Serotonin receptors in hippocampus

Flibanserin conquers murine depressive pseudodementia by amending HPA axis, maladaptive inflammation and AKT/GSK/STAT/BDNF trajectory: Center-staging of the serotonergic/adrenergic circuitry

Depressive pseudodementia (DPD) is a debilitating cognitive dysfunction that accompanies major and/or frequent depressive attacks. DPD has gained significant research attention owing to its negative effects on the patients' quality of life and productivity. This study tested the procognitive potential of Flibanserin (FBN), the serotonin (5HT) receptor modulator, against propranolol (PRP), as β/5HT1A receptors blocker. Serving this purpose, female Wistar Albino rats were subjected to chronic unpredictable stress (CUS) and subsequently treated with FBN only (3 mg/kg/day, p.o), PRP only (10 mg/kg/day, p.o), or PRP followed by FBN, using the same doses. FBN ameliorated the behavioral/cognitive alterations and calmed the hypothalamic-pituitary-adrenal (HPA) axis storm by reducing the levels of stress-related hormones, viz, corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), corticosterone (CORT) parallel to epinephrine (EPI) hyperstimulation. The maladaptive inflammatory response, comprising of interleukin (IL)-1β/6, and tumor necrosis factor (TNF)-α, was consequently blunted. This was contemporaneous to the partial restoration of the protein kinase-B (AKT)/glycogen synthase kinase (GSK)3β/signal transducer and activator of transcription (STAT)-3 survival trajectory and the reinstatement of the levels of brain derived neurotrophic factor (BDNF). Microscopically, FBN repaired the hippocampal architecture and lessened CD68/GFAP immunoreactivity. Pre-administration of PRP partially abolished FBN effect along the estimated parameters, except for 5HT2A receptor expression and epinephrine level, to prove 5HT1A receptor as a fulcrum initiator of the investigated pathway, while its sole administration worsened the underlying condition. Ultimately, these findings highlight the immense procognitive potential of FBN, offering a new paradigm for halting DPD advancement via synchronizing adrenergic/serotonergic circuitry.

Mechanistic study on vasodilatory and antihypertensive effects of hesperetin: ex vivo and in vivo approaches

Hesperetin is one of the prominent flavonoids found in citrus fruit. Several research studies have reported that hesperetin can promote vasodilation in vascular tissue by increasing the level of nitric oxide and cyclic nucleotides. However, these may not be the only pathway for hesperetin to exert its vasodilatory effect. In addition to vasodilation, hesperetin has been found to carry an antihypertensive effect through intraperitoneal injection, although no study has comprehensively investigated the antihypertensive effect of hesperetin through oral administration. Therefore, this study aimed to determine the possible mechanism pathways involved in hesperetin-induced vasodilation and investigated its antihypertensive effects on hypertensive rats' model via oral administration. The ex vivo experimental findings showed that the NO/sGC/cGMP signalling pathway was involved in hesperetin-mediated vasodilation. Moreover, hesperetin activated the AC/cAMP/PKA pathway through PGI2 and activated the β2-adrenergic receptor. Hesperetin can act as a voltage-gated potassium channel (KV) and ATP-sensitive potassium channel (KATP) opener. The intracellular calcium in vascular smooth muscle was reduced by hesperetin through blocking the voltage-operated calcium channels (VOCC) and inositol triphosphate receptor (IP3R). In the in vivo assessment, hesperetin shows a significant decrease in Spontaneously Hypertensive rats' blood pressure following 21 days of oral treatment. The sub-chronic toxicity assessment demonstrated that hesperetin exhibited no deleterious effects on the body weights, clinical biochemistry and haematological profile of Sprague-Dawley rats. This study implies that hesperetin holds promise as a potential medication for hypertension treatment, devoid of undesirable side effects.

Neurobiological and psychological factors to depression

Major Depressive Disorder (MDD) is a common condition with complex psychological and biological background. While its aetiology is still unclear, chronic stress stands amongst major risk factors to MDD pathogenesis. When researching on MDD, it is necessary to be familiar with the neurobiological effects of several prominent contributors to the chronic stress factor experienced across hypothalamic-pituitary-adrenal (HPA) axis, neurotransmission, immune system reflexivity, and genetic alterations. Bi-directional flow of MDD pathogenesis suggests that psychological factors produce biological effects. Here, a summary of how the MDD expresses its mechanisms of action across an overactive HPA axis, the negative impacts of reduced neurotransmitter functions, the inflammatory responses and their gene x environment interactions. This paper builds on these conceptual factors and their input towards the MDD symptomatology with a purpose of synthesising the current findings and create an integrated view of the MDD pathogenesis. Finally, relevant treatment implications will be summarised, along with recommendations to a multimodal clinical practice.

Labeling of the serotonergic neuronal circuits emerging from the raphe nuclei via some retrograde tracers

Serotonin (5-hydroxytryptamine, 5-HT) is a very important neurotransmitter emerging from the raphe nuclei to several brain regions. Serotonergic neuronal connectivity has multiple functions in the brain. In this study, several techniques were used to trace serotonergic neurons in the dorsal raphe (DR) and median raphe (MnR) that project toward the arcuate nucleus of the hypothalamus (Arc), dorsomedial hypothalamic nucleus (DM), lateral hypothalamic area (LH), paraventricular hypothalamic nucleus (PVH), ventromedial hypothalamic nucleus (VMH), fasciola cinereum (FC), and medial habenular nucleus (MHb). Cholera toxin subunit B (CTB), retro-adeno-associated virus (rAAV-CMV-mCherry), glycoprotein-deleted rabies virus (RV-ΔG), and simultaneous microinjection of rAAV2-retro-Cre-tagBFP with AAV-dio-mCherry in C57BL/6 mice were used in this study. In addition, rAAV2-retro-Cre-tagBFP was microinjected into Ai9 mice. Serotonin immunohistochemistry was used for the detection of retrogradely traced serotonergic neurons in the raphe nuclei. The results indicated that rAAV2-retro-Cre-tagBFP microinjection in Ai9 mice was the best method for tracing serotonergic neuron circuits. All of the previously listed nuclei exhibited serotonergic neuronal projections from the DR and MnR, with the exception of the FC, which had very few projections from the DR. The serotonergic neuronal projections were directed toward the Arc by the subpeduncular tegmental (SPTg) nuclei. Moreover, the RV-ΔG tracer revealed monosynaptic non-serotonergic neuronal projections from the DR that were directed toward the Arc. Furthermore, rAAV tracers revealed monosynaptic serotonergic neuronal connections from the raphe nuclei toward Arc. These findings validate the variations in neurotropism among several retrograde tracers. The continued discovery of several novel serotonergic neural circuits is crucial for the future discovery of the functions of these circuits. RESEARCH HIGHLIGHTS: Various kinds of retrograde tracers were microinjected into C57BL/6 and Ai9 mice. The optimum method for characterizing serotonergic neuronal circuits is rAAV2-retro-Cre-tagBFP microinjection in Ai9 mice. The DR, MnR, and SPTg nuclei send monosynaptic serotonergic neuronal projections toward the arcuate nucleus of the hypothalamus. Whole-brain quantification analysis of retrograde-labeled neurons in different brain nuclei following rAAV2-retro-Cre-tagBFP microinjection in the Arc, DM, LH, and VMH is shown. Differential quantitative analysis of median and dorsal raphe serotonergic neurons emerging toward the PVH, DM, LH, Arc, VMH, MHb, and FC is shown.

Prenatal Hypoxia Triggers a Glucocorticoid-Associated Depressive-like Phenotype in Adult Rats, Accompanied by Reduced Anxiety in Response to Stress

Fetal hypoxia and maternal stress frequently culminate in neuropsychiatric afflictions in life. To replicate this condition, we employed a model of prenatal severe hypoxia (PSH) during days 14-16 of rat gestation. Subsequently, both control and PSH rats at 3 months old were subjected to episodes of inescapable stress to induce learned helplessness (LH). The results of the open field test revealed an inclination towards depressive-like behavior in PSH rats. Following LH episodes, control (but not PSH) rats displayed significant anxiety. LH induced an increase in glucocorticoid receptor (GR) levels in extrahypothalamic brain structures, with enhanced nuclear translocation in the hippocampus (HPC) observed both in control and PSH rats. However, only control rats showed an increase in GR nuclear translocation in the amygdala (AMG). The decreased GR levels in the HPC of PSH rats correlated with elevated levels of hypothalamic corticotropin-releasing hormone (CRH) compared with the controls. However, LH resulted in a reduction of the CRH levels in PSH rats, aligning them with those of control rats, without affecting the latter. This study presents evidence that PSH leads to depressive-like behavior in rats, associated with alterations in the glucocorticoid system. Notably, these impairments also contribute to increased resistance to severe stressors.

