Variation of serotonergic gene expression: neurodevelopment and the complexity of response to psychopharmacologic drugs

Threat-Avoidance Tendencies Moderate the Link Between Serotonin Transporter Genetic Variation and Reactive Aggression

The short (S) allele of the serotonin transporter-linked promoter region (5-HTTLPR) polymorphism has been linked to reactive aggression in men, but this association is less consistent in females. Reactive aggression has been particularly described as a result of fear-driven defense to threat, but how this interaction between defensive behavior and aggression is expressed in S-allele carriers remains unknown. In order to explore this interplay between 5-HTTLPR genotype, defensive behavior and reactive aggression, we combined genotyping with objective measures of action tendencies toward angry faces in an approach-avoidance task (AAT) and reactive aggression in the Taylor aggression paradigm (TAP) in healthy females, N = 95. This study shows that female S-allele carriers in general display increased implicit reactive aggression (administering aversive white noise) toward opponents. Furthermore, we found that threat-avoidance tendencies moderate the association between 5-HTTLPR genotype and aggression displayed on the TAP. Together, these findings indicate a positive correlation between avoidance of angry faces in the AAT and reactive aggression in the TAP exclusively present in S-allele carriers.

Evaluation of Platelet Parameters in Children with Autism Spectrum Disorder: Elongated Collagen-Adenosine Diphosphate and Collagen-Epinephrine Closure Times

Changes related to the serotonin system play a key role in the etiology of autism spectrum disorder (ASD). Although we know that platelets are associated with the serotonin system, their relation to ASD has not yet been elucidated. In this study, we aim to investigate platelet parameters in children with ASD. Forty patients with ASD according to Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5) and 30 healthy controls were included in the study. A complete blood count was done to measure parameters relating to platelet morphology. Moreover, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were evaluated. Lastly, platelet functions were assessed with a platelet functions analyzer 100 (PFA-100) device by measuring collagen-ADP and collagen-epinephrine (EPI) closure times. There was not a significant difference between the groups in terms of platelet count, mean platelet volume (MPV), platelet distribution width, plateletcrit, PT, or aPTT parameters for ASD patients when compared to the control group (P > 0.05). However, MPV in severe ASD, as quantified by the Childhood Autism Rating Scale, was found to be significantly lower when compared to mild to moderate ASD (P = 0.047). Moreover, in terms of platelet functions, the elongation in collagen-ADP and collagen-EPI closure times were significantly higher for the ASD group (P = 0.044). These results may suggest an impairment in platelet functions rather than in platelet morphology for children with ASD. Considering these results, further investigation of thrombocyte functions in the ASD may lead to a better understanding of the pathogenesis of ASD and to the development of our limited knowledge of this disorder. Autism Res 2019, 12: 1069-1076. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Serotonin is a chemical that is found in brain as wells as in blood cells that function in blood clotting in the human body. There are problems related to serotonin in brains of people who have autism. Thus, blood clotting cells may also be affected in people who have autism. In this study, we compare blood clotting functions of children with autism with that of healthy controls.

Serotonergic polymorphisms in the control of ejaculation

Serotonin has long been implicated in the regulation of the processes that trigger the ejaculatory reflex. Most evidence of serotonergic involvement is, however, indirect, stemming either from studies on rodents or clinical trials investigating effects of serotonergic drugs. In the past decade, emerging evidence for heritability (i.e., genetic effects) of premature ejaculation (PE) symptoms has spawned a number of scholarly attempts to identify genes that regulate ejaculation, most of which have focused on candidate genes related to the serotonergic system. The aim of the present review article was to summarize the literature concerning genetic association studies of PE, with focus on serotonergic genes. However, methodological obstacles relating to the candidate gene approach predict that a priori hypotheses regarding candidate genes are likely to generate ambiguous and spurious results if samples (e.g., if samples are underpowered and/or stratified). Attempts to replicate reported novel associations between PE symptoms and serotonergic candidate genes have largely failed (thereby adding to the growing body of evidence casting doubt on the reliability of the candidate gene approach), and at present, it is not possible to determine with acceptable certainty which serotonergic genes, if any, are involved in ejaculatory function.

Anterior Cingulate Glutamate Is Reduced by Acamprosate Treatment in Patients With Alcohol Dependence

Although the precise drug mechanism of action of acamprosate remains unclear, its antidipsotropic effect is mediated in part through glutamatergic neurotransmission. We evaluated the effect of 4 weeks of acamprosate treatment in a cohort of 13 subjects with alcohol dependence (confirmed by a structured interview, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision) on proton magnetic resonance spectroscopy glutamate levels in the midline anterior cingulate cortex (MACC). We compared levels of metabolites with a group of 16 healthy controls. The Pennsylvania Alcohol Craving Scale was used to assess craving intensity. At baseline, before treatment, the mean cerebrospinal fluid-corrected MACC glutamate (Glu) level was significantly elevated in subjects with alcohol dependence compared with controls (P = 0.004). Four weeks of acamprosate treatment reduced glutamate levels (P = 0.025), an effect that was not observed in subjects who did not take acamprosate. At baseline, there was a significant positive correlation between cravings, measured by the Pennsylvania Alcohol Craving Scale, and MACC (Glu) levels (P = 0.019). Overall, these data would suggest a normalizing effect of acamprosate on a hyperglutamatergic state observed in recently withdrawn patients with alcohol dependence and a positive association between MACC glutamate levels and craving intensity in early abstinence. Further research is needed to evaluate the use of these findings for clinical practice, including monitoring of craving intensity and individualized selection of treatment with antidipsotropic medications in subjects with alcohol dependence.

Biallelic and Triallelic 5-Hydroxytyramine Transporter Gene-Linked Polymorphic Region (5- HTTLPR) Polymorphisms and Their Relationship with Lifelong Premature Ejaculation: A Case-Control Study in a Chinese Population

BACKGROUND This study aimed to explore the relationship between premature ejaculation (PE) and the serotonin transporter gene-linked polymorphic region (5-HTTLPR) with respect to the biallelic and triallelic classifications. MATERIAL AND METHODS A total of 115 outpatients who complained of ejaculating prematurely and who were diagnosed as having lifelong premature ejaculation (LPE) and 101 controls without PE complaint were recruited. All subjects completed a detailed questionnaire and were genotyped for 5-HTTLPR polymorphism using PCR-based technology. We evaluated the associations between 5-HTTLPR allelic and genotypic frequencies and their association with LPE, as well as the intravaginal ejaculation latency time (IELT) of different 5-HTTLPR genotypes among LPE patients. RESULTS The patients and controls did not differ significantly in terms of any characteristic except age. The results showed no significant difference regarding biallelic 5-HTTLPR. According to the triallelic classification, no significant difference was found when comparing the genotypic distribution (P=0.091). However, the distribution of the S, LG, and LA alleles in the cases was significantly different from the controls (P=0.018). We found a significantly lower frequency of LA allele and higher frequency of LG allele in patients. Based on another classification by expression, we found a significantly lower frequency of the L'L' genotype (OR=0.37; 95%CI=0.15-0.91, P=0.025) in patients with LPE. No significant association was detected between IELT of LPE and different genotypes. CONCLUSIONS Contrary to the general classification based on S/L alleles, triallelic 5-HTTLPR was associated with LPE. Triallelic 5-HTTLPR may be a promising field for genetic research in PE to avoid false-negative results in future studies.

Changes induced by prenatal stress in behavior and brain morphology: can they be prevented or reversed?

This chapter presents a critical analysis of the behavioral alterations reported in the offspring of women exposed to stress and/or depression during pregnancy and the neurochemical and structural changes underlying them. Among the alterations attributed to prenatal stress in humans and experimental rats of both sexes is impaired regulation of the hypothalamic-pituitary-adrenal (HPA) axis, anxiety and exaggerated fear of novelty, and decreased social interaction. Learning and attention deficits are more prevalent in boys and male rats. Fear of novelty and anxiety are associated with enlargement of the amygdala and its corticotropin-releasing factor content, and decreased socialization, with lower oxytocin activity in the amygdala. Learning deficits are associated with a decrease in neurogenesis, dendritic complexity, and spine number in the dorsal hippocampus. Fostering prenatally stressed (PS) pups onto control mothers prevents the dysregulation of the HPA axis and heightened anxiety, indicating a role for postnatal factors in their etiology. By contrast, learning impairment and decreased socialization are not affected by this fostering procedure and are therefore prenatally mediated.In spite of their widespread use in depressed pregnant women, selective serotonin reuptake inhibitor (SSRI) antidepressants do not normalize the behavior of their children. When administered during gestation to stressed rats, SSRIs do not reduce anxiety or learning deficits in their offspring. Moreover, when given to unstressed mothers, SSRIs induce anxiety in the offspring. The detrimental effect of SSRIs may result from inhibition of the serotonin transporter exposing the brain to excess amounts of 5-hydroxytryptamine (5-HT) at a critical time during fetal development.

