Maternal serotonin influences cardiac function in adult offspring

Serotonin system in the human placenta - the knowns and unknowns

The biogenic monoamine serotonin (5-hydroxytryptamine, 5-HT) is a chemical messenger widely distributed in the brain and various other organs. Its homeostasis is maintained by the coordinated activity of a variety of proteins, including enzymes of serotonin metabolism, transmembrane transporters of serotonin, and serotonin receptors. The serotonin system has been identified also in the placenta in rodent models as a key component of placental physiology. However, serotonin pathways in the human placenta are far from well understood. Their alterations may have long-lasting consequences for the fetus that can manifest later in life. In this review, we summarize information on the location of the components of the serotonin system in the human placenta, their regulation, function, and alterations in pathological pregnancies. We highlight current controversies and discuss important topics for future research.

Polymorphisms in the serotonin transporter gene and circulating concentrations of neurotransmitters in Cavalier King Charles Spaniels with myxomatous mitral valve disease

Background

The neurotransmitter serotonin (5‐HT) affects valvular degeneration and dogs with myxomatous mitral valve disease (MMVD) exhibit alterations in 5‐HT signaling. In Maltese dogs, 3 single nucleotide polymorphisms (SNPs) in the 5‐HT transporter (SERT) gene are suggested to associate with MMVD.

Hypothesis/Objectives

Determine the association of SERT polymorphisms on MMVD severity and serum 5‐HT concentration in Cavalier King Charles Spaniels (CKCS). Additionally, investigate the association between selected clinical and hematologic variables and serum 5‐HT and assess the correlation between HPLC and ELISA measurements of serum 5‐HT.

Animals

Seventy‐one CKCS (42 females and 29 males; 7.8 [4.7;9.9] years (median [Q1;Q3])) in different MMVD stages.

Methods

This prospective study used TaqMan genotyping assays to assess SERT gene polymorphisms. Neurotransmitter concentrations were assessed by HPLC and ELISA.

Results

TaqMan analyses identified none of the selected SERT polymorphisms in any of the CKCS examined. Serum 5‐HT was associated with platelet count (P < .001) but not MMVD severity, age or medical therapy and did not correlate with serum concentration of the 5‐HT metabolite, 5‐hydroxyindoleacetic acid. The ELISA serum 5‐HT correlated with HPLC measurements (ρ = .87; P < .0001) but was lower (mean difference = −22 ng/mL; P = .02) independent of serum 5‐HT concentration (P = .2).

Conclusions and Clinical Importance

Selected SERT SNPs associated with MMVD in Maltese dogs were not found in CKCS and only platelet count influenced serum 5‐HT concentration. These SNPs are unlikely to be associated with MMVD pathophysiology or serum 5‐HT concentration in CKCS. HPLC and ELISA serum 5‐HT demonstrated good correlation but ELISA systematically underestimated 5‐HT.

Lack of Skeletal Muscle Serotonin Impairs Physical Performance

Low levels of the neurotransmitter serotonin have been associated with the onset of depression. While traditional treatments include antidepressants, physical exercise has emerged as an alternative for patients with depressive disorders. Yet there remains the fundamental question of how exercise is sensed by the brain. The existence of a muscle–brain endocrine loop has been proposed: according to this scenario, exercise modulates metabolization of tryptophan into kynurenine within skeletal muscle, which in turn affects the brain, enhancing resistance to depression. But the breakdown of tryptophan into kynurenine during exercise may also alter serotonin synthesis and help limit depression. In this study, we investigated whether peripheral serotonin might play a role in muscle–brain communication permitting adaptation for endurance training. We first quantified tryptophan metabolites in the blood of 4 trained athletes before and after a long-distance trail race and correlated changes in tryptophan metabolism with physical performance. In parallel, to assess exercise capacity and endurance in trained control and peripheral serotonin–deficient mice, we used a treadmill incremental test. Peripheral serotonin–deficient mice exhibited a significant drop in physical performance despite endurance training. Brain levels of tryptophan metabolites were similar in wild-type and peripheral serotonin–deficient animals, and no products of muscle-induced tryptophan metabolism were found in the plasma or brains of peripheral serotonin–deficient mice. But mass spectrometric analyses revealed a significant decrease in levels of 5-hydroxyindoleacetic acid (5-HIAA), the main serotonin metabolite, in both the soleus and plantaris muscles, demonstrating that metabolization of tryptophan into serotonin in muscles is essential for adaptation to endurance training. In light of these findings, the breakdown of tryptophan into peripheral but not brain serotonin appears to be the rate-limiting step for muscle adaptation to endurance training. The data suggest that there is a peripheral mechanism responsible for the positive effects of exercise, and that muscles are secretory organs with autocrine-paracrine roles in which serotonin has a local effect.

