5-HT-moduline controls serotonergic activity: implication in neuroimmune reciprocal regulation mechanisms

Serotonergic dysfunction impairs locomotor coordination in spinal muscular atrophy

Neuromodulation by serotonin regulates the activity of neuronal networks responsible for a wide variety of essential behaviours. Serotonin (or 5-HT) typically activates metabotropic G protein-coupled receptors, which in turn initiate second messenger signalling cascades and induce short and long-lasting behavioural effects. Serotonin is intricately involved in the production of locomotor activity and gait control for different motor behaviours. Although dysfunction of serotonergic neurotransmission has been associated with mood disorders and spasticity after spinal cord injury, whether and to what extent such dysregulation is implicated in movement disorders has not been firmly established. Here, we investigated whether serotonergic neuromodulation is affected in spinal muscular atrophy (SMA), a neurodegenerative disease caused by ubiquitous deficiency of the SMN protein. The hallmarks of SMA are death of spinal motor neurons, muscle atrophy and impaired motor control, both in human patients and mouse models of disease. We used a severe mouse model of SMA, that closely recapitulates the severe symptoms exhibited by type I SMA patients, the most common and most severe form of the disease. Together, with mouse genetics, optogenetics, physiology, morphology and behavioural analysis, we report severe dysfunction of serotonergic neurotransmission in the spinal cord of SMA mice, both at early and late stages of the disease. This dysfunction is followed by reduction of 5-HT synapses on vulnerable motor neurons. We demonstrate that motor neurons innervating axial and trunk musculature are preferentially affected, suggesting a possible cause for the proximo-distal progression of disease, and raising the possibility that it may underlie scoliosis in SMA patients. We also demonstrate that the 5-HT dysfunction is caused by SMN deficiency in serotonergic neurons in the raphe nuclei of the brainstem. The behavioural significance of the dysfunction in serotonergic neuromodulation is underlined by inter-limb discoordination in SMA mice, which is ameliorated when selective restoration of SMN in 5-HT neurons is achieved by genetic means. Our study uncovers an unexpected dysfunction of serotonergic neuromodulation in SMA and indicates that, if normal function is to be restored under disease conditions, 5-HT neuromodulation should be a key target for therapeutic approaches.

Evaluation of the pharmacological effects and exploration of the mechanism of traditional Chinese medicine preparation Ciwujia tablets in treating insomnia based on ethology, energy metabolism, and urine metabolomic approaches

Ciwujia Tablets (CWT) are produced by concentrating and drying the extract solution of the dried rhizome of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim [Araliaceae; E. senticosus radix et rhizoma]. Besides, CWT is included in the 2020 edition of Chinese Pharmacopoeia and is widely used in the treatment of insomnia. It mainly contains eleutheroside B, eleutheroside E, isofraxidin, eleutheroside C, ciwujiatone, and chlorogenic acid, as well as other chemical components. Although the clinical efficacy of CWT in treating insomnia has been confirmed, its functions and pharmacological effects have not been systematically evaluated and its mechanism of action in the treatment of insomnia remains unclear. Therefore, in this study, behavioral, energy metabolism, and metabonomics methods were applied to systematically evaluate the effect of CWT on insomnia. Additionally, urine metabonomics based on UPLC-Q-TOF-MS/MS were utilized to identify potential endogenous biomarkers of insomnia, detect the various changes before and after CWT treatment, explore the metabolic pathway and potential target of CWT, and reveal its pharmacological mechanism. Results revealed that CWT increased inhibitory neurotransmitter (5-HT and GABA) content and reduced the content of excitatory neurotransmitters (DA and NE). Moreover, CWT enhanced autonomous behavioral activity, stabilized emotions, and promoted the return of daily basic metabolic indexes of insomniac rats to normal levels. The urine metabolomics experiment identified 28 potential endogenous biomarkers, such as allysine, 7,8-dihydroneopterin, 5-phosphonooxy-L-lysine, and N-acetylserotonin. After CWT treatment, the content of 22 biomarkers returned to normal levels. The representative markers included N-acetylserotonin, serotonin, N-methyltryptamine, and 6-hydroxymelatonin. Additionally, the metabolic pathways in rats were significantly reversed, such as tryptophan metabolism, folate biosynthesis, phenylalanine metabolism, and tyrosine metabolism. Ultimately, it is concluded that CWT regulated tryptophan metabolism, folate biosynthesis, phenylalanine metabolism, and other metabolic levels in the body. This drug has been confirmed to be effective in the treatment of insomnia by regulating the content of serotonin, 6-hydroxymelatonin, N-acetylserotonin, and N-methyltryptamine to a stable and normal level in tryptophan metabolism.