The evolutionary history of SLC6A4 and the role of plasticity in Macaca

Serotonin has been repeatedly indicated as a biological marker of behavior. In particular, the serotonin transporter gene, SLC6A4, has been the focus of a large body of research. Interestingly, both rhesus macaques (Macaca mulatta) and humans have independently evolved a number of shared polymorphisms for this gene, which is indicative of parallel evolution between the two species. However, little is known about the evolution of this gene, particularly within macaques. Although there are several hypotheses as to the adaptive values of various polymorphisms, few authors have gone beyond theoretical discussion. Here, we examined the genetic variation in SLC6A4 within and between several species of macaques and investigate whether selection has played a significant role in its evolutionary history. In addition, we assayed the promoter region polymorphism, 5-HTTLPR, which is known to play a significant role in regulating both serotonin turnover and behavior. In examining the distribution of the 5-HTTLPR polymorphism, we identified significant differences between Indian and Chinese populations of Macaca mulatta; furthermore, we discovered its presence in Macaca cyclopis, which has not been described before. In regard to the evolutionary history of SLC6A4, we found little evidence for selection and conclude that SLC6A4 largely evolved through neutral processes, possibly due to its potential role in regulating behavioral plasticity. However, we also found very low levels of linkage between the coding regions and 5-HTTLPR. Because we limited evolutionary analyses to the coding regions, it is possible that the promoter region shows a distinct evolutionary history from SLC6A4.

Effects of high-tryptophan diet on pre- and postnatal development in rats: a morphological study

PURPOSE

Tryptophan is an essential amino acid, precursor of serotonin. Serotonin (5HT) regulates the secretion of pituitary growth hormone (GH), which in turn stimulates the liver to produce insulin-like growth factor-I (IGF-I) that is necessary for development and growth. The aim of our study was to investigate the effects of an excess of tryptophan in the diet of pregnant rats on the differentiation of skeletal muscle tissue.

METHODS

We conducted an immunohistochemical study on the IGF-I expression in hepatic and muscle tissues in offspring, and then, we associated this molecular data with morphological effects on the structure of the muscle fibers and hepatic tissue at different postnatal weeks, from birth to sexual maturity. Measurements of 5HT, GH in blood, and of tryptophan hydroxylase (Tph) activity in gastrointestinal tracts tissue were also taken.

RESULTS

Hyperserotonemia and higher values of Tph activity were detected in both pregnant rats and pups. Very low levels of GH were detected in experimental pups. Morphological alterations of the muscle fibers and lower IGF-I expression in hepatic and muscle tissue in pups were found.

CONCLUSIONS

Our data suggest that an excess of tryptophan in the diet causes hyperserotonemia in fetus. Hyperserotonemia results in an excess of serotonin in the brain where it has an adverse effect on the development of serotonergic neurons. The affected neurons do not regulate optimally the secretion of pituitary GH that consequently decreases. This limits stimulation in the liver to produce IGF-I, crucial for development and growth of pups.

Additive effects of 5-HTTLPR (serotonin transporter) and tryptophan hydroxylase 2 G-703T gene polymorphisms on the clinical response to citalopram among children and adolescents with depression and anxiety disorders

OBJECTIVE

The purpose of this study was to evaluate the association between polymorphisms in two serotonin pathway genes and the clinical response to citalopram among children and adolescents with depression and/or anxiety disorders.

METHODS

Eighty-three children and adolescents with depression and/or anxiety disorders were treated with citalopram for 8 weeks. We assessed the association between the response to citalopram and polymorphisms in the tryptophan hydroxylase-2 (TPH2) and the serotonin transporter gene. The polymorphisms included single nucleotide polymorphisms (SNPs) in the transcriptional control region (G-703T) of the TPH2 gene and the serotonin transporter gene-linked promoter region (5-HTTLPR).

RESULTS

Fifty patients of the 83 (60.2%) achieved satisfactory response (Clinical Global Impressions - Improvement ≤2). We observed an additive effect of the two genes on the clinical response to citalopram. Patients carrying the combination of TPH2 -703G and the 5-HTTLPR L alleles were the most likely to respond (80%). In contrast, patients carrying the combination of TPH2 -703T and the 5-HTTLPR S alleles were least likely to respond (31%). The other patients (with -703G/5-HTTLPR S and -703T/5-HTTLPR L alleles) showed intermediate response (67%).

CONCLUSIONS

This finding suggests that 5-HTTLPR and TPH2 genes may act in concert to modulate the clinical response to citalopram among children and adolescents with depression and/or anxiety disorders.

Influence of the serotonin transporter 5HTTLPR polymorphism on symptom severity in irritable bowel syndrome

5HTTLPR polymorphism of serotonin transporter yields short (S) and long (L) alleles. SS and LS genotypes are associated with reduced expression of serotonin transporter. This cross-sectional study investigated the association of 5HTTLPR with symptom severity of irritable bowel syndrome (IBS). Patients with IBS (Rome III) and healthy controls were included. Genomic DNA was extracted from saliva, and 5HTTLPR alleles were assessed by polymerase chain reaction. IBS symptom severity was evaluated by means of IBS-SSS questionnaire. Two hundreds and four IBS patients (159 females; mean age: 39.6±12.3 years; 106 with constipation: C-IBS; 98 with diarrhea: D-IBS) and 200 healthy controls (154 females; mean age: 40.4±15.8 years) were enrolled. The overall IBS-SSS value was higher in LS/SS than LL patients (319.0±71.5 versus 283.8±62.3; P = 0.0006). LS/SS patients had also higher values of abdominal pain (59.7±21.0 versus 51.0±18.8; P = 0.020) and bowel dissatisfaction (80.1±23.9 versus 70.5±22.8; P = 0.035). The overall IBS-SSS values in C-IBS and D-IBS patients were 317.2±68.3 and 296.1±71.4, respectively (P = 0.192), with significantly higher values for abdominal distension (65.0±24.4 versus 51.4±24.8; P = 0.0006), but not for bowel dissatisfaction (80.5±21.7 versus 72.9±25.7; P = 0.138). Frequencies of 5HTTLPR genotypes did not differ significantly when comparing IBS patients (overall or upon stratification in C-IBS and D-IBS) with healthy controls. In conclusion, the LS and SS genotypes are significantly correlated with IBS symptom severity, although their possible direct causal role remains to be proven. In addition, the present findings do not support an association of 5HTTLPR with IBS or its clinical presentation in terms of bowel habit predominance.

Expression of 5HT-related genes after perinatal treatment with 5HT agonists

Serotonin (5HT) is a biologically active amine with diverse roles in the mammalian organism. Developmental alterations in 5HT homeostasis could lead to exposure of the developing brain to non-optimal serotonin concentrations that may result in developmental and behavioral deficits. In order to explore the molecular basis of the effects of developmental disturbances on 5HT metabolism on adult central 5HT homeostasis, observed in our previous studies, we measured changes in gene expression of the neuronal 5HT-regulating proteins in adult animals after perinatal treatment with the immediate 5HT precursor 5-hydroxytryptophan (5HTP, 25 mg/kg), or monoamine oxidase (MAO) inhibitor tranylcypromine (TCP 2 mg/kg), during the period of the most intensive development of 5HT neurons — from gestational day 12 until postnatal day 21. Adult animals were sacrificed and the relative mRNA levels for tryptophan hydroxylase 2, MAO A, MAO B, receptors 5HT1A and 5HT2A, 5HT transporter (5HTT) and vesicular monoamine transporter (VMAT) were determined in the raphe nuclei region and prefrontal cortex using Real-Time Relative qRT-PCR. In comparison to the saline treated animals, treatment with 5HTP caused mild but significant increase in MAO A and MAO B mRNA abundance. TCP-treated animals, besides an increase in mRNA abundance for both MAO genes, displayed significantly increased 5HTT and VMAT2 mRNA levels and significantly decreased 5HT1A receptor mRNA levels. Our results suggest that perinatal exposure of rats to 5HTP, and especially TCP, induces long-lasting/permanent changes in the expression of 5HT-regulating genes, that presumably underlie 5HT-related neurochemical and behavioral changes in adult animals.

