Expression of BDNF and trkB in the hippocampus of a rat genetic model of vulnerability (Roman low-avoidance) and resistance (Roman high-avoidance) to stress-induced depression

Unleashing lactoferrin's antidepressant potential through the PI3K/Akt/mTOR pathway in chronic restraint stress rats

Depression is a widespread neuropsychiatric illness whose etiology is yet mysterious. Lactoferrin (LF), an iron-binding glycoprotein, is reported to promote neuroprotection through its role in the modulation of oxidative stress and inflammation. The objective of the present research was to evaluate the efficacy of LF against chronic restraint stress (CRS)-induced depressive behavior in rats. Depression was evidenced by a reduced grooming time in the splash test and an increased immobility time in the tail suspension test (TST) and forced swimming test (FST). This effect was also accompanied by reduced GSH and serotonin levels and elevated lipid peroxidation and corticosterone levels in the hippocampus. Additionally, an exaggerated hippocampal inflammatory response was also shown by a rise in NF-κB (p65) and TNF-α levels and a reduced IL-10 level. Moreover, CRS substantially reduced the BDNF content as well as the protein levels of PI3K, Akt, and mTOR while boosting the GSK3β content. Interestingly, LF therapy significantly improved CRS-induced behavioral and biochemical aberrations, an effect which was suppressed upon pretreatment with LY294002 (PI3K inhibitor). This suggests that the antidepressant potential of LF may be mediated through the modulation of the PI3K/Akt/mTOR signaling pathway. Furthermore, LF succeeded in restoring 5-HT and corticosterone levels, diminishing oxidative stress and ameliorating the inflammatory cascades. Therefore, and for the first time, LF might serve as a promising antidepressant drug through targeting the PI3K/Akt/mTOR pathway.

Effects of Tail Pinch on BDNF and trkB Expression in the Hippocampus of Roman Low- (RLA) and High-Avoidance (RHA) Rats

In this article, we describe the effects of tail pinch (TP), a mild acute stressor, on the levels of brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor B (trkB) proteins in the hippocampus (HC) of the outbred Roman High- (RHA) and Low-Avoidance (RLA) rats, one of the most validated genetic models for the study of fear/anxiety- and stress-related behaviors. Using Western blot (WB) and immunohistochemistry assays, we show for the first time that TP induces distinct changes in the levels of BDNF and trkB proteins in the dorsal (dHC) and ventral (vHC) HC of RHA and RLA rats. The WB assays showed that TP increases BDNF and trkB levels in the dHC of both lines but induces opposite changes in the vHC, decreasing BDNF levels in RHA rats and trkB levels in RLA rats. These results suggest that TP may enhance plastic events in the dHC and hinder them in the vHC. Immunohistochemical assays, carried out in parallel to assess the location of changes revealed by the WB, showed that, in the dHC, TP increases BDNF-like immunoreactivity (LI) in the CA2 sector of the Ammon's horn of both Roman lines and in the CA3 sector of the Ammon's horn of RLA rats while, in the dentate gyrus (DG), TP increases trkB-LI in RHA rats. In contrast, in the vHC, TP elicits only a few changes, represented by decreases of BDNF- and trkB-LI in the CA1 sector of the Ammon's horn of RHA rats. These results support the view that the genotypic/phenotypic features of the experimental subjects influence the effects of an acute stressor, even as mild as TP, on the basal BDNF/trkB signaling, leading to different changes in the dorsal and ventral subdivisions of the HC.

Acute Stress Induces Different Changes on the Expression of BDNF and trkB in the Mesocorticolimbic System of Two Lines of Rats Differing in Their Response to Stressors

The present work was undertaken to investigate the effects of acute forced swimming (FS) on the levels of brain-derived neurotrophic factor (BDNF) and tyrosine kinase receptor B (trkB) proteins in: the ventral tegmental area (VTA); the nucleus accumbens (Acb) shell and core compartments; and the anterior cingulate (ACg), prelimbic (PL) and infralimbic (IL) territories of the prefrontal cortex of genetic models of vulnerability (RLA, Roman low-avoidance rats) and resistance (RHA, Roman high-avoidance rats) to stress-induced depression. We report for the first time that FS induced very rapid and distinct changes in the levels of BDNF and trkB proteins in different areas of the mesocorticolimbic system of RHA and RLA rats. Thus, (1) in the VTA and Acb core, FS elicited a significant increase of both BDNF- and trkB-LI in RHA but not RLA rats, whereas in the Acb shell no significant changes in BDNF- and trkB-LI across the line and treatment were observed; (2) in RLA rats, the basal levels of BDNF-LI in the IL/PL cortex and of trkB-LI in the ACg cortex were markedly lower than those of RHA rats; moreover, BDNF- and trkB-LI in the IL/PL and ACg cortex were increased by FS in RLA rats but decreased in their RHA counterparts. These results provide compelling evidence that the genetic background influences the effects of stress on BDNF/trkB signaling and support the view that the same stressor may impact differently on the expression of BDNF in discrete brain areas.

