression of Lsamp with both SERT and Tph2 proteins in raphe. Overactivity of SERT in Lsamp-/- mice is further supported by significant elevation of Maoa transcript and increase of DOPAC, another Mao A product, specifically in the raphe. Again, elevation of DOPAC was reduced to the level of wild-type by chronic SSRI treatment. The activity of Lsamp gene promoters varied in 5-HT producing nuclei: both Lsamp 1a and 1b promoters were active in the dorsal raphe; most of the expression in the median raphe was from 1b promoter, whereas Lsamp 1a promoter was almost exclusively active in the caudal subgroup of raphe nuclei. We suggest that Lsamp may have an impact on the integrity of serotonergic synapses, which is possibly the neurochemical basis of the anxiety- and sociability-related phenotype in Lsamp-deficient mice.

Modulation of feeding behavior and metabolism by dynorphin.

The neuronal regulation of metabolic and behavioral responses to different diets and feeding regimens is an important research area. Herein, we investigated if the opioid peptide dynorphin modulates feeding behavior and metabolism. Mice lacking dynorphin peptides (KO) were exposed to either a normal diet (ND) or a high-fat diet (HFD) for a period of 12 weeks. Additionally, mice had either time-restricted (TR) or ad libitum (AL) access to food. Body weight, food intake and blood glucose levels were monitored throughout the 12-week feeding schedule. Brain samples were analyzed by immunohistochemistry to detect changes in the expression levels of hypothalamic peptides. As expected, animals on HFD or having AL access to food gained more weight than mice on ND or having TR access. Unexpectedly, KO females on TR HFD as well as KO males on AL ND or AL HFD demonstrated a significantly increased body weight gain compared to the respective WT groups. The calorie intake differed only marginally between the genotypes: a significant difference was present in the female ND AL group, where dynorphin KO mice ate more than WT mice. Although female KO mice on a TR feeding regimen consumed a similar amount of food as WT controls, they displayed significantly higher levels of blood glucose. We observed significantly reduced levels of hypothalamic orexigenic peptides neuropeptide Y (NPY) and orexin-A in KO mice. This decrease became particularly pronounced in the HFD groups and under AL condition. The kappa opiod receptor (KOR) levels were higher after HFD compared to ND feeding in the ventral pallidum of WT mice. We hypothesize that HFD enhances dynorphin signaling in this hedonic center to maintain energy homeostasis, therefore KO mice have a more pronounced phenotype in the HFD condition due to the lack of it. Our data suggest that dynorphin modulates metabolic changes associated with TR feeding regimen and HFD consumption. We conclude that the lack of dynorphin causes uncoupling between energy intake and body weight gain in mice; KO mice maintained on HFD become overweight despite their normal food intake. Thus, using kappa opioid receptor agonists against obesity could be considered as a potential treatment strategy.

Blunted leptin sensitivity during hedonic overeating can be reinstated by activating galanin 2 receptors (Gal2R) in the lateral hypothalamus.

AIM: Since foods with high hedonic value are often consumed in excess of energetic needs, this study was designed to identify the mechanisms that may counter anorexigenic signalling in the presence of hedonic foods in lean animals. METHODS: Mice, in different states of satiety (fed/fasted, or fed/fasted and treated with ghrelin or leptin, respectively), were allowed to choose between high-fat/high-sucrose and standard foods. Intake of each food type and the activity of hypothalamic neuropetidergic neurons that regulate appetite were monitored. In some cases, food choice was monitored in leptin-injected fasted mice that received microinjections of galanin receptor agonists into the lateral hypothalamus. RESULTS: Appetite-stimulating orexin neurons in the lateral hypothalamus are rapidly activated when lean, satiated mice consume a highly palatable food (PF); such activation (upregulated c-Fos expression) occurred even after administration of the anorexigenic hormone leptin and despite intact leptin signalling in the hypothalamus. The ability of leptin to restrain PF eating is restored when a galanin receptor 2 (Gal2R) agonist is injected into the lateral hypothalamus. CONCLUSION: Hedonically-loaded foods interrupt the inhibitory actions of leptin on orexin neurons and interfere with the homeostatic control of feeding. Overeating of palatable foods can be curtailed in lean animals by activating Gal2R in the lateral hypothalamus.

Neural cell adhesion molecule Negr1 deficiency in mouse results in structural brain endophenotypes and behavioral deviations related to psychiatric disorders.

