Chronic oral carbamazepine treatment elicits mood-stabilising effects in mice

Exploring test batteries for depression- and anxiety-like behaviours in female and male ICR and black Swiss mice

Objective and rationale: Animal models are critical for the study of mental disorders and their treatments but are repeatedly criticized for problems with validity and reproducibility. One approach to enhance validity and reproducibility of models is to use test batteries rather than single tests. Yet, a question regarding batteries is whether one can expect a consistent individual behavioural phenotype in mice across tests that can be presumed to be part of the same construct. This study was designed to explore the relationship between the behaviours of mice across tests in some variations of test batteries for depression- and anxiety-like behaviours. Methods: Female and male healthy, intact, and untreated mice from the ICR and black Swiss strains were used in four separate experiments. With some variations, mice were exposed to a battery of behavioural tests representing affective- and anxiety-like behaviours. Data were analysed for differences between sexes and for correlations between behaviours within and across the tests in the battery. Results: No differences were found between the sexes. With very few exceptions, we found correlations within tests (when one test has more than one measure or is repeated) but not across different tests within the battery. Conclusions: The results cast some doubt on the utility of behavioural test batteries to represent different facets of emotional behaviour in healthy intact outbred mice, without any interventions or treatments. Additional studies are designed to explore whether stronger relationship between the tests will appear after manipulations or drug treatments.

Revisiting the validity of the mouse tail suspension test: Systematic review and meta-analysis of the effects of prototypic antidepressants

Animal models in neuropsychiatric research need validation. One way to address external validity is systematic reviews and meta-analyses. The present study presents a meta-analysis of the effects of antidepressants in the mouse tail suspension test (TST). A PubMed search identified studies that examined imipramine and fluoxetine effects in the TST. Inclusion criteria were testing in the light phase; trial duration was six minutes; immobility time scored 6 or (last) 4 min; adult mice; acute intraperitoneal (IP) administration. Effect sizes (ES) were estimated using Cohen's d, heterogeneity of ES with Cochran's Q test, correlations between dose and ES with Pearson's correlation and differences between strains with Analysis of variance. Results show that antidepressants decrease immobility time in the TST and a correlation between drug dose and ES but no effects of strain. We suggest that the TST is a valid tool to quantitatively, consistently and reproducibly capture the immobility-reducing aspects of fluoxetine and imipramine and that the lack of strain effects is due to small number of experiments in many of the strains.

Questioning the predictive validity of the amphetamine-induced hyperactivity model for screening mood stabilizing drugs

Animal models are critical for the study of disease mechanisms and the screening of potential novel treatments. In the context of bipolar disorder, amphetamine-induced hyperactivity (AIH) is a frequently used screening model for antimanic effects. Yet, the utility of screening models depends on their predictive (or pharmacological) validity and it is expected that such models will respond to effective treatments. Lithium is the prototypic mood stabilizer but previous data regarding the effects of lithium in the AIH model are not clear and most data comes from studies using acute lithium administration that is not relevant to the therapeutic regimen in patients. To evaluate the pharmacological validity of AIH as a model for mania-like behavior we tested the interaction between chronic oral administration of lithium and amphetamine in ICR (CD-1®) mice and in black Swiss mice. We conducted 4 different experiments where chronic lithium was followed by an acute injection of amphetamine and one experiment where chronic amphetamine was combined with chronic lithium. The results show that amphetamine result in hyperactivity (experiments 1-4) and that lithium has no effects. Moreover, chronic amphetamine (experiment 5) result in sensitization that is not attenuated by lithium. The results clearly show that the predictive validity of the AIH model in ICR or black Swiss mice is problematic and possibly cast doubt on the utilization of the AIH as a screening model for novel mood stabilizers in other strains of mice.

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.

Carbamazepine, a beta-cell protecting drug, reduces type 1 diabetes incidence in NOD mice

Pancreatic beta-cells are selectively destroyed by the host immune system in type 1 diabetes. Thus, drugs that preserve beta-cell mass and/or function have the potential to prevent or slow the progression of this disease. We recently reported that the use-dependent sodium channel blocker, carbamazepine, protects beta-cells from inflammatory cytokines in vitro. Here, we tested the effects of carbamazepine treatment in female non-obese diabetic (NOD) mice by supplementing LabDiet 5053 with 0.5% w/w carbamazepine to achieve serum carbamazepine levels of 14.98 ± 3.19 µM. Remarkably, diabetes incidence over 25 weeks, as determined by fasting blood glucose, was ~50% lower in carbamazepine treated animals. Partial protection from diabetes in carbamazepine-fed NOD mice was also associated with improved glucose tolerance at 6 weeks of age, prior to the onset of diabetes in our colony. Less insulitis was detected in carbamazepine treated NOD mice at 6 weeks of age, but we did not observe differences in CD4⁺ and CD8⁺ T cell composition in the pancreatic lymph node, as well as circulating markers of inflammation. Taken together, our results demonstrate that carbamazepine reduces the development of type 1 diabetes in NOD mice by maintaining functional beta-cell mass.

Revisiting the validity of the mouse forced swim test: Systematic review and meta-analysis of the effects of prototypic antidepressants

One problem area regarding animal models for affective disorders is unclear reproducibility, including external validity or generalizability. One way to evaluate external validity is with systematic reviews and meta-analyses. The current study presents a meta-analysis of the effects of prototypic antidepressants in the mouse forced swim test (FST). We identified studies that examined effects of antidepressants in the FST in mice and used standard protocol, male mice and acute drug administration. We calculated Effect sizes using Cohen's d, homogeneity using Q statistic and correlations using Pearson's correlation. Results indicate that all drugs reduce immobility in the FST. However, effect sizes for most drugs are heterogeneous and do not show a consistent dose/response relationship across variability factors. Reducing variability by examining only one strain or data from individual laboratories partially increases dose response relationship. These findings suggest that whereas the FST is a valid tool to qualitatively screen antidepressant effects its validity in the context of hierarchical comparison between doses or compounds might be relevant only to single experiments.

Antimanic-like effects of (R)-(-)-carvone and (S)-(+)-carvone in mice

Carvone is a monoterpene that is present in spearmint (Mentha spicata) and caraway (Carum carvi) essential oils and has been shown to have anticonvulsant effects, likely through the blockade of voltage-gated sodium channels, and anxiolytic-like effects. Considering that some anticonvulsants that blocked voltage-gated sodium channels (e.g., sodium valproate and carbamazepine) exert clinical antimanic effects, the aim of the present study was to evaluate (R)-(-)-carvone and (S)-(+)-carvone in animal models of mania (i.e., hyperlocomotion induced by methylphenidate and sleep deprivation). Mice that were treated with methylphenidate (5mg/kg) or sleep-deprived for 24h using a multiple-platform protocol exhibited an increase in locomotor activity in an automated activity box. This effect was blocked by pretreatment with acute (R)-(-)-carvone (50-100mg/kg), (S)-(+)-carvone (50-100mg/kg), and lithium (100mg/kg, positive control). These doses did not alter spontaneous locomotor activity in the methylphenidate-induced experiments while (S)-(+)-carvone decreased spontaneous locomotor activity in sleep deprivation experiment, indicating a sedative effect. Chronic 21-day treatment with (R)-(-)-carvone (100mg/kg), (S)-(+)-carvone (100mg/kg), and lithium also prevented methylphenidate-induced hyperactivity. The present results suggest that carvone may have an antimanic-like effect.