Neuroplastic changes in c-Fos, ΔFosB, BDNF, trkB, and Arc expression in the hippocampus of male Roman rats: differential effects of sexual activity

Sexual activity causes differential changes in the expression of markers of neural activation (c‐Fos and ΔFosB) and neural plasticity (Arc and BDNF/trkB), as determined either by Western Blot (BDNF, trkB, Arc, and ΔFosB) or immunohistochemistry (BDNF, trkB, Arc, and c‐Fos), in the hippocampus of male Roman high (RHA) and low avoidance (RLA) rats, two psychogenetically selected rat lines that display marked differences in sexual behavior (RHA rats exhibit higher sexual motivation and better copulatory performance than RLA rats). Both methods showed (with some differences) that sexual activity modifies the expression levels of these markers in the hippocampus of Roman rats depending on: (i) the level of sexual experience, that is, changes were usually more evident in sexually naïve than in experienced rats; (ii) the hippocampal partition, that is, BDNF and Arc increased in the dorsal but tended to decrease in the ventral hippocampus; (iii) the marker considered, that is, in sexually experienced animals BDNF, c‐Fos, and Arc levels were similar to those of controls, while ΔFosB levels increased; and (iv) the rat line, that is, changes were usually larger in RHA than RLA rats. These findings resemble those of early studies in RHA and RLA rats showing that sexual activity influences the expression of these markers in the nucleus accumbens, medial prefrontal cortex, and ventral tegmental area, and show for the first time that also in the hippocampus sexual activity induces neural activation and plasticity, events that occur mainly during the first phase of the acquisition of sexual experience and depend on the genotypic/phenotypic characteristics of the animals.

Anti-Inflammatory Effect of Beta-Caryophyllene Mediated by the Involvement of TRPV1, BDNF and trkB in the Rat Cerebral Cortex after Hypoperfusion/Reperfusion

We have previously shown that bilateral common carotid artery occlusion followed by reperfusion (BCCAO/R) is a model to study early hypoperfusion/reperfusion-induced changes in biomarkers of the tissue physiological response to oxidative stress and inflammation. Thus in this study, we investigate with immunochemical assays if a single dose of beta-caryophyllene (BCP), administered before the BCCAO/R, can modulate the TRPV1, BDNF, and trkB receptor in the brain cortex; the glial markers GFAP and Iba1 were also examined. Frontal and temporal-occipital cortical regions were analyzed in two groups of male rats, sham-operated and submitted to BCCAO/R. Six hours before surgery, one group was gavage fed a dose of BCP (40 mg/per rat in 300 μL of sunflower oil), the other was pre-treated with the vehicle alone. Western blot analysis showed that, in the frontal cortex of vehicle-treated rats, the BCCAO/R caused a TRPV1 decrease, an increment of trkB and GFAP, no change in BDNF and Iba1. The BCP treatment caused a decrease of BDNF and an increase of trkB levels in both sham and BCCAO/R conditions while inducing opposite changes in the case of TRPV1, whose levels became higher in BCCAO/R and lower in sham conditions. Present results highlight the role of BCP in modulating early events of the cerebral inflammation triggered by the BCCAO/R through the regulation of TRPV1 and the BDNF-trkB system.

Jiedu Tongluo Granules Ameliorates Post-stroke Depression Rat Model via Regulating NMDAR/BDNF Signaling Pathway

Post-stroke depression (PSD) is one of the most common stroke complications, which seriously affects stroke’s therapeutic effect and brings great pain for patients. The pathological mechanism of PSD has not been revealed. Jiedu Tongluo granules (JDTLG) is an effective traditional Chinese medicine for PSD treatment which is widely used in clinical treatment. JDTLG has a significant therapeutic effect against PSD, but the mechanism is still unclear. The PSD rat model was established by carotid artery embolization combined with chronic sleep deprivation followed by treating with JDTLG. Neurobehavioral and neurofunctional experiments were engaged in studying the neural function of rats. Histomorphology, proteomics, and western blotting researches were performed to investigate the potential molecular mechanisms related to JDTLG therapy. Oral treatment of JDTLG could significantly improve the symptoms of neurological deficit and depression symptoms of PSD rats. Proteomic analysis identified several processes that may involve the regulation of JDTLG on the PSD animal model, including energy metabolism, nervous system, and N-methyl-D-aspartate receptor (NMDAR)/brain-derived neurotrophic factor (BDNF) signal pathway. Our results showed that JDTLG could reduce glutamate (Glu) level and increase gamma-aminobutyric acid (GABA) level via regulating the NMDAR/BDNF pathway, which may play a vital role in the occurrence and development of PSD.

