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.

Lipopolysaccharide-Induced Strain-Specific Differences in Neuroinflammation and MHC-I Pathway Regulation in the Brains of Bl6 and 129Sv Mice.

Many studies have demonstrated significant mouse-strain-specific differences in behavior and response to pathogenic and pharmacological agents. This study seeks to characterize possible differences in microglia activation and overall severity of neuroinflammation in two widely used mouse strains, C57BL/6NTac (Bl6) and 129S6/SvEvTac (129Sv), in response to acute lipopolysaccharide (LPS) administration. Locomotor activity within the open field arena revealed similar 24 h motor activity decline in both strains. Both strains also exhibited significant bodyweight loss due to LPS treatment, although it was more severe in the Bl6 strain. Furthermore, LPS induced a hypothermic response in Bl6 mice, which was not seen in 129Sv. We found that 24 h LPS challenge significantly increased the inflammatory status of microglia in 129Sv mice. On the other hand, we observed that, under physiological conditions, microglia of Bl6 seemed to be in a higher immune-alert state. Gene and protein expression analysis revealed that LPS induces a significantly stronger upregulation of MHC-I-pathway-related components in the brain of Bl6 compared to 129Sv mice. The most striking difference was detected in the olfactory bulb, where we observed significant LPS-induced upregulation of MHC-I pathway components in Bl6 mice, whereas no alterations were observed in 129Sv. We observed significant positive correlations between bodyweight decline and expressions of MHC-I components in the olfactory bulbs of Bl6 mice and the frontal cortex of 129Sv, highlighting different brain regions most affected by LPS in these strains. Our findings suggest that the brains of Bl6 mice exist in a more immunocompetent state compared to 129Sv mice.

Dopamine System, NMDA Receptor and EGF Family Expressions in Brain Structures of Bl6 and 129Sv Strains Displaying Different Behavioral Adaptation.

C57BL/6NTac (Bl6) and 129S6/SvEvTac (129Sv) mice display different coping strategies in stressful conditions. Our aim was to evaluate biomarkers related to different adaptation strategies in the brain of male 129Sv and Bl6 mice. We focused on signaling pathways related to the dopamine (DA) system, N-methyl-D-aspartate (NMDA) receptor and epidermal growth factor (EGF) family, shown as the key players in behavioral adaptation. Mice from Bl6 and 129Sv lines were divided into either home cage controls (HCC group) or exposed to repeated motility testing and treated with saline for 11 days (RMT group). Distinct stress responses were reflected in severe body weight loss in 129Sv and the increased exploratory behavior in Bl6 mice. Besides that, amphetamine caused significantly stronger motor stimulation in Bl6. Together with the results from gene expression (particularly Maob), this study supports higher baseline activity of DA system in Bl6. Interestingly, the adaptation is reflected with opposite changes of DA markers in dorsal and ventral striatum. In forebrain, stress increased the gene expressions of Egf-Erbb1 and Nrg1/Nrg2-Erbb4 pathways more clearly in 129Sv, whereas the corresponding proteins were significantly elevated in Bl6. We suggest that not only inhibited activity of the DA system, but also reduced activity of EGF family and NMDA receptor signaling underlies higher susceptibility to stress in 129Sv. Altogether, this study underlines the better suitability of 129Sv for modelling neuropsychiatric disorders than Bl6.

Neuroprotective Potential of a Small Molecule RET Agonist in Cultured Dopamine Neurons and Hemiparkinsonian Rats.

