5-HT1A Expression Research Articles

Neurobiología de la depresión mayor y de su tratamiento farmacológico

Resumen Introducción. La depresión mayor (DM) se debe a la interacción de factores ambientales, genéticos y epigenéticos, que atenúan la transmisión monoaminérgica en el cerebro. Sin embargo, poco se conoce sobre los mecanismos fisiopatológicos que subyacen a ella. Objetivo. Proponer una visión integral sobre la fisiopatología de la DM y los mecanismos de acción de los fármacos antidepresivos. Método. Se empleó la base PubMed para la búsqueda bibliográfica. La mayoría son investigaciones experimentales y estudios de genética molecular o de imágenes cerebrales en humanos. Resultados. La DM se asocia con: i) menor volumen de la corteza cingulada anterior; ii) hiper-metabolismo del área Cg25; iii) menor expresión del receptor 5-HT1A; iv) mayor expresión de la monoamino oxidasa A. Algunos polimorfismos están asociados a la fisiopatología. El estrés crónico reduce la expresión del 5-HT1A. Los antidepresivos atenúan el hiper-metabolismo del área Cg25, estimulan la neurogénesis y activan la vía del AMPc. Encontramos que la imipramina aumenta y reduce la expresión de Gαs y Gαz, respectivamente (datos sin publicar). Discusión y conclusión. El déficit en la transmisión monoaminérgica puede deberse a: i) el polimorfismo G1463A en el gen de la enzima hTPH2 que reduce la síntesis de serotonina; ii) el polimorfismo C(-1019)G en el gen del receptor 5-HT1A, aumentando su transcripción en el rafé e implicando menor liberación del neurotransmisor; iii) mayor degradación de las monoaminas. La menor expresión del receptor 5-HT1A se discute considerando su acción inhibitoria en la corteza prefrontal. Los cambios en la expresión de Gαs y Gαz coinciden con la estimulación de la vía del AMPc.

Electroacupuncture Restores 5-HT System Deficit in Chronic Mild Stress-Induced Depressed Rats.

Objective. The current study is designed to investigate the antidepressant efficacy of electroacupuncture (EA) treatment by evaluating its effect on the synthesis, metabolism, reuptake, and receptors of 5-hydroxytryptamine (5-HT), so as to clarify the molecular mechanisms of EA for antidepression. Materials and Methods. Solitary combined with the chronic unpredictable mild stress (CUMS) was used to establish the rat model with depression. The depressed rats were supplied with EA treatment for 4 weeks, and the behavior change and the following indices including 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), monoamine oxidase A (MAO-A), tryptophan hydroxylase (TPH), 5-HT transporter (SERT), 5-HT1A, and 5-HT2A in hippocampus and prefrontal cortex were examined. Results. EA treatment significantly improved the behavior of rats and increased 5-HT level in hippocampus of depressed rats. Similarly, EA treatment could significantly increase protein and mRNA expression of TPH and 5-HT1A during 5-HT synthesis process in hippocampus of depressed rats. However, EA treatment had no effect on the activity of MAO-A and the expression of SERT protein and mRNA. Conclusion. Antidepressant efficacy of EA treatment can be accomplished through enhancing 5-HT synthesis, upregulating 5-HT1A level, and improving 5-HT content in brain and synaptic gaps.

Allergic sensitization modifies the pulmonary expression of 5-hydroxytryptamine receptors in guinea pigs

There is mounting evidence that 5-hydroxytryptamine (5-HT) plays a role in asthma. However, scarce information exists about the pulmonary expression of 5-HT receptors and its modification after allergic sensitization. In the present work, we explored the expression of 5-HT1A, 5-HT2A, 5-HT3, 5-HT4, 5-ht5a, 5-HT6, and 5-HT7 receptors in lungs from control and sensitized guinea pigs through qPCR and Western blot. In control animals, mRNA from all receptors was detectable in lung homogenates, especially from 5-HT2A and 5-HT4 receptors. Sensitized animals had decreased mRNA expression of 5-HT2A and 5-HT4 receptors and increased that of 5-HT7 receptor. In contrast, they had increased protein expression of 5-HT2A receptor in bronchial epithelium and of 5-HT4 receptor in lung parenchyma. The degree of airway response to the allergic challenge was inversely correlated with mRNA expression of the 5-HT1A receptor. In summary, our results showed that major 5-HT receptor subtypes are constitutively expressed in the guinea pig lung, and that allergic sensitization modifies the expression of 5-HT2A, 5-HT4, and 5-HT7 receptors.