The food preservative sodium propionate induces hyperglycaemic state and neurological disorder in zebrafish

Propionate is an effective mould inhibitor widely used as a food preservative. In this study, we used zebrafish to explore the adverse effects of long-term exposure to low concentrations of sodium propionate and the underlying molecular mechanisms (from larvae to adult). When exposed for 3 months, we found that blood glucose, total cholesterol, and triglyceride levels increased, and zebrafish developed a hyperglycaemic state. New tank test results showed depression in zebrafish reduced 5-hydroxytryptamine levels in the brain and damaged the dopamine system. At the same time, the results of the color preference test showed that zebrafish had cognitive impairments. In addition, Hypothalamic-Pituitary-Adrenal axis analysis revealed abnormal gene expression, increased cortisol levels, and reduced glucocorticoid receptor mRNA levels, which were consistent with depressive behavior. We also observed abnormal transcription of inflammatory and apoptotic factors. Overall, we found that chronic exposure to sodium propionate induces depressive symptoms. This may be related to the activation of the HPA axis by the hyperglycaemic state, thereby inducing inflammation and disrupting the dopaminergic system. In summary, this study provides theoretical and technical support for the overlap of the emotional pathogenesis associated with diabetes.

Protection against Neurodegeneration in the Hippocampus Using Sialic Acid- and 5-HT-Moduline-Conjugated Lipopolymer Nanoparticles

Significant involvement of oxidative stress in the brain can develop Alzheimer's disease (AD); however, a great number of clinical trials explains the limited success of antioxidant therapy in dealing with this neurodegenerative disease. Here, we established a lipopolymer system of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) incorporated with phosphatidic acid (PA) and modified with sialic acid (SA) and 5-hydroxytryptamine-moduline (5HTM) to improve quercetin (QU) activity against oxidative stress induced by amyloid-β (Aβ) deposits. Morphological studies revealed a uniform exterior of QU-SA-5HTM-PA-PLGA NPs with a spherical structure and enhanced aggregation with inclusion of PA in the formulation. A better brain-targeted delivery of the lipopolymeric NPs was verified from the high blood-brain barrier (BBB) permeability of QU through strong interactions of surface SA and 5HTM with O-linked N-acetylglucosamine and 5-HT1B receptors, respectively. Immunofluorescence staining images also supported QU-SA-5HTM-PA-PLGA NPs to traverse the microvessels of AD rat brain. Western blot analysis showed that QU-loaded PA-PLGA NPs suppressed caspase-3 expression. The ability of the nanocarriers to recognize Aβ fibrils was demonstrated from the reduced senile plaque formation and the attenuated acetylcholinesterase and malondialdehyde activity in the hippocampus. Hence, the medication of QU-SA-5HTM-PA-PLGA NPs can facilitate the BBB penetration and prevent Aβ accumulation, lipid peroxidation, and neuronal apoptosis for the AD management.

Dopamine Receptor Gene Expression Changes in Peripheral Blood Mononuclear Cells from Schizophrenic Patients Treated with Haloperidol and Olanzapine

We investigated dopamine receptor gene expression in peripheral blood mononuclear cells of schizophrenic patients before and after treatment. Also dopamine receptor genes expression profile was compared in two treatment groups including haloperidol and olanzapine. The peripheral blood mononuclear cells were separated from whole blood by Ficoll-hypaque; the total cellular RNA was extracted and the cDNA was synthesized. This process was followed by real-time polymerase chain reaction using primer pairs specific for five dopamine receptor mRNAs and β-actin as internal control. The results show the presence of all types of dopamine receptor in lymphocytes. Dopamine receptor gene expression profile in dopamine receptor D2 gene and dopamine receptor D4 gene showed significant changes that were correlated with the type of treatment and Clinical Global Impressions score improvement. In conclusion, the present study shows that human lymphocytes express dopamine receptor D1–D5 genes. Moreover, investigated dopamine receptors gene expression in peripheral blood mononuclear cells of schizophrenic patients correlated with clinical symptom improvement.

Successful treatment with risperidone increases 5-HT 3A receptor gene expression in patients with paranoid schizophrenia - data from a prospective study

INTRODUCTION

The relationship between peripheral 5-HT3A receptor mRNA level and risperidone efficiency in paranoid schizophrenia patients is still unknown.