BACKGROUND: Parkinson's disease (PD) is a progressive neurological disorder where loss of dopamine neurons in the substantia nigra and dopamine depletion in the striatum cause characteristic motor symptoms. Currently, no treatment is able to halt the progression of PD. Glial cell line-derived neurotrophic factor (GDNF) rescues degenerating dopamine neurons both in vitro and in animal models of PD. When tested in PD patients, however, the outcomes from intracranial GDNF infusion paradigms have been inconclusive, mainly due to poor pharmacokinetic properties. OBJECTIVE: We have developed drug-like small molecules, named BT compounds that activate signaling through GDNF's receptor, the transmembrane receptor tyrosine kinase RET, both in vitro and in vivo and are able to penetrate through the blood-brain barrier. Here we evaluated the properties of BT44, a second generation RET agonist, in immortalized cells, dopamine neurons and rat 6-hydroxydopamine model of PD. METHODS: We used biochemical, immunohistochemical and behavioral methods to evaluate the effects of BT44 on dopamine system in vitro and in vivo. RESULTS: BT44 selectively activated RET and intracellular pro-survival AKT and MAPK signaling pathways in immortalized cells. In primary midbrain dopamine neurons cultured in serum-deprived conditions, BT44 promoted the survival of the neurons derived from wild-type, but not from RET knockout mice. BT44 also protected cultured wild-type dopamine neurons from MPP+-induced toxicity. In a rat 6-hydroxydopamine model of PD, BT44 reduced motor imbalance and seemed to protect dopaminergic fibers in the striatum. CONCLUSION: BT44 holds potential for further development into a novel, possibly disease-modifying, therapy for PD.

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.

GDNF Receptor Agonist Alleviates Motor Imbalance in Unilateral 6-Hydroxydopamine Model of Parkinson's Disease.

Parkinson's disease (PD) is an incurable neurodegenerative disorder affecting up to 10 million people in the world. Diagnostic motor symptoms of PD appear as a result of progressive degeneration and death of nigrostriatal dopamine neurons. Current PD treatments only relieve symptoms without halting the progression of the disease, and their use is complicated by severe adverse effects emerging as the disease progresses. Therefore, there is an urgent need for new therapies for PD management. We developed a small molecule compound, BT13, targeting receptor tyrosine kinase RET. RET is the signalling receptor for a known survival factor for dopamine neurons called glial cell line-derived neurotrophic factor (GDNF). Previously we showed that BT13 prevents the death of cultured dopamine neurons, stimulates dopamine release and activates pro-survival signalling cascades in naïve rodent brain. In the present study, we evaluate the effects of BT13 on motor imbalance and nigrostriatal dopamine neurons in a unilateral 6-hydroxydopamine rat model of PD. We show that BT13 alleviates motor dysfunction in experimental animals. Further studies are needed to make a conclusion whether BT13 can protect the integrity of the nigrostriatal dopamine system since even the positive control, GDNF protein, was unable to produce a clear neuroprotective effect in the model used in the present work. In contrast to GDNF, BT13 is able to cross the blood-brain barrier, which together with the ability to reduce motor symptoms of the disease makes it a valuable lead for further development as a potential disease-modifying agent to treat PD.

Glial cell line-derived neurotrophic factor receptor Rearranged during transfection agonist supports dopamine neurons in Vitro and enhances dopamine release In Vivo.

BACKGROUND: Motor symptoms of Parkinson's disease (PD) are caused by degeneration and progressive loss of nigrostriatal dopamine neurons. Currently, no cure for this disease is available. Existing drugs alleviate PD symptoms but fail to halt neurodegeneration. Glial cell line-derived neurotrophic factor (GDNF) is able to protect and repair dopamine neurons in vitro and in animal models of PD, but the clinical use of GDNF is complicated by its pharmacokinetic properties. The present study aimed to evaluate the neuronal effects of a blood-brain-barrier penetrating small molecule GDNF receptor Rearranged in Transfection agonist, BT13, in the dopamine system. METHODS: We characterized the ability of BT13 to activate RET in immortalized cells, to support the survival of cultured dopamine neurons, to protect cultured dopamine neurons against neurotoxin-induced cell death, to activate intracellular signaling pathways both in vitro and in vivo, and to regulate dopamine release in the mouse striatum as well as BT13's distribution in the brain. RESULTS: BT13 potently activates RET and downstream signaling cascades such as Extracellular Signal Regulated Kinase and AKT in immortalized cells. It supports the survival of cultured dopamine neurons from wild-type but not from RET-knockout mice. BT13 protects cultured dopamine neurons from 6-Hydroxydopamine (6-OHDA) and 1-methyl-4-phenylpyridinium (MPP+ )-induced cell death only if they express RET. In addition, BT13 is absorbed in the brain, activates intracellular signaling cascades in dopamine neurons both in vitro and in vivo, and also stimulates the release of dopamine in the mouse striatum. CONCLUSION: The GDNF receptor RET agonist BT13 demonstrates the potential for further development of novel disease-modifying treatments against PD. © 2019 International Parkinson and Movement Disorder Society.