Interbreed variation in serum serotonin (5-hydroxytryptamine) concentration in healthy dogs

INTRODUCTION

Serotonin (5-hydroxytryptamine [5-HT]) has several biological functions. In different species, excessive 5-HT has been linked to valvular lesions, similar to those seen in dogs with myxomatous mitral valve disease. Previous studies suggest higher 5-HT in healthy Cavalier King Charles Spaniels (CKCSs), a breed highly affected by myxomatous mitral valve disease, compared to other breeds.

OBJECTIVE

To investigate potential interbreed variation in serum 5-HT in healthy dogs.

ANIMALS

483 healthy dogs of nine breeds aged 1-7 years.

METHODS

Dogs were examined at five European centers. Absence of cardiovascular, organ-related, or systemic diseases was ensured by thorough clinical investigations including echocardiography. Serum was frozen and later analyzed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Median 5-HT concentration was 252.5 (interquartile range = 145.5-390.6) ng/mL. Overall breed difference was found (p<0.0001), and 42% of pairwise breed comparisons were significant. Univariate regression analysis showed association between serum 5-HT concentration and breed, center of examination, storage time, and sex, with higher 5-HT in females. In multiple regression analysis, the final model had an adjusted R² of 0.27 with breed (p<0.0001), center (p<0.0001), and storage time (p=0.014) remaining significant. Within centers, overall breed differences were found at 3/5 centers (p≤0.028), and pairwise comparisons within those centers showed breed differences in 42% of comparisons. Among the included breeds, Newfoundlands, Belgian Shepherds and CKCSs had highest 5-HT concentrations.

CONCLUSIONS

Interbreed variation in serum 5-HT concentration was found in healthy dogs aged 1-7 years. These differences should be taken into account when designing clinical studies.

Peripheral serotonin regulates postoperative intra-abdominal adhesion formation in mice

The aim of the present study is to investigate the role and potential mechanisms of peripheral serotonin in postoperative intra-abdominal adhesion formation in mice. The caecum-rubbing operations were conducted for intra-abdominal adhesion formation modelling in wild-type and Tph1−/− mice. The deficiency of serotonin significantly decreased the adhesion scores, weight loss, and adhesion thickness as well as levels of collagen fibres and hydroxyproline in the adhesive tissues. The Tph1−/− mice exhibited a milder inflammatory response and oxidative stress in the adhesive tissues than did the wild-type mice. Moreover, the deficiency of serotonin reduced the levels of PAI-1 and fibrinogen, and raised the t-PA and t-PA/PAI levels in the peritoneal fluids. Moreover, the expressions of CD34, VEGF, TGF-β and 5-HT_2B receptor in the adhesive tissues were significantly decreased in the Tph1−/− group mice. Furthermore, the Tph1−/− +5-HTP group showed more severe adhesions than did the Tph1−/− group mice, and the p-chlorophenylalanine (PCPA) could markedly alleviated the adhesion formation in the WT mice. In conclusion, the present study showed that peripheral serotonin regulated postoperative intra-abdominal adhesion formation by facilitating inflammation, oxidative stress, disorder of the fibrinolytic system, angiopoiesis and TGF-β1 expression via the 5-HT_2B receptor in the adhesive tissues.