Hippocampal miRNA-144 Modulates Depressive-Like Behaviors in Rats by Targeting PTP1B

BACKGROUND

Depression is the common mental disorder in the world. However, the pathophysiology mechanism underlying depression remains elusive. It has been reported that aberrant expression of miR-144 is closely related to depression. This study was to investigate whether and how miR-144 involves in depressive-like behaviors in a chronic unpredictable mild stress (CUMS) animal model.

METHODS

A rat model of CUMS was established, and qRT-PCR was performed to detect the expression of miR-144 in the hippocampus of a depressed rat. The lentiviral vector carried miR-144 (LV-miR-144) was injected into the hippocampus of the CUMS rat to investigate the effects of miR-144 on the behaviors and PTP1B/TrkB/BDNF signal transduction in the hippocampus of the rat. The interaction between miR-144 and PTP1B was investigated by biological analyses and dual-luciferase reporter assay.

RESULTS

The results showed that CUMS rats had typical depressive behaviors, and the expression of miR-144 in the hippocampus of CUMS rats was significantly lower than that of the control group. In addition, PTP1B protein expression was significantly up-regulated, while the expression of pTrkB and BDNF protein was significantly down-regulated in the hippocampus of CUMS rats. Moreover, PTP1B was a direct target of miR-144, and miR-144 could activate the downstream TrkB/BDNF signaling pathway by inhibiting the expression of PTP1B in primary hippocampus neurons.

CONCLUSION

MiR-144 played an anti-depressive role in hippocampus dysfunction by inhibiting PTP1B and activating the TrkB/BDNF signaling pathway in the hippocampus of CUMS rats.

Combination of syringaresinol-di-O-β-D-glucoside and chlorogenic acid shows behavioral pharmacological anxiolytic activity and activation of hippocampal BDNF-TrkB signaling

Mental stress, such as anxiety and conflict, causes physiological changes such as dysregulation of autonomic nervous activity, depression, and gastric ulcers. It also induces glucocorticoid production and changes in hippocampal brain-derived neurotrophic factor (BDNF) levels. We previously reported that Acanthopanax senticosus HARMS (ASH) exhibited anxiolytic activity. Thus, we attempted to identify the anxiolytic constituents of ASH and investigated its influence on hippocampal BDNF protein expression in male Sprague Dawley rats administered chlorogenic acid (CHA), ( +)-syringaresinol-di-O-β-D-glucoside (SYG), or a mixture of both (Mix) for 1 week using the open field test (OFT) and improved elevated beam walking (IEBW) test. As with ASH and the benzodiazepine anxiolytic cloxazolam (CLO), Mix treatment significantly increased locomotor activity in the OFT. CHA and Mix increased the time spent in the open arm in the IEBW test. SYG and Mix treatment inhibited the significant increase in normalized low-frequency power, indicative of sympathetic nervous activity, and significant decrease in normalized high-frequency power, indicative of parasympathetic nervous activity, as observed in the IEBW test. SYG and Mix treatment significantly increased hippocampal BDNF protein expression. The combination of CHA and SYG possibly induces anxiolytic behavior and modulates autonomic regulation, activates hippocampal BDNF signaling as with ASH.

BDNF Val66Met polymorphism and resilience in major depressive disorder: the impact of cognitive psychotherapy

Objective:

Clinical and biological correlates of resilience in major depressive disorder are scarce. We aimed to investigate the effect of the Val⁶⁶Met polymorphism in the BDNF gene on resilience scores in major depressive disorder patients and evaluate the polymorphism’s moderation effect on resilience scores in response to cognitive therapy.

Method:

A total of 106 major depressive disorder patients were enrolled in this clinical randomized study. The Resilience Scale and the Hamilton Rating Scale for Depression were applied at baseline, post-treatment, and at six months of follow-up. Blood samples were obtained at baseline for molecular analysis.

