Amygdala response to explicit sad face stimuli at baseline predicts antidepressant treatment response to scopolamine in major depressive disorder

Group-Based Symptom Trajectory of Intramuscular Administration of Scopolamine Augmentation in Moderate to Severe Major Depressive Disorder: A Post-Hoc Analysis

Objective

Developing new strategies for rapid and sustained relief of depressive symptom has been the focus of research in the field of major depressive disorder (MDD). Scopolamine exerts rapid antidepressant effect in recent years but is controversial. Therefore, we aimed to identify a sensitive patient who may respond to intramuscular injections of scopolamine added to antidepressants based on distinct trajectory patterns.

Methods

We analyzed longitudinal post hoc data collected from 66 MDD patients at Beijing Anding Hospital, Capital Medical University, over a 4-week period. In addition to demographics, depressive symptoms were assessed using the 16-item Quick Inventory of Depressive Symptomatology and Self-Report (QIDS-SR16) Scale and 17-item Hamilton Rating Scale for Depression (HRSD-17) following an i.m. injection of scopolamine. We explored different longitudinal patterns of depressive symptoms using a group-based trajectory model (GBTM). We used multiple logistic regression models to help identify predictors of different depressive symptom trajectories.

Results

A two-class GBTM was identified as optimal for classifying depressive symptoms: high/rapidly declining (39.4%) and moderate/gradually declining depression trajectories (60.6%) were distinguished based on the HRSD-17. The high/rapidly declining depression trajectory was characterized by high initial depression followed by a rapid decrease at the end of the study. The moderate/gradual decline trajectory was dominated by moderate depression and gradual decline over 4 weeks. There were no significant associations of age, gender, education, or age of onset with the two trajectory groups.

Conclusion

Scopolamine added to antidepressants can effectively relieve the symptoms of patients with severe depression, and it decreases faster than patients with moderate depression.

Combination of spontaneous regional brain activity and HTR1A/1B DNA methylation to predict early responses to antidepressant treatments in MDD

BACKGROUND

Antidepressant medications are suggested as the first-line treatment in patients with major depressive disorder (MDD). However, the drug therapy outcomes vary from person to person. The functional activity of the brain and DNA methylation levels correlate with the antidepressant efficacy. To predict the early antidepressant responses in MDD and establish the prediction framework, we aimed to apply multidimensional data based on the resting-state activity of the brain and HTR1A/1B methylation.

METHODS

The values of Amplitude of Low-Frequency Fluctuations (ALFF) and regional homogeneity (ReHo) were measured as variables in 116 brain regions along with 181 CpG sites in the promoter region of HTR1A/1B and 11 clinical characteristics. After performing the feature reduction step using the least absolute shrinkage and selection operator (LASSO) method, the selected variables were put into Support Vector Machines (SVM), Random Forest (RF), Naïve Bayes (NB), and logistic regression (LR), consecutively, to construct the prediction models. The models' performance was evaluated by the Leave-One-Out Cross-Validation.

RESULTS

The LR model composed of the selected multidimensional features reached a maximum performance of 78.57% accuracy and 0.8340 area under the ROC curve (AUC). The prediction accuracies based on multidimensional datasets were found to be higher than those obtained from the data based only on fMRI or methylation.

LIMITATIONS

A relatively small sample size potentially restricted the usage of our prediction framework in clinical applications.

CONCLUSION

Our study revealed that combining the data of brain imaging and DNA methylation could provide a complementary effect in predicting early-stage antidepressant outcomes.

Neuroimaging Correlates of Treatment Response with Psychedelics in Major Depressive Disorder: A Systematic Review

Preliminary evidence supports the use of psychedelics for major depressive disorder (MDD). However, less attention has been given to the neural mechanisms behind their effects. We conducted a systematic review examining the neuroimaging correlates of antidepressant response following psychedelic interventions for MDD. Through MEDLINE, Embase, and APA PsycINFO, 187 records were identified and 42 articles were screened. Six published studies and one conference abstract were included. Five ongoing trials were included from subjective outcomesTrials.gov. Our search covered several psychedelics, though included studies were specific to psilocybin, ayahuasca, and lysergic acid diethylamide. Three psilocybin studies noted amygdala activity and functional connectivity (FC) alterations that correlated with treatment response. Two psilocybin studies reported that FC changes in the medial and ventromedial prefrontal cortices correlated with treatment response. Two trials from a single study reported global decreases in brain network modularity which correlated with antidepressant response. One ayahuasca study reported increased activity in the limbic regions following treatment. Preliminary evidence suggests that the default mode and limbic networks may be a target for future research on the neural mechanisms of psychedelics. More data is required to corroborate these initial findings as the evidence summarized in this review is based on four datasets.

