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

Cat odour-induced anxiety—a study of the involvement of the endocannabinoid system

Rationale Recent evidence suggests the involvement of the endocannabinoid (EC) system in the regulation of anxiety. Objectives The aim of present work was to study the role of the EC system in cat odour-induced anxiety in rats. Materials and methods Male Wistar rats were exposed to cat odour in home and motility cages. Exposure of rats to elevated zero-maze was used to determine changes in anxiety. Effect of rimonabant (0.3–3 mg/kg), antagonist of CB1 receptors, was studied on cat odour-induced alterations in exploratory behaviour. Real-time PCR was used to determine gene expression levels of EC-related genes in the brain. Results Anxiogenic-like action of cat odour was evident in the elevated zero-maze. Cat odour increased the expression of FAAH, the enzyme responsible for the degradation of anandamide, in the mesolimbic area. By contrast, in the amygdala and periaqueductal grey (PAG) levels of NAPE-PLD, the enzyme related to the synthesis of anandamide, and FAAH were remarkably decreased. Cat odour also decreased the expression of enzymes related to metabolism of 2-archidonoyl-glycerol in the amygdala and PAG. Pre-treatment of rats with rimonabant (0.3–3 mg/kg) reduced the exploratory behaviour of rats, but did not affect cat odour-induced changes. Conclusion Exposure to cat odour induces anxiogenic-like effect on the behaviour in rats. Cat odour also causes moderate increase in expression of EC-related genes in the mesolimbic area, whereas significant down-regulation is established in the amygdala and PAG. Relation of predator odour-induced anxiety to the inhibition of the EC system in the amygdala and PAG is supported by behavioural studies where blockade of CB1 receptors by rimonabant induces anxiogenic-like action

Association analysis of limbic system-associated membrane protein gene polymorphisms in mood and anxiety disorders

Poster abstrac

Targeted invalidation of CCK2 receptor gene induces anxiolytic-like action in light–dark exploration, but not in fear conditioning test

Rationale Evidence suggests that γ-aminobutyric acid (GABA) and cholecystokinin (CCK) have opposite roles in the regulation of anxiety. Objectives The aim of our work was to study the behaviour of CCK2 receptor deficient mice in light–dark exploration and fear conditioning tests. Moreover, the action of diazepam and methyl-6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate (DMCM), having the opposite effect on GABAA receptors, was evaluated on the exploratory behaviour in these mice. Expression levels of GABAA receptor subunit genes were also measured. Methods Light–dark exploration and fear conditioning tests were used to determine changes in anxiety of mice. The action of diazepam (0.5–2 mg/kg i.p.) and DMCM (0.25–1 mg/kg i.p.) was studied in the light–dark box. The effect of DMCM was also evaluated in the motor activity test to demonstrate that its anti-exploratory action was not related to motor suppression. Expression levels of GABAA receptor subunit genes were determined by means of real-time polymerase chain reaction (qRT-PCR). Results Female mice lacking CCK2 receptors displayed increased exploratory activity in the light–dark box compared to their wild-type (+/+) littermates. Locomotor activity in the motility boxes and the intensity of freezing did not differ in wild-type (+/+) and homozygous (−/−) mice. Treatment with diazepam (0.5 mg/kg) increased the number of transitions in wild-type (+/+) animals, whereas in homozygous (−/−) mice diazepam (0.5–2 mg/kg) reduced exploratory activity. Administration of DMCM (0.25–1 mg/kg) induced an anxiogenic-like effect in homozygous (−/−) mice, but did not change their locomotor activity. Gene expression analysis established a 1.6-fold increase in the expression of the α2 subunit of GABAA receptors in the frontal cortex of homozygous (−/−) mice. Conclusion Genetic invalidation of CCK2 receptors induced an anxiolytic-like action in exploratory, but not in conditioned models of anxiety. The observed reduction in anxiety in homozygous (−/−) mice is probably related to an increased function of GABAergic system in the brain