METHODS

A total 52 first-episode and drug-naive paranoid schizophrenia patients who were treated with risperidone and 53 matched healthy controls were enrolled. Patients were naturalistically followed up for 8 weeks. Positive and Negative Syndrome Scale (PANSS) was applied to assess symptom severity of the patients at baseline and at the end of 8th week.

RESULTS

There was no difference in 5-HT3A receptor mRNA level between paranoid schizophrenia patients and healthy controls at baseline (p = .24). Among 47 patients who completed 8-week naturalistic follow-up, 37 were responders to risperidone treatment. 5-HT3A receptor mRNA level of paranoid schizophrenia patients did not change in overall patients after 8-week treatment with risperidone (p = .29). However, 5-HT3A receptor mRNA level in responders increased significantly (p = .04), but not in nonresponders (p = .81).

CONCLUSIONS

Successful treatment with risperidone increases 5-HT3A receptor gene expression in patients with paranoid schizophrenia, indicating that 5-HT3A receptor may be involved in the mechanism of risperidone effect.

Intermittent hypoxia initiated plasticity in humans: A multipronged therapeutic approach to treat sleep apnea and overlapping co-morbidities

Over the past three decades exposure to intermittent hypoxia (IH) has generally been considered a stimulus associated with a number of detrimental outcomes. However, there is sufficient evidence to link IH to many beneficial outcomes but they have largely been ignored, particularly in the field of sleep medicine in the United States. Recent reviews have postulated that this apparent contradiction is related to the severity and duration of exposure to IH; mild forms of IH initiate beneficial outcomes while severe forms of IH are coupled to detrimental consequences. In the present review we explore the role that IH has in initiating respiratory plasticity and the potential this form of plasticity has to mitigate obstructive sleep apnea (OSA) in humans. In taking this approach, we address the possibility that IH could serve as an adjunct therapy coupled with continuous positive airway pressure (CPAP) to treat OSA. Our working hypothesis is that exposure to mild IH leads to respiratory plasticity that manifests in increased stability of the upper airway, which could ultimately reduce the CPAP required to treat OSA. In turn, this reduction could increase CPAP compliance and extend the length of treatment each night, which might improve the magnitude of outcome measures. Improved treatment compliance coupled with the direct effect that IH has on numerous overlapping conditions (i.e. asthma, chronic obstructive pulmonary disease, spinal cord injury) may well lead to substantial improvements that exceed outcomes following treatment with CPAP alone. Overall, this review will consider evidence from the published literature which suggests that IH could serve as an effective multipronged therapeutic approach to treat sleep apnea and its overlapping co-morbidities.

Activation of mouse bronchopulmonary C-fibres by serotonin and allergen-ovalbumin challenge

Abstract  The effect of serotonin on capsaicin-sensitive vagal C-fibre afferent nerves was evaluated in an ex vivo vagally innervated mouse lung preparation. Action potentials arising from receptive fields in the lungs were recorded with an extracellular electrode positioned in the nodose/jugular ganglion. Among the 62 capsaicin-sensitive C-fibres studied (conduction velocity ∼0.5 m s(-1)), 71% were of the nodose phenotype and 29% of the jugular phenotype. The nodose C-fibres responded strongly to serotonin and this effect was blocked with the 5-HT3-receptor antagonist ondansetron. Using single cell RT-PCR, we noted that the vast majority of nodose neurons retrogradely labelled from the lung, expressed 5-HT3 receptor mRNA. The jugular C-fibres also responded strongly to serotonin with action potential discharge, but this effect was not inhibited by ondansetron. Lung-specific jugular neurons did not express 5-HT3 receptor mRNA but frequently expressed 5-HT1 or 5-HT4 receptor mRNA. Mast cells are the major source of serotonin in healthy murine airways. Ovalbumin-induced mast cell activation in actively sensitized lungs caused action potential discharge in jugular but not nodose C-fibres. The data show that vagal C-fibres in the respiratory tract of the mouse are strongly activated by serotonin. Depending on the C-fibre subtype both 5-HT3 and non-5-HT3 mechanisms are involved.