Sex-specific expression of distinct serotonin receptors mediates stress vulnerability of adult hippocampal neural stem cells in mice

Women are more vulnerable to stress and have a higher likelihood of developing mood disorders. The serotonin (5HT) system has been highly implicated in stress response and mood regulation. However, sex-dependent mechanisms underlying serotonergic regulation of stress vulnerability remain poorly understood. Here, we report that adult hippocampal neural stem cells (NSCs) of the Ascl1 lineage (Ascl1-NSCs) in female mice express functional 5HT1A receptors (5HT1ARs), and selective deletion of 5HT1ARs in Ascl1-NSCs decreases the Ascl1-NSC pool only in females. Mechanistically, 5HT1AR deletion in Ascl1-NSCs of females leads to 5HT-induced depolarization mediated by upregulation of 5HT7Rs. Furthermore, repeated restraint stress (RRS) impairs Ascl1-NSC maintenance through a 5HT1AR-mediated mechanism. By contrast, Ascl1-NSCs in males express 5HT7R receptors (5HT7Rs) that are downregulated by RRS, thus maintaining the Ascl1-NSC pool. These findings suggest that sex-specific expression of distinct 5HTRs and their differential interactions with stress may underlie sex differences in stress vulnerability.

Linking alterations in estrogen receptor expression to memory deficits and depressive behavior in an ovariectomy mouse model

The high risk of neurological disorders in postmenopausal women is an emerging medical issue. Based on the hypothesis of altered estrogen receptors (ERα and β) after the decline of estrogen production, we investigated the changes in ERs expressions across brain regions and depressive/amnesic behaviors. C57BL/6J female mice were ovariectomized (OVX) to establish a menopausal condition. Along with behavior tests (anxiety, depression, and memory), the expression of ERs, microglial activity, and neuronal activity was measured in six brain regions (hippocampus, prefrontal cortex, striatum, raphe nucleus, amygdala, and hypothalamus) from 4 to 12 weeks after OVX. Mice exhibited anxiety- and depressive-like behaviors, as well as memory impairment. These behavioral alterations have been linked to a suppression in the expression of ERβ. The decreased ERβ expression coincided with microglial-derived neuroinflammation, as indicated by notable activations of Ionized calcium-binding adapter molecule 1 and Interleukin-1beta. Additionally, the activity of brain-derived neurotrophic factor (BDNF), particularly in the hippocampus, decreased in a time-dependent manner from 4 to 12 weeks post-OVX. Our study provides evidence shedding light on the susceptibility to memory impairment and depression in women after menopause. This susceptibility is associated with the suppression of ERβ and alteration of ERα in six brain regions.

Transcriptomic analysis of alternative splicing events for different stages of growth and development in Sistan Yaghooti grape clusters

Sistan Yaghooti grape variety, despite characteristics such as early ripening, is vulnerable to cluster rot due to small berries and dense clusters. In this regard, AS may serve as a regulatory mechanism during developmental processes and in response to environmental signals. RNA-Seq analysis was performed to measure gene expression and the extent of AS events in the cluster growth and development stages of Sistan Yaghooti grape. The number of AS events increased during stages, suggesting that it contributes to the grapevine's adaptability to various stresses. In addition, DEG and DAS genes showed little overlap in cluster growth stages. Functional analysis of 19,194 DAS -gene sets showed that VIT_06s0004g06670 gene is involved in the activation of calcium channels (Ca2+) through the activation of 5 PLC biosynthetic pathways. Among the 27,229 DEG -sets, VIT_07s0005g05320 gene showed higher expression. Interestingly, this gene is involved in the synthesis of an EF -hand domain-containing protein capable of binding to Ca2+ by activating 4 biochemical pathways. These genes increase cytosolic Ca2+ concentration, enhancing plant stress tolerance and resistance to cracking. These results show that AS can respond independently to different types of stress. Among the other DAS genes, the GA2ox gene (VvGA2ox) showed an increase in AS events during cluster development. This gene is critical for initiating the degradation process of GA and plays a crucial role in different stages of seed development. Therefore, it is very likely that this gene is one of the main factors responsible for the density and seedlessness of Sistan Yaghooti grape.

Pharmacological Evaluation of Signals of Disproportionality Reporting Related to Adverse Reactions to Antiepileptic Cannabidiol in VigiBase

Cannabidiol is the first cannabis-derived drug approved for the treatment of Lennox-Gastaut syndrome, Dravet syndrome, and Tuberous Sclerosis Complex. In the current study, we performed a descriptive analysis followed by a disproportionality analysis of potential adverse events caused by CBD extracted from the VigiBase® database. Furthermore, the biological plausibility of the association between CBD and the serotonin 5-HT1A receptor as a possible cause of adverse events was analyzed and discussed. Data were extracted from the VigiBase® database using the VigiLyze® signal detection and signal management tool. Adverse events in VigiBase® reports were coded using MedDRA, version 19 of Preferred Terms (PTs). Data were uploaded into SPSS software and analyzed via a disproportionality analysis. Statistically significant disproportionality signals for CBD were found for "weight decreased" (5.19 (95% CI: 4.54-5.70)), "hypophagia" (3.68 (95% CI: 3.22-5.27)), and "insomnia" (1.6 (95% CI: 1.40-1.83)). Positive IC025 values were found for "weight decreased" (2.2), "hypophagia" (1.3), and "insomnia" (0.5), indicating a surplus of reported cases. CBD's interactions with 5-HT1A serotonin receptors may offer a potential biological explanation for the occurrence of insomnia in patients. It is noteworthy that the risk profiles mentioned in the information for prescribing CBD as an antiepileptic agent by regulatory agencies showed disparities specifically related to the adverse event "insomnia".

D1R-5-HT2AR Uncoupling Reduces Depressive Behaviours via HDAC Signalling

Dopamine and serotonin signalling are associated with major depressive disorder, which is a prevalent life-threatening illness worldwide. Numerous FDA-approved dopamine/serotonin signalling-modifying drugs are available but are associated with concurrent side effects and limited efficacy. Thus, identifying and targeting their signalling pathway is crucial for improving depression treatment. Here, we determined that serotonin receptor 2A (5-HT2AR) abundantly forms a protein complex with dopamine receptor 1 (D1R) in high abundance via its carboxy-terminus in the brains of mice subjected to various chronic stress paradigms. Furthermore, the D1R/5-HT2AR interaction elicited CREB/ERK/AKT modulation during synaptic regulation. An interfering peptide (TAT-5-HT2AR-SV) agitated the D1R/5-HT2AR interaction and attenuated depressive symptoms accompanied by CREB/ERK molecule costimulation. Interestingly, HDAC antagonism but not TrkB antagonism reversed the antidepressant effect of competitive peptides. These findings revealed a novel D1R/5-HT2AR heteroreceptor complex mechanism in the pathophysiology of depression, and their uncoupling ameliorates depressive-like behaviours through HDAC-, and not BDNF-, dependent mechanisms.

Molecular Docking Assessment of Cathinones as 5-HT2AR Ligands: Developing of Predictive Structure-Based Bioactive Conformations and Three-Dimensional Structure-Activity Relationships Models for Future Recognition of Abuse Drugs

Commercially available cathinones are drugs of long-term abuse drugs whose pharmacology is fairly well understood. While their psychedelic effects are associated with 5-HT2AR, the enclosed study summarizes efforts to shed light on the pharmacodynamic profiles, not yet known at the receptor level, using molecular docking and three-dimensional quantitative structure-activity relationship (3-D QSAR) studies. The bioactive conformations of cathinones were modeled by AutoDock Vina and were used to build structure-based (SB) 3-D QSAR models using the Open3DQSAR engine. Graphical inspection of the results led to the depiction of a 3-D structure analysis-activity relationship (SAR) scheme that could be used as a guideline for molecular determinants by which any untested cathinone molecule can be predicted as a potential 5-HT2AR binder prior to experimental evaluation. The obtained models, which showed a good agreement with the chemical properties of co-crystallized 5-HT2AR ligands, proved to be valuable for future virtual screening campaigns to recognize unused cathinones and similar compounds, such as 5-HT2AR ligands, minimizing both time and financial resources for the characterization of their psychedelic effects.