Anxiety-like behavior and cognitive flexibility in adult rats perinatally exposed to increased serotonin concentrations

Serotonin (5-hydroxytryptamine, 5HT) is a biologically active amine that regulates the development of 5HT neurons and target tissues during neurogenesis, while later it assumes the function of a neurotransmitter. Serotonin mediates many essential behaviors common to all mammals, and is held responsible for anxiety-like behavior and cognitive rigidity. Proper serotonin levels, controlled through 5HT synthesis and metabolism, are crucial for normal brain development. In this study we investigated anxiety-like behavior and cognitive flexibility in adult animals after exposing their developing brains to increased 5HT concentrations. Wistar rats were treated subcutaneously from gestational day 12 to post-natal day 21 with the immediate 5HT precursor 5-hydroxytryptophan (5HTP, 25mg/kg), a non-selective MAO inhibitor tranylcypromine (TCP, 2mg/kg), or saline. After reaching adulthood, animals were tested for anxiety-like behavior (exploratory behavior, thigmotactic behavior, social contact, and reaction to stressful stimulus) and cognitive flexibility (ability for reversal learning). Results of the behavioral studies corresponded with our previous neurochemical findings. Treatment with 5HTP, which has induced mild reduction in cortical 5HT concentrations, caused reduction in only one aspect of anxiety-like behavior (increased exploratory activity). Treatment with TCP, which lead to drastic reduction in 5HT concentration/function, resulted in a highly anxiolytic phenotype (reduced thigmotaxis, reaction to stress, and social anxiety) with improved cognitive flexibility. Although further neurochemical, anatomical and gene-expression studies are needed to elucidate the mechanisms underlying the observed behavior, we hope that our results will contribute to the understanding of the role of serotonin in anxiety-like behavior and cognitive rigidity.

Serotonin transporter gene polymorphism and psychiatric disorders: is there a link?

Though still in infancy, the field of psychiatric genetics holds great potential to contribute to the development of new diagnostic and therapeutic options to treat these disorders. Among a large number of existing neurotransmitter systems, the serotonin system dysfunction has been implicated in many psychiatric disorders and therapeutic efficacy of many drugs is also thought to be based on modulation of serotonin. Serotonin transporter gene polymorphism is one of the most extensively studied polymorphisms in psychiatric behavioral genetics. In this article, we review the status of evidence for association between the serotonin gene polymorphism and some common mental disorders like affective disorders, post-traumatic stress disorder, obsessive-compulsive disorder, suicide, autism, and other anxiety and personality disorders. Going beyond traditional association studies, gene-environment interaction, currently gaining momentum, is also discussed in the review. While the existing information of psychiatric genetics is inadequate for putting into practice genetic testing in the diagnostic work-up of the psychiatric patient, if consistent in future research attempts, such results can be of great help to improve the clinical care of a vast majority of patients suffering from such disorders.

The effects of the perinatal treatment with 5-hydroxytryptophan or tranylcypromine on the peripheral and central serotonin homeostasis in adult rats

Serotonin (5HT) is a biologically active amine present in mammals in the brain and the peripheral tissues. Autism is a neurodevelopmental disorder in which 5HT homeostasis is disturbed both centrally and peripherally, but the relationship between the 5HT disturbances in the two compartments is not understood. In an attempt to explore the relationship between the disturbed peripheral 5HT homeostasis and central 5HT functioning, we exposed the developing rat brain to increased 5HT concentrations, by treatment of rats with subcutaneous injections of the immediate 5HT precursor 5-hydroxy-L-tryptophan (5HTP, 25 mg/kg), or the non-selective MAO inhibitor tranylcypromine (TCP, 2 mg/kg), during the period of the most intensive development of 5HT neurons--from gestational day 13 to post-natal day 21. The effects of the mentioned treatments on peripheral and central 5HT levels were then studied in adult rats. Platelet and plasma 5HT concentrations (measured by ELISA), as well as cortical and midbrain 5HT, tryptophan and 5-hydroxyindoleacetic acid levels (measured by HPLC) were determined in twelve 5HTP treated and eight TCP treated rats, and compared with the values measured in 10 control, saline treated rats. Treatment with 5HTP significantly raised peripheral but not central 5HT concentrations. At adult age, peripheral 5HT homeostasis was re-established, while modest decrease in 5HT concentration was observed in frontal cortex, presumably due to hyperserotonemia-induced loss of 5HT terminals during brain development. Treatment with TCP induced significant 5HT elevations in both compartments. At adult age, permanent changes in 5HT homeostasis were observed, both peripherally (as hyperserotonemia) and centrally (as altered 5HT metabolism with decreased 5HT concentrations). Further studies are planned in order to explore the nature of the different disturbances of 5HT homeostasis induced by the two compounds, and their results are expected to shed some light on the role of hyperserotonemia in autism.

Gene-environment interactions and response to social intrusion in male and female rhesus macaques

BACKGROUND

Genetic factors interact with environmental stressors to moderate risk for human psychopathology, but sex may also be an important mediating factor. Different strategies for coping with environmental stressors have evolved in males and females, and these differences may underlie the differential prevalence of certain types of psychopathology in the two sexes. In this study, we investigated the possibility of sex-specific gene-environment interactions in a nonhuman primate model of response to social threat.

METHODS

Rhesus macaques (77 males and 106 females) were exposed to an unfamiliar conspecific. Using factor analysis, we identified three behavioral factors characterizing the response to social threat. Monkeys were genotyped for the serotonin transporter-linked polymorphism (5-HTTLPR), and the effects of genotype, early life stress, and sex on behavioral responses were evaluated.

RESULTS

Factor analysis produced five factors: High-Risk Aggression, Impulsivity/Novelty-Seeking, Gregariousness/Boldness, Harm Avoidance, and Redirected Aggression. Overall, males displayed higher levels of High-Risk Aggression and Gregariousness/Boldness than females. Levels of High-Risk Aggression in males carrying the s allele were significantly higher if they were also exposed to early adversity in the form of peer rearing.

CONCLUSIONS

Our findings support those from studies in humans suggesting that males are more vulnerable to externalizing or aggression-related disorders. The results highlight the importance of interactions that exist among behavior, genes, and the environment and suggest that sex differences in vulnerability to psychopathology may be grounded in our evolutionary history.

Serotonin transporter genotype, morning cortisol and subsequent depression in adolescents

BACKGROUND

The short (s) allele of the serotonin transporter gene promoter (5-HTTLPR) may be associated with exposure to social adversities and the subsequent onset of depressive illness in adulthood.

AIMS

To test in adolescents at high risk for depression whether the short 's' allele is associated with levels of morning cortisol and the subsequent onset of a depressive episode.

METHOD

High-risk adolescents (n = 403) were genotyped for 5-HTTLPR. Salivary samples were obtained on four consecutive school days within 1 h of waking from 393 (97.5%) individuals and 367 (91%) underwent a mental state reassessment at 12 months.

RESULTS

Multilevel analysis revealed higher levels of salivary cortisol in short allele carriers (s/s>s/l>l/l). A subsequent episode of depression was increased in those with higher cortisol and the 's' allele, and independently by depressive symptoms at entry, in both genders.

CONCLUSIONS

The short allele of 5-HTTLPR may moderate the association between morning cortisol and the subsequent onset of a depressive episode.

Hyperserotonemia in autism: activity of 5HT-associated platelet proteins

Disturbances in serotonin (5HT) neurotransmission have been indicated as biological substrates in several neuropsychiatric disorders including autism. Blood 5HT concentrations, elevated in about one-third of autistic subjects, are regulated through the action of peripheral 5HT-associated proteins. We have measured the activity of two platelet 5HT-associated proteins: 5HT transporter (5HTT) and monoamine oxidase B (MAOB), and indirectly studied the activity of 5HT(2A) receptor (5HT(2A)r) in 15 hyperserotonemic (HS) and 17 normoserotonemic (NS) autistic subjects, and 15 healthy controls (C). While mean velocities of 5HTT kinetics did not significantly differ among the groups, significant elevation in the mean velocity of MAOB kinetics was observed in NS subjects and was even more pronounced in HS subjects in comparison to controls. Also, a decrease in adenosine 5'-diphosphate-induced platelet aggregation of borderline significance was observed in NS subjects, compared to C subjects. The results suggest a possibility of upregulation of monoaminergic synthesis/degradation and, probably consequential, downregulation of 5HT(2A)r in autistic subjects.