Ovarian hormones ameliorate memory impairment, cholinergic deficit, neuronal apoptosis and astrogliosis in a rat model of Alzheimer's disease

Ovarian hormones, including progesterone (P4) and 17 β-estradiol (E2), have been shown to affect memory functions; however, the underlying mechanism whereby ovarian hormone replacement therapy may decrease the risk of Alzheimer's disease (AD) is currently unclear. The present study aimed to investigate the effects of P4 and E2 on spatial and learning memory in an ovariectomized rat model of AD. β-amyloid (Aβ) or saline were stereotaxically injected into the hippocampus of the rats and, after 1 day, ovariectomy or sham operations were performed. Subsequently, the rats were treated with P4 alone, E2 alone, or a combination of P4 and E2. Treatment with E2 and/or P4 was shown to improve the learning and memory functions of the rats, as demonstrated by the Morris water maze test. In addition, treatment with E2 and P4 was associated with increased expression levels of choline acetyltransferase and 5-hydroxytryptamine receptor 2A (5-HT2A), and decreased expression levels of the glial fibrillary acidic protein in the hippocampus of the rats. Furthermore, E2 and P4 treatment significantly attenuated neuronal cell apoptosis, as demonstrated by terminal deoxynucleotidyl transferase dUTP nick end labeling assays; thus suggesting that the ovarian hormones were able to protect against Aβ-induced neuronal cell toxicity. The results of the present study suggested that the neuroprotective effects of P4 and E2 were associated with amelioration of the cholinergic deficit, suppression of apoptotic signals and astrogliosis, and upregulation of 5-HT2A expression levels. Therefore, hormone replacement therapy may be considered an effective strategy for the treatment of patients with cognitive disorders and neurodegenerative diseases.

Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats

Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation.

Chronic mild stress and antidepressant treatment alter 5-HT1A receptor expression by modifying DNA methylation of a conserved Sp4 site

The serotonin 1A receptor (5-HT1A), a critical regulator of the brain serotonergic tone, is implicated in major depressive disorder (MDD) where it is often found to be dys-regulated. However, the extent to which stress and antidepressant treatment impact 5-HT1A expression in adults remains unclear. To address this issue, we subjected adult male BALB/c mice to unpredictable chronic mild stress (UCMS) to induce a depression-like phenotype that was reversed by chronic treatment with the antidepressant imipramine. In prefrontal cortex (PFC) and midbrain tissue, UCMS increased 5-HT1A RNA and protein levels, changes that are expected to decrease the brain serotonergic activity. The stress-induced increase in 5-HT1A expression was paralleled by a specific increase in DNA methylation of the conserved −681 CpG promoter site, located within a Sp1-like element. We show that the −681 CpG site is recognized and repressed by Sp4, the predominant neuronal Sp1-like factor and that Sp4-induced repression is attenuated by DNA methylation, despite a stress-induced increase in PFC Sp4 levels. These results indicate that adult life stress induces DNA methylation of a conserved promoter site, antagonizing Sp4 repression to increase 5-HT1A expression. Chronic imipramine treatment fully reversed the UCMS-induced increase in methylation of the −681 CpG site in the PFC but not midbrain of stressed animals and also increased 5-HT1A expression in the PFC of control animals. Incomplete reversal by imipramine of stress-induced changes in 5-HT1A methylation and expression indicates a persistence of stress vulnerability, and that sustained reversal of behavioral impairments may require additional pathways.