Ameliorating the Role of Aripiprazole in Memory Deficits Induced by Intracerebroventricular Streptozotocin-Induced Dementia of Alzheimer's Type

Alzheimer's disease (AD) is a progressive neurodegenerative disorder causing immense suffering for the patients. Dopamine D2 and 5-hydroxytryptamine receptor 1A (5-HT1A) receptors' activation has been reported to play a crucial role in managing neurological outcomes in the brain and other health disorders. This study aimed to investigate the role of aripiprazole, a dopamine D2 and 5-HT1A selective receptors' activator, in the restoration of memory deficit induced by streptozotocin in mice. The cognitive functions of animals were determined using the Morris water maze. Brain sections were stained with hematoxylin and eosin and Congo red to examine the structural deviations. Brain oxidative stress (thiobarbituric acid reactive substance and glutathione), acetylcholinesterase activity, IL-6, and IL-10 were measured to assess biochemical alterations. Activation of D2 and 5-HT1A with aripiprazole attenuated STZ-induced cognitive deficit, increased brain GSH levels, reduced TBARS levels, AChE activity, IL-6 levels, and IL-10 levels and prevented STZ-induced brain anomalies in mice. Hence, the present study concluded that aripiprazole mitigated STZ-induced memory impairment and can be used as an efficacious therapeutic target for the management of AD.

Hippocampus: Molecular, Cellular, and Circuit Features in Anxiety

Anxiety disorders are currently a major psychiatric and social problem, the mechanisms of which have been only partially elucidated. The hippocampus serves as a major target of stress mediators and is closely related to anxiety modulation. Yet so far, its complex anatomy has been a challenge for research on the mechanisms of anxiety regulation. Recent advances in imaging, virus tracking, and optogenetics/chemogenetics have permitted elucidation of the activity, connectivity, and function of specific cell types within the hippocampus and its connected brain regions, providing mechanistic insights into the elaborate organization of the hippocampal circuitry underlying anxiety. Studies of hippocampal neurotransmitter systems, including glutamatergic, GABAergic, cholinergic, dopaminergic, and serotonergic systems, have contributed to the interpretation of the underlying neural mechanisms of anxiety. Neuropeptides and neuroinflammatory factors are also involved in anxiety modulation. This review comprehensively summarizes the hippocampal mechanisms associated with anxiety modulation, based on molecular, cellular, and circuit properties, to provide tailored targets for future anxiety treatment.

The role of hippocampal 5-HT1D and 5-HT1F receptors on learning and memory in rats

Serotonin is a neurotransmitter, which is involved in memory via its receptors. The 5-HT_1D and 5-HT_1F receptors mainly exist in the hippocampus, which plays an important role in memory processing. However, few studies have assessed the effect of these serotonin receptors on memory. We evaluated the effect of a 5-HT_1D receptor agonist, PNU142633, 5-HT_1D receptor antagonist, BRL15572 hydrochloride, and 5-HT1F receptor agonist, LY344864, on the recognition and avoidance memory in the hippocampus area. Fifty adult male Wistar rats weighing 200-250 g were divided into the control, sham-operated, PNU, BRL, and LY groups (n=10 per group). Bilateral guide cannulas were implanted into the dentate gyrus area of the hippocampus. The drugs were administered at the dose of 1 μg/μl before the novel object recognition (NOR) and passive avoidance learning (PAL) tests. The results showed that in the NOR test, the administration of PNU and LY had no significant effect on recognition index; however, the recognition index was increased by BRL. In the PAL test, the administration of PNU had no significant effect on recognition index, but the administration of BRL and LY increased the time spent in the dark compartment of the apparatus and decreased the step-through latency into the dark compartment apparatus. It can be concluded that the inhibition of the hippocampal 5-HT_1D receptor improved cognition memory but impaired avoidance memory. Activation of the hippocampal 5-HT_1F receptor had no effect on cognitive memory but impaired avoidance memory.

Differentiated HT22 cells as a novel model for in vitro screening of serotonin reuptake inhibitors

The mouse hippocampal neuronal cell line HT22 is frequently used as an in vitro model to investigate the role of hippocampal cholinergic neurons in cognitive functions. HT22 cells are derived from hippocampal neuronal HT4 cells. However, whether these cells exhibit the serotonergic neuronal phenotype observed in mature hippocampal neurons has not been determined yet. In this present study, we examined whether the differentiation of HT22 cells enhances the serotonergic neuronal phenotype, and if so, whether it can be used for antidepressant screening. Our results show that differentiation of HT22 cells promoted neurite outgrowth and upregulation of N-methyl-D-aspartate receptor and choline acetyltransferase, which is similar to that observed in primary cultured hippocampal neurons. Furthermore, proteins required for serotonergic neurotransmission, such as tryptophan hydroxylase 2, serotonin (5-hydroxytryptamine, 5-HT)_1a receptor, and serotonin transporter (SERT), were significantly upregulated in differentiated HT22 cells. The transcription factor Pet-1 was upregulated during HT22 differentiation and was responsible for the regulation of the serotonergic neuronal phenotype. Differentiation also enhanced the functional serotonergic properties of HT22 cells, as evidenced by increase in intracellular 5-HT levels, serotonin transporter SERT glycosylation, and 5-HT reuptake activity. The sensitivity of 5-HT reuptake inhibition by venlafaxine in differentiated HT22 cells (IC_50, 27.21 nM) was comparable to that in HEK293 cells overexpressing serotonin transporter SERT (IC_50, 30.65 nM). These findings suggest that the differentiation of HT22 cells enhances their functional serotonergic properties, and these cells could be a potential in vitro system for assessing the efficacy of antidepressant 5-HT reuptake inhibitors.

Role of G-Proteins and GPCRs in Cardiovascular Pathologies

Cell signaling is a fundamental process that enables cells to survive under various ecological and environmental contexts and imparts tolerance towards stressful conditions. The basic machinery for cell signaling includes a receptor molecule that senses and receives the signal. The primary form of the signal might be a hormone, light, an antigen, an odorant, a neurotransmitter, etc. Similarly, heterotrimeric G-proteins principally provide communication from the plasma membrane G-protein-coupled receptors (GPCRs) to the inner compartments of the cells to control various biochemical activities. G-protein-coupled signaling regulates different physiological functions in the targeted cell types. This review article discusses G-proteins' signaling and regulation functions and their physiological relevance. In addition, we also elaborate on the role of G-proteins in several cardiovascular diseases, such as myocardial ischemia, hypertension, atherosclerosis, restenosis, stroke, and peripheral artery disease.

Evaluation of vasodilatory effect and antihypertensive effect of chrysin through in vitro and sub-chronic in vivo study

Chrysin, a bioflavonoid belonging to the flavone, occurs naturally in plants such as the passionflower, honey and propolis. Few studies have demonstrated that chrysin can promote vasorelaxant activities in rats' aorta and mesenteric arteries. To date, no research has explored the signalling system routes that chrysin may utilise to produce its vasorelaxant action. Therefore, this study aimed to investigate the underlying mechanisms involved in chrysin-induced vasorelaxant in rats' aortic rings and assess the antihypertensive effect of chrysin in spontaneously hypertensive rats (SHRs). The findings revealed that chrysin utilised both endothelium-dependent and endothelium-independent mechanisms. The presence of L-NAME (endothelial NO synthase inhibitor), ODQ (sGC inhibitor), methylene blue (cGMP lowering agent), 4-AP (voltage-gated potassium channel inhibitor), atropine (muscarinic receptors inhibitor) and propranolol (β-adrenergic receptors inhibitor) significantly reduced the chrysin's vasorelaxant action. Furthermore, chrysin can reduce intracellular Ca²⁺ levels by limiting the extracellular intake of Ca²⁺ through voltage-operated calcium channels and blocking the intracellular release of Ca²⁺ from the sarcoplasmic reticulum via the IP₃ receptor. These indicate that chrysin-induced vasorelaxants involved NO/sGC/cGMP signalling cascade, muscarinic and β-adrenergic receptors, also the potassium and calcium channels. Although chrysin had vasorelaxant effects in in vitro studies, the in vivo antihypertensive experiment discovered chrysin does not significantly reduce the blood pressure of SHRs following 21 days of oral treatment. This study proved that chrysin utilised multiple signalling pathways to produce its vasorelaxant effect in the thoracic aorta of rats; however, it had no antihypertensive effect on SHRs.

Mitochondrial Dysfunction Links to Impaired Hippocampal Serotonin Release in a Mouse Model of Alzheimer's Disease

BACKGROUND

Deprivation of extracellular serotonin has been linked to cognitive decline and neuropsychiatric disturbances in Alzheimer's disease (AD). However, despite degeneration of serotonin-producing neurons, whether serotonin release is affected in AD-sensitive brain regions is unknown.

OBJECTIVE

This study investigated the impact of mitochondrial dysfunction in decreased hippocampal serotonin release in AD amyloidosis mouse model 5xFAD mice.