SEROTONERGIC MECHANISMS IN AMYOTROPHIC LATERAL SCLEROSIS

Serotonin (5-HT) has been intimately linked with global regulation of motor behavior, local control of motoneuron excitability, functional recovery of spinal motoneurons as well as neuronal maturation and aging. Selective degeneration of motoneurons is the pathological hallmark of amyotrophic lateral sclerosis (ALS). Motoneurons that are preferentially affected in ALS are also densely innervated by 5-HT neurons (e.g., trigeminal, facial, ambiguus, and hypoglossal brainstem nuclei as well as ventral horn and motor cortex). Conversely, motoneuron groups that appear more resistant to the process of neurodegeneration in ALS (e.g., oculomotor, trochlear, and abducens nuclei) as well as the cerebellum receive only sparse 5-HT input. The glutamate excitotoxicity theory maintains that in ALS degeneration of motoneurons is caused by excessive glutamate neurotransmission, which is neurotoxic. Because of its facilitatory effects on glutaminergic motoneuron excitation, 5-HT may be pivotal to the pathogenesis and therapy of ALS. 5-HT levels as well as the concentrations 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of 5-HT, are reduced in postmortem spinal cord tissue of ALS patients indicating decreased 5-HT release. Furthermore, cerebrospinal fluid levels of tryptophan, a precursor of 5-HT, are decreased in patients with ALS and plasma concentrations of tryptophan are also decreased with the lowest levels found in the most severely affected patients. In ALS progressive degeneration of 5-HT neurons would result in a compensatory increase in glutamate excitation of motoneurons. Additionally, because 5-HT, acting through presynaptic 5-HT1B receptors, inhibits glutamatergic synaptic transmission, lowered 5-HT activity would lead to increased synaptic glutamate release. Furthermore, 5-HT is a precursor of melatonin, which inhibits glutamate release and glutamate-induced neurotoxicity. Thus, progressive degeneration of 5-HT neurons affecting motoneuron activity constitutes the prime mover of the disease and its progression and treatment of ALS needs to be focused primarily on boosting 5-HT functions (e.g., pharmacologically via its precursors, reuptake inhibitors, selective 5-HT1A receptor agonists/5-HT2 receptor antagonists, and electrically through transcranial administration of AC pulsed picotesla electromagnetic fields) to prevent excessive glutamate activity in the motoneurons. In fact, 5HT1A and 5HT2 receptor agonists have been shown to prevent glutamate-induced neurotoxicity in primary cortical cell cultures and the 5-HT precursor 5-hydroxytryptophan (5-HTP) improved locomotor function and survival of transgenic SOD1 G93A mice, an animal model of ALS.

Gene expression changes in peripheral mononuclear cells from schizophrenic patients treated with a combination of antipsychotic with fluvoxamine

Antipsychotic treatment combined with Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant can improve negative symptoms in schizophrenic patients that are unresponsive to antipsychotic drugs alone. The mechanism of this therapeutic effect is not clear. The current study examined molecular changes induced by the combined treatment in human peripheral mononuclear cells (PMC) in order to get insight into its mechanism of action. Gene expression profile of PMC from antipsychotic-treated patients was examined before addition of the SSRI fluvoxamine, and 3 and 6 weeks after. Gene expression patterns screened with a cDNA array, comprising 1176 genes, revealed homologous changes in a range of transcripts related to G-protein coupled receptors (GPCR). Genes related to GPCR-family were assayed using customized cDNA array and the results verified by real-time RT-PCR. The mRNA expression of chemokine receptors, IL8RA and CCR1, and of RGS7 was significantly down-regulated following fluvoxamine augmentation. The clinical assessments showed improvement in negative symptoms following the combined treatment. The transcriptional analysis suggests that the therapeutic mechanism of the combined antipsychotic-fluvoxamine treatment may involve genes associated with G-protein coupled receptors (GPCR). Our findings suggest that gene expression changes in PMC may be useful in investigating the mechanism of drug action in schizophrenia.