Transfer of maternal psychosocial stress to the fetus

Psychosocial maternal stress experienced during different vulnerable periods throughout gestation is thought to increase the individual's risk to develop neuropsychiatric, cardiovascular and metabolic disease in later life. Cortisol has generally been identified as the major mediator of maternal stress transfer to the fetus. Its lipophilic nature allows a trans-placental passage and thus excessive maternal cortisol could persistently impair the development of the fetal hypothalamic-pituitary-adrenal axis (HPAA). However, cortisol alone cannot fully explain all effects of maternal stress especially during early to mid pregnancy before maturation of the fetal HPAA has even begun and expression of fetal glucocorticoid receptors is limited. This review focuses on mediators of maternal fetal stress transfer that in addition to cortisol have been proposed as transmitters of maternal stress: catecholamines, cytokines, serotonin/tryptophan, reactive-oxygen-species and the maternal microbiota. We propose that the effects of psychosocial maternal stress on fetal development and health and disease in later life are not a consequence of a single pathway but are mediated by multiple stress-transfer mechanisms acting together in a synergistic manner.

Serotonin competence of mouse beta cells during pregnancy

Pregnancy is a key mammalian reproductive event in which growth and differentiation of the fetus imposes extra metabolic and hormonal demands on the mother. Its successful outcome depends on major changes in maternal blood circulation, metabolism and endocrine function. One example is the endocrine pancreas, where beta cells undergo a number of changes in pregnancy that result in enhanced functional beta cell mass in order to compensate for the rising metabolic needs for maternal insulin. During the last 5 years, a series of studies have increased our understanding of the molecular events involved in this functional adaptation. In the mouse, a prominent functional change during pregnancy is the capacity of some beta cells to produce serotonin. In this review we will discuss the mechanism and potential effects of pregnancy-related serotonin production in beta cells, considering functional consequences at the local intra-islet and systemic level.

Changes in the cardiac metabolome caused by perhexiline treatment in a mouse model of hypertrophic cardiomyopathy

Energy depletion has been highlighted as an important contributor to the pathology of hypertrophic cardiomyopathy (HCM), a common inherited cardiac disease. Pharmacological reversal of energy depletion appears an attractive approach and the use of perhexiline has been proposed as it is thought to shift myocardial metabolism from fatty acid to glucose utilisation, increasing ATP production and myocardial efficiency. We used the Mybpc3-targeted knock-in mouse model of HCM to investigate changes in the cardiac metabolome following perhexiline treatment. Echocardiography indicated that perhexiline induced partial improvement of some, but not all hypertrophic parameters after six weeks. Non-targeted metabolomics, applying ultra-high performance liquid chromatography-mass spectrometry, described a phenotypic modification of the cardiac metabolome with 272 unique metabolites showing a statistically significant change (p < 0.05). Changes in fatty acids and acyl carnitines indicate altered fatty acid transport into mitochondria, implying reduction in fatty acid beta-oxidation. Increased glucose utilisation is indirectly implied through changes in the glycolytic, glycerol, pentose phosphate, tricarboxylic acid and pantothenate pathways. Depleted reduced glutathione and increased production of NADPH suggest reduction in oxidative stress. These data delineate the metabolic changes occurring during improvement of the HCM phenotype and indicate the requirements for further targeted interventions.

Pharmacological and genetic identification of serotonin receptor subtypes on Drosophila larval heart and aorta

Serotonin, 5-hydroxytryptamine (5-HT), plays various roles in the fruit fly, Drosophila melanogaster. Previous studies have shown that 5-HT modulates the heart rate in third instar larvae. However, the receptor subtypes that mediate 5-HT action in larval cardiac tissue had yet to be determined. In this study, various 5-HT agonists and antagonists were employed to determine which 5-HT receptor subtypes are responsible for the positive chronotropic effect by 5-HT. The pharmacological results demonstrate that a 5-HT2B agonist significantly increases the heart rate; however, 5-HT1A, 5-HT1B, and 5-HT7 agonists do not have a significant effect on the heart rate. Furthermore, 5-HT2 antagonist, ketanserin, markedly reduces the positive chronotropic effect of 5-HT in a dose-response manner. Furthermore, we employed genetic approaches to confirm the pharmacological results. For this purpose, we used RNA interference line to knock down 5-HT2ADro and also used 5-HT2ADro and 5-HT2BDro insertional mutation lines. The results show that 5-HT2ADro or 5-HT2BDro receptor mutations reduce the response of the heart to 5-HT. Given these results, we conclude that these 5-HT2 receptor subtypes are involved in the action of 5-HT on the heart rate in the larval stage.