METHODS

Electrochemical assays were applied to examine hippocampal serotonin release. We also employed multidisciplinary techniques to determine the role of oligomeric amyloid-β (Aβ) in hippocampal mitochondrial deficits and serotonin release deficiency.

RESULTS

5xFAD mice exhibited serotonin release decrease and relatively moderate downregulation of serotonergic fiber density as well as serotonin content in the hippocampal region. Further experiments showed an inhibitory effect of oligomeric amyloid-β (Aβ) on hippocampal serotonin release without affecting the density of serotonergic fibers. Pharmaceutical uncoupling of mitochondrial oxidative phosphorylation (OXPHOS) disrupted hippocampal serotonin release in an ex vivo setting. This echoes the mitochondrial defects in serotonergic fibers in 5xFAD mice and oligomeric Aβ-challenged primary serotonergic neuron cultures and implicates a link between mitochondrial dysfunction and serotonin transmission defects in AD-relevant pathological settings.

CONCLUSION

The most parsimonious interpretation of our findings is that mitochondrial dysfunction is a phenotypic change of serotonergic neurons, which potentially plays a role in the development of serotonergic failure in AD-related conditions.

Maternal nutrient restriction and dietary melatonin alter neurotransmitter pathways in placental and fetal tissues

INTRODUCTION

Recent research indicates an important role in the placental fetal brain axis, with a paucity of information reported in large animals. Melatonin supplementation has been investigated as a potential therapeutic to negate fetal growth restriction. We hypothesized that maternal nutrient restriction and melatonin supplementation would alter neurotransmitter pathways in fetal blood, cotyledonary and hypothalamus tissue.

METHODS

On day 160 of gestation, Brangus heifers (n = 29 in fall study; n = 25 in summer study) were assigned to one of four treatments: adequately fed (ADQ-CON; 100% NRC recommendation), nutrient restricted (RES-CON; 60% NRC recommendation), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL; RES-MEL). Placentomes, fetal blood, and hypothalamic tissue were collected at day 240 of gestation. Neurotransmitters were analyzed in fetal blood and fetal and placental tissues. Transcript abundance of genes in the serotonin pathway and catecholamine pathway were determined in fetal hypothalamus and placental cotyledon.

RESULTS

Serotonin was increased (P < 0.05) by 12.5-fold in the blood of fetuses from RES dams versus ADQ in the fall study. Additionally, melatonin supplementation increased (P < 0.05) neurotransmitter metabolites and transcript abundance of the monoamine oxidase A (MAOA) enzyme in the cotyledon. In the summer study, plasma dopamine and placental dopamine receptors were decreased (P < 0.05) in RES dams versus ADQ.

DISCUSSION

In conclusion, these data indicate novel evidence of the presence of neurotransmitters and their synthesis and metabolism in the bovine conceptus, which could have greater implications in establishing postnatal behavior.

Spin state dependent peroxidase activity of heme bound amyloid β peptides relevant to Alzheimer's disease

The colocalization of heme rich deposits in the senile plaque of Aβ in the cerebral cortex of the Alzheimer's disease (AD) brain along with altered heme homeostasis and heme deficiency symptoms in AD patients has invoked the association of heme in AD pathology. Heme bound Aβ complexes, depending on the concentration of the complex or peptide to heme ratio, exhibit an equilibrium between a high-spin mono-His bound peroxidase-type active site and a low-spin bis-His bound cytochrome b type active site. The high-spin heme-Aβ complex shows higher peroxidase activity than free heme, where compound I is the reactive oxidant. It is also capable of oxidizing neurotransmitters like serotonin in the presence of peroxide, owing to the formation of compound I. The low-spin bis-His heme-Aβ complex on the other hand shows enhanced peroxidase activity relative to high-spin heme-Aβ. It reacts with H2O2 to produce two stable intermediates, compound 0 and compound I, which are characterized by absorption, EPR and resonance Raman spectroscopy. The stability of compound I of low-spin heme-Aβ is accountable for its enhanced peroxidase activity and oxidation of the neurotransmitter serotonin. The effect of the second sphere Tyr10 residue of Aβ on the formation and stability of the intermediates of low-spin heme-Aβ has also been investigated. The higher stability of compound I for low-spin heme-Aβ is likely due to H-bonding interactions involving Tyr10 in the distal pocket.

Sex-biased effects on hippocampal circuit development by perinatal SERT expression in CA3 pyramidal neurons

Neurodevelopmental disorders ranging from autism to intellectual disability display sex-biased prevalence and phenotypical presentations. Despite increasing knowledge about temporospatial cortical map development and genetic variants linked to neurodevelopmental disorders, when and how sex-biased neural circuit derailment may arise in diseased brain remain unknown. Here, we identify in mice that serotonin uptake transporter (SERT) in non-serotonergic neurons - hippocampal and prefrontal pyramidal neurons - confers sex-biased effects specifically during neural circuit development. A set of gradient-patterned CA3 pyramidal neurons transiently express SERT to clear extracellular serotonin, coinciding with hippocampal synaptic circuit establishment. Ablating pyramidal neuron SERT (SERTPyramidΔ) alters dendritic spine developmental trajectory in the hippocampus, and precipitates sex-biased impairments in long-term activity-dependent hippocampal synaptic plasticity and cognitive behaviors. Transcriptomic analyses identify sex-biased alterations in gene sets associated with autism, dendritic spine structure, synaptic function and male-specific enrichment of dysregulated genes in glial cells in early postnatal SERTPyramidΔ hippocampus. Our data suggest that SERT function in these pyramidal neurons underscores a temporal- and brain region-specific regulation of normal sex-dimorphic circuit development and a source for sex-biased vulnerability to cognitive and behavioral impairments. This article has an associated 'The people behind the papers' interview.

Adverse maternal environment affects hippocampal HTR2c variant expression and epigenetic characteristics in mouse offspring

BACKGROUND

An adverse maternal environment (AME) predisposes progeny towards cognitive impairment in humans and mice. Cognitive impairment associates with hippocampal dysfunction. An important regulator of hippocampal function is the hippocampal serotonergic system. Dysregulation of hippocampal serotonin receptor 2c (HTR2c) expression is linked with cognitive impairment. HTR2c contains multiple mRNA variants and isoforms that are epigenetically regulated including DNA methylation, histone modifications, and small nucleolar RNA MBII-52. We tested the hypotheses that AME increases HTR2c variant expression and alters epigenetic modifications along the HTR2c gene locus.

METHODS

We create an AME through maternal Western diet and prenatal environmental stress in the mouse. We analyzed hippocampal HTR2c and variants' expression, DNA methylation and histone modifications along the gene locus, and MBII-52 levels in postnatal day 21 offspring.

RESULTS

AME significantly increased the expressions of total HTR2c and full-length variants (V201 and V202) concurrently with an altered epigenetic profile along the HTR2c gene locus in male offspring hippocampi. Moreover, increased full-length variants' expression in AME males was in line with increased MBII-52 levels.

CONCLUSIONS

AME affects male offspring hippocampal expression of HTR2c and full-length variants via epigenetic mechanisms. Altered hippocampal HTR2c expression may contribute to cognitive impairment seen in adult males in this model.

IMPACT

The key message of our article is that an adverse maternal environment increases expression of total HTR2c mRNA and protein, alters proportions of HTR2c mRNA variants, and impacts HTR2c epigenetic modifications in male offspring hippocampi relative to controls. Our findings add to the literature by providing the first report of altered HTR2c mRNA variant expression in association with altered epigenetic modifications in the hippocampus of offspring mice exposed to an adverse maternal environment. Our findings suggest that an adverse maternal environment affects the expression of genes previously determined to regulate cognitive function through an epigenetic mechanism in a sex-specific manner.