Expression of mRNA for multiple serotonin (5-HT) receptor types/subtypes by the peripheral blood mononuclear cells of rhesus macaques

To find out whether rhesus macaque peripheral blood mononuclear cells (PBMCs) express mRNA for 5-HT receptors, blood samples from normal healthy rhesus monkeys were used to isolate PBMCs by Ficoll-paque density gradient centrifugation. Total RNA was extracted from MT-2 cells, Hut-78 cells, naive or phytohemagglutinin (PHA) stimulated human and monkey PBMCs. One tube RT-PCR was performed using primers specific for human 5-HT1A, 5-HT1B, 5-HT1E, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT4, 5-HT6, and 5-HT7 receptors. Amplicons of expected sizes were obtained from human cell lines as well as both human and monkey PBMCs. Both PHA stimulated human and monkey PBMCs express mRNAs for 5-HT1A, 5-HT1B, 5-HT1E, 5-HT2A, 5-HT3, 5-HT4, 5-HT6 receptor types/subtypes. However, mRNAs for 5-HT1B, 5-HT1E and 5-HT2A cannot be confidently detected in some of the PBMC samples without PHA stimulation. 5-HT2B and 5-HT7 receptor mRNA was not detected in most of the samples and 5-HT2C receptor mNRA was not detected at all. FACS analysis revealed that CD3+ lymphocyte increased more than 20% among lymphocytes in the PHA stimulated PBMCs. These data indicate that similar to human PBMC, rhesus macaque PBMC may express multiple types of 5-HT receptors and the expression profile could change after PHA stimulation due to either the changes in cell composition or changes in gene transcription level. This provided a basis for further studies on the neuroimmunomodulatory interactions of 5-HT in rhesus macaques.

Effects of an intense training on functional activity of 5-HT(1B) receptors in human peripheral blood lymphocytes

Serotonin (5-HT) is a neurotransmitter and an immune modulator. At the periphery, the serotonergic system appears to possess a regulatory activity via 5-HT 1B receptors. The present study investigated the effects of a 5-day military course following 3 weeks of combat training on the functional activity of 5-HT 1B/1D receptors in peripheral blood lymphocytes of male soldiers. The results of [35S]GTPgammaS binding assays showed that h5-HT 1B/1D receptors were desensitized after the training program, although serum 5-HT was unchanged. These data suggest the existence of a control on T cells mediated through h5-HT 1B/1D receptors leading cytokine production modulation after a physical training.

Effects of serotonin and serotonergic agonists and antagonists on the production of tumor necrosis factor alpha and interleukin-6

Serotonin (5-HT) is a neurotransmitter and immune modulator. The effect of 5-HT on the production of cytokines by human macrophages and lymphocytes is poorly recognized. In the present article we examine the role of 5-HT in modulating the production of two pro-inflammatory cytokines, i.e. interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNFalpha), as well as the role of 5-HT(1A) and 5-HT(2) receptors in this process. The specific aims were to examine the effects of 5-HT, p-chlorophenylalanine (PCPA), a 5-HT depleting agent, flesinoxan, a 5-HT(1A) agonist, m-chlorophenylpiperazine (mCPP), a 5-HT(2B/2C) agonist, and ritanserin, a 5-HT(2A/2C) antagonist, on the production of the above cytokines. We found that: (1) 5-HT, 15 microg/ml, significantly decreased IL-6 and TNFalpha production; (2) pCPA, 5 microM, significantly suppressed the production of IL-6 and TNFalpha; and (3) mCPP, 2.7 microg/ml, significantly increased the production of IL-6 and TNFalpha. It is concluded that intracellular 5-HT is necessary for optimal synthesis of IL-6 and TNFalpha; 5-HT in physiological concentrations may increase IL-6 and TNFalpha production by stimulating 5-HT(2) receptors; and extracellular 5-HT concentrations above the baseline physiological levels may suppress the production of the above cytokines.

Evidence for serotonin influencing the thalamic infiltration of mast cells in rat

Serotonin (5-HT) is involved in neuroimmunomodulation. We analyzed the effects of sumatriptan, a 5-HT(1B/1D) receptor agonist, and ondansetron, a 5-HT(3) receptor antagonist, on thalamic mast cell (TMC) population, the only immunocytes known to infiltrate the brain in physiological conditions. Only sumatriptan was effective, significantly increasing TMC numbers versus controls, and especially those containing 5-HT. 5-HT(1B) receptors are concentrated in the median eminence on non-serotonergic axonal endings, probably hypothalamic terminal fibers, involved in hypothalamic-pituitary neuroendocrine modulating processes. TMC variations could reflect serotonergic actions on these fibers. TMCs would thus be cellular interfaces mediating immune action in the nervous system in relation with the hormonal status of the organism.