Attenuated alpha-gamma coupling in emotional dual pathways with right-Amygdala predicting ineffective antidepressant response

Aims

The diversity of treatment outcomes for major depressive disorder (MDD) remains uncertain in neuropathology. The current study aimed at exploring electrophysiological biomarkers associated with treatment response.

Methods

The present study recruited 130 subjects including 100 MDD patients and 30 healthy controls. All subjects participated in a sad expression recognition task while their magnetoencephalography data were recorded. Patients who had a reduction of at least 50% in disorder severity at endpoint (>2 weeks) were considered as responders. Within‐frequency power and phase‐amplitude coupling were measured for the brain regions involved in the emotional visual information processing pathways.

Results

The significant alpha–gamma decoupling from the right thalamus to the right amygdala in unconscious processing and from right orbital frontal cortices to the right amygdala in conscious processing was found in non‐responders relative to responders and healthy controls. These kinds of dysregulation could also predict the potential treatment response.

Conclusion

The attenuated alpha–gamma coupling in dual pathways indicated increased sensitivity to the negative emotional information and reduced moderated effect of the amygdala, which might cause insensitivity to antidepressant treatment and could be regarded as potential neural mechanisms for treatment response prediction.

Effective Connectivity of Right Amygdala Subregions Predicts Symptom Improvement Following 12-Week Pharmacological Therapy in Major Depressive Disorder

The low rates of treatment response still exist in the pharmacological therapy of major depressive disorder (MDD). Exploring an optimal neurological predictor of symptom improvement caused by pharmacotherapy is urgently needed for improving response to treatment. The amygdala is closely related to the pathological mechanism of MDD and is expected to be a predictor of the treatment. However, previous studies ignored the heterogeneousness and lateralization of amygdala. Therefore, this study mainly aimed to explore whether the right amygdala subregion function at baseline can predict symptom improvement after 12-week pharmacotherapy in MDD patients. We performed granger causality analysis (GCA) to identify abnormal effective connectivity (EC) of right amygdala subregions in MDD and compared the EC strength before and after 12-week pharmacological therapy. The results show that the abnormal EC mainly concentrated on the frontolimbic circuitry and default mode network (DMN). With relief of the clinical symptom, these abnormal ECs also change toward normalization. In addition, the EC strength of right amygdala subregions at baseline showed significant predictive ability for symptom improvement using a regularized least-squares regression predict model. These findings indicated that the EC of right amygdala subregions may be functionally related in symptom improvement of MDD. It may aid us to understand the neurological mechanism of pharmacotherapy and can be used as a promising predictor for symptom improvement in MDD.

Pharmacological evidence of a cholinergic contribution to elevated impulsivity and risky decision-making caused by adding win-paired cues to a rat gambling task

BACKGROUND

Pairing rewards with sensory stimulation, in the form of auditory and visual cues, increases risky decision-making in both rats and humans. Understanding the neurobiological basis of this effect could help explain why electronic gambling machines are so addictive, and inform treatment development for compulsive gambling and gaming. Numerous studies implicate the dopamine system in mediating the motivational influence of reward-paired cues; recent data suggest the cholinergic system also plays a critical role. Previous work also indicates that cholinergic drugs alter decision-making under uncertainty.

AIMS

We investigated whether the addition of reward-concurrent cues to the rat gambling task (crGT) altered the effects of peripherally administered cholinergic compounds.

METHODS

Muscarinic and nicotinic agonists and antagonists were administered to 16 male, Long-Evans rats trained on the crGT. Measures of optimal/risky decision-making and motor impulsivity were the main dependent variables of interest.

RESULTS

The muscarinic receptor antagonist scopolamine improved decision-making overall, decreasing selection of one of the risky options while increasing choice of the more advantageous options. The muscarinic agonist oxotremorine increased choice latency but did not significantly affect option preference. Neither the nicotinic antagonist mecamylamine nor the agonist nicotine affected choice patterns, but mecamylamine decreased premature responding, an index of motor impulsivity.

CONCLUSIONS

These results contrast sharply from those obtained previously using the uncued rGT, and suggest that the deleterious effects of win-paired cues on decision-making and impulse control may result from elevated cholinergic tone.

