Failure to detect the action of antidepressants in the forced swim test in Swiss mice

The need for guidance in antidepressant drug development: Revisiting the role of the forced swim test and tail suspension test

Depressive disorders are one of the most common mental disorders globally and progress in treating these disorders has been hampered, in part, by a lack of suitable nonclinical efficacy tests. Two common tests used in nonclinical efficacy studies of antidepressants-the forced swim test (FST) and tail suspension test (TST)-have come under criticism in recent years for their inconsistency and lack of validity, yet they continue to be used in the pharmaceutical industry. In this review, we provide a rationale for why international pharmaceutical regulatory and guidance agencies should begin issuing direction on methods for non-clinical efficacy testing that traditionally use the FST and TST, particularly considering that some regulators, such as those in the U.S. and E.U., allow the authorization of clinical trials to proceed without requiring tests in animals. The area of antidepressant drug discovery represents an important opportunity for reducing the attrition of psychiatric drugs, harmonizing regulatory requirements, and reducing animal use. Specific recommendations for the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) have been provided.

A suitable model to investigate acute neurological consequences of coronavirus infection

OBJECTIVE AND DESIGN

The present study aimed to investigate the neurochemical and behavioral effects of the acute consequences after coronavirus infection through a murine model.

MATERIAL

Wild-type C57BL/6 mice were infected intranasally (i.n) with the murine coronavirus 3 (MHV-3).

METHODS

Mice underwent behavioral tests. Euthanasia was performed on the fifth day after infection (5 dpi), and the brain tissue was subjected to plaque assays for viral titration, ELISA, histopathological, immunohistochemical and synaptosome analysis.

RESULTS

Increased viral titers and mild histological changes, including signs of neuronal degeneration, were observed in the cerebral cortex of infected mice. Importantly, MHV-3 infection induced an increase in cortical levels of glutamate and calcium, which is indicative of excitotoxicity, as well as increased levels of pro-inflammatory cytokines (IL-6, IFN-γ) and reduced levels of neuroprotective mediators (BDNF and CX3CL1) in the mice brain. Finally, behavioral analysis showed impaired motor, anhedonia-like and anxiety-like behaviors in animals infected with MHV-3.

CONCLUSIONS

In conclusion, the data presented emulate many aspects of the acute neurological outcomes seen in patients with COVID-19. Therefore, this model may provide a preclinical platform to study acute neurological sequelae induced by coronavirus infection and test possible therapies.

In Vitro Human Monoamine Oxidase Inhibition and Human Dopamine D4 Receptor Antagonist Effect of Natural Flavonoids for Neuroprotection

Natural flavone and isoflavone analogs such as 3',4',7-trihydroxyflavone (1), 3',4',7-trihydroxyisoflavone (2), and calycosin (3) possess significant neuroprotective activity in Alzheimer's and Parkinson's disease. This study highlights the in vitro human monoamine oxidase (hMAO) inhibitory potential and functional effect of those natural flavonoids at dopamine and serotonin receptors for their possible role in neuroprotection. In vitro hMAO inhibition and enzyme kinetics studies were performed using a chemiluminescent assay. The functional effect of three natural flavonoids on dopamine and serotonin receptors was tested via cell-based functional assays followed by a molecular docking simulation to predict interactions between a compound and the binding site of the target protein. A forced swimming test was performed in the male C57BL/6 mouse model. Results of in vitro chemiluminescent assays and enzyme kinetics depicted 1 as a competitive inhibitor of hMAO-A with promising potency (IC50 value: 7.57 ± 0.14 μM) and 3 as a competitive inhibitor of hMAO-B with an IC50 value of 7.19 ± 0.32 μM. Likewise, GPCR functional assays in transfected cells showed 1 as a good hD4R antagonist. In docking analysis, these active flavonoids interacted with a determinant-interacting residue via hydrophilic and hydrophobic interactions, with low docking scores comparable to reference ligands. The post-oral administration of 1 to male C57BL/6 mice did not reduce the immobility time in the forced swimming test. The results of this study suggest that 1 and 3 may serve as effective regulators of the aminergic system via hMAO inhibition and the hD4R antagonist effect, respectively, for neuroprotection. The route of administration should be considered.

Sigma-1 receptor agonist properties that mediate the fast-onset antidepressant effect of hypidone hydrochloride (YL-0919)

The most intriguing characteristic of the sigma-1 receptor is its ability to regulate multiple functional proteins directly via protein-protein interactions, giving the sigma-1 receptor the powerful ability to regulate several survival and metabolic functions in cells, fine tune neuronal excitability, and regulate the transmission of information within brain circuits. This characteristic makes sigma-1 receptors attractive candidates for the development of new drugs. Hypidone hydrochloride (YL-0919), a novel structured antidepressant candidate developed in our laboratory, possess a selective sigma-1 receptor agonist profile, as evidenced by molecular docking, radioligand receptor binding assays, and receptor functional experiments. In vivo studies have revealed that YL-0919 elicits a fast-onset antidepressant activity (within one week) that can be attenuated with pretreatment of the selective sigma-1 receptor antagonist, BD-1047. Taken together, the findings of the current study suggest that YL-0919 activates the sigma-1 receptor to partially mediate the rapid onset antidepressant effects of YL-0919. Thus, YL-0919 is a promising candidate as a fast-onset antidepressant that targets the sigma-1 receptor.

