Tail Suspension Stress Research Articles

Basolateral amygdala parvalbumin and cholecystokinin-expressing GABAergic neurons modulate depressive and anxiety-like behaviors.

The basolateral amygdala (BLA) is increasingly recognized as a key regulator of depression and anxiety-like behaviors. However, the specific contribution of individual BLA neurons to these behaviors remains poorly understood. Building on our previous study, which demonstrated increased activity in glutamatergic BLA neurons in response to aversive stimuli and that enhancing inhibition in the BLA can alleviate depressive-like behaviors, we investigated the role of individual BLA GABAergic neurons (BLAGABA) in depressive and anxiety-like phenotypes. To address this question, we employed a comprehensive array of techniques, including c-fos staining, fiber photometry recording, optogenetic and chemogenetic manipulation, and behavior analysis. Our findings indicate that BLAGABA neurons show decreased activity during tail suspension and after chronic social defeat stress (CSDS) during social interaction. High-frequency activation of BLAGABA neurons attenuated depressive and anxiety-like behaviors, while low-frequency activation had no effect. Fiber photometry recordings revealed increased activity in BLA GABAergic neurons expressing somatostatin (SST), parvalbumin (PV), and cholecystokinin (CCK) during footshock aversive stimuli. Moreover, we found increased activity in PV and SST neurons and decreased activity in CCK-GABA neurons in the BLA during tail suspension stress. However, after CSDS, BLAPV neurons displayed decreased activity, while SST and CCK neurons showed no changes during the social interaction test. Behavioral analysis demonstrated that chemogenetic inhibition of PV and CCK-GABA neurons induced depressive and anxiety-like behaviors. whereas SST neuron inhibition had no effect. Conversely, chemogenetic activation of BLAPV neurons alleviated depressive behaviors, and activation of BLACCK-GABA neurons alleviated at least partly both depressive and anxiety-like behaviors. This study provides compelling evidence that BLAPV neurons play a critical role in regulating depressive-like behaviors, and that BLACCK-GABA neurons are involved, at least in part, in modulating both depressive-like and anxiety-like behaviors in mice.

Convergence of Clinically Relevant Manipulations on Dopamine-Regulated Prefrontal Activity Underlying Stress Coping Responses

BackgroundDepression is pleiotropic and influenced by diverse genetic, environmental, and pharmacological factors. Identifying patterns of circuit activity on which many of these factors converge would be important, because studying these patterns could reveal underlying pathophysiological processes and/or novel therapies. Depression is commonly assumed to involve changes within prefrontal circuits, and dopamine D2 receptor (D2R) agonists are increasingly used as adjunctive antidepressants. Nevertheless, how D2Rs influence disease-relevant patterns of prefrontal circuit activity remains unknown. MethodsWe used brain slice calcium imaging to measure how patterns of prefrontal activity are modulated by D2Rs, antidepressants, and manipulations that increase depression susceptibility. To validate the idea that prefrontal D2Rs might contribute to antidepressant responses, we used optogenetic and genetic manipulations to test how dopamine, D2Rs, and D2R+ neurons contribute to stress-coping behavior. ResultsPatterns of positively correlated activity in prefrontal microcircuits are specifically enhanced by D2R stimulation as well as by two mechanistically distinct antidepressants, ketamine and fluoxetine. Conversely, this D2R-driven effect was disrupted in two etiologically distinct depression models, a genetic susceptibility model and mice that are susceptible to chronic social defeat. Phasic stimulation of dopaminergic afferents to the prefrontal cortex and closed-loop stimulation of D2R+ neurons increased effortful responses to tail suspension stress, whereas prefrontal D2R deletion reduced the duration of individual struggling episodes. ConclusionsCorrelated prefrontal microcircuit activity represents a point of convergence for multiple depression-related manipulations. Prefrontal D2Rs enhance this activity. Through this mechanism, prefrontal D2Rs may promote network states associated with antidepressant actions and effortful responses to stress.