Targeted mutation of CCK2 receptor gene modifies the behavioural effects of diazepam in female mice

Rationale Evidence suggests that GABA and CCK have opposite roles in the regulation of anxiety. Objective The aim of the present work was to study diazepam-induced anxiolytic-like action and impairment of motor co-ordination, and the parameters of benzodiazepine receptors in mice lacking CCK2 receptors. Methods The action of diazepam (0.5–3 mg/kg IP) was studied in the elevated plus-maze model of anxiety and rotarod test using mice lacking CCK2 receptors. The parameters of benzodiazepine receptors were analysed using [3H]-flunitrazepam binding. Results In the plus-maze test, the exploratory activity of the homozygous (−/−) mice was significantly higher compared to their wild-type (+/+) littermates. However, the wild-type (+/+) mice displayed higher sensitivity to the anxiolytic-like action of diazepam. Even the lowest dose of diazepam (0.5 mg/kg) induced a significant increase of open arm entries in the wild-type (+/+) mice. A similar effect in the homozygous (−/−) mice was established after the administration of diazepam 1 mg/kg. The highest dose of diazepam (3 mg/kg) caused a prominent anxiolytic-like effect in the wild-type (+/+) mice, whereas in the homozygous (−/−) animals suppression of locomotor activity was evident. The performance of the homozygous (−/−) mice in the rotarod test did not differ from that of the wild-type (+/+) littermates. However, a difference between the wild-type (+/+) and homozygous (−/−) animals became evident after treatment with diazepam. Diazepam (0.5 and 3 mg/kg) induced significantly stronger impairment of motor co-ordination in the homozygous (−/−) mice compared to their wild-type (+/+) littermates. The density of benzodiazepine binding sites was increased in the cerebellum, but not in the cerebral cortex and hippocampus, of the homozygous (−/−) mice. Conclusions Female mice lacking CCK2 receptors are less anxious than their wild-type (+/+) littermates. The reduced anxiety in homozygous (−/−) mice probably explains why the administration of a higher dose of diazepam is necessary to induce an anxiolytic-like action in these animals. The highest dose of diazepam (3 mg/kg) induced significantly stronger suppression of locomotor activity and impairment of motor co-ordination in the homozygous (−/−) mice compared to the wild-type (+/+) littermates. The increase in the action of diazepam is probably related to the elevated density of benzodiazepine receptors in the cerebellum of homozygous (−/−) mice. The present study seems to be in favour of increased tone of the GABAergic system in mice without CCK2 receptors

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

Early Intervention and Lifelong Treatment with GLP1 Receptor Agonist Liraglutide in a Wolfram Syndrome Rat Model with an Emphasis on Visual Neurodegeneration, Sensorineural Hearing Loss and Diabetic Phenotype

Wolfram syndrome (WS), also known as a DIDMOAD (diabetes insipidus, early-onset diabetes mellitus, optic nerve atrophy and deafness) is a rare autosomal disorder caused by mutations in the Wolframin1 (WFS1) gene. Previous studies have revealed that glucagon-like peptide-1 receptor agonist (GLP1 RA) are effective in delaying and restoring blood glucose control in WS animal models and patients. The GLP1 RA liraglutide has also been shown to have neuroprotective properties in aged WS rats. WS is an early-onset, chronic condition. Therefore, early diagnosis and lifelong pharmacological treatment is the best solution to control disease progression. Hence, the aim of this study was to evaluate the efficacy of the long-term liraglutide treatment on the progression of WS symptoms. For this purpose, 2-month-old WS rats were treated with liraglutide up to the age of 18 months and changes in diabetes markers, visual acuity, and hearing sensitivity were monitored over the course of the treatment period. We found that treatment with liraglutide delayed the onset of diabetes and protected against vision loss in a rat model of WS. Therefore, early diagnosis and prophylactic treatment with the liraglutide may also prove to be a promising treatment option for WS patients by increasing the quality of life

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