Hypothermia augments stress response in mammalian cells.

Mild hypothermia (32 °C) is routinely used in medical practice to alleviate hypoxic ischemic damage, however, the mechanisms that underlie its protective effects remain uncertain. Using a systems approach based on genome-wide expression screens, reporter assays and biochemical studies, we find that cellular hypothermia response is associated with the augmentation of major stress-inducible transcription factors Nrf2 and HIF1Α affecting the antioxidant system and hypoxia response pathways, respectively. At the same time, NF-κB, a transcription factor involved in the control of immune and inflammatory responses, was not induced by hypothermia. Furthermore, mild hypothermia did not trigger unfolded protein response. Lower temperatures (27 °C and 22 °C) did not activate Nrf2 and HIF1A pathways as efficiently as mild hypothermia. Current findings are discussed in the context of the thermodynamic hypothesis of therapeutic hypothermia. We argue that the therapeutic effects are likely to stem both from metabolic suppression (inhibitory component) and augmentation of stress tolerance (activating component). We argue that systems coping with cellular stressors are plausible targets of therapeutic hypothermia and deserve more attention in clinical hypothermia research.

Altered Expression Profile of IgLON Family of Neural Cell Adhesion Molecules in the Dorsolateral Prefrontal Cortex of Schizophrenic Patients.

Neural adhesion proteins are crucial in the development and maintenance of functional neural connectivity. Growing evidence suggests that the IgLON family of neural adhesion molecules LSAMP, NTM, NEGR1, and OPCML are important candidates in forming the susceptibility to schizophrenia (SCZ). IgLON proteins have been shown to be involved in neurite outgrowth, synaptic plasticity and neuronal connectivity, all of which have been shown to be altered in the brains of patients with the diagnosis of schizophrenia. Here we optimized custom 5'-isoform-specific TaqMan gene-expression analysis for the transcripts of human IgLON genes to study the expression of IgLONs in the dorsolateral prefrontal cortex (DLPFC) of schizophrenic patients (n = 36) and control subjects (n = 36). Uniform 5'-region and a single promoter was confirmed for the human NEGR1 gene by in silico analysis. IgLON5, a recently described family member, was also included in the study. We detected significantly elevated levels of the NEGR1 transcript (1.33-fold increase) and the NTM 1b isoform transcript (1.47-fold increase) in the DLPFC of schizophrenia patients compared to healthy controls. Consequent protein analysis performed in male subjects confirmed the increase in NEGR1 protein content both in patients with the paranoid subtype and in patients with other subtypes. In-group analysis of patients revealed that lower expression of certain IgLON transcripts, mostly LSAMP 1a and 1b, could be related with concurrent depressive endophenotype in schizophrenic patients. Additionally, our study cohort provides further evidence that cannabis use may be a relevant risk factor associated with suicidal behaviors in psychotic patients. In conclusion, we provide clinical evidence of increased expression levels of particular IgLON family members in the DLPFC of schizophrenic patients. We propose that alterations in the expression profile of IgLON neural adhesion molecules are associated with brain circuit disorganization in neuropsychiatric disorders, such as schizophrenia. In the light of previously published data, we suggest that increased level of NEGR1 in the frontal cortex may serve as molecular marker for a wider spectrum of psychiatric conditions.

