Chrono-Gerontology: Integrating Circadian Rhythms and Aging in Stroke Research.

Stroke is a significant public health concern for elderly individuals. However, the majority of pre-clinical studies utilize young and healthy rodents, which may result in failure of candidate therapies in clinical trials. In this brief review/perspective, the complex link between circadian rhythms, aging, innate immunity, and the gut microbiome to ischemic injury onset, progression, and recovery is discussed. Short-chain fatty acids and nicotinamide adenine dinucleotide+ (NAD+ ) production by the gut microbiome are highlighted as key mechanisms with profound rhythmic behavior, and it is suggested to boost them as prophylactic/therapeutic approaches. Integrating aging, its associated comorbidities, and circadian regulation of physiological processes into stroke research may increase the translational value of pre-clinical studies and help to schedule the optimal time window for existing practices to improve stroke outcome and recovery.

Inhibition of FKBP51 induces stress resilience and alters hippocampal neurogenesis.

Stress-related psychiatric disorders such as depression are among the leading causes of morbidity and mortality. Considering that many individuals fail to respond to currently available antidepressant drugs, there is a need for antidepressants with novel mechanisms. Polymorphisms in the gene encoding FK506-binding protein 51 (FKBP51), a co-chaperone of the glucocorticoid receptor, have been linked to susceptibility to stress-related psychiatric disorders. Whether this protein can be targeted for their treatment remains largely unexplored. The aim of this work was to investigate whether inhibition of FKBP51 with SAFit2, a novel selective inhibitor, promotes hippocampal neuron outgrowth and neurogenesis in vitro and stress resilience in vivo in a mouse model of chronic psychosocial stress. Primary hippocampal neuronal cultures or hippocampal neural progenitor cells (NPCs) were treated with SAFit2 and neuronal differentiation and cell proliferation were analyzed. Male C57BL/6 mice were administered SAFit2 while concurrently undergoing a chronic stress paradigm comprising of intermittent social defeat and overcrowding, and anxiety and depressive -related behaviors were evaluated. SAFit2 increased neurite outgrowth and number of branch points to a greater extent than brain derived neurotrophic factor (BDNF) in primary hippocampal neuronal cultures. SAFit2 increased hippocampal NPC neurogenesis and increased neurite complexity and length of these differentiated neurons. In vivo, chronic SAFit2 administration prevented stress-induced social avoidance, decreased anxiety in the novelty-induced hypophagia test, and prevented stress-induced anxiety in the open field but did not alter adult hippocampal neurogenesis in stressed animals. These data warrant further exploration of inhibition of FKBP51 as a strategy to treat stress-related disorders.

Proposing the sweet solution preference test as a screening assay for anti-manic effects of mood stabilizers.

BACKGROUND: There is a desperate need for in-vivo behavioral screening tests for anti-manic effects. The frequently used psychostimulant-induced hyperactivity test appears to have lower validity than previously described, but other quick, simple and high throughput tests are currently unavailable. NEW METHOD: In the context of modeling the behavioral facets of mania, we previously suggested that the sweet solution preference test (SSP) in naive mice might have predictive validity for screening anti-manic effects. The current study further examined this proposal by testing the effects of lithium, valproate and imipramine on SSP in three strains of mice (male mice from the black Swiss, ICR and C57bl/6 strains) and an exploratory test in females (black Swiss strain). RESULTS: Data demonstrate that lithium and valproate at appropriate dosing schedules significantly and reliably reduce SSP in all three strains (including in females) but that the antidepressant imipramine has no effects. COMPARISON WITH EXISTING METHODS: The results support the utilization of the SSP as mice screening model for anti-manic effects of drugs with stronger predictive validity compared with other methods. CONCLUSIONS: The SSP is not a comprehensive model for bipolar disorder but it has good predictive validity and strong practical value that can be applied towards simple and fast screening of large numbers of animals, without the need for specialized equipment or complicated/prolonged procedures. We therefore propose that the SSP is an advantageous screening assay for testing novel mood stabilizing drugs for anti-manic properties.

Chronic Stress May Not Be a Factor in the Behavioral Response to Chronic Lithium in ICR Mice.

BACKGROUND: Lithium (Li) is the prototypic mood-stabilizing drug, but the individual response to Li is highly heterogeneous. Some evidence suggest interactions between Li and stress, and it is possible to hypothesize that lithium's effects are modified by stress conditions. The current study examines the interaction between 2 chronic stressors, constant light (CL) and restrain and the behavioral responses to chronic Li in female and male mice. METHODS: Female and male ICR mice were exposed to 3 weeks of either (1) CL; (2) daily restrain or (3) no stress control. One week after the start of the stress intervention, mice started chronic oral Li treatment or control. After 2 weeks of stress and Li, mice were tested in a number of behavioral tests including spontaneous activity, sweet solution preference, plus-maze and forced swim test. RESULTS: There were no effects of stressors on behavior. Effects of Li were demonstrated in males but not females with no interactions between stress and Li. CONCLUSIONS: The behavioral effects of Li in this study were not affected by stress. The lack of effects of the stressors themselves on behavior suggests that the application of more intrusive stressors might be needed to further explore the issue.