Effects of prenatal stress and neonatal handling on anxiety, spatial learning and serotonergic system of male offspring mice

Environmental factors during perinatal period have various effects on behavior. The present study examined the effects of prenatal stress and neonatal handling on anxiety and spatial learning of offspring. Prenatal stress increased anxiety-related behavior of adult offspring, whereas neonatal handling had no effect. In contrast, spatial learning was not affected by prenatal stress, but improved by neonatal handling in both prenatally stressed and non-stressed mice. Next, to elucidate possible brain mechanisms mediating effects of environmental factors on behavior, we focused on serotonin (5-HT) system in the frontal cortex and hippocampus which is involved in anxiety and learning. We examined effects of environmental factors on the mRNA expression of 5-HT1A, 5-HT2A and 5-HT2C receptors in the frontal cortex and hippocampus during postnatal period and adulthood. Both prenatal stress and neonatal handling altered the mRNA expression of 5-HT receptors. These effects were dependent on environmental factors, brain regions and developmental stages. In summary, the present study revealed that prenatal stress and neonatal handling had differential effects on anxiety and spatial learning of offspring, and concomitantly the expression of 5-HT receptors. It was also shown that the effects of prenatal stress on 5-HT system were recovered partially by neonatal handling.

Different stress-related gene expression in depression and suicide

ObjectiveSuicide occurs in some, but not all depressed patients. So far, it remains unknown whether the studied stress-related candidate genes change in depression, suicide or both. The prefrontal cortex (PFC) is involved in, among other things, impulse control and inhibitory behavior and plays an important role in both suicide and depression. MethodsWe have employed qPCR to study 124 anterior cingulate cortex (ACC) and dorsolateral PFC (DLPFC) brain samples, obtained from two brain banks, from: i) young depressed patients (average age 43 years) who committed suicide (MDD-S) and depressed patients who died from causes other than suicide (MDD-NS) and from ii) elderly depressed patients (average age 75 years) who did not commit suicide (DEP). Both cohorts were individually matched with non-psychiatric non-suicide control subjects. We determined the transcript levels of hypothalamic–pituitary–adrenal axis-regulating molecules (corticotropin-releasing hormone (CRH), CRH receptors, CRH binding protein, mineralocorticoid receptor/glucocorticoid receptor), transcription factors that regulate CRH expression, CRH-stimulating cytokines, chaperone proteins, retinoid signaling, brain-derived neurotrophic factor and tropomyosin-related kinase B, cytochrome proteins, nitric oxide synthase (NOS) and monoamines. ResultsIn the MDD-S group, expression levels of CRH and neuronal NOS-interacting DHHC domain-containing protein with dendritic mRNA (NIDD) were increased. Other changes were only present in the DEP group, i.e. decreased NIDD, and increased and 5-hydroxytryptamine receptor 1A (5-HT1A) expression levels. Changes were found to be more pronounced in the anterior cingulate cortex than in the dorsolateral PFC. ConclusionDepressed patients who committed suicide have different gene expression patterns than depressed patients who died of causes other than suicide.

Toll-like receptors 2 and 4 modulate the contractile response induced by serotonin in mouse ileum: analysis of the serotonin receptors involved.