The influence of 5-HTTLPR and STin2 polymorphisms in the serotonin transporter gene on treatment effect of selective serotonin reuptake inhibitors in depressive patients

BACKGROUND

Serotonin transporter gene (SLC6A4) variations have been proposed as an explanation for interindividual differences in selective serotonin reuptake inhibitors (SSRIs) effects. Quantitative assessment of genetic influences is necessary to evaluate whether genetic testing before antidepressant prescription would lead to earlier treatment effects. This study evaluates the influence of two polymorphisms (5-HTTLPR and STin2) on SSRI treatment outcome in depression.

METHODS

We included 50 SSRI nonresponders (cases) and 164 referents meeting Diagnostic and Statistical Manual Of Mental Disorder-IV criteria for major depression and using an SSRI for at least 6 weeks. Blood samples or buccal swabs were gathered to determine 5-HTTLPR (N=48 for cases and 161 for referents) and STin2 (N=50 for cases and 162 for referents) genotypes. The association between genotype and SSRI response was assessed by use of logistic regression.

RESULTS

Patients with the 5-HTTLPR s-allele had a nonsignificantly increased risk of SSRI nonresponse; odds ratio (OR) 1.60, 95% confidence interval (CI) 0.66-3.89. 5-HTTLPR effects were strongest in female patients (OR 3.54, 95% CI 1.05-11.92), and for male patients 5-HTTLPR seemed to have no effect (OR 0.29, 95% CI 0.04-2.34). An age-dependent effect of 5-HTTLPR was observed; patients under 44 years of age had an increased nonresponse risk (OR 9.34, 95% CI 1.41-61.98). STin2 genotype had no clear influence on treatment outcome.

CONCLUSION

Our findings indicate that women with the 5-HTTLPR s-allele have a less favorable response to SSRI treatment. To our knowledge, this is the first time that a gender-dependent influence of 5-HTTLPR is reported. More research is needed, particularly in subgroups of patients, before implementation of genetic testing can be recommended.

5-HT1A receptor gene C -1019 G polymorphism and amygdala volume in borderline personality disorder

Alterations of amygdala structure and function have been repeatedly described in patients with borderline personality disorder (BPD). The aim of our study was to determine whether a functional polymorphism of the 5-hydroxytryptamine(1A) receptor (5-HTR(1A)) gene C -1019 G (identity number: rs6295 G/C) is associated with structural changes of the amygdala in patients with BPD. Twenty-five right-handed female inpatients with BPD according to DSM IV and 25 healthy controls matched for age, sex, handedness and educational status were enrolled. Brain volumetry of the amygdala was performed with a 1.5-T Magnetom Vision apparatus (Siemens, Erlangen, Germany) and analyzed by the software program 'BRAINS'. Patients who have the 5-HTR(1A) gene G allele had significantly smaller amygdala volumes than C/C genotype carriers (P = 0.02). While no difference of allelic distribution between patients and controls was detected, the described effect of 5-HTR(1A) genotype on amygdala volume was found for the whole group of patients, as well as in the subgroup of patients with comorbid major depression (P = 0.004) but not in controls. In contrast to these subgroups of BPD patients who had significant amygdala volume differences, the mean amygdala volume of the whole group of BPD patients was not significantly different from that of controls. In summary, our study provides first evidence that 5-HTR(1A) gene C -1019 G polymorphism is associated with structural changes in the limbic system of BPD patients, a finding that might be disease related and might contribute to explanation of previous discrepant results regarding amygdala volume changes in BPD. Future research is recommended to clarify possible interactions between this functional polymorphism and symptoms, course and treatment responses in this disorder.

Acute antipyschotic efficacy and side effects in schizophrenia: association with serotonin transporter promoter genotypes

BACKGROUND

The serotonin transporter (5-HTT) plays an important role in serotonergic neurotransmission. In the present study, we investigated the effects of the 44 bp insertion/deletion polymorphism in the promoter region of 5-HTT gene (5-HTTLPR) on symptomatology of psychosis and clinical response to antipsychotic drugs.

METHODS

In total 56 patients acutely treated with haloperidol or risperidone either for the first episode of schizophrenia, schizophreniform or schizoaffective disorders, or for the relapse of these psychotic disorders after tapering their maintenance treatment, were genotyped for the 5-HTTLPR L and S alleles and for the new A/G functional variant within the L alelle (La/g). Psychopathological symptoms were assessed with the Brief Psychiatric Rating Scale (BPRS) and with Clinical Global Impression (CGI) twice: at 8-12 days after the first dose of antipsychotic and after 4 weeks. Extrapyramidal side effects were assessed with the Simpson-Angus Extrapyramidal Side Effects Scale (EPS), the Barnes Akathisia Scale (BARS) and the Abnormal Involuntary Movement Scale (AIMS).

RESULTS

Age, body mass index (BMI), illness duration, drug type and dosage were considered as covariates when analysing association with genetic variants as they were associated with baseline or final BPRS and CGI scores and/or extrapyramidal side effects. 5-HTTLPR was not associated with baseline and final BPRS and CGI scores or with the CGI% reduction. However, the 5-HTTLPR S allele was associated with a lower improvement in BPRS scores (P=0.022) and this effect was even stronger after pooling subjects with S or Lg containing alleles (P=0.006). We did not observe any effect of 5-HTTLPR on acute antipsychotics side effects.

CONCLUSION

Present result supports a contribution of serotonin system to neuroleptics efficacy for the treatment of schizophrenia. The analysis of the La/g functional variant may significantly improve the predictive power of 5-HTTLPR genotyping and represent a step further towards the development of the personalized antipsychotic treatment.

5-HT1A gene variants and psychiatric disorders: a review of current literature and selection of SNPs for future studies

5-HT1A receptors are key components of the serotonin system, acting both pre- and post- synaptically in different brain areas. There is a growing amount of evidence showing the importance of 5-HT1A in different psychiatric disorders, from mood to anxiety disorders, moving through suicidal behaviour and psychotic disorders. Findings in the literature are not consistent with any definite 5-HT1A influence in psychiatric disorders. 5-HT1A gene variants have been reported to play some role in mood disorders, anxiety disorders and psychotic disorders. Again, the literature findings are not unequivocal. Concerning response to treatment, the C(-1019)G variant seems to be of primary interest in antidepressant response: C allele carriers generally show a better response to treatment, especially in Caucasian samples. Together with the C(-1019)G (rs6295) variant, the Ile28Val (rs1799921), Arg219Leu (rs1800044) and Gly22Ser (rs1799920) variants have been investigated in possible associations with psychiatric disorders, also with no definitive results. This lack of consistency can be also due to an incomplete gene investigation. To make progress on this point, a list of validated single nucleotide polymorphisms (SNPs) covering the whole gene is proposed for further investigations.

Serotonergic candidate genes and puerperal psychosis: an association study

BACKGROUND

Altered serotonergic function is implicated in the aetiology and pathogenesis of a host of psychiatric disorders, and structural variations/polymorphisms in genes encoding the serotonin transporter and various serotonin receptor subtypes are attractive candidates to investigate the biological component underlying these disorders. Specific phenotypic subtypes, that perhaps represent homogeneous forms of the disorder, may increase the power to detect genes in complex diseases.

OBJECTIVE

We investigated regulatory and functional polymorphic DNA markers of serotonergic candidate genes using a case-control approach in puerperal psychosis and bipolar affective disorder probands.

METHODS

We genotyped 320 female participants (104 puerperal psychosis probands, 102 bipolar disorder participants and 114 controls) at the serotonin transporter SERT (5-HTT) 5-HTTVNTR and 5-HTTLPR locus; serotonin receptor 2A (5-HT2A)-T102C and His452Tyr loci, the serotonin receptor 2C (5-HT2C)-Cys23Ser locus, and seven unrelated Alu polymorphic markers.