Results:

The baseline resilience scores were higher in patients with the Met allele (114.6±17.6) than in those with the Val/Val genotype (104.04±21.05; p = 0.037). Cognitive therapy treatment increased resilience scores (p ≤ 0.001) and decreased depressive symptoms (p ≤ 0.001). In the mixed-effect model, the Val/Val genotype represented a decrease in resilience scores (t₂₁₈ = -1.98; p = 0.048), and the Val⁶⁶Met polymorphism interacted with sex to predict an increase in total resilience scores during cognitive treatment (t₂₁₈ = 2.69; p = 0.008).

Conclusion:

Our results indicate that cognitive therapy intervention could improve resilience in follow-up, considering that gender and genetic susceptibility are predicted by the Val⁶⁶Met polymorphism.

A Tellurium-Based Small Immunomodulatory Molecule Ameliorates Depression-Like Behavior in Two Distinct Rat Models

Major depressive disorder (MDD) is a leading cause of morbidity, and the fourth leading cause of disease burden worldwide. While MDD is a treatable condition for many individuals, others suffer from treatment-resistant depression (TRD). Here, we suggest the immunomodulatory compound AS101 as novel therapeutic alternative. We previously showed in animal models that AS101 reduces anxiety-like behavior and elevates levels of the brain-derived neurotrophic factor (BDNF), a protein that has a key role in the pathophysiology of depression. To explore the potential antidepressant properties of AS101, we used the extensively characterized chronic mild stress (CMS) model, and the depressive rat line (DRL Finally, in Exp. 3 to attain insight into the mechanism we knocked down BDNF in the hippocampus, and demonstrated that the beneficial effect of AS101 was abrogated. Together with the previously established safety profile of AS101 in humans, these results may represent the first step towards the development of a novel treatment option for MDD and TRD.

Therapeutic Effects of Spirulina platensis Against Adolescent Stress-Induced Oxidative Stress, Brain-Derived Neurotrophic Factor Alterations and Morphological Remodeling in the Amygdala of Adult Female Rats

Objective

The amygdala structural and functional abnormalities have been implicated in numerous neuropsychiatric and neurodevelopmental disorders. Given the important role of the amygdala in stress responses and the susceptibility of the females to adolescent stress, the present study investigated the beneficial effects of Spirulina platensis microalgae (SP) as a neuroprotective supplement against adolescent stress-induced oxidative stress, brain-derived neurotrophic factor (BDNF) alterations, molecular and morphological remodeling in the basolateral amygdala (BLA) of adult female rats.

Methods

During the adolescent period (PNDs 30–40) rats were subjected to restraint stress (2 h/day for 10 days). Then, the animals were subjected to 15 days treatment (PNDs 41–55) with SP (200 mg/kg/day) followed by biochemical (BDNF and stress oxidative markers), molecular (BDNF and its receptor tropomyosin receptor kinase B [TrkB] mRNA expression), and morphological (dendritic length and spines) assessments in the BLA.

Results

The study revealed that adolescent stress decreased BDNF levels and reduced apical dendritic length and branch points of pyramidal neurons in the BLA. In addition, chronic stress significantly increased oxidative stress parameters and decreased BDNF and TrkB mRNA expression in the BLA. Treatment with SP alleviated both biochemical, molecular, and neuroanatomical deficits that induced by adolescent stress.

Conclusion

Our findings provide important evidence that SP as a non-pharmacological intervention during adolescent period can protect against chronic stress-induced neuroanatomical biochemical, and molecular deficits in adulthood, and thus, reduce stress-related disorders.

The antidepressant effects of l-arginine on chronic mild stress-induced depression by augmenting the expression of brain-derived neurotrophic factor in rats

In the present study, the antidepressant effects of l-arginine in a rat model of chronic mild stress-induced depression were investigated. Animals were divided into group I (sham), group II (control, depression), group III (10 mg/kg l-arginine), group IV (20 mg/kg l-arginine), and group V (10 mg/kg venlafaxine, positive control). The doses were orally administered for 30 consecutive days. Sucrose preference analysis as well as forced swim and open field tests were performed. Serum cortisol, nitric oxide (NO), and monoamine levels in brain tissue were then measured. Brain-derived neurotrophic factor (BDNF) expression was also examined. Supplementation with l-arginine significantly increased the sucrose preference ratio, locomotor activity, and monoamines and decreased serum cortisol and NO levels. The mRNA and protein expression of BDNF in the brain tissue was significantly reduced (>50 %) in control rats. However, supplementation with l-arginine significantly increased BDNF mRNA expression (>50 %) in both groups. Similarly, increased BDNF protein expression after l-arginine treatment was confirmed using Western blot and immunohistochemical analyses. In conclusion, l-arginine supplementation may be effective against chronic stress-induced depression.