New monoamine antidepressant, hypidone hydrochloride (YL-0919), enhances the excitability of medial prefrontal cortex in mice via a neural disinhibition mechanism

Hypidone hydrochloride (YL-0919) is a novel antidepressant in clinical phase II trial. Previous studies show that YL-0919 is a selective 5-HT (serotonin) reuptake inhibitor, 5-HT_1A receptor partial agonist, and 5-HT₆ receptor agonist, which exerts antidepressant effects in various animal models, but its effects on neural function remain unclear. Medial prefrontal cortex (mPFC), a highly evolved brain region, controls highest order cognitive functions and emotion regulation. In this study we investigated the effects of YL-0919 on the mPFC function, including the changes in neuronal activities using electrophysiological recordings. Extracellular recording (in vivo) showed that chronic administration of YL-0919 significantly increased the spontaneous discharges of mPFC neurons. In mouse mPFC slices, whole-cell recording revealed that perfusion of YL-0919 significantly increased the frequency of sEPSCs, but decreased the frequency of sIPSCs. Then we conducted whole-cell recording in mPFC slices of GAD67-GFP transgenic mice, and demonstrated that YL-0919 significantly inhibited the excitability of GABAergic neurons. In contrast, it did not alter the excitability of pyramidal neurons in mPFC slices of normal mice. Moreover, the inhibition of GABAergic neurons by YL-0919 was prevented by pre-treatment with 5-HT_1A receptor antagonist WAY 100635. Finally, chronic administration of YL-0919 significantly increased the phosphorylation levels of mTOR and GSK-3β in the mPFC as compared with vehicle. Taken together, our results demonstrate that YL-0919 enhances the excitability of mPFC via a disinhibition mechanism to fulfill its rapid antidepressant neural mechanism, which was accomplished by 5-HT_1A receptor-mediated inhibition of inhibitory GABAergic interneurons.

Effect of simultaneous testing of two mice in the tail suspension test and forced swim test

In mouse studies, the results of behavioural experiments are greatly affected by differences in the experimental environment and handling methods. The Porsolt forced swim test and tail suspension test are widely used to evaluate predictive models of depression-like behaviour in mice. It has not been clarified how the results of these tests are affected by testing single or multiple mice simultaneously. Therefore, this study evaluated the differences between testing two mice simultaneously or separately. To investigate the effect of testing multiple mice simultaneously, the Porsolt forced swim test and tail suspension test were performed in three patterns: (1) testing with an opaque partition between two mice, (2) testing without a partition between two mice, and (3) testing a single mouse. In the Porsolt forced swim test, the mice tested simultaneously without a partition demonstrated increased immobility time as compared to mice tested alone. No difference in immobility time was observed between the three groups in the tail suspension test. Our results showed that the environment of behavioural experiments investigating depression-like behaviour in mice can cause a difference in depression-like behaviour. The results of this experiment indicated that it is necessary to describe the method used for behavioural testing in detail.

Systematic heterogenisation to improve reproducibility in animal studies

A recent study published in PLoS Biology investigated whether the systematic use of multiple experimenters boosts the reproducibility of behavioural assays in mice. This Primer explores study designs to investigate systematic heterogenization in single-or multi-laboratory settings.

2-Phenyl-3-(phenylselanyl)benzofuran elicits acute antidepressant-like action in male Swiss mice mediated by modulation of the dopaminergic system and reveals therapeutic efficacy in both sexes

RATIONALE

Depression is a psychiatric disorder that constitutes one of the leading causes of disability worldwide. 2-Phenyl-3-(phenylselanyl)benzofuran (SeBZF1) has been studied as a potential antidepressant drug, but its pharmacological action needs more investigation.

OBJECTIVES AND METHODS

Our aim was to extend information about the antidepressant-like action of SeBZF1 using the mouse tail suspension test (TST). Initial experiments investigated the mechanisms involved in the acute antidepressant-like action of SeBZF1 in male Swiss mice. For this purpose, males received noradrenergic or dopaminergic receptor antagonists before acute SeBZF1 administration (50 mg/kg, per oral). In parallel, effects of combined treatment with SeBZF1 and bupropion at sub-effective doses (1 and 3 mg/kg, respectively) were tested. The next experiments were designed to determine the acute effects of SeBZF1 in females through a dose-response curve (5-50 mg/kg). Lastly, the efficacy of a 7-day repeated treatment with SeBZF1 (1 and 5 mg/kg) in mice of both sexes and its safety were evaluated. TST and the open-field test (OFT) were employed in all behavioral experiments.