Microbiota through toll-like receptors (TLR) may regulate gastrointestinal motility by activating neuroendocrine mechanisms. We evaluated the influence of TLR2 and TLR4 in the spontaneous contractions and serotonin (5-HT)-induced motor response in mouse ileum, and the 5-HT receptors involved. Muscle contractility studies to evaluate the spontaneous intestinal motility and the response to 5-HT were performed in the ileum from wild type (WT), TLR2(-/-), TLR4(-/-), and TLR2/4 double knockout (DKO) mice. 5-HT receptor expression was determined by real-time PCR. The amplitude of spontaneous contractions in ileum was higher in TLR2(-/-), TLR4(-/-), and TLR2/4 DKO mice with respect to WT. 5-HT evoked concentration-dependent contractile responses in the ileum from TLR2(-/-) and TLR4(-/-) mice similar to WT. However, in ileum from TLR2/4 DKO, 5-HT did not induce any contractile response. Expression of 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT3 receptors resulted increased in ileum from TLR4(-/-) and TLR2/4 DKO. Expression of the 5-HT4 receptor was diminished in TLR2(-/-) and TLR2/4 DKO. High levels of 5-HT7 receptor expression were found in TLR2/4 DKO but not in TLR2(-/-) or TLR4(-/-). In WT and TLR4(-/-), 5-HT2, 5-HT3, 5-HT4, and 5-HT7 receptor antagonists reduced the contractile response evoked by 5-HT. In TLR2(-/-) mice, 5-HT4 antagonist did not reduce the 5-HT response. In TLR2/4 DKO mice, only 5-HT4 and 5-HT7 receptor antagonists reduced the relaxing response induced by 5-HT. TLR2 and TLR4 signaling may modulate the spontaneous contractions and the serotonin contractile response by acting on 5-HT2, 5-HT3, 5-HT4, and 5-HT7 receptors.

Disruption of 5-HT1A function in adolescence but not early adulthood leads to sustained increases of anxiety

Current evidence suggests that anxiety disorders have developmental origins. Early insults to the circuits that sub-serve emotional regulation are thought to cause disease later in life. Evidence from studies in mice demonstrate that the serotonergic system in general, and serotonin 1A (5-HT1A) receptors in particular, are critical during the early postnatal period for the normal development of circuits that subserve anxious behavior. However, little is known about the role of serotonin signaling through 5-HT1A receptors between the emergence of normal anxiety behavior after weaning, and the mature adult phenotype. Here, we use both transgenic and pharmacological approaches in male mice, to identify a sensitive period for 5-HT1A function in the stabilization of circuits mediating anxious behavior during adolescence. Using a transgenic approach we show that suppression of 5-HT1A receptor expression beginning in early adolescence results in an anxiety-like phenotype in the open field test. We further demonstrate that treatment with the 5-HT1A antagonist WAY 100,635 between postnatal day (P)35 and P50, but not at later timepoints, results in altered anxiety in ethologically based conflict tests like the open field test and elevated plus maze. This change in anxiety behavior occurs without impacting behavior in the more depression-related sucrose preference test or forced swim test. The treatment with WAY 100,635 does not affect adult 5-HT1A expression levels, but leads to increased expression of the serotonin transporter in the raphe, along with enhanced serotonin levels in both the prefrontal cortex and raphe that correlate with the behavioral changes observed in adult mice. This work demonstrates that signaling through 5-HT1A receptors during adolescence (a time when pathological anxiety emerges), but not early adulthood, is critical in regulating anxiety setpoints. These data suggest the possibility that brief interventions in the serotonergic system during adolescence could lead to profound and enduring changes in physiology and behavior.

Serotonin-mediated modulation of hypoxia-induced intracellular calcium responses in glomus cells isolated from rat carotid body

In the present study, we examined serotonin (5-HT)-induced intracellular Ca2+ ([Ca2+]i) responses to hypoxia in glomus cells isolated from carotid body (CB) of the rat. 5-HT did not induce any [Ca2+]i responses in clustered glomus cells during normoxia (21% O2), whereas, the perfusion of hypoxic solution (1% O2) induced repetitive increases in [Ca2+]i in the same specimens. The frequency and magnitude of hypoxia-induced [Ca2+]i changes observed in the glomus cells were enhanced in the presence of 5-HT, and this response was inhibited by the 5-HT2 receptor antagonist, ketanserin. Furthermore, RT-PCR analysis detected the expression of 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT3A, and 5-HT3B receptor mRNAs in extracts of the CB. These results suggest that 5-HT increases hypoxia-induced [Ca2+]i responses in glomus cells. 5-HT may elevate hypoxic responses in glomus cells in order to increase chemosensory activity of the CB.