Wfs1 is expressed in dopaminoceptive regions of the amniote brain and modulates levels of D1-like receptors.

During amniote evolution, the construction of the forebrain has diverged across different lineages, and accompanying the structural changes, functional diversification of the homologous brain regions has occurred. This can be assessed by studying the expression patterns of marker genes that are relevant in particular functional circuits. In all vertebrates, the dopaminergic system is responsible for the behavioral responses to environmental stimuli. Here we show that the brain regions that receive dopaminergic input through dopamine receptor D1 are relatively conserved, but with some important variations between three evolutionarily distant vertebrate lines-house mouse (Mus musculus), domestic chick (Gallus gallus domesticus) / common quail (Coturnix coturnix) and red-eared slider turtle (Trachemys scripta). Moreover, we find that in almost all instances, those brain regions expressing D1-like dopamine receptor genes also express Wfs1. Wfs1 has been studied primarily in the pancreas, where it regulates the endoplasmic reticulum (ER) stress response, cellular Ca2+ homeostasis, and insulin production and secretion. Using radioligand binding assays in wild type and Wfs1-/- mouse brains, we show that the number of binding sites of D1-like dopamine receptors is increased in the hippocampus of the mutant mice. We propose that the functional link between Wfs1 and D1-like dopamine receptors is evolutionarily conserved and plays an important role in adjusting behavioral reactions to environmental stimuli.

Promoter-Specific Expression and Genomic Structure of IgLON Family Genes in Mouse.

IgLON family is composed of five genes: Lsamp, Ntm, Opcml, Negr1, and Iglon5; encoding for five highly homologous neural adhesion proteins that regulate neurite outgrowth and synapse formation. In the current study we performed in silico analysis revealing that Ntm and Opcml display similar genomic structure as previously reported for Lsamp, characterized by two alternative promotors 1a and 1b. Negr1 and Iglon5 transcripts have uniform 5' region, suggesting single promoter. Iglon5, the recently characterized family member, shares high level of conservation and structural qualities characteristic to IgLON family such as N-terminal signal peptide, three Ig domains, and GPI anchor binding site. By using custom 5'-isoform-specific TaqMan gene-expression assay, we demonstrated heterogeneous expression of IgLON transcripts in different areas of mouse brain and several-fold lower expression in selected tissues outside central nervous system. As an example, the expression of IgLON transcripts in urogenital and reproductive system is in line with repeated reports of urogenital tumors accompanied by mutations in IgLON genes. Considering the high levels of intra-family homology shared by IgLONs, we investigated potential compensatory effects at the level of IgLON isoforms in the brains of mice deficient of one or two family members. We found that the lack of IgLONs is not compensated by a systematic quantitative increase of the other family members. On the contrary, the expression of Ntm 1a transcript and NEGR1 protein was significantly reduced in the frontal cortex of Lsamp-deficient mice suggesting that the expression patterns within IgLON family are balanced coherently. The actions of individual IgLONs, however, can be antagonistic as demonstrated by differential expression of Syp in deletion mutants of IgLONs. In conclusion, we show that the genomic twin-promoter structure has impact on both anatomical distribution and intra-family interactions of IgLON family members. Remarkable variety in the activity levels of 1a and 1b promoters both in the brain and in other tissues, suggests complex functional regulation of IgLONs by alternative signal peptides driven by 1a and 1b promoters.

Cerebral 5-HT release correlates with [11C]Cimbi36 PET measures of 5-HT2A receptor occupancy in the pig brain.