RESULTS

We observed an association of the puerperal psychosis phenotype with the allele 10 of 5-HTTVNTR of SERT (P=0.004) and a modest association with the genotypic frequencies of the 5-HTTLPR (P=0.036). A nominal P value of 0.006 was observed with the S-10 haplotype in the PP group as compared with bipolar affective disorder probands. Significant association was observed with bipolar affective disorder phenotype with Tyr allele of the 5-HT2A His452Tyr gene polymorphism (P=0.00043) even after a conservative multiple test correction. No association was observed, however, with the 5-HT2A T102C locus, and the distribution of the other seven Alu markers did not differ between the groups.

CONCLUSION

The association between polymorphisms in serotonergic genes (SERT and 5-HT2A, 5-HT2C) suggests that these genetic factors can modulate vulnerability to puerperal psychosis in female bipolar participants.

Specific personality traits and dopamine, serotonin genes in anxiety-depressive alcoholism among Han Chinese in Taiwan

BACKGROUND

Cloninger [Cloninger CR. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-416.] had proposed a psychobiological model suggesting that three main personality dimensions distinguish the alcoholism into two subtypes (type I and type II). However, the classification was equivocal for clinical diagnosis. Recently, anxiety-depressive alcohol dependence (ANX/DEP ALC) has been posited as a genetically specific subtype of alcoholism. Its clinical characteristics were similar to individuals with type I alcoholism [Cloninger, C.R. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-6.] such as having a high comorbidity with mood disorder, late-onset and more anxious/depressed traits. We attempted to investigate whether the dopamine D2 receptor (DRD2) and the serotonin transporter promoter region (5-HTTLPR) genes were involved in Novelty Seeking (NS) and Harm Avoidance (HA) of ANX/DEP ALC.

METHODS

We recruited 46 pure alcohol dependents (Pure ALC) and 87 anxiety-depression alcohol dependents (ANX/DEP ALC). All participants were diagnosed by DSM-IV criteria, genotyped by the PCR method and assessed with Tridimensional Personality Questionnaire (TPQ).

RESULTS

Both NS and HA were high in ANX/DEP ALC (p = 0.021; p = 0.001, respectively). The association between NS and ANX/DEP ALC only existed in subjects with DRD2 TaqI A1(+) allele (A1/A1 or A1/A2 genotypes) (p = 0.004) and in those with S/S genotype of 5-HTTLPR (p = 0.005). With the stratification of DRD2 TaqI A1(+) allele, high NS of ANX/DEP ALC existed only in carriers of 5-HTTLPR S/S genotype (p=0.001). Moreover, ANX/DEP ALC was related to high HA only in samples carrying 5-HTTLPR S/L or L/L genotype (p = 0.02).

CONCLUSIONS

These findings provided the empirical genetic characterization of the specific personality traits in ANX/DEP ALC among Han Chinese population in Taiwan.

Association study of olanzapine-induced weight gain and therapeutic response with SERT gene polymorphisms in female schizophrenic patients

We investigated the relationships between L/S promoter (SERTPR) and l/s intron2 (SERTin2) genetic variants of serotonin transporter (SERT) polymorphisms with olanzapine-induced weight gain and treatment response in 94 female schizophrenic patients treated with olanzapine for up to 3 months. Body mass index (BMI) was calculated for each patient prior to olanzapine administration and 3 months afterwards. To assess and evaluate improvement of clinical psychotic symptoms and therapeutic response to the antipsychotic, all patients were rated using the Positive and Negative Syndrome ScaLe (PANSS). Overall, the presence of S SERTPR allelic variant and SS genotype was associated with significantly higher weight gain in subjects who were non-obese at the time of admission. The presence of L SERTPR variant was associated with significantly better treatment response measured with total PANSS and general PANSS subscale, while the presence of l SERTin2 variant determined better treatment response only in several items. No evidence of linkage disequilibrium between the two loci was found in the sample. These findings identify genetic factors associated with oLanzapine-induced weight gain and treatment response in femaLe schizophrenic patients.

Does pretreatment testing for serotonin transporter polymorphisms lead to earlier effects of drug treatment in patients with major depression? A decision-analytic model

BACKGROUND

An estimated 30% to 40% of patients with depression do not sufficiently respond to treatment with selective serotonin reuptake inhibitors (SSRIs) and the period in which treatment efficacy can be assessed is relatively long. Therefore, a test to identify potential nonresponders could be useful in the treatment of depression. Serotonin transporter gene (SLC6A4) variations have been reported to account for differences in the way individuals respond to SSRI treatment.

OBJECTIVE

A decision-analytic model was used to assess whether pretreatment genetic testing for 5-HTTLPR, a polymorphism of the SLC6A4 genotype, could be an efficient tool in the treatment of depression.

METHODS

A theoretical clinical decision-analytic model was constructed to compare the current treatment strategy in The Netherlands with an alternative strategy for the treatment of depression. Under treatment guidelines in The Netherlands, all patients with depression receive SSRI treatment (nontesting strategy). Under the alternative strategy, genetic testing would be performed to identify which class of antidepressant would be the best choice for initiation of treatment (genetic testing strategy). Probabilities (predicted results) for this model were based on data from previous studies and the opinions of experts in the field of psychopharmacology. To test the robustness of the model, 6- and 12-week remission rates for patients treated with SSRIs were varied in a sensitivity analysis using a predetermined range that was established based on expert opinion. Threshold analyses were performed on the parameters of serotonin transporter genotype frequency and response and nonresponse rates for patients receiving SSRIs, serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants (TCAs) to determine the value for a variable at which it could be concluded that a change in treatment strategy would be preferred.

RESULTS

When genetic testing was performed before an antidepressant was prescribed, 64.6% of patients were predicted to be in remission after 6 weeks of treatment compared with 60.0% of patients who did not receive genetic testing. After 12 weeks, 79.5% of patients in the testing group who received an SNRI as initial treatment and 83.2% of those who received a TCA initially were predicted to be in remission compared with 76.7% of patients in the nontesting group. Sensitivity analyses indicated that the model was robust to variation of probability estimates within their plausible ranges. However, these findings were based on a theoretic model and did not include cost assessment. Pretreatment genetic testing must be evaluated further in randomized clinical trials and costs must be assessed before implementing this strategy in routine psychiatric practice can be recommended.

CONCLUSIONS

The findings of this study suggest that performing genetic testing before prescribing antidepressant treatment may lead to greater numbers of patients experiencing remission early in treatment.

Serotonergic vulnerability and depression: assumptions, experimental evidence and implications

In recent years, the term serotonergic vulnerability (SV) has been used in scientific literature, but so far it has not been explicitly defined. This review article attempts to elucidate the SV concept. SV can be defined as increased sensitivity to natural or experimental alterations of the serotonergic (5-HTergic) system. Several factors that may disrupt the 5-HTergic system and hence contribute to SV are discussed, including genetic factors, female gender, personality characteristics, several types of stress and drug use. It is explained that SV can be demonstrated by means of manipulations of the 5-HTergic system, such as 5-HT challenges or acute tryptophan depletion (ATD). Results of 5-HT challenge studies and ATD studies are discussed in terms of their implications for the concept of SV. A model is proposed in which a combination of various factors that may compromise 5-HT functioning in one person can result in depression or other 5-HT-related pathology. By manipulating 5-HT levels, in particular with ATD, vulnerable subjects may be identified before pathology initiates, providing the opportunity to take preventive action. Although it is not likely that this model applies to all cases of depression, or is able to identify all vulnerable subjects, the strength of the model is that it may enable identification of vulnerable subjects before the 5-HT related pathology occurs.

Serotonin transporter gene (5-Htt): association analysis with temporal lobe epilepsy

Two functional polymorphisms, a 44bp insertion/deletion polymorphism in the 5' regulatory region and a variable number of tandem repeat polymorphisms in the second intron of the serotonin transporter gene (5-HTT), were previously identified and suggested to modulate transcription. The current study was designed to determine the contribution of these polymorphisms in the 5-HTT gene to susceptibility to temporal lobe epilepsy (TLE). Two hundred and seventy six patients with TLE, and 309 age- and sex-matched healthy controls from Calabria (Southern Italy) were studied. Patients and controls were genotyped using the WAVE TM DNA Fragment Analysis System for the insertion/deletion polymorphism in the promoter region (5-HTTLPR), and the GENESCAN TM System for the variable number tandem repeat (VNTR) in the second intron of the 5-HTT gene (5-HTTVNTR). The program UNPHASED was used to compare genotype, allele and haplotype frequencies between cases and controls, including age and gender as covariates in the model. No significant differences between cases and controls were observed for 5-HTTLPR, but a significant association was obtained for the 5-HTTVNTR polymorphism, both modeling genotypes (P-value=0.0145) or alleles (P-value=0.0086). Patients with TLE showed lower frequencies of the 10 repeat at 5-HTTVNTR than the controls (26.2% in patients versus 40.8% in controls). The frequency of homozygous individuals for the 10 allele was observed to be lower among patients than the controls (5.2% of patients were 10/10 versus 18.8% of controls). Haplotype analysis did not increase the evidence for association. These results suggest that the serotonin transporter gene may play a role in the etiology of TLE.