Individual responses of rodents in modelling of affective disorders and in their treatment: prospective review.

IntroductionLack of good animal models for affective disorders, including major depression and bipolar disorder, is noted as a major bottleneck in attempts to study these disorders and develop better treatments. We suggest that an important approach that can help in the development and use of better models is attention to variability between model animals. RESULTS: Differences between mice strains were studied for some decades now, and sex differences get more attention than in the past. It is suggested that one factor that is mostly neglected, individual variability within groups, should get much more attention. The importance of individual differences in behavioral biology and ecology was repeatedly mentioned but its application to models of affective illness or to the study of drug response was not heavily studied. The standard approach is to overcome variability by standardization and by increasing the number of animals per group. CONCLUSIONS: Possibly, the individuality of specific animals and their unique responses to a variety of stimuli and drugs, can be helpful in deciphering the underlying biology of affective behaviors as well as offer better prediction of drug responses in patients.

Mood-stabilizing effects of rapamycin and its analog temsirolimus: relevance to autophagy.

Accumulated data support a relationship between mood disorders and cellular plasticity and resilience, some suggesting relevance to autophagy. Our previous data show that pharmacological enhancement of autophagy results in antidepressant-like effects in mice. The current study was designed to further examine the effects of autophagy enhancement on mood by testing the effects of subchronic treatment with the mammalian target of rapamycin (mTOR) inhibitors and autophagy enhancers rapamycin and temsirolimus in a model for mania and in a model for antidepressant action, respectively. The results show that rapamycin reduced mania-like aggression and reward-seeking behaviors, with no effects on locomotion. Temsirolimus reduced depression-related immobility in the forced-swim test without effects on locomotion in the open field or on anxiety-related measures in the elevated plus maze. Taken together with our previous findings, these data support the notion that enhancing autophagy may have mood-stabilizing effects.

Effects of repeated asenapine in a battery of tests for anxiety-like behaviours in mice.

OBJECTIVE: A number of atypical antipsychotic drugs were demonstrated to have anxiolytic effects in patients and in animal models. These effects were mostly suggested to be the consequence of the drugs' affinity to the serotonin system and its receptors. Asenapine is a relatively new atypical antipsychotic that is prescribed for schizophrenia and for bipolar mania. Asenapine has a broad pharmacological profile with significant effects on serotonergic receptors, hence it is reasonable to expect that asenapine may have some anxiolytic effects. The present study was therefore designed to examine possible effects of asenapine on anxiety-like behaviour of mice. METHOD: Male ICR mice were repeatedly treated with 0.1 or 0.3 mg/kg injections of asenapine and then tested in a battery of behavioural tests related to anxiety including the open-field test, elevated plus-maze (EPM), defensive marble burying and hyponeophagia tests. In an adjunct experiment, we tested the effects of acute diazepam in the same test battery. RESULTS: The results show that diazepam reduced anxiety-like behaviour in the EPM, the defensive marble burying test and the hyponeophagia test but not in the open field. Asenapine has anxiolytic-like effects in the EPM and the defensive marble burying tests but had no effects in the open-field or the hyponeophagia tests. Asenapine had no effects on locomotor activity. CONCLUSION: The results suggest that asenapine may have anxiolytic-like properties and recommends that clinical trials examining such effects should be performed.

Partial effects of the AMPAkine CX717 in a strain specific battery of tests for manic-like behavior in black Swiss mice.

BACKGROUND: AMPA receptors are highly expressed throughout the central nervous system and are suggested to be involved in mood regulation. Studies found changes in glutamate, its metabolites and receptors in patients with bipolar disorder (BPD) or major depression (MD) and in animal models of stress. Additional data suggest that the glutamatergic system and AMPA receptors specifically, have an important role in modulating the therapeutic effects of mood stabilizers. Further research on the role of AMPA receptors in mood regulation can be done using AMPAkines, positive modulators of AMPA receptors. AMPAkines have been studied for cognitive enhancement in neurodegenerative disorders and some were also examined in preclinical studies of mood disorders. In that context, the present study was designed to test the effects of the AMPAkine CX717 in a strain specific battery of tests for mania-like behaviors. METHODS: Black Swiss male mice were sub-chronically treated with 5 different doses of CX717 or vehicle and tested in a battery of behavioral tests including spontaneous activity, sweet solution preference, resident-intruder, forced swim and amphetamine-induced hyperactivity. RESULTS: Data show that CX717 doses of 30mg/kg and above, but not lower, reduce activity levels. Moreover, 45mg/kg and above reduce interactions in the resident-intruder test and ameliorate amphetamine-induced hyperactivity. CONCLUSIONS: The results therefore show a partial effect of CX717 on manic-like behavior, somewhat similar to previously demonstrated effects of atypical antipsychotic drugs in this strain. It is therefore suggested that further work related to AMPAkines in the treatment of affective disorders might be warranted.

Introducing Female Black Swiss Mice: Minimal Effects of Sex in a Strain-Specific Battery of Tests for Mania-Like Behavior and Response to Lithium.