Positron emission tomography (PET) can, when used with appropriate radioligands, non-invasively generate temporal and spatial information about acute changes in brain neurotransmitter systems. We for the first time evaluate the novel 5-HT2A receptor agonist PET radioligand, [11C]Cimbi-36, for its sensitivity to detect changes in endogenous cerebral 5-HT levels, as induced by different pharmacological challenges. To enable a direct translation of PET imaging data to changes in brain 5-HT levels, we calibrated the [11C]Cimbi-36 PET signal in the pig brain by simultaneous measurements of extracellular 5-HT levels with microdialysis and [11C]Cimbi-36 PET after various acute interventions (saline, citalopram, citalopram + pindolol, fenfluramine). In a subset of pigs, para-chlorophenylalanine pretreatment was given to deplete cerebral 5-HT. The interventions increased the cerebral extracellular 5-HT levels to 2-11 times baseline, with fenfluramine being the most potent pharmacological enhancer of 5-HT release, and induced a varying degree of decline in [11C]Cimbi-36 binding in the brain, consistent with the occupancy competition model. The observed correlation between changes in the extracellular 5-HT level in the pig brain and the 5-HT2A receptor occupancy indicates that [11C]Cimbi-36 binding is sensitive to changes in endogenous 5-HT levels, although only detectable with PET when the 5-HT release is sufficiently high.

Variability in the effect of antidepressants upon Wfs1-deficient mice is dependent on the drugs' mechanism of actions.

There is significant comorbidity between mood disorders and diabetes. Wolfram syndrome-related to deficient WFS1 gene function-causes diabetes and mood disorders in humans. Mice lacking the Wfs1 gene display impaired emotional behaviour and glucose metabolism. Various antidepressant drugs are used for alleviating the symptoms of mood disorders. For this study the tail suspension test and locomotor activity test were used to compare the effects of different antidepressants upon homozygous Wfs1-deficient, heterozygous Wfs1-deficient and wild-type mice. Mouse glucose metabolism was concurrently studied using the glucose tolerance test. We showed that ketamine(10mg/kg),NMDA antagonist, escitalopram(2.5-10mg/kg), selective serotonin reuptake inhibitor(SSRI), and amitriptyline(10mg/kg), noradrenaline and serotonin reuptake inhibitor, elicited a stronger antidepressant-like effect in homozygous Wfs1-deficient mice compared to wild-type mice. The effect of noradrenaline and serotonin reuptake inhibitor desipramine(10 and 20mg/kg) did not differ between genotypes. The dopamine and noradrenaline reuptake inhibitor bupropion(5-20mg/kg) had no significant antidepressant-like effect upon any genotype. Amitriptyline and desipramine potentiated a glucose elevation, escitalopram and bupropion did not affect glucose concentrations, and ketamine improved impaired glucose metabolism in homozygous Wfs1-deficient mice. Therefore, the results of this study suggest that SSRIs are the drugs of choice for the treatment of depressive symptoms in diabetic patients. The efficacy of ketamine for these patients remains to be established. Nonetheless, employing the mechanism of action of ketamine that affected glucose metabolism positively, could be an approach for development of improved antidepressants. Wfs1-deficient mice are likely the good animal model to develop new antidepressants more suitable for depressed patients with diabetes.

Deletion of the Wolfram syndrome-related gene Wfs1 results in increased sensitivity to ethanol in female mice.

Wolfram syndrome, induced by mutation in WFS1 gene, increases risk of developing mood disorders in humans. In mice, Wfs1 deficiency cause higher anxiety-like behaviour and increased response to anxiolytic-like effect of diazepam, a GABAA receptor agonist. As GABAergic system is also target for ethanol, we analysed its anxiolytic-like and sedative properties in Wfs1-deficient mice using elevated plus-maze test and tests measuring locomotor activity and coordination, respectively. Additionally loss of righting reflex test was conducted to study sedative/hypnotic properties of ethanol, ketamine and pentobarbital. To evaluate pharmacokinetics of ethanol in mice enzymatic colour test was used. Finally, gene expression of alpha subunits of GABAA receptors following ethanol treatment was studied by real-time-PCR. Compared to wild-types, Wfs1-deficient mice were more sensitive to ethanol-induced anxiolytic-like effect, but less responsive to impairment of motor coordination. Ethanol and pentobarbital, but not ketamine, caused longer duration of hypnosis in Wfs1-deficient mice. The expression of Gabra2 subunit at 30 minutes after ethanol injection was significantly increased in the frontal cortex of Wfs1-deficient mice as compared to respective vehicle-treated mice. For the temporal lobe, similar change in Gabra2 mRNA occurred at 60 minutes after ethanol treatment in Wfs1-deficient mice. No changes were detected in Gabra1 and Gabra3 mRNA following ethanol treatment. Taken together, increased anxiolytic-like effect of ethanol in Wfs1-deficient mice is probably related to altered Gabra2 gene expression. Increased anti-anxiety effect of GABAA receptor agonists in the present work and earlier studies (Luuk et al., 2009) further suggests importance of Wfs1 gene in the regulation of emotional behaviour.