Formononetin recovered injured nerve functions by enhancing synaptic plasticity in ischemic stroke rats

BACKGROUND AND OBJECTIVES

Formononetin has protective effect against ischemic stroke. It's unclear whether it can restore the nerve functions after stroke.

METHODS

SD rats were subjected with middle cerebral artery occlusion (MCAO), and divided into sham, model and formononetin (30 mg/kg) groups. Neurobehavioral tests (modified Neurological Severity Score [mNSS] and rotarod) were performed before and at 1, 3, 7 and 14 days after MCAO. Then, the rats were sacrificed and the brain sections were processed for neuronal differentiation and synaptic plasticity.

RESULTS

Compared with the sham group, the scores of mNSS were significantly increased, and the residence time on the rotating drum was significantly decreased in the MCAO rats. Compared with the model group, the scores of mNSS were significantly decreased, and the residence time on the rotating drum was increased in the formononetin (30 mg/kg) group. Formononetin significantly increased the number of neuronal dendritic spines and the expression of β III-tubulin, GAP-43, NGF, BDNF, p-Trk A, p-Trk B, p-AKT and p-ERK 1/2.

CONCLUSIONS

Formononetin recovered injured nerve functions after ischemic stroke. PI3K/AKT/ERK pathway might involve in the beneficial effect of formononetin on the neuronal differentiation and synaptic plasticity.

Si-Ni-San Prevents Reserpine-Induced Depression by Inhibiting Inflammation and Regulating CYP450 Enzymatic Activity

Depression is becoming a major public health concern worldwide. Si-Ni-San (SNS) is a famous formula in Traditional Chinese Medicine (TCM) with potent antidepressant effects. However, the antidepressant mechanism of SNS has not been clearly elucidated. This study was performed to verify whether the antidepressant effects of SNS were related to its anti-inflammatory effects, the levels of brain-derived neurotrophic factor (BDNF) and Cytochrome P450 (CYP450) enzymatic activity. In our study, behavioral tests such as the forced swim test, sucrose preference test and open-field test were evaluated to ensure the establishment of depressive rats. The levels of IL-1β, IL-6, and TNF-α in the serum, liver, and hippocampus of rats were measured by enzyme-linked immunosorbent assays (ELISA). Furthermore, the key proteins NF-κB, BDNF, and TrkB were analyzed by Western blot (WB) analysis in the hippocampus. In addition, CYP450 enzymatic activity analysis was performed using LC-MS/MS in conjunction with drug and statistics (DAS 3.0) after oral administration of six probe drugs. Our results showed that SNS attenuated reserpine-induced increases in IL-1β, IL-6, and TNF-α expression in the serum, liver, and hippocampus. The levels of NF-κB, BDNF, and TrkB in the hippocampus of depressive rats were also altered. According to the pharmacokinetic parameters, SNS had moderate inhibitory effects in the reserpine-induced depression model on CYP1A2, CYP2D1, CYP2E1, and CYP3A2, but no significant metabolic changes to CYP2C6 and CYP2D2. These findings suggested that SNS has a protective effect on reserpine-induced depressive rats, which may be related to the improvement of the inflammatory factors, the level of BDNF and the activity of CYP450 enzymes.

Differential expression of synaptic markers regulated during neurodevelopment in a rat model of schizophrenia-like behavior

Schizophrenia is considered a neurodevelopmental disorder. Recent reports relate synaptic alterations with disease etiology. The inbred Roman High- (RHA-I) and Low- (RLA-I) Avoidance rat strains are a congenital neurobehavioral model, with the RHA-I displaying schizophrenia-related behaviors and serotonin 2A (5-HT2A) and metabotropic glutamate 2 (mGlu2) receptor alterations in the prefrontal cortex (PFC). We performed a comprehensive characterization of the RHA-I/RLA-I rats by real-time qPCR and Western blotting for 5-HT1A, 5-HT2A, mGlu2, dopamine 1 and dopamine 2 receptors (DRD1 and DRD2), AMPA receptor subunits Gria1, Gria2 and NMDA receptor subunits Grin1, Grin2a and Grin2b, as well as pre- and post-synaptic components in PFC and hippocampus (HIP). Besides corroborating decreased mGlu2 (Grm2) expression, we found increased mRNA levels for Snap25, Synaptophysin (Syp), Homer1 and Neuregulin-1 (Nrg1) in the PFC of the RHA-I and decreased expression of Vamp1, and Snapin in the HIP. We also showed alterations in Vamp1, Grin2b, Syp, Snap25 and Nrg1 at protein levels. mRNA levels of Brain Derived Neurotrophic Factor (BDNF) were increased in the PFC of the RHA-I rats, with no differences in the HIP, while BDNF protein levels were decreased in PFC and increased in HIP. To investigate the temporal dynamics of these synaptic markers during neurodevelopment, we made use of the open source BrainCloud™ dataset, and found that SYP, GRIN2B, NRG1, HOMER1, DRD1 and BDNF expression is upregulated in PFC during childhood and adolescence, suggesting a more immature neurobiological endophenotype in the RHA-I strain.