RESULTS

Pre-administration of dopaminergic antagonists (SCH23390, a selective D₁R antagonist; sulpiride, a selective D₂/D₃R antagonist; and haloperidol, a non-selective antagonist), but not of adrenergic α₁, α₂, and β-R antagonists, blocked the acute antidepressant-like effects of SeBZF1 in males. Co-administration of sub-effective doses of SeBZF1 and bupropion reduced the depressive phenotype. In addition, acute treatment with SeBZF1 at 50 mg/kg produced a reduction of female immobility. Finally, repeated treatment with SeBZF1 (1 and 5 mg/kg) was effective in causing antidepressant-like effects in both sexes. Locomotor activity, plasma transaminases, and urea levels remained unaltered after SeBZF1 exposure.

CONCLUSION

Our findings provide evidence of the involvement of the dopaminergic system in the acutely antidepressant-like action of SeBZF1 in male mice and reveal the compound efficacy when acute or repeatedly administered in both sexes.

The forced swim test has poor accuracy for identifying novel antidepressants

Despite the prevalence of treatment-resistant depression, many pharmaceutical companies have abandoned the development of new antidepressants. Experts have attributed this, in part, to the low quality of preclinical tests available in this field, often citing over-reliance on animal behavioral screens, such as the forced swim test (FST). This retrospective review assessed whether compounds tested in the FST by major pharmaceutical companies were shown to have antidepressant effects in humans. Of 109 compounds identified, only 28% had been explored for antidepressant effects in humans. Of these, there were only three for which the FST appeared to positively predict antidepressant efficacy, but none are currently approved to treat any type of depression. With such poor accuracy for identifying novel antidepressants, the FST might not be a useful screening tool for this purpose.

A single injection of imipramine affected proliferation in the hippocampus of adult Swiss mice depending on the route of administration, doses, survival time and lodging conditions

Swiss mice may be valuable for the screening of antidepressants in preclinical trials. Acute treatment with antidepressants may affect the behaviour of Swiss mice, but the effects on their hippocampal neurogenesis remain unknown. The present work aims to assess the influence of acute treatment with antidepressants on cell proliferation in the dentate gyrus of the hippocampus of adult Swiss mice. Cell proliferation was estimated by ex vivo counting of Ki-67 immunoreactive nuclei (Ki-67-ir) in the dentate gyrus of Swiss mice housed in standard or enriched environments, at survival-times 2 or 24 h after imipramine injection Independent of the experimental group, intraperitoneal imipramine (0 or 30 mg/kg) failed to change the number of Ki-67-ir in the hippocampus of mice. Through intracerebroventricular route, imipramine reduced the number of Ki-67-ir in the hippocampus of Swiss mice at the dose of 0.06 nmol and increased it at the dose 0.2 nmol. At the dose 0.2 nmol, not 0.06 nmol, imipramine increased the immunoreactivity to doublecortin (a marker for immature neurons) in the hippocampus of mice. The effects of intracerebroventricular injection of imipramine on neurogenesis markers were seen 24 h after the injection in mice housed in standard conditions. The effects of intracerebroventricular injection of imipramine on neurogenesis markers were absent in mice housed in enrichment or 2 h after the injection. These data suggest that acute treatment with imipramine may affect proliferation in the hippocampus of adult Swiss mice depending on the route of administration, doses, survival time and lodging conditions.

Bioactive β-Carbolines in Food: A Review

Harman and norharman, two neuroactive β-carbolines, are present in several plants and in thermally processed foods. They exhibited a wide spectrum of biological and pharmacological effects, including antioxidant, neuroprotective, and anti-inflammatory effects. In this article, we review the progress of recent research on the presence of these compounds in food, as well as their various biological and neuroactive properties. Our findings strongly suggest that some foods, especially coffee, can act as a rich source of β-carbolines, which may possibly be associated with a reduced risk for serious neurodegenerative diseases, such as Parkinson's and Alzheimer's.

Mouse Strain Affects Behavioral and Neuroendocrine Stress Responses Following Administration of Probiotic Lactobacillus rhamnosus JB-1 or Traditional Antidepressant Fluoxetine

Currently, there is keen interest in the development of alternative therapies in the treatment of depression. Given the explosion of research focused on the microbiota-gut-brain axis, consideration has turned to the potential of certain probiotics to improve patient outcomes for those suffering from mood disorders. Here we examine the abilities of a known antidepressant, fluoxetine, and the probiotic Lactobacillus rhamnosus JB-1™, to attenuate responses to two established criteria for depressive-like behavior in animal models, the tail suspension test (TST) and the corticosterone response to an acute restraint stressor. We examine two different strains of mice known to differ in the extent to which they express both anxiety-like behavior and measures of despair—BALB/c and Swiss Webster—with respectively high and normal behavioral phenotypes for each. While adult male BALB/c mice responded with increased antidepressive-like behavior to both fluoxetine and L. rhamnosus JB-1 in both the TST and the corticosterone stress response, SW mice did not respond to either treatment as compared to controls. These findings highlight the importance of investigating putative antidepressants in mouse strains known to express face validity for some markers of depression. Clinical studies examining the activity of L. rhamnosus JB-1 in patients suffering from mood disorders are warranted, as well as further pre-clinical work examining how interactions between host genotype and intestinal microbial alterations may impact behavioral responses. This study adds to the literature supporting the possibility that modifying the intestinal microbiota via probiotics represents a promising potential therapeutic breakthrough in the treatment of psychiatric disease.