Serotonin is a key factor for mouse red blood cell survival

Serotonin (5-HT) is a monoamine originally purified from blood as a vasoactive agent. In nonneuronal tissues, its presence is linked with the expression of tryptophan hydroxylase 1 (TPH1) that catalyzes the rate-limiting step of its synthesis. Targeted disruption in mice of the TPH1 gene results in very low levels of circulating 5-HT. Previous analysis of the TPH1 knockout (TPH1^−/−) mouse revealed that they develop a phenotype of macrocytic anemia with a reduced half-life of their circulating red blood cells (RBC). In this study, to establish whether the observed reduced half-life of TPH1^−/− RBC is an intrinsic or an extrinsic characteristic, we compared their survival to RBC isolated from wild-type mice. Both in vivo and in vitro data converge to demonstrate an extrinsic protective effect of 5-HT since presence of 5-HT in the RBC environment protects RBC from senescence. The protective effect played by 5-HT is not mediated through activation of a classical pharmacological pathway as no 5-HT receptors were detected on isolated RBC. Rather, 5-HT acts as an effective antioxidant since reduction of 5-HT circulating levels are associated with a decrease in the plasma antioxidant capacity. We further demonstrate a link between oxidation and the removal of damaged RBC following transfusion, as supplementation with 5-HT improves RBC post-transfusion survival in a mouse model of blood banking.

Gut-derived serotonin is a multifunctional determinant to fasting adaptation

Energy release from cellular storage is mandatory for survival during fasting. This is achieved through lipolysis and liver gluconeogenesis. We show here that in the mouse, gut-derived serotonin (GDS) is upregulated during fasting and that it favors both mechanisms. In adipocytes, GDS signals through the Htr2b receptor to favor lipolysis by increasing phosphorylation and activity of hormone-sensitive lipase. In hepatocytes, GDS signaling through Htr2b promotes gluconeogenesis by enhancing activity of two rate-limiting gluconeogenic enzymes, FBPase and G6Pase. In addition, GDS signaling in hepatocytes prevents glucose uptake in a Glut2-dependent manner, thereby further favoring maintenance of blood glucose levels. As a result, inhibition of GDS synthesis can improve glucose intolerance caused by high-fat diet. Hence, GDS opposes deleterious consequences of food deprivation by favoring lipolysis and liver gluconeogenesis while preventing glucose uptake by hepatocytes. As a result, pharmacological inhibition of its synthesis may contribute to improve type 2 diabetes.

Serotonin: good or bad for bone

Besides its action as a neurotransmitter, serotonin has multiple physiological functions in several peripheral organs. Recently, Yadav et al. suggested that peripheral serotonin produced in the gut was a major negative regulator of osteoblast proliferation. These data were challenged by Cui et al. that showed no change in bone density in mature mice with a global invalidation of tryptophan hydroxylase 1, the enzyme responsible of serotonin synthesis in the periphery. In this context, we showed that osteoclasts are able to synthetize serotonin that acts locally to induce osteoclast precursors differentiation. Our data and previous results from others suggest that rather than acting as a hormone, serotonin produced in the bone could act locally on osteoclast and osteoblast realizing in the bone a complete micro-serotoninergic system.

Altered gene expression in pulmonary tissue of tryptophan hydroxylase-1 knockout mice: implications for pulmonary arterial hypertension

The use of fenfluramines can increase the risk of developing pulmonary arterial hypertension (PAH) in humans, but the mechanisms responsible are unresolved. A recent study reported that female mice lacking the gene for tryptophan hydroxylase-1 (Tph1(−/−) mice) were protected from PAH caused by chronic dexfenfluramine, suggesting a pivotal role for peripheral serotonin (5-HT) in the disease process. Here we tested two alternative hypotheses which might explain the lack of dexfenfluramine-induced PAH in Tph1(−/−) mice. We postulated that: 1) Tph1(−/−) mice express lower levels of pulmonary 5-HT transporter (SERT) when compared to wild-type controls, and 2) Tph1(−/−) mice display adaptive changes in the expression of non-serotonergic pulmonary genes which are implicated in PAH. SERT was measured using radioligand binding methods, whereas gene expression was measured using microarrays followed by quantitative real time PCR (qRT-PCR). Contrary to our first hypothesis, the number of pulmonary SERT sites was modestly up-regulated in female Tph1(−/−) mice. The expression of 51 distinct genes was significantly altered in the lungs of female Tph1(−/−) mice. Consistent with our second hypothesis, qRT-PCR confirmed that at least three genes implicated in the pathogenesis of PAH were markedly up-regulated: Has2, Hapln3 and Retlna. The finding that female Tph1(−/−) mice are protected from dexfenfluramine-induced PAH could be related to compensatory changes in pulmonary gene expression, in addition to reductions in peripheral 5-HT. These observations emphasize the intrinsic limitation of interpreting data from studies conducted in transgenic mice that are not fully characterized.