Biomarker monitoring and long-acting insulin treatment in a stress model to facilitate personalized diabetic control

Diabetes is a chronic disease involving elevated blood glucose levels. Controlled insulin delivery is an ideal method to achieve glycemic control. However, glucose levels vary as a result of changes in the body's physiological conditions resulting from different daily events, such as meals, exercise and stress. It is essential to develop and to monitor appropriate biomarkers for these natural physiological perturbations in order to achieve a holistic understanding of metabolic changes in diabetic patients to facilitate optimal glucose management and make possible personalized medicine for this very debilitating disease. The novel aspects of the current research include the combination of the tail suspension stress animal model and microdialysis for stress biomarker monitoring. A tail suspension test was optimized and used as a stress inducer for different groups of model rats (normal, untreated diabetic and insulin-treated diabetic rats). The levels of multiple metabolic analytes in the subcutaneous tissue were monitored continuously using subcutaneous microdialysis analysis. Different analytes, including pH, glucose and lactate were monitored and analyzed. Another important and original aspect of the reported work is that revelation that the pH, lactate and glucose levels increased under the stress conditions and the changes tended to be more pronounced in diabetic rats (both untreated and long-acting insulin-treated) compared to normal rats. Long-acting insulin treatment was shown to shorten the duration of the pH and glucose changes in response to stress when compared to the untreated diabetic rats. An additional novel aspect of the research is that subcutaneous pH was shown to be a sensitive stress biomarker for diabetic rats as pH changes rapidly after stress initiation. This research provides insight into the importance of accurate glycemic control and diabetes management for individual patients through highlighting stress management and appropriate biomarker monitoring, especially the value of combining pH and lactate monitoring with typical glucose monitoring. This research will pave the way for individualized medicine for diabetic patients through helping to obtain a holistic understanding of the various important biomarkers, rather than solely depending on glucose monitoring to determine appropriate insulin dosing.

Dopaminergic Signaling in the Nucleus Accumbens Modulates Stress-Coping Strategies during Inescapable Stress.

Maladaptation to stress is a critical risk factor in stress-related disorders, such as major depression and post-traumatic stress disorder (PTSD). Dopamine signaling in the nucleus accumbens (NAc) has been shown to modulate behavior by reinforcing learning and evading aversive stimuli, which are important for the survival of animals under environmental challenges such as stress. However, the mechanisms through which dopaminergic transmission responds to stressful events and subsequently regulates its downstream neuronal activity during stress remain unknown. To investigate how dopamine signaling modulates stress-coping behavior, we measured the subsecond fluctuation of extracellular dopamine concentration and pH using fast scanning cyclic voltammetry (FSCV) in the NAc, a postsynaptic target of midbrain dopaminergic neurons, in male mice engaged in a tail suspension test (TST). The results revealed a transient decrease in dopamine concentration and an increase in pH levels when the animals changed behaviors, from being immobile to struggling. Interestingly, optogenetic inhibition of dopamine release in NAc, potentiated the struggling behavior in animals under the TST. We then addressed the causal relationship of such a dopaminergic transmission with behavioral alterations by knocking out both the dopamine receptors, i.e., D1 and D2, in the NAc using viral vector-mediated genome editing. Behavioral analyses revealed that male D1 knock-out mice showed significantly more struggling bouts and longer struggling durations during the TST, while male D2 knock-out mice did not. Our results therefore indicate that D1 dopaminergic signaling in the NAc plays a pivotal role in the modulation of stress-coping behaviors in animals under tail suspension stress.SIGNIFICANCE STATEMENT The tail suspension test (TST) has been widely used as a despair-based behavioral assessment to screen the antidepressant so long. Despite its prevalence in the animal studies, the neural substrate underlying the changes of behavior during the test remains unclear. This study provides an evidence for a role of dopaminergic transmission in the modulation of stress-coping behavior during the TST, a despair test widely used to screen the antidepressants in rodents. Taking into consideration the fact that the dopamine metabolism is upregulated by almost all antidepressants, a part of which acts directly on the dopaminergic transmission, current results would uncover the molecular mechanism through which the dopaminergic signaling mediates antidepressant effect with facilitation of the recovery from the despair-like behavior in the TST.

Dentate gyrus-CA3 glutamate release/NMDA transmission mediates behavioral despair and antidepressant-like responses to leptin

Compelling evidence supports the important role of the glutamatergic system in the pathophysiology of major depression and also as a target for rapid-acting antidepressants. However, the functional role of glutamate release/transmission in behavioral processes related to depression and antidepressant efficacy remains to be elucidated. In this study, glutamate release and behavioral responses to tail suspension, a procedure commonly used for inducing behavioral despair, were simultaneously monitored in real time. The onset of tail suspension stress evoked a rapid increase in glutamate release in hippocampal field CA3, which declined gradually after its offset. Blockade of NMDA receptors by intra-CA3 infusion of MK-801, a non-competitive NMDA receptor antagonist, reversed behavioral despair. The CA3 was innervated by granule neurons expressing the leptin receptor (LepRb) in the dentate gyrus (DG), representing a subpopulation of granule neurons that were devoid of stress-induced activation. Leptin treatment dampened tail suspension-evoked glutamate release in CA3. On the other hand, intra-CA3 infusion of NMDA blocked the antidepressant-like effect of leptin in reversing behavioral despair in both the tail suspension and forced swim tests, which involved activation of Akt signaling in DG. Together, these results suggest that the DG-CA3 glutamatergic pathway is critical for mediating behavioral despair and antidepressant-like responses to leptin.