Activation and blockade of 5-HT4 receptors in the dorsal hippocampus enhance working and hippocampus-dependent memories in the unilateral 6-hydroxydopamine lesioned rats

Cognitive dysfunction is a common symptom in Parkinson's disease (PD). Serotonin4 (5-HT₄) receptors are richly expressed in the dorsal hippocampus (dHIPP) and play an important role in cognitive activities. However, the mechanism underlying the role of dHIPP 5-HT₄ receptors in PD-related cognitive dysfunction remains unclear. Here we found that unilateral 6-hydroxydopamine lesions of the medial forebrain bundle increased the protein expression of 5-HT₄ receptors in the dHIPP, decreased hippocampal theta rhythm, and impaired working memory and hippocampus-dependent memory in the T-maze and hole-board test, respectively. Both activation and blockade of dHIPP 5-HT₄ receptors (agonist BIMU8 and antagonist GR113808) improved working memory and hippocampus-dependent memory in the lesioned rats, but not in sham rats. Activation of dHIPP 5-HT₄ receptors increased hippocampal theta rhythm in the lesioned rats. The neurochemical studies showed that injection of BIMU8, GR113808 or GR113808/BIMU8 in the dHIPP increased the levels of dopamine in the medial prefrontal cortex (mPFC), dHIPP and amygdala, and the level of 5-HT in the amygdala in the lesioned rats, but not in sham rats. Injection of GR113808 or GR113808/BIMU8 into the dHIPP also increased the levels of noradrenaline in the mPFC, dHIPP and amygdala only in the lesioned rats. These results suggest that activation or blockade of dHIPP 5-HT₄ receptors may improve the cognitive impairments in parkinsonian rats, which may be due to the increase of hippocampal theta rhythm, up-regulated expressions of 5-HT₄ receptors in the dHIPP and the changes in the levels of monoamines in the relative brain areas.

Serotonin G Protein-Coupled Receptor-Based Biosensing Modalities in Yeast

Serotonin is a key neurotransmitter involved in numerous physiological processes and serves as an important precursor for manufacturing bioactive indoleamines and alkaloids used in the treatment of human pathologies. In humans, serotonin sensing and signaling can occur by 12 G protein-coupled receptors (GPCRs) coupled to Gα proteins. In yeast, human serotonin GPCRs coupled to Gα proteins have previously been shown to function as whole-cell biosensors of serotonin. However, systematic characterization of serotonin biosensing modalities between variant serotonin GPCRs and application thereof for high-resolution serotonin quantification is still awaiting. To systematically assess GPCR signaling in response to serotonin, we characterized reporter gene expression at two different pHs of a 144-sized library encoding all 12 human serotonin GPCRs in combination with 12 different Gα proteins engineered in yeast. From this screen, we observed changes in the biosensor sensitivities of >4 orders of magnitude. Furthermore, adopting optimal biosensing designs and pH conditions enabled high-resolution high-performance liquid chromatography-validated sensing of serotonin produced in yeast. Lastly, we used the yeast platform to characterize 19 serotonin GPCR polymorphisms found in human populations. While major differences in signaling were observed among the individual polymorphisms when studied in yeast, a cross-comparison of selected variants in mammalian cells showed both similar and disparate results. Taken together, our study highlights serotonin biosensing modalities of relevance to both biotechnological and potential human health applications.

Dopamine and serotonin interplay for valence-based spatial learning

Dopamine (DA) and serotonin (5-HT) are important neuromodulators of synaptic plasticity that have been linked to learning from positive or negative outcomes or valence-based learning. In the hippocampus, both affect long-term plasticity but play different roles in encoding uncertainty or predicted reward. DA has been related to positive valence, from reward consumption or avoidance behavior, and 5-HT to aversive encoding. We propose DA produces overall LTP while 5-HT elicits LTD. Here, we compare two reward-modulated spike timing-dependent plasticity (R-STDP) rules to describe the action of these neuromodulators. We examined their role in cognitive performance and flexibility for computational models of the Morris water maze task and reversal learning. Our results show that the interplay of DA and 5-HT improves learning performance and can explain experimental evidence. This study reinforces the importance of neuromodulation in determining the direction of plasticity.

Hytrin loaded polydopamine-serotonin nanohybrid induces IDH2 mediated neuroprotective effect to alleviate Parkinson's disease

Parkinson's disease (PD) is the second most neurodegenerative disease caused due to synucleinopathy leads to the death of dopaminergic and serotonergic neurons. The approach to reduce synucleinopathy paves the therapeutic way in PD management. Recent studies highlight anti-Parkinsonism effect of Hytrin that regulates energy homeostasis via activation of mitochondrial redox regulator; IDH2 leading to attenuation of synucleinopathy. However, the burst release kinetics of Hytrin restricts its therapeutic potential. Therefore, we aimed to improve Hytrin release kinetics through nanocarrier mediated delivery, replenish dopamine and serotonin by formulating Hytrin loaded polydopamine serotonin nanohybrid for PD protection. Present study also explores IDH2 mediated neuroprotective action in retardation of synucleinopathy for PD prevention. Nanoformulation has shown effective neurotherapeutic potential by improving Hytrin release profile in the reduction of PD symptoms in vitro and ex vivo. The neuroprotective effect has been attributed to IDH2 induction and alpha-synuclein reduction against rotenone insults. The direct physical interaction of IDH2 and alpha-synuclein, PD hallmark has been uncovered. The study divulges that the restorative effect of our nanoformulation significantly retards the PD deficits byinducing IDH2 mediated alpha-synuclein ubiquitination and proteasomal degradation pathway.

Utilizing network pharmacology and experimental validation to explore the potential molecular mechanisms of BanXia-YiYiRen in treating insomnia

BanXia-YiYiRen (Pinellia Ternata and Coix Seed, BX-YYR) has been clinically proven to be an effective Chinese medicine compatible with the treatment of insomnia. However, the underlying mechanism of BX-YYR against insomnia remains unclear. This study aimed to explore the pharmacological mechanisms of BX-YYR in treating insomnia based on network pharmacology and experimental validation. The drug-disease targets were obtained using publicly available databases. The analysis revealed 21 active compounds and 101 potential targets of BX-YYR from the pharmacological database of Chinese medicine system and analysis platform (TCMSP) and 1020 related targets of insomnia from the GeneCards and Online Mendelian Inheritance in Man (OMIM) databases. Furthermore, 38 common targets of BX-YYR against insomnia were identified, and these common targets were used to construct a protein–protein interaction (PPI) network. The visual PPI network was constructed by Cytoscape software. The top three genes from PPI according to degree value are FOS, AKT1, and CASP3. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were applied to reveal the potential targets and signaling pathways involved in BX-YYR against insomnia, especially the serotonergic pathway. In addition, molecular docking revealed that baicalein, beta-sitosterol, and stigmasterol displayed strong binding to AKT1, FOS, PRKCA, and VEGFA. Experimental study found that BX-YYR against insomnia might play a role in improving sleep by modulating the serotonergic pathway. In summary, our findings revealed the underlying mechanism of BX-YYR against insomnia and provided an objective basis for further experimental study and clinical application.

MDMA related neuro-inflammation and adenosine receptors

3,4-methylenedioxymethamphetamine (MDMA) is a world-wide abused psychostimulant, which has the neurotoxic effects on dopaminergic and serotonergic neurons in both rodents and non-human primates. Adenosine acts as a neurotransmitter in the brain through the activation of four specific G-protein-coupled receptors and it acts as a neuromodulator of dopamine neurotransmission. Recent studies suggest that stimulation of adenosine receptors oppose many behavioral effects of methamphetamines. This review summarizes the specific cellular mechanisms involved in MDMA neuroinflammatory effects, along with the protective effects of adenosine receptors.

Imaging of cerebral tryptophan metabolism using 7-[18F]FTrp-PET in a unilateral Parkinsonian rat model

Degradation products of the essential amino acid tryptophan (Trp) are important signaling molecules in the mammalian brain. Trp is metabolized either through the kynurenine pathway or enters serotonin and melatonin syntheses. The aim of the present work was to examine the potential of the novel PET tracer 7-[¹⁸F]fluorotryptophan ([¹⁸F]FTrp) to visualize all three pathways in a unilateral 6-OHDA rat model. [¹⁸F]FDOPA-PET scans were performed in nine 6-OHDA-injected and six sham-operated rats to assess unilateral dopamine depletion severity four weeks after lesion placement. Afterwards, 7-[¹⁸F]FTrp-PET scans were conducted at different timepoints up to seven months after 6-OHDA injection. In addition, two 6-OHDA-injected rats were examined for neuroinflammation using [¹⁸F]DAA1106-PET. 7-[¹⁸F]FTrp-PET showed significantly increased tracer uptake at the 6-OHDA injection site which was negatively correlated to time after lesion placement. Accumulation of [¹⁸F]DAA1106 at the injection site was increased as well, suggesting that 7-[¹⁸F]FTrp uptake in this region may reflect kynurenine pathway activity associated with inflammation. Bilaterally in the dorsal hippocampus, 7-[¹⁸F]FTrp uptake was significantly decreased and was inversely correlated to dopamine depletion severity, indicating that it reflects reduced serotonin synthesis. Finally, 7-[¹⁸F]FTrp uptake in the pineal gland was significantly increased in relation with dopamine depletion severity, providing evidence that melatonin synthesis is increased in the 6-OHDA rat model. We conclude that 7-[¹⁸F]FTrp is able to detect alterations in both serotonin/melatonin and kynurenine metabolic pathways, and can be applied to visualize pathologic changes related to neurodegenerative processes.