Placental lactogens induce serotonin biosynthesis in a subset of mouse beta cells during pregnancy

AIMS/HYPOTHESIS

Upregulation of the functional beta cell mass is required to match the physiological demands of mother and fetus during pregnancy. This increase is dependent on placental lactogens (PLs) and prolactin receptors, but the mechanisms underlying these events are only partially understood. We studied the mRNA expression profile of mouse islets during pregnancy to gain a better insight into these changes.

METHODS

RNA expression was measured ex vivo via microarrays and quantitative RT-PCR. In vivo observations were extended by in vitro models in which ovine PL was added to cultured mouse islets and MIN6 cells.

RESULTS

mRNA encoding both isoforms of the rate-limiting enzyme of serotonin biosynthesis, tryptophan hydroxylase (TPH), i.e. Tph1 and Tph2, were strongly induced (fold change 25- to 200-fold) during pregnancy. This induction was mimicked by exposing islets or MIN6 cells to ovine PLs for 24 h and was dependent on janus kinase 2 and signal transducer and activator of transcription 5. Parallel to Tph1 mRNA and protein induction, islet serotonin content increased to a peak level that was 200-fold higher than basal. Interestingly, only a subpopulation of the beta cells was serotonin-positive in vitro and in vivo. The stored serotonin pool in pregnant islets and PL-treated MIN6 cells was rapidly released (turnover once every 2 h).

CONCLUSIONS/INTERPRETATION

A very strong lactogen-dependent upregulation of serotonin biosynthesis occurs in a subpopulation of mouse islet beta cells during pregnancy. Since the newly formed serotonin is rapidly released, this lactogen-induced beta cell function may serve local or endocrine tasks, the nature of which remains to be identified.

Contribution of gene-modified mice and rats to our understanding of the cardiovascular pharmacology of serotonin

This review focuses on new insights provided by gene-modified animals into the cardiovascular pharmacology of serotonin. During their development, mice mutant for tryptophan hydroxylase 1 and lacking peripheral serotonin, or mutant for 5-HT(2B) receptors, display cardiac defects and dilated cardiomyopathy. The 5-HT(4) receptor is important for the maturation of cardiac conduction. In fact, transgenic approaches have revealed that adult cardiac status is strongly influenced by maternal serotonin. Serotonin has long been known to be a vasoconstrictor in adult physiology. Analysis of animals knocked-out for the serotonin transporter suggested a role in blood pressure control and revealed an effect of 5-HT(2B) receptor antagonists in hypertension. In the lung vasculature, mice lacking the 5-HT(2B) receptor gene that are exposed to chronic hypoxia are resistant to pulmonary hypertension, while 5-HT(1B) receptor and serotonin transporter mutant animals show partial resistance. In platelets, mutant mice revealed that serotonin transporter regulates not only the mechanisms by which serotonin is packaged and secreted but also platelet aggregation. Studies looking at adult cardiac remodeling showed that mice lacking the 5-HT(2B) receptor gene were protected from cardiac hypertrophy. Their fibroblasts were unable to secrete cytokines. Crossing these animals with mice overexpressing the receptor in cardiomyocytes revealed the contribution of cardiac fibroblasts and 5-HT(2B) receptors to cardiac hypertrophy. In mice lacking the monoamine oxidase-A gene, the role of serotonin degradation in cardiac hypertrophy was confirmed. Works with gene-modified animals has contributed strongly to the re-evaluation of the influence of serotonin on cardiovascular regulation, though several unknowns remain to be investigated.

Genetic models of serotonin (5-HT) depletion: what do they tell us about the developmental role of 5-HT?