Parental Education, Household Income, Race, and Children's Working Memory: Complexity of the Effects

Background. Considerable research has linked social determinants of health (SDoHs) such as race, parental education, and household income to school performance, and these effects may be in part due to working memory. However, a growing literature shows that these effects may be complex: while the effects of parental education may be diminished for Blacks than Whites, household income may explain such effects. Purpose. Considering race as sociological rather than a biological construct (race as a proxy of racism) and built on Minorities' Diminished Returns (MDRs), this study explored complexities of the effects of SDoHs on children's working memory. Methods. We borrowed data from the Adolescent Brain Cognitive Development (ABCD) study. The total sample was 10,418, 9- and 10-year-old children. The independent variables were race, parental education, and household income. The primary outcome was working memory measured by the NIH Toolbox Card Sorting Test. Age, sex, ethnicity, and parental marital status were the covariates. To analyze the data, we used mixed-effect regression models. Results. High parental education and household income were associated with higher and Black race was associated with lower working memory. The association between high parental education but not household income was less pronounced for Black than White children. This differential effect of parental education on working memory was explained by household income. Conclusions. For American children, parental education generates unequal working memory, depending on race. This means parental education loses some of its expected effects for Black families. It also suggests that while White children with highly educated parents have the highest working memory, Black children report lower working memory, regardless of their parental education. This inequality is mainly because of differential income in highly educated White and Black families. This finding has significant public policy and economic implications and suggests we need to do far more than equalizing education to eliminate racial inequalities in children's cognitive outcomes. While there is a need for multilevel policies that reduce the effect of racism and social stratification for middle-class Black families, equalizing income may have more returns than equalizing education.

Socioeconomic Status Inequalities Partially Mediate Racial and Ethnic Differences in Children's Amygdala Volume

BACKGROUND

While race/ethnicity and socioeconomic status (SES) impact brain structures such as the amygdala, less is known on whether or not family SES partially explains why amygdala volume is smaller for racial and ethnic minority groups.

PURPOSE

This study tested the mediating effects of family SES on racial and ethnic differences in right and left amygdala volume.

METHODS

We borrowed the structural Magnetic Resonance Imaging (sMRI) data of the Children Brain Cognitive Development (ABCD) study, a brain imaging investigation of childhood brain development in the US. The total sample was 8977, 9-10-year-old children. The independent variables were race and ethnicity. The primary outcomes were right and left amygdala volume. Age, sex, household size, and marital status were the covariates. Multiple SES indicators such as family income, subjective family SES, parental employment, parental education, and neighborhood income were the mediators. To analyze the data, we used regression models without and with our mediators. Sobel test was used to test if these mediational paths are statistically significant.

RESULTS

Black and Latino children had smaller amygdala sizes than non-Latino White children. The effects of race and ethnicity on amygdala volume were partially mediated by SES indicators, suggesting that one of the many reasons Black and Latino children have smaller volumes of right and left amygdala is their lower SES.

CONCLUSIONS

For American children, lower family and neighborhood SES indicators partially, but not fully, explain smaller amygdala sizes of Black and Latino children compared to non- Latino White children.

Subjective Socioeconomic Status and Children's Amygdala Volume: Minorities' Diminish Returns

Considerable research has suggested that low socioeconomic status (SES) negatively influences brain structure, including but not limited to decreased amygdala volume. Considering race and ethnicity as sociological rather than biological constructs, this study was built on minorities' diminished returns (MDRs) to test if the effects of family SES on the total amygdala volume is weaker for black and Latino children than white and non-Latino children. We borrowed data from the Adolescent Brain Cognitive Development (ABCD) study, a national multi-center brain imaging investigation of childhood brain development in the US. The total sample was 9380 9-10-year-old children. The independent variables were subjective family SES and parental education. The primary outcome was total amygdala volume. High subjective SES and parental education were independently associated with larger total amygdala size. The association between high subjective SES and larger total amygdala volume was less pronounced for black and Latino children than white and non-Latino children. For American children, family SES has unequal effects on amygdala size and function, a pattern that is consistent with MDRs. This result suggests that SES loses some of its expected effects for racial and ethnic minority families.