Tryptophan hydroxylase and serotonin receptor 1A expression in the retina of the sea lamprey

The dual development of the retina of lampreys is exceptional among vertebrates and offers an interesting EvoDevo (evolutionary developmental biology) model for understanding the origin and evolution of the vertebrate retina. Only a single type of photoreceptor, ganglion cell and bipolar cell are present in the early-differentiated central retina of lamprey prolarvae. A lateral retina appears later in medium-sized larvae (about 3 years after hatching in the sea lamprey), growing and remaining largely neuroblastic until metamorphosis. In this lateral retina, only ganglion cells and optic fibers differentiate in larvae, whereas differentiation of amacrine, horizontal, photoreceptor and bipolar cells mainly takes place during metamorphosis, which gives rise to the adult retina. Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter found in the retina of vertebrates whose synthesis is mediated by the rate-limiting enzyme tryptophan hydroxylase (TPH). TPH is also the first enzyme in the biosynthetic pathways of melatonin in photoreceptor cells. The serotonin 1A receptor (5-HT1A) is a major determinant of the activity of both serotonergic cells and their targets due to its pre- and post-synaptic location. Here, we report the developmental pattern of expression of tph and 5-ht1a transcripts in the sea lamprey retina by means of in situ hybridization. In larvae, strong tph mRNA signal was observed in photoreceptors and putative ganglion cells of the central retina, and in some neuroblasts of the lateral retina. In adults, strong tph expression was observed in bipolar, amacrine and ganglion cells and in photoreceptors. In the prolarval (central) retina, all the differentiated retinal cells expressed 5-ht1a transcripts, which were not observed in undifferentiated cells. In larvae, photoreceptors, bipolar cells and ganglion cells in the central retina, and neuroblasts in the lateral retina, showed 5-ht1a expression. In the adult retina, expression of 5-ht1a transcript was mainly observed in the myoid region of both short and long photoreceptors, and was also observed in bipolar, amacrine and ganglion cells. Some 5-HT-immunoreactive amacrine cells have already been reported in the adult lamprey retina. Our study supports the serotonergic phenotype of these amacrine cells of lampreys and also suggests that other retinal neurons could synthesize serotonin at levels not detectable by immunohistochemistry. The expression of the tph transcript in retinal photoreceptors of lampreys strongly suggests that they synthesize melatonin and that this pathway appeared early and has been conserved throughout evolution in vertebrates. The expression of tph and 5-ht1a in neuroblasts also indicates that serotonin might be playing developmental roles in the larval lamprey retina.

Effect of prenatal stress on memory, nicotine withdrawal and 5HT1A expression in raphe nuclei of adult rats

Maternal distress has often been associated with cognitive deficiencies and drug abuse in rats. This study examined these behavioral effects in offspring of mothers stressed during gestation. To this end, pregnant dams were subjected to daily electric foot shocks during the last 10 days of pregnancy. We measured litter parameters and body weights of the descendants after weaning (21 days) and at adulthood (80 days). Afterwards, prenatally stressed and control rats’ performances in the novel object recognition test were compared in order to evaluate their memory while others underwent the Water consumption test to assess the nicotine withdrawal intensity after perinatal manipulations. Meanwhile, another set of rats were sacrificed and 5HT1A receptors’ mRNA expression was measured in the raphe nuclei by quantitative Real Time PCR. We noticed no significant influence of maternal stress on litter size and body weight right after weaning. However, control rats were heavier than the stressed rats in adulthood. The results also showed a significant decrease in the recognition score in rats stressed in utero compared to the controls. Moreover, a heightened anxiety symptom was observed in the prenatally stressed offspring following nicotine withdrawal. Additionally, the Real Time PCR method revealed that prenatal stress induced a significant decrease in 5HT1A receptors’ levels in the raphe nuclei. Nicotine had a similar effect on these receptors’ expression in both nicotine-treated control and prenatally stressed groups. Taken together, these findings suggest that the cognitive functions and drug dependence can be triggered by early adverse events in rats.

Variation in Dopamine D2 and Serotonin 5-HT2A Receptor Genes is Associated with Working Memory Processing and Response to Treatment with Antipsychotics.