Atypical, but Not Typical, Antipsychotic Drugs Reduce Hypersynchronized Prefrontal-Hippocampal Circuits during Psychosis-Like States in Mice: Contribution of 5-HT2A and 5-HT1A Receptors

Neural synchrony and functional connectivity are disrupted in schizophrenia. We investigated changes in prefrontal-hippocampal neural dynamics during psychosis-like states induced by the NMDAR antagonist phencyclidine and subsequent rescue by two atypical antipsychotic drugs (AAPDs), risperidone and clozapine, and the classical APD haloperidol. The psychotomimetic effects of phencyclidine were associated with prefrontal hypersynchronization, hippocampal desynchronization, and disrupted circuit connectivity. Phencyclidine boosted prefrontal oscillatory power at atypical bands within delta, gamma, and high frequency ranges, while irregular cross-frequency and spike-LFP coupling emerged. In the hippocampus, phencyclidine enhanced delta rhythms but suppressed theta oscillations, theta-gamma coupling, and theta-beta spike-LFP coupling. Baseline interregional theta-gamma coupling, theta phase coherence, and hippocampus-to-cortex theta signals were redirected to delta frequencies. Risperidone and clozapine, but not haloperidol, reduced phencyclidine-induced prefrontal and cortical-hippocampal hypersynchrony. None of the substances restored hippocampal and circuit desynchronization. These results suggest that AAPDs, but not typical APDs, target prefrontal-hippocampal pathways to elicit antipsychotic action. We investigated whether the affinity of AAPDs for serotonin receptors could explain their distinct effects. Serotonin 5-HT2AR antagonism by M100907 and 5-HT1AR agonism by 8-OH-DPAT reduced prefrontal hypersynchronization. Our results point to fundamentally different neural mechanisms underlying the action of atypical versus typical APDs with selective contribution of serotonin receptors.

Role of Receptors in Relation to Plaques and Tangles in Alzheimer's Disease Pathology

Despite the identification of Aβ plaques and NFTs as biomarkers for Alzheimer’s disease (AD) pathology, therapeutic interventions remain elusive, with neither an absolute prophylactic nor a curative medication available to impede the progression of AD presently available. Current approaches focus on symptomatic treatments to maintain AD patients’ mental stability and behavioral symptoms by decreasing neuronal degeneration; however, the complexity of AD pathology requires a wide range of therapeutic approaches for both preventive and curative treatments. In this regard, this review summarizes the role of receptors as a potential target for treating AD and focuses on the path of major receptors which are responsible for AD progression. This review gives an overall idea centering on major receptors, their agonist and antagonist and future prospects of viral mimicry in AD pathology. This article aims to provide researchers and developers a comprehensive idea about the different receptors involved in AD pathogenesis that may lead to finding a new therapeutic strategy to treat AD.

Hippocampal cAMP regulates HCN channel function on two time scales with differential effects on animal behavior

[Figure: see text].

Memory Disorders Related to Hippocampal Function: The Interest of 5-HT4Rs Targeting

The hippocampus has long been considered as a key structure for memory processes. Multilevel alterations of hippocampal function have been identified as a common denominator of memory impairments in a number of psychiatric and neurodegenerative diseases. For many years, the glutamatergic and cholinergic systems have been the main targets of therapeutic treatments against these symptoms. However, the high rate of drug development failures has left memory impairments on the sideline of current therapeutic strategies. This underscores the urgent need to focus on new therapeutic targets for memory disorders, such as type 4 serotonin receptors (5-HT₄Rs). Ever since the discovery of their expression in the hippocampus, 5-HT₄Rs have gained growing interest for potential use in the treatment of learning and memory impairments. To date, much of the researched information gathered by scientists from both animal models and humans converge on pro-mnesic and anti-amnesic properties of 5-HT₄Rs activation, although the mechanisms at work require more work to be fully understood. This review addresses a fundamental, yet poorly understood set of evidence of the potential of 5-HT₄Rs to re-establish or limit hippocampal alterations related to neurological diseases. Most importantly, the potential of 5-HT₄Rs is translated by refining hypotheses regarding the benefits of their activation in memory disorders at the hippocampal level.

Does Alzheimer's disease stem in the gastrointestinal system?

Over the last decades, our knowledge of the key pathogenic mechanisms of Alzheimer's disease (AD) has dramatically improved. Regarding the limitation of current therapeutic strategies for the treatment of multifactorial diseases, such as AD, to be translated into the clinic, there is a growing trend in research to identify risk factors associated with the onset and progression of AD. Here, we review the current literature with a focus on the relationship between gastrointestinal (GI)/liver diseases during the lifespan and the incidence of AD, and discuss the possible mechanisms underlying the link between the diseases. We also aim to review studies evaluating the possible link between the chronic use of the most common GI medications and the future risk of AD development.

Polyphenols and IUGR Pregnancies: Intrauterine Growth Restriction and Hydroxytyrosol Affect the Development and Neurotransmitter Profile of the Hippocampus in a Pig Model

Intrauterine growth restriction (IUGR) refers to poor growth of a fetus during pregnancy due to deficient maternal nutrition or oxygen supply. Supplementation of a mother's diet with antioxidants, such as hydroxytyrosol (HTX), has been proposed to ameliorate the adverse phenotypes of IUGR. In the present study, sows were treated daily with or without 1.5 mg of HTX per kilogram of feed from day 35 of pregnancy (at 30% of the total gestational period), and fetuses were sampled at day 100 of gestation. Fetuses were classified as normal body weight (NBW) or low body weight (LBW) as a consequence of IUGR, constituting four groups: NBW-Control, NBW-HTX, LBW-Control, and LBW-HTX. The brain was removed, and the hippocampus, amygdala, and prefrontal cortex were rapidly dissected. Neuronal markers were studied by immunohistochemistry, and a decrease in the number of mature neurons in the hippocampal Cornu Ammonis subfield 1 (CA1) and the Dentate Gyrus (DG) regions was observed in LBW fetuses together with a higher number of immature neurons and other alterations in neuronal morphology. Furthermore, IUGR conditions altered the neurotransmitter (NT) profile, since an increase in the serotonin (5-HT) pathway was observed in LBW fetuses. Supplementation with HTX was able to reverse the morphological and neurochemical changes, leading both characteristics to values similar to those of NBW fetuses.

Behavioral assessment of children and adolescents with Graves' disease: A prospective study

Previous studies have identified frequent comorbid neuropsychiatric disorders and conditions in adults with thyrotoxicosis. These studies are scarce or even lacking in pediatric population. This work aimed to study the behavior of children and adolescents with Graves’ disease (GD). This study included 35 children with GD (boys = 15; girls = 25; mean age: 11.45±1.50yrs) and 40 healthy children (boys = 20; girls = 20; mean age: 12.54±1.62yrs). Behavior was assessed using Child Behavior Checklist (CBCL). Children with GD were assessed during periods of thyroid hormone elevation (active disease) and normalized thyroid hormones (with anti-thyroid drugs or ATDs). Compared to healthy children, patients during periods of thyroid hormone elevation (74.29%) and normalized thyroid hormones (31.43%) had higher frequencies of behavioral abnormalities and scorings of total CBCL scale (P = 0.01; P = 0.04, respectively) and its subscales’ [Anxious/Depressed (P = 0.02; P = 0.04), Withdrawn/Depressed (P = 0.03; P = 0.04) and Somatic Complaints (P = 0.03; P = 0.127) and Social (P = 0.01; P = 0.225), Thought (P = 0.01; P = 0.128) and Attention (P = 0.01; P = 0.01) problems], indicating internalizing and externalizing problems. The majority of patients had at least two different behavioral problems. Marked improvement was found during period of normalized thyroid hormones (P = 0.001). Correlation analyses showed significant associations between total CBCL scoring and age at onset (P = 0.01; P = 0.001) and lower concentrations of thyroid stimulating hormone (TSH) (P = 0.001; P = 0.04) and higher concentrations of free thyroxine (fT4) (P = 0.01; P = 0.02), triiodothyronine (fT3) (P = 0.01; P = 0.03) and thyrotropin receptor antibodies (TRAbs) (P = 0.001; P = 0.01) during periods of thyroid hormone elevation and normalized thyroid hormones, respectively. Multiple linear regression analysis showed that "at presentation" lower concentrations of TSH (P = 0.001; P = 0.03) and higher concentrations of fT4 (P = 0.001, P = 0.01), fT3 (P = 0.01; P = 0.06) and TRAbs (P = 0.001; P = 0.001) were predictors of behavioral problems during periods of active disease and normalized thyroid hormones. We conclude that GD is associated with higher frequencies and severities of anxiety, depression and inattention during periods of thyroid hormone elevation as well as normalized thyroid hormones with ATDs. Therefore, early diagnosis and optimizing management are required to improve children’s social life.