The neurobiology of stress and development

Stress is a part of every life to varying degrees, but individuals differ in their stress vulnerability. Stress is usefully viewed from a biological perspective; accordingly, it involves activation of neurobiological systems that preserve viability through change or allostasis. Although they are necessary for survival, frequent neurobiological stress responses increase the risk of physical and mental health problems, perhaps particularly when experienced during periods of rapid brain development. Recently, advances in noninvasive measurement techniques have resulted in a burgeoning of human developmental stress research. Here we review the anatomy and physiology of stress responding, discuss the relevant animal literature, and briefly outline what is currently known about the psychobiology of stress in human development, the critical role of social regulation of stress neurobiology, and the importance of individual differences as a lens through which to approach questions about stress experiences during development and child outcomes.

Meta-analysis of serotonin transporter gene promoter polymorphism (5-HTTLPR) association with selective serotonin reuptake inhibitor efficacy in depressed patients

The serotonin transporter gene promoter polymorphism (5-HTTLPR) has been repeatedly associated with antidepressant response in mood disorder patients, but findings are not consistent across studies. A meta-analysis was performed on 15 studies including data of 1435 subjects. We tested three phenotypes: remission rate, response rate and response rate within 4 weeks using the cochrane review manager. We observed a significant association of the s/s variant of 5-HTTLPR with remission rate (P<0.0001) and both s/s and s/l variants with response rate (P=0.0002). Response rate within 4 weeks was associated in both models (P=0.003-P<0.00001). This effect is quite robust to ethnic differences although a significant heterogeneity is present in Asian samples.

Cerebrospinal fluid monoamine metabolite levels in human newborn infants born in winter differ from those born in summer

An earlier study has shown significant differences in the CSF monoamine metabolite levels in adults born during different seasons of the year. We study here the relationship between season of birth and CSF monoamine metabolite levels in 283 newborn febrile infants without neurological abnormalities, with an age distribution ranging from birth to about 3 months, adjusting for the confounding variables age and time at lumbar puncture, weight at birth, estimated gestational age at birth, gender, race, and medicaid status. Each of the three metabolite levels as well as their ratios HVA/5-HIAA and 5-HIAA/MHPG showed significant month-of-birth variations, but not the ratio HVA/MHPG. For HVA and MHPG levels, the maximum was obtained around the winter birth months November-December, whereas for 5-HIAA level, the maximum was obtained around the summer birth months June-July. The correlations between HVA and 5-HIAA were, in general, significantly positive within the different birth seasons and races. Among summer-born Caucasian infants, MHPG was significantly positively correlated with HVA and with 5-HIAA, whereas among winter-born Black infants, MHPG was significantly positively correlated with HVA. Season of birth is an unspecific environmental factor that may be proxy for several possible seasonally varying environmental circumstances such as the length of photoperiod, temperature, infections, nutrition, stress and lifestyle. Studies relating season of birth to monoaminergic turnover at different stages of life may yield important clues about the gestational and perinatal origins of neurodevelopment.

Neuroimaging studies of serotonin gene polymorphisms: exploring the interplay of genes, brain, and behavior

Because of the unique ability it provides to investigate information processing at the level of neural systems, functional neuroimaging is a powerful tool to explore the relationship between genes, brain, and behavior. Recently, functional neuroimaging has provided dramatic illustrations of how a promoter polymorphism in the human serotonin transporter gene, which has been weakly related to several dimensions of emotional behaviors (such as neuroticism and anxiety traits), is strongly related to the engagement of neural systems--namely, the amygdala and subgenual prefrontal cortex, subserving emotional information processing. This review will outline the experimental strategy by which these genetic effects on brain function have been explored and highlight the effectiveness of this strategy to delineate biological pathways and mechanisms contributing to the emergence of individual differences in brain function that potentially bias behavior and risk for psychiatric illness.

Neurotoxins and neurotoxicity mechanisms. an overview

Neurotoxins represent unique chemical tools, providing a means to 1) gain insight into cellular mechanisms of apopotosis and necrosis, 2) achieve a morphological template for studies otherwise unattainable, 3) specifically produce a singular phenotype of denervation, and 4) provide the starting point to delve into processes and mechanisms of nerve regeneration and sprouting. There are many other notable uses of neurotoxins in neuroscience research, and ever more being discovered each year. The objective of this review paper is to highlight the broad areas of neuroscience in which neurotoxins and neurotoxicity mechanism come into play. This shifts the focus away from neurotoxins per se, and onto the major problems under study today. Neurotoxins broadly defined are used to explore neurodegenerative disorders, psychiatric disorders and substance use disorders. Neurotoxic mechanisms relating to protein aggregates are indigenous to Alzheimer disease, Parkinson's disease. NeuroAIDS is a disorder in which microglia and macrophages have enormous import. The gap between the immune system and nervous system has been bridged, as neuroinflammation is now considered to be part of the neurodegenerative process. Related mechanisms now arise in the process of neurogenesis. Accordingly, the entire spectrum of neuroscience is within the purview of neurotoxins and neurotoxicity mechanisms. Highlights on discoveries in the areas noted, and on selective neurotoxins, are included, mainly from the past 2 to 3 years.

Ziprasidone-associated mania: a review and report of 2 additional cases

Although mania was not reported as an adverse event in the pivotal trials of ziprasidone, there have been 7 reports of ziprasidone-induced mania in 12 patients. We now report 2 additional cases wherein the introduction of ziprasidone resulted in new-onset manic episodes. In 1 case, the patient required hospitalization and lost his job. In the other, time to mania was 5 months, considerably longer than previously reported. Of the 14 cases, 9 were in a depressive episode when ziprasidone was prescribed, and 8 had a history of current or past exposure to antidepressants. Ziprasidone, like many antidepressants, can block reuptake of norepinephrine and serotonin, although mania has developed in patients treated with atypical antipsychotics that are less potent in this regard. However, ziprasidone and other atypical antipsychotics have in common a high ratio of 5-HT2a to D2 receptor blockade, which may also play a role in this phenomenon. Clinicians and patients need to be aware of the potential for the induction of mania with ziprasidone, even after lengthy exposure.

Pharmacogenetics of the serotonin transporter

Response to psychopharmacologic drugs is genetically complex, results from an interplay of multiple genomic variations with environmental influences, and depends on the structure or functional expression of gene products, which are direct drug targets or indirectly modify the development and synaptic plasticity of neural networks critically involved in their effects. During brain development, the serotonin (5HT) system, which is commonly targeted by antidepressant, anxiolytic, and antipsychotic drugs, controls neuronal specification, differentiation, and phenotype maintenance. While formation and integration of these neural networks is dependent on the action of multiple proteins, converging lines of evidence indicate that genetically controlled variability in the expression of the 5HT transporter (5HTT) is critical to the development and plasticity of distinct neurocircuits. The most promising finding to date indicate an association between the response time as well as overall response to serotonin reuptake inhibitors (SSRIs) and a common polymorphism (5HTTLPR) within the transcriptional control region of the 5HTT gene (SLC6A4) in patients with depressive disorders. The formation and maturation of serotonergic and associated systems, in turn, are influencing the efficacy of serotonergic compounds in a variety of psychiatric conditions. Based on the notion that complex gene x gene and gene x environment interactions in the regulation of brain plasticity are presumed to contribute to individual differences in psychopharmacologic drug response, the concept of developmental psychopharmacogenetics is emerging.