Own or dam's genotype? Classical colony breeding may bias spontaneous and stress-challenged activity in DAT-mutant rats

There is considerable interest in understanding what makes an individual vulnerable or resilient to the deleterious effects of stressful events. From candidate genes, dopamine (DA) and dopamine transporter (DAT) have been linked to anxiety, depression, and post-traumatic stress disorder. We investigated role of DAT using the new DAT heterozygous (DAT-HET) and homozygous mutant (DAT-KO) rat models of hyperdopaminergia. We studied the impact of two breeding conditions in spontaneous locomotor behavior of female rats. The classical colony, through mating DAT-HET males × DAT-HET females (breeding HET-HET), was used. A second WT colony was derived and maintained (breeding WT-WT). Additionally, a subgroup of rats was bred through mating DAT-KO males × WT females (atypical HET, breeding KO-WT). We studied the effects of genotype and its interaction with maternal care (depending by breeding condition). HET-HET breeding led to reduced activity in HET females compared to WT rats (from WT-WT breeding). However, HET females from KO-WT breeding did not differ so much from WT rats (WT-WT breeding). The maternal-care impact was then confirmed: HET mothers (breeding HET-HET) showed reduced liking/grooming of pups and increased digging away from nest, compared to WT mothers (breeding WT-WT). In their female offspring (HET, breeding HET-HET vs. WT, breeding WT-WT), isolation plus wet bedding induced higher and more persistent impact on activity of HET rats, even when the stressor was removed. Our results highlight the importance of epigenetic factors (e.g., maternal care) in responses to stress expressed by offspring at adulthood, quite independently of genotype. DAT hypofunction could determinate vulnerability to stressful agents via altered maternal care.

Resveratrol Regulates BDNF, trkB, PSA-NCAM, and Arc Expression in the Rat Cerebral Cortex after Bilateral Common Carotid Artery Occlusion and Reperfusion

The polyphenol resveratrol (RVT) may drive protective mechanisms of cerebral homeostasis during the hypoperfusion/reperfusion triggered by the transient bilateral common carotid artery occlusion followed by reperfusion (BCCAO/R). This immunochemical study investigates if a single dose of RVT modulates the plasticity-related markers brain-derived neurotrophic factor (BDNF), the tyrosine kinase trkB receptor, Polysialylated-Neural Cell Adhesion Molecule (PSA-NCAM), and Activity-regulated cytoskeleton-associated (Arc) protein in the brain cortex after BCCAO/R. Frontal and temporal-occipital cortical regions were examined in male Wistar rats randomly subdivided in two groups, sham-operated and submitted to BCCAO/R. Six hours prior to surgery, half the rats were gavage fed a dose of RVT (180 mg·kg⁻¹ in 300 µL of sunflower oil as the vehicle), while the second half was given the vehicle alone. In the frontal cortex of BCCAO/R vehicle-treated rats, BDNF and PSA-NCAM decreased, while trkB increased. RVT pre-treatment elicited an increment of all examined markers in both sham- and BCCAO/R rats. No variations occurred in the temporal-occipital cortex. The results highlight a role for RVT in modulating neuronal plasticity through the BDNF-trkB system and upregulation of PSA-NCAM and Arc, which may provide both trophic and structural local support in the dynamic changes occurring during the BCCAO/R, and further suggest that dietary supplements such as RVT are effective in preserving the tissue potential to engage plasticity-related events and control the functional response to the hypoperfusion/reperfusion challenge.