The response of reproducing Japanese quail to dietary valine

1. A feeding trial was conducted to measure the responses of Japanese quail to dietary valine. In total, 280 Japanese quail were randomly assigned to eight treatments giving seven replicates (cage - 35 cm length, 35 cm width × 15 cm high). Experimental diets were formulated using a dilution technique to give a range dietary Val concentration (1.97 to 9.85 g/kg).2. Feed intake was maximised at 6.66 g Val/kg and above, but declined linearly below this level. Body weight reached a maximum of 170 g on 6.66 g Val/kg. Egg output peaked at 9.5 ± 0.3 g/bird/d with an egg weight of 11 g for the 6.66 g Val/kg diet. Rate of laying for the group that received the feed with the lowest Val content was close to zero (1.40%), but egg weight on this treatment was 70% of the maximum egg weight. Valine required per gram of egg output was estimated as 10.6 mg/g, whereas the maintenance requirement was 159 mg/kg body weight. Val required for maximum egg output was estimated in 154 mg/d.3. The marginal cost of Val in Brazil currently is negative below a level of 8.0 g/kg feed, which is above that required for maximum egg output. Consequently, Val cannot be regarded as a limiting amino acid currently, as the optimum economic intake exceeds the requirements of all the individuals in the population. The price of a quail egg weighing 11 g in Brazil at the time of the experiment was R$ 0.021. Even if the marginal revenue for these eggs was doubled to 0.4 c/g, there would be no reason to increase the intake of Val.

Activation and blockade of dorsal hippocampal serotonin4 receptors produce antidepressant effects in the hemiparkinsonian rats

Depression is a common non-motor symptom in Parkinson's disease (PD). Although serotonin4 (5-HT4) receptors and the dorsal hippocampus (dHIP) are regarded to be involved in the depression, the mechanism underlying the effects of 5-HT4 receptors in the dHIP on PD-related depression should be further investigated. In the present study, unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB) increased the expressions of 5-HT4 receptors and its co-localization with glutamate neurons in the CA1, CA3 and dentate gyrus. Additionally, MFB lesions induced depressive-like behaviors in the sucrose preference and forced swimming tests. The activation or blockade of dHIP 5-HT4 receptors produced antidepressant effects in the MFB lesioned rats but not in control rats. Neurochemical results showed no changes of monoamines levels in the striatum, medial prefrontal cortex (mPFC), lateral habenula (LHb), and ventral hippocampus (vHIP) in control rats after intra-dHIP injection of 5-HT4 receptors agonist BIMU8 (26 μg/rat), antagonist GR 113808 (16 μg/rat) or GR 113808/BIMU8 (26 μg/16 μg/rat). But in the lesioned rats, BIMU8, GR113808 or GR 113808/BIMU8 injection increased dopamine levels in the striatum, mPFC, LHb, and vHIP and increased 5-HT levels in the LHb. Intra-dHIP injection of GR 113808 or GR 113808/BIMU8 also increased the noradrenaline levels in the mPFC and LHb. All these results suggest that activation or blockade dHIP 5-HT4 receptors produce antidepressant effects in the hemiparkinsonian rats, which may be related to the upregulation of 5-HT4 receptors in the dHIP and the changes of monoamines in the limbic and limbic-related brain regions.

Serotonin modulation of hippocampal functions: From anatomy to neurotherapeutics

The hippocampal region receives a dense serotoninergic innervation originating from both medial and dorsal raphe nuclei. This innervation regulates hippocampal activity through the activation of distinct receptor families that are expressed in excitatory and inhibitory neurons, terminals of several afferent neurotransmitter systems, and glial cells. Preclinical and clinical studies indicate that hippocampal dysfunctions are involved in learning and memory deficits, dementia, Alzheimer's disease, epilepsy and mood disorders such as anxiety, depression and post-traumatic syndrome disorder, whereas the hippocampus participates also in the therapeutic mechanisms of numerous medicines. Not surprisingly, several drugs acting via 5-HT mechanisms are efficacious to some extent in some diseases and the link between 5-HT and the hippocampus although clear remains difficult to untangle. For this reason, we review reported data concerning the distribution and the functional roles of the 5-HT receptors in the hippocampal region in health and disease. The impact of the 5-HT systems on the hippocampal function is such that the research of new 5-HT mechanisms and drugs is still very active. It concerns notably drugs acting at the 5-HT_1A,_2A,_2C,_4,6 receptor subtypes, in addition to the already existing drugs including the selective serotonin reuptake inhibitors.

Identification and characterization of a novel 5-hydroxytryptamine receptor in the sea cucumber Apostichopus japonicus (Selenka)

Serotonin (5-hydroxytryptamine [5-HT]) receptors (5-HTRs) mediate neuroendocrine signaling via interactions with the ligand serotonin (5-HT). The 5-HT signaling system has been well studied in vertebrates, but rarely known in invertebrate animals, especially in the marine invertebrates. In this study, we identified and characterized a novel 5-HTR from the sea cucumber Apostichopus japonicus (Aj5-HT_4/6 ). The cloned Aj5-HT_4/6 open reading frame comprised 1290 bp and encoded 429 amino acids. Bioinformatic analysis of the receptor indicated that it was a member of the class A of the G protein-coupled receptor family. Further experiments using Aj5-HT_4/6 -transfected HEK293 cells demonstrated that treatment with 5-HT could induce rapid internalization of Aj5-HT_4/6 fused with enhanced green fluorescent protein from the cell surface into the cytoplasm and triggered a significant increase in levels of the second messenger cAMP as well as mitogen-activated protein kinase phosphorylation in a 5-HT dose-dependent manner. Quantitative real time-polymerase chain reaction demonstrated that Aj5-HT_4/6 was predominantly expressed in the muscle and respiratory tree, and its expression was significantly decreased during estivation. Taken together, these results imply that Aj5-HT_4/6 is potentially involved in the movement and metabolism of the sea cucumber.

Involvement of the Dorsal Hippocampus 5-HT1A Receptors in the Regulation of Depressive-Like Behaviors in Hemiparkinsonian Rats

BACKGROUND

Depression is one of the most common neuropsychiatric disturbances in Parkinson's disease (PD), but its pathophysiology is not definite. Lines of evidence have indicated that the hippocampus and serotonin 1A (5-HT1A) receptors are related to the regulation of depression.

OBJECTIVE

The purpose of the present study was to observe the effect of 5-HT1A receptors in the dorsal hippocampus (dHIP) on PD-related depression in rats.

METHODS

Unilateral 6-hydroxydopamine lesioning of the medial forebrain bundle (MFB) was used to establish the hemiparkinsonian rat model. The effects of intra-dHIP injection of the 5-HT1A receptor -agonist 8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) or antagonist WAY-100635 on depressive-like behaviors were observed in sucrose preference and forced swim tests in control and lesioned rats. Monoamine levels including dopamine (DA), 5-HT, and noradrenaline (NA) in depression-related brain regions were determined by a neurochemical method in all groups.

RESULTS

Behavioral results showed that MFB lesions induced depressive-like behaviors. Intra-dHIP injection of 8-OH-DPAT produced antidepressant effects, while WAY-100635 induced or increased the depressive-like behaviors in both control and the lesioned rats. Neurochemical results found that intra-dHIP injection of 8-OH-DPAT significantly increased DA and 5-HT levels in the medial prefrontal cortex (mPFC), lateral habenula (LHb), ventral hippocampus and amygdala in the lesioned group and decreased NA levels in the mPFC and LHb in the control group. Moreover, after injection of WAY-100635, NA levels in all these regions of the lesioned group were significantly increased.

CONCLUSIONS

These findings suggest that hippocampal 5-HT1A receptors regulate depression and PD-related depression by neurochemical mechanisms.