Dopamine D2 and serotonin 5-HT2A receptors contribute to modulate prefrontal cortical physiology and response to treatment with antipsychotics in schizophrenia. Similarly, functional variation in the genes encoding these receptors is also associated with these phenotypes. In particular, the DRD2 rs1076560 T allele predicts a lower ratio of expression of D2 short/long isoforms, suboptimal working memory processing, and better response to antipsychotic treatment compared with the G allele. Furthermore, the HTR2A T allele is associated with lower 5-HT2A expression, impaired working memory processing, and poorer response to antipsychotics compared with the C allele. Here, we investigated in healthy subjects whether these functional polymorphisms have a combined effect on prefrontal cortical physiology and related cognitive behavior linked to schizophrenia as well as on response to treatment with second-generation antipsychotics in patients with schizophrenia. In a total sample of 620 healthy subjects, we found that subjects with the rs1076560 T and rs6314 T alleles have greater fMRI prefrontal activity during working memory. Similar results were obtained within the attentional domain. Also, the concomitant presence of the rs1076560 T/rs6314 T alleles also predicted lower behavioral accuracy during working memory. Moreover, we found that rs1076560 T carrier/rs6314 CC individuals had better responses to antipsychotic treatment in two independent samples of patients with schizophrenia (n=63 and n=54, respectively), consistent with the previously reported separate effects of these genotypes. These results indicate that DRD2 and HTR2A genetic variants together modulate physiological prefrontal efficiency during working memory and also modulate the response to antipsychotics. Therefore, these results suggest that further exploration is needed to better understand the clinical consequences of these genotype-phenotype relationships.

The effects of Acorus tatarinowii Schott on 5-HT concentrations, TPH2 and 5-HT1B expression in the dorsal raphe of exercised rats

Ethnopharmacological relevanceAcorus tatarinowii Schott (Shi Chang Pu) belongs to the family of Acoraceae. The plant is used as an important herb for prolonging life many years in traditional Chinese medicine. It is an ancient herbal tonic nutriment and can be used as anti-fatigue medicine. However, the effects of Acorus tatarinowii Schott on the endurance exercise in relation to central nervous system have not yet been clarified. In this study, the effects of Acorus tatarinowii Schott on treadmill running endurance, 5-HT concentrations, TPH2, 5-HT1B expression in the dorsal raphe of exercised rats were investigated. Materials and methodsSixty adult male Sprague–Dawley rats were randomly divided into six groups: the normal group, the exercise group, the exercise and the rhizomes of Acorus tatarinowii Schott (ATS)(1mg/kg)-treated group, the exercise and ATS (10mg/kg)-treated group, the exercise and ATS (100mg/kg)-treated group, the exercise and caffeine (10mg/kg)-treated group. The effects of Acorus tatarinowii Schott on endurance exercise were determined by the time to exhaustion during treadmill exercise. The detection of 5-HT concentrations in the dorsal raphe was performed by HPLC analysis. The levels of TPH2, 5-HT1A and 5-HT1B expression were measured by western blot analysis and real-time PCR. ResultsWe found Acorus tatarinowii Schott could prolong the time to exhaustion in treadmill exercise and suppress the exercise-induced increase of 5-HT synthesis, TPH2 mRNA and protein expression and prevent the exercise-induced decrease of 5-HT1B mRNA and protein expression in the dorsal raphe. Acorus tatarinowii Schott was as effective as caffeine in prolonging the exhaustion time in treadmill running and in decreasing the exercise-induced increase of 5-HT synthesis and TPH2 mRNA and protein expression and in preventing the exercise-induced decrease of 5-HT1B mRNA and protein expression in the dorsal raphe. ConclusionsThe results indicated that the effects of Acorus tatarinowii Schott in inhibiting the exercise-induced synthesis of 5-HT and TPH2 expression and in preventing the exercise-induced decrease of 5-HT1B expression in the dorsal raphe might be the anti-fatigue mechanism of Acorus tatarinowii Schott.