Rats bred for high anxiety exhibit distinct fear-related coping behavior, hippocampal physiology, and synaptic plasticity-related gene expression

The hippocampus is essential for learning and memory but also regulates emotional behavior. We previously identified the hippocampus as a major brain region that differs in rats bred for emotionality differences. Rats bred for low novelty response (LRs) exhibit high levels of anxiety- and depression-like behavior compared to high novelty responder (HR) rats. Manipulating the hippocampus of high-anxiety LR rats improves their behavior, although no work to date has examined possible HR/LR differences in hippocampal synaptic physiology. Thus, the current study examined hippocampal slice electrophysiology, dendritic spine density, and transcriptome profiling in HR/LR hippocampus, and compared performance on three hippocampus-dependent tasks: The Morris water maze, contextual fear conditioning, and active avoidance. Our physiology experiments revealed increased long-term potentiation (LTP) at CA3-CA1 synapses in HR versus LR hippocampus, and Golgi analysis found an increased number of dendritic spines in basal layer of CA1 pyramidal cells in HR versus LR rats. Transcriptome data revealed glutamate neurotransmission as the top functional pathway differing in the HR/LR hippocampus. Our behavioral experiments showed that HR/LR rats exhibit similar learning and memory capability in the Morris water maze, although the groups differed in fear-related tasks. LR rats displayed greater freezing behavior in the fear-conditioning task, and HR/LR rats adopted distinct behavioral strategies in the active avoidance task. In the active avoidance task, HRs avoided footshock stress by pressing a lever when presented with a warning cue; LR rats, on the other hand, waited until footshocks began before pressing the lever to stop them. Taken together, these findings concur with prior observations of HR rats generally exhibiting active stress coping behavior while LRs exhibit reactive coping. Overall, our current findings coupled with previous work suggest that HR/LR differences in stress reactivity and stress coping may derive, at least in part, from differences in the developing and adult hippocampus.

Effect of Acute Stress on the Expression of BDNF, trkB, and PSA-NCAM in the Hippocampus of the Roman Rats: A Genetic Model of Vulnerability/Resistance to Stress-Induced Depression

The Roman High-Avoidance (RHA) and the Roman Low-Avoidance (RLA) rats, represent two psychogenetically-selected lines that are, respectively, resistant and prone to displaying depression-like behavior, induced by stressors. In the view of the key role played by the neurotrophic factors and neuronal plasticity, in the pathophysiology of depression, we aimed at assessing the effects of acute stress, i.e., forced swimming (FS), on the expression of brain-derived neurotrophic factor (BDNF), its trkB receptor, and the Polysialilated-Neural Cell Adhesion Molecule (PSA-NCAM), in the dorsal (dHC) and ventral (vHC) hippocampus of the RHA and the RLA rats, by means of western blot and immunohistochemical assays. A 15 min session of FS elicited different changes in the expression of BDNF in the dHC and the vHC. In RLA rats, an increment in the CA2 and CA3 subfields of the dHC, and a decrease in the CA1 and CA3 subfields and the dentate gyrus (DG) of the vHC, was observed. On the other hand, in the RHA rats, no significant changes in the BDNF levels was seen in the dHC and there was a decrease in the CA1, CA3, and DG of the vHC. Line-related changes were also observed in the expression of trkB and PSA-NCAM. The results are consistent with the hypothesis that the differences in the BDNF/trkB signaling and neuroplastic mechanisms are involved in the susceptibility of RLA rats and resistance of RHA rats to stress-induced depression.

Changes in brain metabolites related to stress resilience: Metabolomic analysis of the hippocampus in a rat model of depression

The ability to cope successfully with stress is known as 'resilience', and those with resilience are not prone to developing depression. One preclinical animal model for depression is the chronic mild stress (CMS) model. There are CMS-resilient (do not manifest anhedonia) and CMS-susceptible (manifest anhedonia) rats. This study aimed to investigate the differences in the profiles of hippocampal metabolites between susceptible and resilient rats, and to identify a biomarker that can distinguish the two. We divided stress-loaded rats into susceptible and resilient types based on their sucrose preference values. We then conducted brain-derived neurotrophic factor (BDNF) quantification and metabolomic analysis in the hippocampus. Compared to the controls, no significant differences were observed in the hippocampal BDNF levels of susceptible and resilient rats. However, the control rats were clearly distinguishable from the susceptible rats in terms of their brain metabolite profiles; the control rats were difficult to distinguish from the resilient rats. CMS model rats showed an increase in the levels of N-acetylaspartate and glutamate, and a decrease in the levels of aspartate and γ-aminobutyric acid in the hippocampus. Of the 12 metabolites measured in the present study, N-acetylaspartate was the only one that could differentiate the three types (control, susceptible, and resilient) of rats. Thus, brain metabolomic analyses can not only distinguish CMS model rats from control rats, but also indicate stress susceptibility. The variation in the levels of N-acetylaspartate in the hippocampus of control, resilient, and susceptible rats demonstrated that it could be a biomarker for stress susceptibility.