The effect of natural clinoptilolite on the serotonergic receptors in the brain of mice with mammary carcinoma

The ex vivo effect of tribomechanically micronized zeolite (MZ) on the binding of 3H-8-OH-DPAT to 5-HT(1A) and 3H-5-HT to 5-HT(1B) receptors was investigated in the brain of nontumorous (control) and mammary carcinoma bearing female mice. During 14 and 28 days mice were fed with standard food, standard food supplemented with 25% of MZ, or standard food supplemented with 25% of non tribomechanically micronized zeolite (non-MZ). A reduced binding of 3H-8-OH-DPAT to 5-HT(1A) receptors in mammary carcinoma bearing mice was found when compared to control mice fed with standard food for 28 days, suggesting a time dependent alteration of 5-HT(1A) receptors in mammary carcinoma. The addition of MZ for 28 days in these mice abolished the decrease in 5-HT(1A) receptors binding, indicating a possible beneficial effect of MZ, at least on 5-HT(1A) receptors in mammary carcinoma bearing mice. The preliminary data show that MZ administered as a food supplement (25%) for 14 days induced a transient decrease in the binding of 3H-5-HT to brain 5-HT(1B) receptors only in control, but not in tumor-bearing mice, that disappeared after 28 days of MZ-supplemented food administration. The mechanism of the indirect action of MZ on the brain serotonergic receptors might be achieved by the alterations in the electrolytes balance, and/or by the regulation of the immune system.

5-HT moduline: an endogenous inhibitor of 5-HT(1B/1D)-mediated contraction in pulmonary arteries

(1) 5-HT moduline (5-HTm) is tetrapeptide (Leu-Ser-Ala-Leu) previously shown to act as a specific endogenous antagonist to central 5-HT(1B/1D) receptors. Its effects were investigated in rat and rabbit pulmonary arteries (PAs). (2) In rabbit PAs, contractile responses to the 5-HT(1B/1D) receptor agonist 5-carboxamidotryptamine (5-CT) were inhibited by 1 and 10 micro M 5-HTm in a non-competitive fashion with the maximum contractile response (E(max), per cent of response to 50 mM KCl) being reduced from 65.6+/-7% (n=6) to 39.7+/-6.5% (n=6) and 25.2+/-7.9 (n=4), respectively. The ability of 5-HTm to inhibit responses to 5-CT was increased by the aminopeptidase inhibitor bestatin (10 micro M). (3) In the rabbit PAs, the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methylester (L-NAME) potentiated responses to 5-CT (E(max): 106+/-22.5 (n=4)) and this response was also inhibited by 10 micro M 5-HTm (E(max): 38+/-13% (n=8)). (4) 5-HTm (10 micro M) inhibited responses to 5-CT in rat PAs, the E(max) being reduced from 24.8+/-4.1% (n=7) to 15.5+/-3.7% (n=9). 5-HTm induced relaxation of 5-CT-pre-constricted rat PAs with a pIC(50) of 9.0+/-0.6 (n=9). (5) In PAs from chronic hypoxic, pulmonary hypertensive rats, the maximum response to 5-CT was increased to 80+/-8.5% (n=11). 5-HTm reduced this response to 34.4+/-6.3% (n=12). L-NAME markedly inhibited the ability of 5-HTm to inhibit responses to 5-CT (E(max) before 5-HTm: 100.5+/-16% (n=5), E(max) after 5-HTm: 107+/-11.3% (n=4)). (6) In conclusion we show here for the first time that 5-HTm is a non-competitive inhibitor of 5-HT(1B/1D) receptor-mediated constriction in PAs. In rat PAs, L-NAME can inhibit this effect of 5-HTm.

Serotonergic regulation of somatosensory cortical development: lessons from genetic mouse models

Monoaminergic neurotransmitter systems appear early during embryogenesis, suggesting that they could play important roles in brain development. Accumulated evidence indicates that serotonin (5-hydroxytryptamine, 5-HT) regulates neural as well as nonneural development, including early aspects of embryonic development, differentiation of neuronal progenitors, and morphogenesis of the craniofacial region, heart and limb. Recent studies using monoamine oxidase-A (MAO-A), 5-HT transporter, vesicular monoamine transporter-2 (VMAT2) and 5-HT1B receptor single, double and triple knockout mice have provided evidence that the serotonergic system plays important roles in barrel field formation in the developing somatosensory cortex. Here we review evidence from these genetic mouse models and, based on the accumulated evidence, propose a testable model for future studies of mechanisms underlying serotonergic regulation of cortical development.