Preventive effect of theanine intake on stress-induced impairments of hippocamapal long-term potentiation and recognition memory

Theanine, γ-glutamylethylamide, is one of the major amino acid components in green tea. On the basis of the preventive effect of theanine intake after birth on mild stress-induced attenuation of hippocamapal CA1 long-term potentiation (LTP), the present study evaluated the effect of theanine intake after weaning on stress-induced impairments of LTP and recognition memory. Young rats were fed water containing 0.3% theanine for 3 weeks after weaning and subjected to water immersion stress for 30min, which was more severe than tail suspension stress for 30s used previously. Serum corticosterone levels were lower in theanine-administered rats than in the control rats even after exposure to stress. CA1 LTP induced by a 100-Hz tetanus for 1s was inhibited in the presence of 2-amino-5-phosphonovalerate (APV), an N-methyl-d-aspartate (NMDA) receptor antagonist, in hippocampal slices from the control rats and was attenuated by water immersion stress. In contrast, CA1 LTP was not significantly inhibited in the presence of APV in hippocampal slices from theanine-administered rats and was not attenuated by the stress. Furthermore, object recognition memory was impaired in the control rats, but not in theanine-administered rats. The present study indicates the preventive effect of theanine intake after weaning on stress-induced impairments of hippocampal LTP and recognition memory. It is likely that the modification of corticosterone secretion after theanine intake is involved in the preventive effect.

Zinc signaling in the hippocampus and its relation to pathogenesis of depression

Histochemically reactive zinc (Zn2+) is co-released with glutamate from zincergic neurons, a subclass of glutamatergic neurons. Zn2+ serves as a signal factor in both the extracellular and intracellular compartments. Glucocorticoid–glutamatergic interactions have been proposed as a potential model to explain stress-mediated impairment of hippocampal function, i.e., cognition. However, it is unknown whether glucocorticoid–zincergic interactions are involved in this impairment. In the present study, involvement of synaptic Zn2+ in stress-induced attenuation of CA1 LTP was examined in hippocampal slices from young rats after exposure to tail suspension stress for 30s, which significantly increased serum corticosterone. Stress-induced attenuation of CA1 LTP was ameliorated by administration of clioquinol, a membrane permeable zinc chelator, to rats prior to exposure to stress, implying that the reduction of synaptic Zn2+ by clioquinol participates in this amelioration. To pursue the involvement of corticosterone-mediated Zn2+ signal in the attenuated CA1 LTP by stress, dynamics of synaptic Zn2+ was checked in hippocampal slices exposed to corticosterone. Corticosterone increased extracellular Zn2+ levels measured with ZnAF-2 dose-dependently, as well as the intracellular Ca2+ levels measured with calcium orange AM, suggesting that corticosterone excites zincergic neurons in the hippocampus and increases Zn2+ release from the neuron terminals. Intracellular Zn2+ levels measured with ZnAF-2DA were also increased dose-dependently, but not in the coexistence of CaEDTA, a membrane-impermeable zinc chelator, suggesting that intracellular Zn2+ levels is increased by the influx of extracellular Zn2+. Furthermore, corticosterone-induced attenuation of CA1 LTP was abolished in the coexistence of CaEDTA. The present study suggests that corticosterone-mediated increase in postsynaptic Zn2+ signal in the cytosolic compartment is involved in the attenuation of CA1 LTP after exposure to acute stress. We propose that corticosterone-mediated increase in postsynaptic Zn2+ signal, which is induced by acute stress, changes hippocampal function and then is possibly a risk factor under chronic stress circumstances to induce depressive symptoms.