Functional Neurochemistry of the Ventral and Dorsal Hippocampus: Stress, Depression, Dementia and Remote Hippocampal Damage

The hippocampus is not a homogeneous brain area, and the complex organization of this structure underlies its relevance and functional pleiotropism. The new data related to the involvement of the ventral hippocampus in the cognitive function, behavior, stress response and its association with brain pathology, in particular, depression, are analyzed with a focus on neuroplasticity, specializations of the intrinsic neuronal network, corticosteroid signaling through mineralocorticoid and glucocorticoid receptors and neuroinflammation in the hippocampus. The data on the septo-temporal hippicampal gradient are analyzed with particular emphasis on the ventral hippocampus, a region where most important alteration underlying depressive disorders occur. According to the recent data, the existing simple paradigm "learning (dorsal hippocampus) versus emotions (ventral hippocampus)" should be substantially revised and specified. A new hypothesis is suggested on the principal involvement of stress response mechanisms (including interaction of released glucocorticoids with hippocampal receptors and subsequent inflammatory events) in the remote hippocampal damage underlying delayed dementia and depression induced by focal brain damage (e.g. post-stroke and post-traumatic). The translational validity of this hypothesis comprising new approaches in preventing post-stroke and post-trauma depression and dementia can be confirmed in experimental and clinical studies.

Cannabinoid CB2 Receptor Gene and Environmental Interaction in the Development of Psychiatric Disorders

CB2 cannabinoid receptor (CB2R) gene is associated with depression. We investigated the gene-environment interaction between CB2R function and diverse stressors. First, anxiety-like behavior during chronic-mild-stress (CMS) was evaluated in C57BL/6JJmsSlc mice following treatment with CB2R agonist JWH015 or inverse-agonist AM630. Second, locomotor activity and anxiety-like behavior were measured following exposure to an immune poly I:C stressor. Gene expressions of HPA axis related molecules, Fkbp5, Nr3c1 and Crf and pro-inflammatory cytokine Il-1b, as well as Bdnf as a key neurotrophin that supports neuron health, function, and synaptic plasticity, were determined in hippocampus of Cnr2 knockout mice, as indicators of stressful environment. CMS-induced anxiety-like behavior was enhanced by AM630 and reduced by JWH015 and fluvoxamine. Poly I:C reduced locomotor activity and increased anxiety-like behavior, and these effects were pronounced in the heterozygote than in the wild type mice. Fkbp5 and Nr3c1 expression were lower in the Cnr2 heterozygotes than in the wild type mice with Poly I:C treatment. These findings indicate that interaction between CB2R gene and stressors increases the risk of depression-like behaviors that may be linked with neuro-immune crosstalk. Further studies in human subjects are necessary to determine the role of CB2R and environmental interaction in the development of depression.

Expression of BDNF and trkB in the hippocampus of a rat genetic model of vulnerability (Roman low-avoidance) and resistance (Roman high-avoidance) to stress-induced depression

INTRODUCTION

The selective breeding of Roman High- (RHA) and Low-Avoidance (RLA) rats for, respectively, rapid versus poor acquisition of the active avoidance response has generated two distinct phenotypes differing in many behavioral traits, including coping strategies to aversive conditions. Thus, RLA rats are considered as a genetic model of vulnerability to stress-induced depression whereas RHA rats are a model of resilience to that trait. Besides the monoamine hypothesis of depression, there is evidence that alterations in neuronal plasticity in the hippocampus and other brain areas are critically involved in the pathophysiology of mood disorders.

MATERIALS AND METHODS

Western blot (WB) and immunohistochemistry were used to investigate the basal immunochemical occurrence of brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine-kinase receptor trkB in the dorsal and ventral hippocampus of adult RHA and RLA rats.

RESULTS

WB analysis indicated that the optical density of BDNF- and trkB-positive bands in the dorsal hippocampus is, respectively, 48% and 25% lower in RLA versus RHA rats. Densitometric analysis of BDNF- and trkB-like immunoreactivity (LI) in brain sections showed that BDNF-LI is 24% to 34% lower in the different sectors of the Ammon's horn of RLA versus RHA rats, whereas line-related differences are observed in the dentate gyrus (DG) only in the ventral hippocampus. As for trkB-LI, significant differences are observed only in the dorsal hippocampus, where density is 23% lower in the DG of RLA versus RHA rats, while no differences across lines occur in the Ammon's horn.

CONCLUSION

These findings support the hypothesis that a reduced BDNF/trkB signaling in the hippocampus of RLA versus RHA rats may contribute to their more pronounced vulnerability to stress-induced depression.