The negative immunoregulatory effects of serotonin (5-HT) moduline, an endogenous 5-HT1B receptor antagonist with anti-anxiety properties

BACKGROUND

Serotonin (5-HT) has negative immunoregulatory effects by reducing the interferon-gamma (IFNgamma)/interleukin-10 (IL-10) production ratio by stimulated immune cells. Leukocytes have functional 5-HT1B receptors. 5-HT moduline, an endogenous 5-HT1B receptor antagonist, may antagonize the 5-HT1B agonist-induced proliferation of immune cells.

AIMS

To examine the effects of 5-HT moduline on the stimulated production of IFNgamma, tumor necrosis factor alpha (TNFalpha) and IL-10.

RESULTS

5-HT moduline, 10(-6) M and 10(-5)M, significantly reduced the production of IFNgamma and the IFNgamma/IL-10 ratio. 5-HT moduline 10(-5)M significantly reduced the production of TNFalpha. The combination of 5-HT, 15 microg/mL, with 5-HT moduline, 10(-6)M and 10(-5)M, further decreases the IFNgamma/IL-10 production ratio.

INTERPRETATION

5-HT moduline has negative immunoregulatory effects.

Association between allergy and anxiety disorders in youth

OBJECTIVE

Studies have documented associations between anxiety disorders and allergy in adults, but these associations have not been studied extensively in children. The objective of this study is to examine the associations between allergy and six anxiety disorders (AD) in youth.

METHOD

This is a data analysis of two epidemiologic-services studies: (i) alternative service use patterns of youth with serious emotional disturbance (n = 936), and (ii) methods for the epidemiology of child and adolescent mental disorders (n = 1285). Child psychiatric diagnoses were measured by the diagnostic interview schedule for children. Allergy was assessed by the service utilization and risk factors interview.

RESULTS

Among ADs, the strongest association found was between allergy and panic disorder (adjusted odds ratio 5.0; p < or = 0.001). Associations of allergy and the other ADs do not seem to be clinically significant.

CONCLUSIONS

Findings suggest that in some patients panic disorder may be associated with hypersensitivity of immune system. Panic disorder should be considered in anxious children reporting allergy when no organic cause of allergy is found, and likewise allergy should considered in children with panic disorder.

Could the 5-HT1B receptor inverse agonism affect learning consolidation?

Diverse evidence indicates that, the 5-HT system might play a role in learning and memory, since it occurs in brain areas mediating such processes and 5-HT drugs modulate them. Hence in this work, in order to explore further 5-HT involvement on learning and memory 5-HT1B receptors' role is investigated. Evidence indicates that SB-224289 (a 5-HT1B receptor inverse agonist) post-training injection facilitated learning consolidation in an associative autoshaping learning task, this effect was partially reversed by GR 127935 (a 5-HT1B/1D receptor antagonist), but unaffected by MDL 100907 (a 5-HT2A receptor antagonist) or ketanserin (a 5-HT1D/2A/7 receptor antagonist) at low doses. Moreover, SB-224289 antagonized the learning deficit produced by TFMPP (a 5-HT1A/1B/1D/2A/2C receptor agonist), GR 46611 (a 5-HT1A/1B/1D receptor agonist), mCPP (a 5-HT2A/2C/3/7 receptor agonist/antagonist) or GR 127935 (at low dose). SB-224289 did not alter the 8-OH-DPAT (a 5-HT1A/7 receptor agonist) learning facilitatory effect. SB-224289 eliminated the deficit learning produced by the anticholinergic muscarinic scopolamine or the glutamatergic antagonist dizocilpine. Administration of both, GR 127935 (5mg/kg) plus ketanserin (0.01 mg/kg) did not modify learning consolidation; nevertheless, when ketanserin dose was increased (0.1-1.0mg/kg) and SB-224289 dose was maintained constant, a learning facilitation effect was observed. Notably, SB-224289 at 1.0mg/kg potentiated a subeffective dose of the 5-HT1B/1D receptor agonist/antagonist mixed GR 127935, which facilitated learning consolidation and this effect was abolished by ketanserin at a higher dose. Collectively, the data confirm and extend the earlier findings with GR 127935 and the effects of non-selective 5-HT(1B) receptor agonists. Clearly 5-HT1B agonists induced a learning deficit which can be reversed with SB-224289. Perhaps more importantly, SB-224289 enhances learning consolidation when given alone and can reverse the deficits induced by both cholinergic and glutamatergic antagonist. Hence, 5-HT1B receptor inverse agonists or antagonists could represent drugs for the treatment of learning and memory dysfunctions.