P.6.a.011 Role of C1473G polymorphism in mouse tryptophan hydroxylase 2 gene in ethanol treatment effect on behaviour and brain serotonin system

Dysfunction in brain serotonin (5-HT) system has been implicated in the psychopathology of anxiety, depression, drug addiction, and schizophrenia. The 5-HT1A receptors play a central role in the control of 5-HTergic neurotransmission. There are some scarce data showing cross-regulation between 5-HT receptors. Here, we investigated whether interaction exists between 5-HT1A receptor and genes encoding key members in brain 5-HT system. Chronic treatment with selective agonist of 5-HT1A receptor 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (1.0 mg/kg i.p., 14 days) produced considerable decrease in hypothermic response to acute administration of 8-OH-DPAT in CBA/Lac mice indicating desensitization of 5-HT1A receptors. The decrease in 5-HT1A gene expression as well as decrease in the expression of gene encoding key enzyme in 5-HT synthesis, tryptophan hydroxylase-2 (TPH-2) in the midbrain, and the expression of the gene encoding 5-HT2A receptor in the frontal cortex was shown. There were no significant changes in 5-HT transporter mRNA level in the midbrain. Despite considerable decrease in the expression of the genes encoding tryptophan hydroxylase-2, 5-HT1A and 5-HT2A receptors, chronic 8-OH-DPAT treatment failed to produce significant changes in 5-HT1A-linked behavior (intermale aggression, open-field behavior, light-dark box, and pinch-induced catalepsy), suggesting compensatory and adaptive effect of genes suppression. The obtained data on the effect of 8-OH-DPAT-induced desensitization of 5-HT1A receptors on 5-HT1A, 5-HT2A and TPH-2 gene expression demonstrated the role of 5-HT1A receptor as indirect regulator of gene expression. The results provide the first evidence of receptor-key genes interaction in brain 5-HT system and may have profound implications in understanding the functioning of the brain neurotransmitter systems.

P.1.h.009 Local inactivation of G protein-coupled receptor 88 restores motor and cognitive functions impaired in a rat model of schizophrenia

all experiment procedure to demonstrate their effectiveness. The expression of genes coding serotonin receptors (5-HT1, 5-HT2 subtypes), SERT, BDNF and VEGF were measured in prefrontal cortex, midbrain and hippocampus using Quantitative real-time PCR analysis. Moreover, immunohistochemical assay of BDNF and VEGF expression in rat’s hippocampus (CA1) was carried out. Analysis of the expression of genes involved in pathogenesis of depression was performed to show structural validity of model. Diffusion tensor imaging study of the corpus callosum of rats with depression-like behavior were performed with a 7.0 Tesla Bruker BioSpin ClinScan MRI tomograph equipped with a head gradient insert. Results: Action of ultrasonic waves of variable frequency led to a marked reduction of social activity (total time of social contacts, s) in the Social Interaction Test in the experimental group 107±9.8 compared to the control group 216±30.5, (p< 0.001). Fluoxetine and Tianeptine led to restoration of social activity to control levels (228±21.4 and 236±40.6, respectively). Bupropion had no effect on social activity − 142±30.5. In the Porsolt Test, experimental animals showed a significantly higher immobility time (s) (213±15.6) compared to the control group (83±16.3, p< 0.001). Administration of Fluoxetine, Bupropion and Tianeptine reduced the immobility time to control values (129±22.5; 70±16.8; 58±17, respectively). Study of anhedonia development revealed a significant decrease in sucrose preference index in experimental group compared to the control group. RT-qPCR gene expression analysis showed increased expression of SERT gene in all studied structures, decrease expression of 5-HT2A in prefrontal cortex and midbrain, increase 5-HT1A in hippocampus and decrease BDNF in hippocampus of rats after ultrasound. Immunohistochemical assay showed decrease BDNF expression in hippocampus in rats after ultrasound radiation. Diffusion tensor imaging study of the corpus callosum showed decrease numbers of white matter hyperintensities in rats with depression-like behavior, a phenomenon suggested to be linked with white matter pathology. Conclusion: The obtained data allow to conclude that this model meets the main requirements set to animal models of neuropsychiatric disease (face, predictive and construct validity) and can be used in studies of affective disorders and in pre-clinical development of new antidepressants.