The antidepressant efficacy of the muscarinic antagonist scopolamine: Past findings and future directions

Scopolamine is a nonselective muscarinic antagonist that has shown relatively rapid antidepressant effects, although to date the results are from limited clinical studies. Scopolamine reportedly has downstream signaling effects thought to be linked to neuroplasticity within glutamatergic synapses and consequent antidepressant action. In psychiatry, clinically validated pathways are unusual and thus merit further research in an effort develop more effect medicines for patients with mood disorders. Thus, we are faced with a unique opportunity to build on the clinical observation associated with scopolamine through reverse translation to identify of targets that retain the clinical efficacy while reducing the side effect profile. This chapter reviews the clinical antidepressant findings with scopolamine, including discussion of differential response across patient subgroups, as well as a review of biomarkers that predict clinical outcome. The preclinical data associated with scopolamine also are reviewed and convey a vision for narrowing in on the therapeutic muscarinic receptor subtype(s) that support the antidepressant effects to guide the development of next generation antimuscarinic drug targets for depression.

Involvement of muscarinic receptor mechanisms in antidepressant drug action

Conventional antidepressants typically require weeks of daily dosing to achieve full antidepressant response in antidepressant responders. A newly evolving group of compounds can engender more rapid response times in depressed patients. These drugs include the newly approved antidepressant (S)-ketamine (esketamine, Spravato). A seminal study by Furey and Drevets in 2006 showed antidepressant response in patients after only a few doses with the antimuscarinic drug scopolamine. Several clinical reports have generally confirmed scopolamine as a rapid-acting antidepressant. The data with scopolamine are consistent with the adrenergic/cholinergic hypothesis of mania/depression derived from clinical reports originating in the 1970s from Janowsky and colleagues. Additional support for a role for muscarinic receptors in mood disorders comes from the greater efficacy of conventional antidepressants that have relatively high levels of muscarinic receptor blocking actions (e.g., the tricyclic antidepressant amitriptyline vs the selective serotonin reuptake inhibitor fluoxetine). There appears to be appreciable overlap in the mechanisms of action of scopolamine and other rapid-acting antidepressants (ketamine) or putative rapid-acting agents (mGlu2/3 receptor antagonists) although gaps exist in the experimental literature. Current hypotheses regarding the mechanisms underlying the rapid antidepressant response to scopolamine posit an M₁ receptor subtype-initiated cascade of biological events that involve the amplification of AMPA receptors. Consequent impact on brain-derived neurotrophic factor and mTor signaling pathways result in the induction of dendritic spines that enable augmented functional connectivity in brain areas regulating mood. Two major goals for research in this area focus on finding ways in which scopolamine might best be utilized for depressed patients and the discovery of alternative compounds that improve upon the efficacy and safety of scopolamine.

Neighborhood Poverty and Amygdala Response to Negative Face

Introduction

Considerable research has established a link between socioeconomic status (SES) and brain function. While studies have shown a link between poverty status and amygdala response to negative stimuli, a paucity of knowledge exists on whether neighborhood poverty is also independently associated with amygdala hyperactive response to negative stimuli.

Purpose

Using functional brain imaging data, this study tested the association between neighborhood SES and the amygdala's response to negative stimuli. Considering race as a sociological rather than a biological construct, we also explored racial heterogeneity in this association between non-Hispanic Black and non-Hispanic White youth.

Methods

We borrowed the functional Magnetic Resonance Imaging (fMRI) data of the Adolescent Brain Cognitive Development (ABCD) study. The sample was 2,490 nine to ten year old non-Hispanic Black and non-Hispanic White adolescents. The independent variable was neighborhood income which was treated as a continuous measure. The primary outcomes were the right and left amygdala response to negative face during an N-Back task. Age, sex, race, marital status, and family SES were the covariates. To analyze the data, we used linear regression models.

Results

Low neighborhood income was independently associated with a higher level of amygdala response to negative face. Similar results were seen for the right and left amygdala. These effects were significant net of race, age, sex, marital status, and family SES. An association between low neighborhood SES and higher left but not right amygdala response to negative face could be observed for non-Hispanic Black youth. No association between neighborhood SES and left or right amygdala response to negative face could be observed for non-Hispanic White youth.

Conclusions

For American youth, particularly non-Hispanic Black youth, living in a poor neighborhood predicts the left amygdala reaction to negative face. This result suggested that Black youth who live in poor neighborhoods are at a high risk of poor emotion regulation. This finding has implications for policy making to reduce inequalities in undesired behavioral and emotional outcomes. Policy solutions to health inequalities should address inequalities in neighborhood SES.