Gender specific gene-environment interactions on laboratory-assessed aggression

We examined gene-environment interactive effects on aggressive behavior among men and women genotyped (short versus long alleles) for the serotonin transporter gene. Aggressive behavior was indexed via a laboratory paradigm that measured the intensity and duration of shocks delivered to a putative "employee". Half of the participants were exposed to a physical stressor during the procedure (stress) and half were not (no-stress). Participants' physiological responses were gauged via acoustic startle eyeblink reactions (startle reactivity). Results were that men with the homozygous short (s/s) genotype showed increased aggression only under stress, whereas women and men carrying the long allele did not show differences in aggression in stress versus no-stress. However, although stress exposure produced increases in startle reactivity, there were no genotype or gender differences in physiology. These results replicate longitudinal research findings confirming the interactive effects of genes and environment on behavioral reactivity and on the development of externalizing psychopathological syndromes, at least in men.

Genetic alterations of the murine serotonergic gene pathway: the neurodevelopmental basis of anxiety

The relative contribution of genetic and environmental factors in the configuration of behavioral differences is among the most prolonged and contentious controversies in intellectual history. Although current views emphasize the joint influence of genes and environmental sources during early brain development, the physiological complexities of multiple gene-gene and gene-environment interactions in the developmental neurobiology of fear and anxiety remain elusive. Variation in genes coding for proteins that control serotonin (5-hydroxytryptamine, 5-HT) system development and plasticity, establish 5-HT neuron identity, and modulate 5-HT receptor-mediated signal transduction as well as cellular pathways have been implicated in the genetics of anxiety and related disorders. This review selects anxiety and avoidance as paradigmatic traits and behaviors, and it focuses on mouse models that have been modified by deletion of genes coding for key players of serotonergic neurotransmission. In particular, pertinent approaches regarding phenotypic changes in mice bearing inactivation mutations of 5-HT receptors, 5-HT transporter, and monoamine oxidase A and other genes related to 5-HT signaling will be discussed and major findings highlighted.

Peripheral and central neurochemical effects of the selective serotonin reuptake inhibitors (SSRIs) in humans and nonhuman primates: assessing bioeffect and mechanisms of action

It is clear that selective serotonin reuptake inhibitors (SSRIs) act powerfully to inhibit serotonin (5-hydroxytryptamine, 5-HT) uptake centrally and peripherally. However, there are a number of critical unanswered questions concerning the effects of the drugs in adults and children. The influence of age and duration of treatment on the extent of uptake inhibition and on the enhancement of central serotonergic functioning are unclear. In addition, the relationship of these factors and effects to the therapeutic and adverse effects of the SSRIs remain to be clarified. The general clinical utility of platelet 5-HT measurement is reviewed and studies assessing central and peripheral uptake blockade in infants and children and non-human primates are discussed. Recent investigations of central neurochemical effects of the SSRIs in primates assessed through measurement of 5-HT and related compounds in cisternal cerebrospinal fluid (CSF) of the rhesus monkey are presented. In summary, the studies described have found that: human fetal exposure to SSRIs has substantial effects on 5-HT transport in utero; exposure to SSRIs through breastmilk of mothers treated for postpartum depression usually has negligible effects on 5-HT uptake; prescribed SSRIs appear to exert similar effects on 5-HT transporter blockade in children and adults; and rapid and sustained increases are seen in monkey cisternal CSF levels of 5-HT upon initiation of SSRI administration. The implications of the observations in terms of behavioral effects, clinical practice, and underlying mechanisms of action of the SSRIs are discussed.

Platelet serotonin in newborns and infants: ontogeny, heritability, and effect of in utero exposure to selective serotonin reuptake inhibitors

Ontogeny of platelet serotonin (5-hydroxytryptamine, 5-HT) during the first year of life was examined in newborns and infants. The effects of in utero exposure to selective serotonin reuptake inhibitors (SSRI, including fluoxetine, sertraline, and citalopram) were examined by comparing cord blood 5-HT levels in exposed and unexposed newborns. Heritability was assessed by correlation of the platelet 5-HT values observed for mother-infant pairs. No age effect was observed in 1-49 wk-old infants (r = 0.13, p = 0.49) and mean platelet 5-HT levels in infants (241 +/- 102 ng/mL, n = 33; 615 +/- 320 ng/10(9) platelets, n = 32) were similar to those reported for older children and adults. However, significantly lower blood 5-HT levels were observed in newborns (81.3 +/- 32.5 ng/mL, n = 16, p < 0.0001; 297 +/- 101 ng/10(9) platelets, n = 11, p = 0.0007) compared with the 1-49 wk-old infants. The mean cord blood 5-HT concentrations in newborns exposed in utero to SSRI (n = 8) were substantially lower than that seen in unexposed (n = 16) newborns (20.6 +/- 14.4 versus. 81.3 +/- 32.5 ng/mL, p = 0.0001; 90.7 +/- 55.4 versus. 297 +/- 101 ng/10(9) platelets, p = 0.0005). Platelet serotonin levels (ng/10(9) platelets) in mother-child pairs (n = 32) were significantly correlated (r = 0.415, p = 0.018). The results indicate that, although platelet 5-HT is low at birth, values quickly increase and stabilize at near-adult levels by 1 mo of age. Gestational exposure to SSRI appears to substantially reduce platelet 5-HT uptake in the fetus, strongly suggesting that such exposure has important physiologic effects. The observed mother-infant correlation agrees with a previous report of high heritability in a large adult population.

Serotonin transporter promoter and intron 2 polymorphisms: relationship between allelic variants and gene expression

BACKGROUND

Two polymorphic regions of serotonin transporter (5-HTT) gene: a 44 base pair (bp) insertion/deletion in the promoter region (5-HTTLPR) and a 17 bp variable number of tandem repeats in second intron (VNTR-2), seem to modulate the gene's transcription in allele-dependent manner.

METHODS

We have earlier demonstrated association with 5-HTT gene in families multiply affected by schizophrenia. Here, we investigated separate and combined effects of VNTR-2 and 5-HTTLPR on the rate of peripheral 5-HTT transcription in a sample of offspring from those families. Relative 5-HTT mRNA levels were determined in 53 permanent lymphoblast cell lines by semiquantitative real-time polymerase chain reaction using beta-actin as reference.

RESULTS

Since the low-expressing alleles (short [S], 10) appeared to act dominantly, genotypes were grouped as "high-expressing" (long [L]/L, 12/12) versus "low-expressing" (S, 10). At both loci, nonsignificant differences in 5-HTT mRNA levels ( approximately 30%) were observed between "high"- and "low-expressing" genotypes. In order to search for the potential combined effect of 5-HTTLPR and VNTR-2, levels of 5-HTT mRNA were compared among three groups of samples having "low-expressing" genotype at none, one, or both loci. Increase in number of "low-expressing" genotypes significantly reduced relative 5-HTT gene expression (p <.02).

CONCLUSIONS

Our results indicate weak individual influence, but possible combined effect, of 5-HTTLPR and VNTR-2 polymorphisms on 5-HTT gene expression.

Influence of SERTPR and STin2 in the serotonin transporter gene on the effect of selective serotonin reuptake inhibitors in depression: a systematic review

Large differences in clinical response to selective serotonin reuptake inhibitors (SSRIs) are observed in depressive patients with different genotypes. Quantification of these differences is needed to decide if genetic testing prior to antidepressant treatment is useful. We conducted a systematic review of the literature on the influence of polymorphisms in the serotonin transporter gene (SERTPR (or 5-HTTLPR) and STin2) on SSRI response. Studies were identified by the use of MEDLINE, EmBase and PsycINFO, references of articles, reviews and information from pharmaceutical companies. Nine studies assessing the influence of SERTPR or STin2 on treatment response were included. Outcome was expressed as the percentage of decrease in depression score (HAM-D or MADRS) or as the percentage of responders (> or =50% reduction on the depression scale). Both study methodologies and study outcomes showed large heterogeneity. Weighted mean decreases in depression score for patients with the s/s, s/l and l/l genotypes were 35.4, 46.3 and 48.0% at week 4, respectively, and 53.9, 54.6 and 48.3% at week 6. Among Caucasian patients, both mean decrease in depression score and response rate were lowest in the s/s group, while among Asian patients, results were inconsistent. Weighted response rates were 36.1% for the 10/12 genotype of the STin2 polymorphism and 80.7% for the 12/12 genotype (chi2=27.8, P<0.001) (only Asians). The available evidence points to a less favourable response to SSRI treatment among Caucasian patients with the SERTPR s/s genotype and among (Asian) patients with the STin2 10/12 genotype. In view of the scarcity and heterogeneity of the studies, however, current information is insufficiently reliable as a basis for implementing genetic testing in the diagnostic work-up of the depressive patient.