Involvement of glucocorticoid-mediated Zn2+ signaling in attenuation of hippocampal CA1 LTP by acute stress

Glucocorticoid–glutamatergic interactions have been proposed as a potential model to explain stress-mediated impairment of cognition. However, it is unknown whether glucocorticoid–zincergic interactions are involved in this impairment. Histochemically reactive zinc (Zn2+) is co-released with glutamate from zincergic neurons. In the present study, involvement of synaptic Zn2+ in stress-induced attenuation of CA1 LTP was examined in hippocampal slices from young rats after exposure to tail suspension stress for 30s, which significantly increased serum corticosterone. Stress-induced attenuation of CA1 LTP was ameliorated by administration of clioquinol, a membrane permeable zinc chelator, to rats prior to exposure to stress, implying that the reduction of synaptic Zn2+ by clioquinol participates in this amelioration. To pursue the involvement of corticosterone-mediated Zn2+ signal in the attenuated CA1 LTP by stress, dynamics of synaptic Zn2+ was checked in hippocampal slices exposed to corticosterone. Corticosterone increased extracellular Zn2+ levels measured with ZnAF-2 dose-dependently, as well as the intracellular Ca2+ levels measured with calcium orange AM, suggesting that corticosterone excites zincergic neurons in the hippocampus and increases Zn2+ release from the neuron terminals. Intracellular Zn2+ levels measured with ZnAF-2DA were also increased dose-dependently, but not in the coexistence of CaEDTA, a membrane-impermeable zinc chelator, suggesting that intracellular Zn2+ levels is increased by the influx of extracellular Zn2+. Furthermore, corticosterone-induced attenuation of CA1 LTP was abolished in the coexistence of CaEDTA. The present study suggests that corticosterone-mediated increase in postsynaptic Zn2+ signal in the cytosolic compartment is involved in the attenuation of CA1 LTP after exposure to acute stress.

Impairment effects of tail suspension stress on spatial memory and its reversal learning in mice

Present work investigated the effects of tail suspension stress (TSS) on spatial memory acquisition, consolidation, and its reversal learning in mice. Eighty-one adult male KM mice were divided into four groups (each group including a TSS subgroup and its control subgroup): absolute spatial memory acquisition and consolidation groups (group AA and CA); relative spatial memory acquisition and consolidation groups (group AR and CR). TSS (20 min) was performed immediately before (acquisition) or after (consolidation) a daily training. Results showed that there was no significant difference between control animals and TSS animals in each group in early spatial memory training days (5-8 d of training). Along with training, the performance of control animals improved significantly, but the performance of TSS animals improved slightly (group AA, CA and AR) or even did not change (group CR) (P<0.01). Reversal learning was also impaired in TSS animals (P<0.01). The results indicated that TSS could impair spatial memory acquisition, consolidation and reversal learning (especially the relative spatial memory consolidation and its reversal learning) in mice.

Acute stress enhances anxiolytic-like drug responses of mice tested in a black and white test box

Drug-induced facilitation of exploration of a two-compartment black and white test box was studied in mice applying different stressors before test. Tail suspension suppressed exploration of both compartments and enhanced diazepam- or eltoprazine-induced increase of exploration of the white compartment. (−)-Penbutolol reversed the effects of eltoprazine suggesting involvement of 5-HT 1A/1B receptors. Buspirone had weak effects both under standard conditions, and after tail suspension. Ritanserin suppressed exploratory behavior, and this effect was potentiated by tail suspension. In conclusion, application of acute tail suspension stress immediately before test in the black and white box enhanced the sensitivity to drugs. In contrast to this, forced swimming suppressed general behavioral activity, but in this case diazepam facilitated the behavior in both compartments. Foot shocks immediately before test reduced activity in the black compartment and did not affect the behavior in the white compartment. Thus different acute stressors modified behavior in the black and white box differently. Chronic stress (crowded housing) produced an anxiolytic-like response.

Central nervous system regulation of adrenocorticotropin secretion: role of somatostatins.

Somatostatin-28 (SS-28) and desAA1,2,4,5,12,13[D-Trp8]somatostatin (ODT8-SS), but not somatostatin-14, given intracerebroventricularly, but not when given iv, inhibit stress-induced pituitary ACTH and adrenomedullary epinephrine secretion in rats. The elevation of ACTH after tail-suspension stress is totally prevented by iv administration of antisera raised against corticotropin-releasing factor (CRF). SS-28 and ODT8-SS do not inhibit CRF-induced ACTH secretion in vivo or in vitro. These results are consistent with the hypothesis that SS-28 and ODT8-SS prevent stress-induced ACTH secretion by inhibition of CRF release.