Risk neurogenes for long-term spaceflight: dopamine and serotonin brain system.

Mice were exposed to 1month of spaceflight on Russian biosatellite BION-M1 to determine its effect on the expression of key genes in the brain dopamine (DA) and serotonin (5-HT) systems. Spaceflight decreased the expression of crucial genes involved in DA synthesis and degradation, as well as the D1 receptor. However, spaceflight failed to alter the expression of tryptophan hydroxylase-2, 5-HT transporter, 5-HT1A, and 5-HT3 receptor genes, though it reduced 5-HT2A receptor gene expression in the hypothalamus. We revealed risk DA and 5-HT neurogenes for long-term spaceflight for the first time, as well as microgravity-responsive genes (tyrosine hydroxylase, catechol-O-methyltransferase, and D1 receptor in the nigrostriatal system; D1 and 5-HT2A receptors in the hypothalamus; and monoamine oxidase A (MAO A) in the frontal cortex). Decreased genetic control of the DA system may contribute to the spaceflight-induced locomotor impairment and dyskinesia described for both humans and rats.

Arsenic decreases antinociceptive activity of paracetamol: Possible involvement of serotonergic and endocannabinoid receptors

We assessed whether repeated arsenic exposure can decrease paracetamol-mediated antinociception by modulating serotonergic and endocannabinoid pathways. Rats were preexposed to elemental arsenic (4ppm) as sodium arsenite through drinking water for 28 days. Next day paracetamol's (400mg/kg, oral) antinociceptive activity was assessed through formalin-induced nociception. Serotonin content and gene expression of 5-HT1A, 5-HT2A and CB1 receptors were evaluated in brainstem and frontal cortex. Arsenic decreased paracetamol-mediated analgesia. Paracetamol, but not arsenic, increased serotonin content in these regions. Arsenic attenuated paracetamol-mediated increase in serotonin level. Paracetamol did not alter 5-HT1A expression, but caused down-regulation of 5-HT2A and up-regulation of CB1 receptors. Arsenic down-regulated these receptors. However, paracetamol-mediated down-regulation of 5-HT2A was more pronounced. Arsenic did not modify paracetamol's effect on 5-HT1A expression, but reduced paracetamol-mediated down-regulation of 5-HT2A and reversed up-regulation of CB1 receptors. Results suggest arsenic reduced paracetamol-induced analgesia possibly by interfering with pronociceptive 5-HT2A and antinociceptive CB1 receptors.

Postnatal maintenance of the 5-Ht1a-Pet1 autoregulatory loop by serotonin in the raphe nuclei of the brainstem.

BackgroundDespite the importance of 5-HT1A as a major target for the action of several anxiolytics/antidepressant drugs, little is known about its regulation in central serotonin (5-hydroxytryptamine, 5-HT) neurons.ResultsWe report that expression of 5-HT1A and the transcription factor Pet1 was impaired in the rostral raphe nuclei of mice lacking tryptophan hydroxylase 2 (Tph2) after birth. The downregulation of Pet1 was recapitulated in 5-Ht1a -/- mice. Using an explant culture system, we show that reduction of Pet1 and 5-HT1A was rescued in Tph2 -/- brainstem by exogenous 5-HT. In contrast, 5-HT failed to rescue reduced expression of Pet1 in 5-Ht1a -/- brainstem explant culture.ConclusionsThese results suggest a causal relationship between 5-HT1A and Pet1, and reveal a potential mechanism by which 5-HT1A-Pet1 autoregulatory loop is maintained by 5-HT in a spatiotemporal-specific manner during postnatal development. Our results are relevant to understanding the pathophysiology of certain psychiatric and developmental disorders.