Black Swiss (BS) mice were shown to be an advantageous strain to model behavioral domains of mania, but to date only male mice were tested, whereas bipolar disorder (BPD) is equally prevalent in women and men. This study was therefore designed to examine the possibility of using both male and female BS mice in future studies. Groups of male and female BS mice were compared with each other, with or without lithium treatment, in tests for domains of mania-like behavior including activity in an open field, sweet solution preference, elevated plus maze, forced swim and amphetamine-induced hyperactivity. The results indicate mostly a similarity between female and male BS mice, both naïve and after chronic lithium treatment. The results are discussed in the context of the deficiency in utilizing female mice in animal models research and suggest that both male and female BS mice can be used to model domains of mania-like behavior.

The effects of the atypical antipsychotic asenapine in a strain-specific battery of tests for mania-like behaviors.

Asenapine is indicated for the treatment of schizophrenia and manic episodes in bipolar disorder (BPD). There is a paucity of information on the effects of asenapine in animal models of BPD, but such work is essential to discover its scope of effects and its mechanisms of therapeutic action. This study evaluated the effects of asenapine in a validated test battery for manic-like behaviors in Black Swiss mice. Male Black Swiss mice received asenapine at 0.03, 0.1, and 0.3 mg/kg twice daily for 7 days and were tested for spontaneous activity, sweet solution preference, forced-swim test, social interaction, and amphetamine-induced hyperactivity. Asenapine treatment resulted in dose-dependent, clinically relevant plasma levels. Asenapine, at the 0.1 and 0.3 mg/kg doses, reduced activity, with the 0.3 mg/kg dose also resulting in increased time in the center of an open field, increased immobility in the forced-swim test, and reduced amphetamine-induced hyperactivity. Asenapine exerted no effects in the social interaction or sweet solution preference tests. The results suggest that asenapine exerts antimanic-like effects in some of the behavioral tests performed in Black Swiss mice. These data support the utilization of asenapine in the treatment of BPD.

Chronic oral carbamazepine treatment elicits mood-stabilising effects in mice.

OBJECTIVE: The underlying biology of bipolar disorder and the mechanisms by which effective medications induce their therapeutic effects are not clear. Appropriate use of animal models are essential to further understand biological mechanisms of disease and treatment, and further understanding the therapeutic mechanism of mood stabilisers requires that clinically relevant administration will be effective in animal models. The clinical regimens for mood-stabilising drugs include chronic oral administration; however, much of the work with animal models includes acute administration via injection. An effective chronic and oral administration of the prototypic mood stabiliser lithium was already established and the present study was designed to do the same for the mood stabiliser carbamazepine. METHODS: Mice were treated for 3 weeks with carbamazepine in food. ICR mice were treated with 0.25%, 0.5% and 0.75%, and C57bl/6 mice with 0.5% and 0.75%, carbamazepine in food (w/w, namely, 2.5, 5.0 or 7.5 g/kg food). Mice were then tested for spontaneous activity, forced swim test (FST), tail suspension test (TST) and amphetamine-induced hyperactivity. RESULTS: Oral carbamazepine administration resulted in dose-dependent blood levels reaching 3.65 µg/ml at the highest dose. In ICR mice, carbamazepine at the 0.5% dose had no effect on spontaneous activity, but significantly reduced immobility in the TST by 27% and amphetamine-induced hyperactivity by 28%. In C57bl/6 mice, carbamazepine at the 0.75% dose reduced immobility time in the FST by 26%. CONCLUSIONS: These results demonstrate a behaviourally effective oral and chronic regimen for carbamazepine with mood stabilising-like activity in a standard model for mania-like behaviour and two standard models for depression-like behaviour.

Beware of your mouse strain; differential effects of lithium on behavioral and neurochemical phenotypes in Harlan ICR mice bred in Israel or the USA.

Animal models are crucial components in the search for better understanding of the biological basis of psychiatric disorders and for the development of novel drugs. Research, in general, and research with animal models, in particular, relies on the consistency of effects of investigated drugs or manipulations across experiments. In that context, it had been noted that behavioral responses to lithium in ICR (CD-1) mice from Harlan Israel have changed across the last years. To examine this change, the present study compared the effect of lithium treatment in ICR mice from Harlan Israel with the ICR mice from Harlan USA. The mice were treated with chronic oral lithium. Their lithium serum levels were measured and their behavior in the forced swim test (FST) was evaluated. The mice were also treated with [(3)H]-inositol ICV and lithium injection and their frontal cortex [(3)H]-phosphoinositols accumulation was measured. Results show that lithium serum levels in Israeli mice were significantly lower compared with the USA mice, that lithium had no behavioral effect in the Israeli mice but significantly reduced FST immobility time of the USA mice, and that phosphoinositols accumulation was much more strongly affected by lithium in the USA mice compared with the Israeli mice. These results suggest that the Israeli Harlan colony of ICR mice changed significantly from the original ICR colony in Harlan USA and that the differences might be related to absorption or secretion of lithium.