A large number of hyposerotonergic genetic models have been generated over the past few years. Serotonin (5-HT) depletion has been obtained via targeting of genes involved in 5-HT synthesis (Tph1 and Tph2), specification and determination of the 5-HT phenotype during development (GATA3, Pet1, and Lmx1b), and 5-HT storage or clearance (Vmat2 and SERT). Here we review these various models from a developmental perspective, beginning with a description of the sources of 5-HT during development. We then summarize the neurological and behavioral alterations that have been observed in the genetic hyposerotonergic models. Although these models appear to have normal brain development and do not exhibit any gross morphological defects, problems in somatic growth and physiological functions have been observed. Abnormal adult behavior is also seen, although whether it results from depletion of 5-HT during development or functional 5-HT deficiencies in adult life remains unclear. Evidence from these hyposerotonergic models suggests that the developing brain may not need 5-HT for the establishment of general organization and structure. However, central 5-HT appears to be necessary for postnatal body growth, maturation of respiratory and vegetative control, and possibly for the development of normal adult behavior.

The nuclear receptor PPARγ individually responds to serotonin- and fatty acid-metabolites

The nuclear receptor, peroxisome proliferator-activated receptor γ (PPARγ), recognizes various synthetic and endogenous ligands by the ligand-binding domain. Fatty-acid metabolites reportedly activate PPARγ through conformational changes of the Ω loop. Here, we report that serotonin metabolites act as endogenous agonists for PPARγ to regulate macrophage function and adipogenesis by directly binding to helix H12. A cyclooxygenase inhibitor, indomethacin, is a mimetic agonist of these metabolites. Crystallographic analyses revealed that an indole acetate functions as a common moiety for the recognition by the sub-pocket near helix H12. Intriguingly, a serotonin metabolite and a fatty-acid metabolite each bind to distinct sub-pockets, and the PPARγ antagonist, T0070907, blocked the fatty-acid agonism, but not that of the serotonin metabolites. Mutational analyses on receptor-mediated transcription and coactivator binding revealed that each metabolite individually uses coregulator and/or heterodimer interfaces in a ligand-type-specific manner. Furthermore, the inhibition of the serotonin metabolism reduced the expression of the endogenous PPARγ-target gene. Collectively, these results suggest a novel agonism, in which PPARγ functions as a multiple sensor in response to distinct metabolites.

[Treatment of depressed pregnant women by selective serotonin reuptake inhibitors: risk for the foetus and the newborn]

INTRODUCTION

This article is a review of literature data concerning the use of selective serotonin reuptake inhibitors (SSRIs) by depressed pregnant women.

LITERATURE FINDINGS

The adverse effects for the foetus, the newborn and the child were evaluated. The prevalence of depression during pregnancy is of around 10 to 20% of the population of childbearing women. Depression is often misdiagnosed and underestimated in pregnant women. Starting a pharmacological treatment for depression in these women is not easy because data concerning the safety of antidepressants during pregnancy are still unclear. The non-treated pathology is associated with higher risk of maternal morbidity, including arterial hypertension, which could lead to preeclampsia or eclampsia, ideation and suicide attempts, and postpartum depression. Foetal development is also affected and adverse outcomes such as prematurity, low birth weight, irritability, and sleep disorders are frequent. Pharmacological therapy is necessary when non-pharmacological treatment is insufficient. Suicide attempts and relapse of depression have been described when depressive women stopped their pharmacological treatment during pregnancy. Pregnant women diagnosed with depression must be treated. Selective SSRIs are now largely used in this pathology and have replaced tricyclic antidepressants because of fewer side effects. In general, drugs have a low teratogenic potential, only 4 to 5% of malformations are iatrogenic. Teratogenic risk is high between conception until the end of the second month of gestation. Safety of SSRIs treatment during pregnancy and potential risk for the foetus and newborn were unquestioned before publication, in the late 2005, of some alarming data concerning a possible teratogenic effect. Studies showed an increased risk for all congenital malformations with SSRIs and particularly with paroxetin. A few studies after 2005 have also found an association between prenatal exposure to SSRIs (especially paroxetin) and congenital malformations. However, other studies failed to demonstrate this association and the risk for cardiovascular malformations also does not seem to be significantly increased. Numerous studies in pregnant women have shown that SSRI treatments are associated with a significant increase of spontaneous abortion, preterm birth, and low birth weight. Exposure to SSRIs in late pregnancy has been associated with a three-fold increased risk of neonatal behavioural syndrome, including signs of withdrawal or serotonin impregnation. Restlessness, poor tone, respiratory distress, hypoglycaemia were the most frequent signs. These symptoms occur during the first days of life and are usually brief and not serious. Recent studies have also documented an increased risk of persistent pulmonary hypertension and cases of cerebral haemorrhage have been described. Data concerning a possible effect on motor and cognitive development at school age in children prenatally exposed to SSRIs are limited.