A systematic review of the impact of social cognitive deficits on psychosocial functioning in major depressive disorder and opportunities for therapeutic intervention

Social cognition is the ability to identify, perceive and interpret socially relevant information from the external world. It is an important adaptive trait, but is frequently affected in major depressive disorder by a mood-congruent interpretive bias. The present review examined the existing body of literature to determine (i) the impact social cognitive deficits in depression have on psychosocial functioning; and (ii) the utility of psychotropic, psychological and procedural interventions employed to target these deficits. A total of 107 studies met inclusion criteria for review. Social cognitive performance was found to adversely impact depressed patients' psychosocial functioning across the key domains of general cognitive functioning and quality of life. Secondly, many current therapies were found to have a normalising effect on the social cognitive abilities of subjects with major depressive disorder, both at a neural and functional level. In particular, certain anti-depressant medications corrected facial affect recognition deficits, while several psychotherapeutic approaches improved impairments in theory of mind and negative interpretive bias.

Neuroimaging biomarkers as predictors of treatment outcome in Major Depressive Disorder

BACKGROUND

Current practice for selecting pharmacological and non-pharmacological antidepressant treatments has yielded low response and remission rates in Major Depressive Disorder (MDD). Neuroimaging biomarkers of brain structure and function may be useful in guiding treatment selection by predicting response vs. non-response outcomes.

METHODS

In this review, we summarize data from studies examining predictors of treatment response using structural and functional neuroimaging modalities, as they pertain to pharmacotherapy, psychotherapy, and stimulation treatment strategies. A literature search was conducted in OVID Medline, EMBASE, and PsycINFO databases with coverage from January 1990 to January 2017.

RESULTS

Several imaging biomarkers of therapeutic response in MDD emerged: frontolimbic regions, including the prefrontal cortex, anterior cingulate cortex, hippocampus, amygdala, and insula were regions of interest. Since these sub-regions are implicated in the etiology of MDD, their association with response outcomes may be the result of treatments having a normalizing effect on structural or activation abnormalities.

LIMITATIONS

The direction of findings is inconsistent in studies examining these biomarkers, and variation across 'biotypes' within MDD may account for this. Limitations in sample size and differences in methodology likely also contribute.

CONCLUSIONS

The identification of accurate, reliable neuroimaging biomarkers of treatment response holds promise toward improving treatment outcomes and reducing burden of illness for patients with MDD. However, before these biomarkers can be translated into clinical practice, they will need to be replicated and validated in large, independent samples, and integrated with data from other biological systems.

Ethanol Extract of Oldenlandia diffusa Herba Attenuates Scopolamine-Induced Cognitive Impairments in Mice via Activation of BDNF, P-CREB and Inhibition of Acetylcholinesterase

Though Oldenlandia diffusa Herba (ODH) has been known to exhibit anti-cancer and anti-inflammatory effects, its anti-amnestic effect has never been reported so far. The aim of this present study was to elucidate the anti-amnestic effect of ODH. ODH pretreatment significantly reduced escape latency of scopolamine treated Institute of Cancer Research (ICR) mice compared to untreated control groups in a Morris water maze test. Similarly, the passive avoidance test showed that ODH treatment recovered the scopolamine induced amnesia in the ICR mouse model. Concentration of Ach in brains of ODH treated mice was increased compared to that of scopolamine treated mice. In addition, activity of acetylcholinesterase (AChE) was notably decreased by ODH. The protein expression of brain-derived neurotrophic factor (BDNF) and phospho-cAMP response element-binding protein (p-CREB) (Ser133) was increased in ODH pretreated group compared to control group. Consistently, immunohistochemistry (IHC) revealed the elevated expression of brain-derived neurotrophic factor (BDNF) and p-CREB in brains of ODH treated mice compared to the control group. Overall, these findings suggest that ODH has anti-amnestic potential via activation of BDNF and p-CREB and inhibition of AChE in mice with scopolamine induced amnesia.

Incapacity to control emotion in major depression may arise from disrupted white matter integrity and OFC-amygdala inhibition

BACKGROUND

Disturbances in emotion regulation are the hallmarks of major depressive disorder (MDD). The incapacity to control negative emotion in patients has been associated with abnormal hyperactivation of the limbic system and hypoactivation of the frontal cortex. The amygdala and orbital frontal cortex (OFC) are two critical regions of the emotion regulation neural systems.