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.

Wfs1-deficient mice display altered function of serotonergic system and increased behavioral response to antidepressants.

It has been shown that mutations in the WFS1 gene make humans more susceptible to mood disorders. Besides that, mood disorders are associated with alterations in the activity of serotonergic and noradrenergic systems. Therefore, in this study, the effects of imipramine, an inhibitor of serotonin (5-HT) and noradrenaline (NA) reuptake, and paroxetine, a selective inhibitor of 5-HT reuptake, were studied in tests of behavioral despair. The tail suspension test (TST) and forced swimming test (FST) were performed in Wfs1-deficient mice. Simultaneously, gene expression and monoamine metabolism studies were conducted to evaluate changes in 5-HT- and NA-ergic systems of Wfs1-deficient mice. The basal immobility time of Wfs1-deficient mice in TST and FST did not differ from that of their wild-type littermates. However, a significant reduction of immobility time in response to lower doses of imipramine and paroxetine was observed in homozygous Wfs1-deficient mice, but not in their wild-type littermates. In gene expression studies, the levels of 5-HT transporter (SERT) were significantly reduced in the pons of homozygous animals. Monoamine metabolism was assayed separately in the dorsal and ventral striatum of naive mice and mice exposed for 30 min to brightly lit motility boxes. We found that this aversive challenge caused a significant increase in the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of 5-HT, in the ventral and dorsal striatum of wild-type mice, but not in their homozygous littermates. Taken together, the blunted 5-HT metabolism and reduced levels of SERT are a likely reason for the elevated sensitivity of these mice to the action of imipramine and paroxetine. These changes in the pharmacological and neurochemical phenotype of Wfs1-deficient mice may help to explain the increased susceptibility of Wolfram syndrome patients to depressive states.

Evidence for impaired function of dopaminergic system in Wfs1-deficient mice.

Immunohistological studies suggest abundant expression of Wfs1 protein in neurons and nerve fibers that lie in the vicinity of dopaminergic (DA-ergic) fibers and neurons. Therefore, we sought to characterize the function of DA-ergic system in Wfs1-deficient mice. In wild-type mice, amphetamine, an indirect agonist of DA, caused significant hyperlocomotion and increase in tissue DA levels in the dorsal and ventral striatum. Both effects of amphetamine were significantly blunted in homozygous Wfs1-deficient mice. Motor stimulation caused by apomorphine, a direct DA receptor agonist, was somewhat stronger in Wfs1-deficient mice compared to their wild-type littermates. However, apomorphine caused a similar reduction in levels of DA metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) in the dorsal and ventral striatum in all genotypes. Behavioral sensitization to repeated treatment with amphetamine (2.5 mg/kg) was observed in wild-type, but not in Wfs1-deficient mice. The expression of DA transporter gene (Dat) mRNA was significantly lower in the midbrain of male and female homozygous mice compared to wild-type littermates. Altogether, the blunted effects of amphetamine and the reduced gene expression of DA transporter are probably indicative of an impaired functioning of the DA-ergic system in Wfs1-deficient mice.

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.