The effect of 5-HT4 serotonin receptors in the CA3 hippocampal region on D-AP5-induced anxiolytic-like effects: Isobolographic analyses

Increasing evidence shows the close relationship between hippocampal glutamatergic and serotonergic systems through the modulation of behavioral responses. This study aimed to investigate the possible involvement of 5-HT₄ receptors in the CA3 hippocampal region in anxiolytic-like effects induced by D-AP5 (a competitive antagonist of the glutamate NMDA [N-Methyl-D-aspartate] receptor). Male Wistar rats were placed in the elevated plus maze (EPM) apparatus that is used to assess anxiety-related behaviors, and the percentages of open arm time (%OAT) and open arm entries (%OAE) which are associated with anxiety-related behaviors were measured. The close arm entries (CAE) which is correlated with locomotor activity was also evaluated. The results showed that, intra-CA3 injection of D-AP5 (0.4 μg/rat), RS67333 (1.2 μg/rat; a 5-HT₄ receptor agonist), and RS23597-190 (1.2 μg/rat; a 5-HT₄ receptor antagonist) increased %OAT and %OAE, indicating the anxiolytic-like effect of these drugs. Also, only RS23597-190 (1.2 μg/rat) decreased CAE. Intra-CA3 injection of sub-threshold dose of RS67333 (0.012 μg/rat) or RS23597-190 (0.012 μg/rat), 5 min before the injection of D-AP5 (0.2 μg/rat) increased %OAT, indicating potentiating the anxiolytic-like effect of D-AP5. The isobolographic analyses also showed the additive or synergistic anxiolytic-like effect of intra-CA3 co-administration of D-AP5 with RS67333 or RS23597-190, respectively. In conclusion, CA3 5-HT₄ receptors are involved in D-AP5-induced anxiolytic-like behaviors in rats.

Depression-Associated Gene Negr1-Fgfr2 Pathway Is Altered by Antidepressant Treatment

The Negr1 gene has been significantly associated with major depression in genetic studies. Negr1 encodes for a cell adhesion molecule cleaved by the protease Adam10, thus activating Fgfr2 and promoting neuronal spine plasticity. We investigated whether antidepressants modulate the expression of genes belonging to Negr1-Fgfr2 pathway in Flinders sensitive line (FSL) rats, in a corticosterone-treated mouse model of depression, and in mouse primary neurons. Negr1 and Adam10 were the genes mostly affected by antidepressant treatment, and in opposite directions. Negr1 was down-regulated by escitalopram in the hypothalamus of FSL rats, by fluoxetine in the hippocampal dentate gyrus of corticosterone-treated mice, and by nortriptyline in hippocampal primary neurons. Adam10 mRNA was increased by nortriptyline administration in the hypothalamus, by escitalopram in the hippocampus of FSL rats, and by fluoxetine in mouse dorsal dentate gyrus. Similarly, nortriptyline increased Adam10 expression in hippocampal cultures. Fgfr2 expression was increased by nortriptyline in the hypothalamus of FSL rats and in hippocampal neurons. Lsamp, another IgLON family protein, increased in mouse dentate gyrus after fluoxetine treatment. These findings suggest that Negr1-Fgfr2 pathway plays a role in the modulation of synaptic plasticity induced by antidepressant treatment to promote therapeutic efficacy by rearranging connectivity in corticolimbic circuits impaired in depression.

Genetic and Neuroimaging Approaches to Understanding Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a highly disabling condition, increasingly recognized as both a disorder of mental health and social burden, but also as an anxiety disorder characterized by fear, stress, and negative alterations in mood. PTSD is associated with structural, metabolic, and molecular changes in several brain regions and the neural circuitry. Brain areas implicated in the traumatic stress response include the amygdala, hippocampus, and prefrontal cortex, which play an essential role in memory function. Abnormalities in these brain areas are hypothesized to underlie symptoms of PTSD and other stress-related psychiatric disorders. Conventional methods of studying PTSD have proven to be insufficient for diagnosis, measurement of treatment efficacy, and monitoring disease progression, and currently, there is no diagnostic biomarker available for PTSD. A deep understanding of cutting-edge neuroimaging genetic approaches is necessary for the development of novel therapeutics and biomarkers to better diagnose and treat the disorder. A current goal is to understand the gene pathways that are associated with PTSD, and how those genes act on the fear/stress circuitry to mediate risk vs. resilience for PTSD. This review article explains the rationale and practical utility of neuroimaging genetics in PTSD and how the resulting information can aid the diagnosis and clinical management of patients with PTSD.

Peroxidase activity of heme bound amyloid β peptides associated with Alzheimer's disease

The amyloid cascade hypothesis attributes the neurodegeneration observed in Alzheimer's disease (AD) to the deposition of the amyloid β (Aβ) peptide into plaques and fibrils in the AD brain. The metal ion hypothesis which implicates several metal ions, viz. Zn²⁺, Cu²⁺ and Fe³⁺, in the AD pathology on account of their abnormal accumulation in the Aβ plaques along with an overall dyshomeostasis of these metals in the AD brain was proposed a while back. Metal ion chelators and ionophores, put forward as possible drug candidates for AD, are yet to succeed in clinical trials. Heme, which is widely distributed in the mammalian body as the prosthetic group of several important proteins and enzymes, has been thought to be associated with AD by virtue of its colocalization in the Aβ plaques along with the similarity of several heme deficiency symptoms with those of AD and most importantly, due to its ability to bind Aβ. This feature article illustrates the active site environment of heme-Aβ which resembles those of peroxidases. It also discusses the peroxidase activity of heme-Aβ, its ability to effect oxidative degradation of neurotransmitters like serotonin and also the identification of the highly reactive high-valent intermediate, compound I. The effect of second sphere residues on the formation and peroxidase activity of heme-Aβ along with the generation and decay of compound I is highlighted throughout the article. The reactivities of heme bound Aβ peptides give an alternative theory to understand the possible cause of this disease.

Corticosterone in the ventral hippocampus differentially alters accumbal dopamine output in drug-naïve and amphetamine-withdrawn rats

Dysregulation in glucocorticoid stress and accumbal dopamine reward systems can alter reward salience to increase motivational drive in control conditions while contributing to relapse during drug withdrawal. Amphetamine withdrawal is associated with dysphoria and stress hypersensitivity that may be mediated, in part, by enhanced stress-induced corticosterone observed in the ventral hippocampus. Electrical stimulation of the ventral hippocampus enhances accumbal shell dopamine release, establishing a functional connection between these two regions. However, the effects of ventral hippocampal corticosterone on this system are unknown. To address this, a stress-relevant concentration of corticosterone (0.24ng/0.5 μL) or vehicle were infused into the ventral hippocampus of urethane-anesthetized adult male rats in control and amphetamine withdrawn conditions. Accumbal dopamine output was assessed with in vivo chronoamperometry. Corticosterone infused into the ventral hippocampus rapidly enhanced accumbal dopamine output in control conditions, but produced a biphasic reduction of accumbal dopamine output in amphetamine withdrawal. Selectively blocking glucocorticoid-, mineralocorticoid-, or cytosolic receptors prevented the effects of corticosterone. Overall, these results suggest that the ability of corticosterone to alter accumbal dopamine output requires cooperative activation of mineralocorticoid and glucocorticoid receptors in the cytosol, which is dysregulated during amphetamine withdrawal. These findings implicate ventral hippocampal corticosterone in playing an important role in driving neural systems involved in positive stress coping mechanisms in healthy conditions, whereas dysregulation of this system may contribute to relapse during withdrawal.

How obsessive-compulsive and bipolar disorders meet each other? An integrative gene-based enrichment approach

BACKGROUND

The novel approaches to psychiatric classification assume that disorders, contrary to what was previously thought, are not completely separate phenomena. In this regard, in addition to symptom-based criteria, disturbances are also considered on the basis of lower level components. With this viewpoint, identifying common biochemical markers would be beneficial in adopting a comprehensive strategy for prevention, diagnosis and treatment.

MAIN BODY

One of the problematic areas in clinical settings is the coexistence of both obsessive-compulsive disorder (OCD) and bipolar disorder (BD) that is challenging and difficult to manage. In this study, using a system biologic approach we aimed to assess the interconnectedness of OCD and BD at different levels. Gene Set Enrichment Analysis (GSEA) method was used to identify the shared biological network between the two disorders. The results of the analysis revealed 34 common genes between the two disorders, the most important of which were CACNA1C, GRIA1, DRD2, NOS1, SLC18A1, HTR2A and DRD1. Dopaminergic synapse and cAMP signaling pathway as the pathways, dopamine binding and dopamine neurotransmitter receptor activity as the molecular functions, dendrite and axon part as the cellular component and cortex and striatum as the brain regions were the most significant commonalities.

SHORT CONCLUSION

The results of this study highlight the role of multiple systems, especially the dopaminergic system in linking OCD and BD. The results can be used to estimate the disease course, prognosis, and treatment choice, particularly in the cases of comorbidity. Such perspectives, going beyond symptomatic level, help to identify common endophenotypes between the disorders and provide diagnostic and therapeutic approaches based on biological in addition to the symptomatic level.