METHODS

This study investigated the anatomical basis of abnormal emotion regulation by tracking the fiber tracts connecting the amygdala and OFC. In addition, using dynamic casual modeling on resting-state fMRI data of 20 MDD patients and equivalent controls, we investigated the exact neural mechanism through which abnormal communications between these two nodes were mediated in MDD.

KEY RESULTS

The results revealed disrupted white matter integrity of fiber tracts in MDD, suggesting that functional abnormalities were accompanied by underlying anatomical basis. We also detected a failure of inhibition of the OFC on the activity of the amygdala in MDD, suggesting dysconnectivity was mediated through "top-down" influences from the frontal cortex to the amygdala. Following 8 weeks of antidepressant treatment, the patients showed significant clinical improvement and normalization of the abnormal OFC-amygdala structural and effective connectivity in the left hemisphere.

CONCLUSIONS & INFERENCES

Our findings suggest that pathways connecting these two nodes may be core targets of the antidepressant treatment. In particular, it raised the intriguing question: Does the reversal of structural markers of connectivity reflect a response to antidepressant medication or activity-dependent myelination following a therapeutic restoration of effective connectivity?

Neural and Behavioral Predictors of Treatment Efficacy on Mood Symptoms and Cognition in Mood Disorders: A Systematic Review

Background: The clinical and etiological heterogeneity of mood disorders impede identification of effective treatments for the individual patient. This highlights a need for early neuronal and behavioral biomarkers for treatment efficacy, which can provide a basis for more personalized treatments. The present systematic review aimed to identify the most consistent neuronal and behavioral predictors of treatment efficacy on mood symptoms and cognitive impairment in mood disorders. Methods: We identified and included 60 original peer-reviewed studies investigating neuroimaging and behavioral predictors of treatment efficacy within the domains of emotional and non-emotional cognition, structural neuroimaging, and resting state functional connectivity in patients with unipolar or bipolar disorder. Results: Lower baseline responsivity in limbic regions coupled with heightened medial and dorsal prefrontal responses to emotional stimuli were the most consistent predictors of response to pharmacotherapy for depression. In contrast, heightened limbic and ventral prefrontal reactivity to emotional stimuli seemed to predict efficacy of psychological interventions. Early modulation of fronto-limbic activity and reduction in negative bias were also associated with treatment response. Better performance on non-emotional tests at baseline was relatively consistently associated with efficacy on mood symptoms, whereas the association between neural activity during non-emotional tests and treatment response was less clear. Other baseline factors associated with treatment response were greater white matter integrity, resting state functional connectivity, more prefrontal gray matter volume as well as an early increase following short administered treatment. Finally, emerging evidence indicates that baseline cognitive deficits are associated with greater chances of achieving treatment efficacy on cognition. Conclusions: Patients' profile of emotional and non-emotional cognition and neural activity-and the early treatment-associated changes in neural and cognitive function-may be useful for guiding treatments for depression. While cognitive deficits at baseline seem to improve chances of treatment efficacy on cognition, more studies of this association are urgently needed.

The antidepressant-like effects of biperiden may involve BDNF/TrkB signaling-mediated BICC1 expression in the hippocampus and prefrontal cortex of mice

Preclinical and clinical studies suggest that neuronal muscarinic acetylcholine receptor (M-AchR) antagonists have antidepressant-like properties. Despite the recent interest in bicaudal C homolog 1 gene (BICC1) as a target for the treatment of depression, the upstream signaling molecules that regulate BICC1 are unknown, and very few studies have addressed the involvement of BICC1 in the antidepressant-like effects of the selective M1-AchR inhibitor, biperiden. Growing evidence indicates that activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase receptor B (TrkB) signaling may be involved in antidepressant-like activities. In this study, we investigated the role of BDNF/TrkB signaling in the regulation of BICC1 expression in the chronic unpredictable stress (CUS) mouse model of depression. Furthermore, we also examined whether BDNF/TrkB signaling contributes to the antidepressant-like effects of biperiden via down-regulation of BICC1 in the hippocampus and prefrontal cortex of mice. Our current data show that CUS exposure induced significant depression-like behaviors, down-regulation of BDNF/TrkB signaling and up-regulation of BICC1 in the hippocampus and prefrontal cortex of mice. However, biperiden significantly alleviated the CUS-induced abnormalities. Moreover, we found that the effects of biperiden were antagonized by pretreatment with the TrkB antagonist K252a. Our results indicate that BDNF/TrkB signaling may be the major upstream mediator of BICC1 involvement in the antidepressant-like effects of biperiden.