DISCUSSION

Although a number of studies revealed that SSRIs are not teratogenic, some of them showed congenital malformations associated with use of these antidepressants; in particular an increased risk of cardiac defects with paroxetin. In practice, the potential risk implies that the decision to treat a pregnant woman with SSRIs (notably paroxetin) should be taken carefully; this means double-checking the diagnosis, the potential benefits, adverse effects and possible alternatives. Neonatal toxicity seems to be relatively frequent when SSRIs are prescribed during late pregnancy. For all depressed pregnant women, the severity of the depression must be taken into consideration before introducing a pharmacological treatment. When depressive women are already treated, studies have shown that antidepressants must be maintained during pregnancy to prevent relapse and suicide attempts.

Relationships among body mass, brain size, gut length, and blood tryptophan and serotonin in young wild-type mice

Background

The blood hyperserotonemia of autism is one of the most consistent biological findings in autism research, but its causes remain unclear. A major difficulty in understanding this phenomenon is the lack of information on fundamental interactions among the developing brain, gut, and blood in the mammalian body. We therefore investigated relationships among the body mass, the brain mass, the volume of the hippocampal complex, the gut length, and the whole-blood levels of tryptophan and 5-hydroxytryptamine (5-HT, serotonin) in young, sexually immature wild-type mice.

Results

Three-dimensional reconstructions of the hippocampal complex were obtained from serial, Nissl-stained sections and the gut was allowed to attain its maximal relaxed length prior to measurements. The tryptophan and 5-HT concentrations in the blood were assessed with high-performance liquid chromatography (HPLC) and the sex of mice was confirmed by genotyping. Statistical analysis yielded information about correlative relationships among all studied variables. It revealed a strong negative correlation between blood 5-HT concentration and body mass and a strong negative correlation between the brain mass/body mass ratio and gut length. Also, a negative correlation was found between the volume of the hippocampal complex and blood tryptophan concentration.

Conclusion

The study provides information on the covariance structure of several central and peripheral variables related to the body serotonin systems. In particular, the results indicate that body mass should be included as a covariate in studies on platelet 5-HT levels and they also suggest a link between brain growth and gut length.

Periodic variation in R-R intervals and cardiovascular autonomic regulation in young adult Syrian hamsters

Several hamster strains are commonly used as models for cardiomyopathic phenotypes evolving toward heart failure. However, little is known about heart rate variability (HRV) in this species. Prolonged surface ECG recording, a prerequisite to HRV studies, can be obtained either by telemetry or by restraints. Here, we performed long time ECG recording using telemetry on young adult Syrian hamsters and we analyzed time series of interbeat intervals. Standard statistics showed that the mean of normal R-R intervals slightly increased with age, with standard deviation of normal R-R intervals remaining stable over time. However, time domain analysis using Poincaré plots revealed dynamic changes in the HRV. Analysis of frequency domains revealed that the ratio of spectral components (low frequency/high frequency) exhibited a maturation pattern. Thus refined analysis of HRV revealed a more complex pattern than common statistical analysis would translate. Unlike other rodents, hamsters display a great spontaneous variability of their heart rate. As the complexity canvas of HRV might be the consequence of extracardiac regulation factors, we assessed the sympathovagal balance in both time and frequency domain of heart rate. Pharmacological tests revealed that both sympathetic and vagal tones contribute to HRV in Syrian hamsters. Thus Syrian hamsters have a broad intrinsic HRV with large influences of the neurovegetative system. However, the influence of the previous beat seems to prevail over the autonomic oscillators. These animals present a high sensitivity to artificially altered cardiac regulation and might be great models for the diagnosis of early alterations in the HRV related to pathology. Therefore, Syrian hamsters represent a unique model for HRV studies.