Neuronal growth regulator 1 (NEGR1) belongs to the immunoglobulin (IgLON) superfamily of cell adhesion molecules involved in cortical layering. Recent functional and genomic studies implicate the role of NEGR1 in a wide spectrum of psychiatric disorders, such as major depression, schizophrenia and autism. Here, we investigated the impact of Negr1 deficiency on brain morphology, neuronal properties and social behavior of mice. In situ hybridization shows Negr1 expression in the brain nuclei which are central modulators of cortical-subcortical connectivity such as the island of Calleja and the reticular nucleus of thalamus. Brain morphological analysis revealed neuroanatomical abnormalities in Negr1-/- mice, including enlargement of ventricles and decrease in the volume of the whole brain, corpus callosum, globus pallidus and hippocampus. Furthermore, decreased number of parvalbumin-positive inhibitory interneurons was evident in Negr1-/- hippocampi. Behaviorally, Negr1-/- mice displayed hyperactivity in social interactions and impairments in social hierarchy. Finally, Negr1 deficiency resulted in disrupted neurite sprouting during neuritogenesis. Our results provide evidence that NEGR1 is required for balancing the ratio of excitatory/inhibitory neurons and proper formation of brain structures, which is prerequisite for adaptive behavioral profiles. Therefore, Negr1-/- mice have a high potential to provide new insights into the neural mechanisms of neuropsychiatric disorders.

Restoring Serotonergic Homeostasis in the Lateral Hypothalamus Rescues Sleep Disturbances Induced by Early-Life Obesity.

Early-life obesity predisposes to obesity in adulthood, a condition with broad medical implications including sleep disorders, which can exacerbate metabolic disturbances and disrupt cognitive and affective behaviors. In this study, we examined the long-term impact of transient peripubertal diet-induced obesity (ppDIO, induced between 4 and 10 weeks of age) on sleep-wake behavior in male mice. EEG and EMG recordings revealed that ppDIO increases sleep during the active phase but reduces resting-phase sleep quality. This impaired sleep phenotype persisted for up to 1 year, although animals were returned to a non-obesiogenic diet from postnatal week 11 onwards. To better understand the mechanisms responsible for the ppDIO-induced alterations in sleep, we focused on the lateral hypothalamus (LH). Mice exposed to ppDIO did not show altered mRNA expression levels of orexin and melanin-concentrating hormone, two peptides that are important for sleep-wake behavior and food intake. Conversely, the LH of ppDIO-exposed mice had reduced contents of serotonin (5-hydroxytryptamine, 5-HT), a neurotransmitter involved in both sleep-wake and satiety regulation. Interestingly, an acute peripheral injection of the satiety-signaling peptide YY 3-36 increased 5-HT turnover in the LH and ameliorated the ppDIO-induced sleep disturbances, suggesting the therapeutic potential of this peptide. These findings provide new insights into how sleep-wake behavior is programmed during early life and how peripheral and central signals are integrated to coordinate sleep.SIGNIFICANCE STATEMENT Adult physiology and behavior are strongly influenced by dynamic reorganization of the brain during puberty. The present work shows that obesity during puberty leads to persistently dysregulated patterns of sleep and wakefulness by blunting serotonergic signaling in the lateral hypothalamus. It also shows that pharmacological mimicry of satiety with peptide YY3-36 can reverse this neurochemical imbalance and acutely restore sleep composition. These findings add insight into how innate behaviors such as feeding and sleep are integrated and suggest a novel mechanism through which diet-induced obesity during puberty imposes its long-lasting effects on sleep-wake behavior.

Gene expression patterns and environmental enrichment-induced effects in the hippocampi of mice suggest importance of Lsamp in plasticity.

Limbic system associated membrane protein (Lsamp) gene is involved in behavioral adaptation in social and anxiogenic environments and has been associated with a broad spectrum of psychiatric diseases. Here we studied the activity of alternative promoters of Lsamp gene in mice in three rearing conditions (standard housing, environmental enrichment and social isolation) and in two different genetic backgrounds (129S6/SvEv and C57BL/6). Isolation had no effect on the expression levels of Lsamp. Environmental enrichment elevated the expression levels of Lsamp 1b transcript specifically in the hippocampus in B6 mice, and the same tendency existed across both mouse lines and both transcripts. Furthermore, we showed that the density of cells exhibiting 1b promoter activity is remarkably higher in the subgranular zone of the dentate gyrus in the hippocampal formation which is a specific area of enrichment-induced neurogenesis in adult rodents. On the contrary to 1b, 1a promoter is selectively active in the pyramidal and granule cell layers. We provide evidence that Lsamp modulates enrichment-induced activation of Bdnf as the enrichment-induced elevation of Bdnf in the hippocampus is significantly diminished in Lsamp-deficient mice; furthermore, a significant correlation was found between the expression levels of Lsamp and Bdnf transcripts in the hippocampus and frontal cortex. Significant strain differences in Lsamp expression were detected in the hippocampus, frontal cortex and thalamus that could be related to the different behavioral phenotype of B6 and 129Sv mice. Our data provides further evidence that LSAMP is implicated in the hippocampal connectivity and plasticity thereby modulating adaptability in changing environments.