Structural Effects and Neurofunctional Sequelae of Developmental Exposure to Psychotherapeutic Drugs: Experimental and Clinical Aspects

The advent of psychotherapeutic drugs has enabled management of mental illness and other neurological problems such as epilepsy in the general population, without requiring hospitalization. The success of these drugs in controlling symptoms has led to their widespread use in the vulnerable population of pregnant women as well, where the potential embryotoxicity of the drugs has to be weighed against the potential problems of the maternal neurological state. This review focuses on the developmental toxicity and neurotoxicity of five broad categories of widely available psychotherapeutic drugs: the neuroleptics, the antiepileptics, the antidepressants, the anxiolytics and mood stabilizers, and a newly emerging class of nonprescription drugs, the herbal remedies. A brief review of nervous system development during gestation and following parturition in mammals is provided, with a description of the development of neurochemical pathways that may be involved in the action of the psychotherapeutic agents. A thorough discussion of animal research and human clinical studies is used to determine the risk associated with the use of each drug category. The potential risks to the fetus, as demonstrated in well described neurotoxicity studies in animals, are contrasted with the often negative findings in the still limited human studies. The potential risk fo the human fetus in the continued use of these chemicals without more adequate research is also addressed. The direction of future research using psychotherapeutic drugs should more closely parallel the methodology developed in the animal laboratories, especially since these models have already been used extremely successfully in specific instances in the investigation of neurotoxic agents.

Anxiety-related traits in mice with modified genes of the serotonergic pathway

The neurobiology of anxiety is complex, reflecting the cumulative physiological effects of multiple genes. These genes are interactive with each other and with the environment in which they are expressed. Variation in genes coding for proteins that control serotonin (5-HT) system development and plasticity, establish 5-HT neuron identity, and modulate 5-HT receptor-mediated signal transduction and cellular pathways have been implicated in the genetics of anxiety and related disorders. Here, we selected anxiety and avoidance as paradigmatic traits and behavior and cover both traditional studies with inbred murine strains and selected lines which have been modified by gene knockout technologies. The design of a mouse model partially or completely lacking a gene of interest during all stages of development (constitutive knockout) or in a spatio-temporal context (conditional knockout) is among the prime strategies directed at elucidating the role of genetic factors in fear and anxiety. In many cases, knockout mice have been able to confirm what has already been anticipated based on pharmacological studies. In other instances, knockout studies have changed views of the relevance of 5-HT homeostasis in brain development and plasticity as well as processes underlying emotional behavior. In this review, we discuss the pertinent literature regarding phenotypic changes in mice bearing inactivation mutations of 5-HT receptors, 5-HT transporter, monoamine oxidase A and other components of the serotonergic pathway. Finally, we attempt to identify future directions of genetic manipulation in animal models to advance our understanding of brain dysregulation characteristic of anxiety disorders.

Maternal fluoxetine treatment in the postpartum period: effects on platelet serotonin and plasma drug levels in breastfeeding mother-infant pairs

OBJECTIVE

Postpartum major depression, a frequently (10%) occurring complication of childbirth, adversely affects the mother's functioning, the mother-infant relationship, and the child's subsequent development and propensity for later psychopathology. Although selective serotonin reuptake inhibitors (SSRIs) are effective in treating postpartum depression, concerns have been raised regarding their use in lactating women. Although plasma drug levels of infants who are exposed to SSRIs through breast milk are low compared with those typically seen in patients, infant levels in some reports do seem to be at or near the drugs' reported affinities (K(D)s) and IC(50)s for inhibition at the serotonin (5-hydroxytryptamine [5-HT]) transporter. The impact of central serotonin 5-HT modulation by SSRIs during critical periods of brain development is unknown. These concerns have led our group to examine whether exposure through breast milk has a discernible effect on platelet 5-HT uptake. Taking advantage of the similarities between platelet and neuronal serotonin transporters, we previously used measurements of platelet 5-HT before and during maternal sertraline treatment to determine the degree of 5-HT transporter blockade in breastfed infants. We found that infants who were exposed to sertraline through their mothers' breast milk experienced little to no change in platelet 5-HT levels, suggestive of minimal effects on peripheral and central 5-HT transporter blockade. Compared with sertraline and most other SSRIs, fluoxetine and its active metabolite, norfluoxetine, have substantially longer plasma half-lives, and both compounds have been found in measurable quantities in plasma of nursing infants. Thus, to extend our previous work in this area, we measured platelet 5-HT levels and plasma drug levels in breastfeeding mother-infant pairs before and during maternal treatment with fluoxetine.

METHODS

Maternal and infant transporter blockade was assessed by measurement of platelet 5-HT in 11 breastfeeding mother-infant pairs before and after 4 to 12 weeks of maternal fluoxetine (20-40 mg/d) treatment for postpartum depression. The study was approved by the Human Investigation Committee of Yale University School of Medicine, and each mother (mean age: 34.5 years; standard deviation [SD]: 5.3) gave written informed consent. Whole-blood 5-HT levels and plasma fluoxetine and norfluoxetine levels were determined by high-performance liquid chromatography.

RESULTS

Five mothers were taking 20 mg of fluoxetine daily, 4 were taking 30 mg daily, and 2 were taking 40 mg daily. Mean infant age at the start of the study was 16.8 (SD: 8.8) weeks. All infants except 1 were <6 months of age and 4 were <3 months of age when their mothers began treatment. Six infants were breastfed exclusively; the remaining were breastfed between 3 and 8 times daily and were given supplemental feedings. Mean maternal postexposure 5-HT levels of 22.9 ng/mL (SD: 12.5) were markedly lower than mean preexposure (baseline) levels of 156.6 ng/mL (SD: 71.4; paired t = 6.9, df = 10). In contrast, the mean infant pre- and postexposure 5-HT concentrations of 217.1 (SD: 66.5) and 229.9 (SD: 83.5) ng/mL, respectively, were similar (paired t = -0.24, df = 10). However, the 1 infant with measurable plasma fluoxetine had a substantial decline in 5-HT to 40% of baseline. In samples obtained from the same infant 4 months later, plasma drug levels were undetectable (<1 ng/mL) and the platelet serotonin levels were no longer reduced (12% increase from baseline).

CONCLUSIONS

The marked declines (to 9%-28% of baseline) in platelet 5-HT concentrations seen in mothers who were treated with the SSRI fluoxetine were similar to those observed in our study of sertraline in breastfeeding and other previous studies. In contrast, all but 1 infant experienced little or no decline in whole-blood (platelet) 5-HT concentrations after exposure to fluoxetine through breast milk. The substantial drop in platelet 5-HT seen in 1 infant and the coupling of this drop with measurable plasma fluoxetine leves drop with measurable plasma fluoxetine level raises some concern. Possible reasons for the infant's measurable plasma fluoxetine level include his mother's high plasma drug level and his being breastfed exclusively. However, the observations may be coincidental, and the infant experienced no discernible adverse effects. These data suggest that most infants may continue to breastfeed without experiencing meaningful changes in platelet 5-HT transport while their mothers are treated with 20 to 40 mg of fluoxetine daily. Given the limited data regarding occurrence and extent of SSRI exposure and the uncertainties concerning the possible effects of exposure, it is premature to propose treatment guidelines. Our own advice to women who are thinking of combining breastfeeding and SSRI treatment will weigh a range of factors, including severity of postpartum depression, any demonstrated preferential response to a specific SSRI, and the mother's commitment to breastfeeding. Additional research is needed to establish more definitively the frequency of physiologically meaningful infant SSRI exposure during breastfeeding and to determine the behavioral consequences of such exposure.

Pharmacogenomics of psychiatric drug treatment

It is the goal of pharmacogenomics in psychiatry to establish predictive relationships between polymorphisms of candidate genes and therapeutic response to drug treatment. Polymorphisms of candidate genes related to drug mechanisms and pathophysiology of illness and defined clinical phenotype are the foundations for pharmacogenomic studies. Pharmacogenomic studies of antipsychotic response have focused on polymorphisms of genes for dopamine and serotonin receptors with most positive results reported for polymorphisms of genes of the 5HT2a and 5HT2c serotonin receptor subtypes. Although the goal of establishing individualized medicine predicated on an individual patient's genetic code has yet to be achieved, the fundamentals are now in place for second-generation investigation and more application to health care.