Enrichment and individual housing reinforce the differences in aggressiveness and amphetamine response in 129S6/SvEv and C57BL/6 strains.

As different kinds of enrichment equipment are applied to standard rodent laboratory housing conditions in Europe (Directive 2010/63/EU) and worldwide, it is essential to understand how it may influence the brain and behaviour of animals. We observed common inbred mouse strains 129S6/SvEv/Tac (129) and C57BL/6 Bkl (B6) reared in 3 different environments: standard housing (SH), individual housing (IH) and enriched environment (EE). We measured common behavioural parameters, social behaviour and BDNF mRNA expression in hippocampus and frontal cortex. Our results demonstrate that the robust behavioural differences between B6 and 129 mouse strains which are well studied in the literature persist in varied housing conditions, but the response to these conditions has different directionality in studied strains. EE appears to reinforce the existing coping strategies in both strains: B6 became more agile, sensitive and venturous in behavioural models, whereas 129 became even more inhibited than they are in standard conditions. The stimulating effect of amphetamine is decreased in 129 animals that have been reared in EE. This may indicate desensitisation or inhibition of their dopamine system by EE. A frequently used biomarker in enrichment studies, BDNF, is a likely mediator for the long-term phenotype effects of EE. In this paper we demonstrate the differences of BDNF expression pattern in 129 and B6 mice.

Lsamp⁻/⁻ mice display lower sensitivity to amphetamine and have elevated 5-HT turnover.

In mice, the limbic system-associated membrane protein (Lsamp) gene has been implicated in locomotion, anxiety, fear reaction, learning, social behaviour and adaptation. Human data links the LSAMP gene to several psychiatric disorders and completed suicide. Here, we investigated changes in major monoamine systems in mice lacking the Lsamp gene. First, the locomotor and rewarding effects of amphetamine were studied in Lsamp(-/-) mice and Lsamp(+/+) mice. Second, monoamine levels in major brain regions in response to saline and amphetamine injections were measured and, third, the expression levels of dopamine system-related genes in the brain were studied in these mice. Lsamp(-/-) mice displayed lower sensitivity to amphetamine in the motility box. Likewise, in the place preference test, the rewarding effect of amphetamine was absent in Lsamp(-/-) mice. In all brain regions studied, Lsamp(-/-) mice displayed lower serotonin (5-HT) baseline levels, but a greater 5-HT turnover rate, and amphetamine increased the level of 5-HT and lowered 5-HT turnover to a greater extent in Lsamp(-/-) mice. Finally, Lsamp(-/-) mice had lower level of dopamine transporter (DAT) mRNA in the mesencephalon. In conclusion, Lsamp-deficiency leads to increased endogenous 5-HT-ergic tone and enhanced 5-HT release in response to amphetamine. Elevated 5-HT function and reduced activity of DAT are the probable reasons for the blunted effects of amphetamine in these mice. Lsamp(-/-) mice are a promising model to study the neurobiological mechanisms of deviant social behaviour and adaptation impairment observed in many psychiatric disorders.

Lower anxiety and a decrease in agonistic behaviour in Lsamp-deficient mice.

In rodents, the Lsamp gene has been implicated in trait anxiety, fear reaction and fear conditioning. Human data link the LSAMP gene to several psychiatric disorders. In this study, we presented a general phenotypic characterization of Lsamp gene-deficient mouse line, created by deleting exon 1b. These mice displayed no gross sensory-motor deficiencies, no overt abnormalities and performed normally in memory and learning tests. However, they responded with increased activity to new environments. Moreover, they displayed reduced anxiety and notable deviations in social behaviour, such as lack of whisker trimming, reduced aggressiveness and reduced dominance. One possible explanation for the anxiolytic-like effect of the deletion of the Lsamp gene is a shift in balance in the Gabra1 and Gabra2 genes in the temporal lobe in favor of the Gabra2 transcript, encoding α2 subunit of GABA(A) receptors that mediate the stimulating effect of GABA agonists. The overall phenotype of Lsamp-deficient mice, characterized by decreased anxiety and several alterations in social behaviour, makes them a good model for studying the molecular mechanisms behind inadequate social behaviours observed in several psychiatric disorders.