Effects of monoamine uptake inhibitors on extracellular and platelet 5-hydroxytryptamine in rat blood: different effects of clomipramine and fluoxetine

The role of peripheral serotonin and norepinephrine in the gastroprotective effect against stress of duloxetine

Duloxetine has been shown to produce gastroprotective effect against gastric ulcer induced by water immersion restraint stress (WIRS) via modulation of NADPH oxidases in the gastric mucosa and neurometabolites of central nucleus of amygdala. However, the underlying mechanism based on the basic pharmacological function of duloxetine-regulation on serotonin (5-HT) and norepinephrine (NE) remains unclear. Here, we found that 5-HT level in platelet-poor plasma (PPP) was decreased but NE level in plasma was increased in rats exposed to WIRS, while pretreatment with duloxetine increased 5-HT in PPP dose-dependently and decreased NE in plasma of rats after WIRS. We further showed that depletion of 5-HT by 4-chloro-DL-phenylalanine (PCPA) aggravated gastric mucosa damage and supplement of 5-HT alleviated gastric ulcers induced by WIRS. Blockade of NE receptors also mitigated the stress gastric ulcers. Using adrenalectomy and chemical blocking, we identified that it was NE from adrenal medulla rather than sympathetic nerve that was more critical in the gastroprotection of duloxetine, and intriguingly, glucocorticoid did not make a difference in WIRS-provoked gastric ulcers as a classic stress hormone. Together, our work demonstrated prophylactic protection of duloxetine from the stress gastric ulcer depended on enhancing peripheral 5-HT content and reducing NE from adrenal medulla, which provided insight into treatments of WIRS-induced gastric ulcer.

Inhibition of Tryptophan Hydroxylases and Monoamine Oxidase-A by the Proton Pump Inhibitor, Omeprazole-In Vitro and In Vivo Investigations

Serotonin (5-HT) is a hormone and neurotransmitter that modulates neural activity as well as a wide range of other physiological processes including cardiovascular function, bowel motility, and platelet aggregation. 5-HT synthesis is catalyzed by tryptophan hydroxylase (TPH) which exists as two distinct isoforms; TPH1 and TPH2, which are responsible for peripheral and central 5-HT, respectively. Due to the implication of 5-HT in a number of pathologies, including depression, anxiety, autism, sexual dysfunction, irritable bowel syndrome, inflammatory bowel disease, and carcinoid syndrome, there has been a growing interest in finding modulators of these enzymes in recent years. We thus performed high-throughput screening (HTS) using a fluorescence-based thermal shift assay (DSF) to search the Prestwick Chemical Library containing 1,280 compounds, mostly FDA-approved drugs, for TPH1 binders. We here report the identification of omeprazole, a proton pump inhibitor, as an inhibitor of TPH1 and TPH2 with low micromolar potency and high selectivity over the other aromatic amino acid hydroxylases. The S-enantiomer of omeprazole, esomeprazole, has recently also been described as an inhibitor of monoamine oxidase-A (MAO-A), the main enzyme responsible for 5-HT degradation, albeit with lower potency compared to the effect on TPH1 and TPH2. In order to investigate the net effect of simultaneous inhibition of TPH and MAO-A in vivo, we administered high-dose (100 mg/kg) omeprazole to CD-1 mice for 4 days, after which the animals were subjected to the tail suspension test. Finally, central (whole brain) and peripheral (serum) 5-HT content was measured using liquid chromatography-mass spectrometry (LC-MS). Omeprazole treatment significantly increased 5-HT concentrations, both in brain and in serum, and reduced the time spent immobile in the tail suspension test relative to vehicle control. Thus, the MAO-A inhibition afforded by high-dose omeprazole appears to overcome the opposing effect on 5-HT produced by inhibition of TPH1 and TPH2. Further modification of proton pump inhibitor scaffolds may yield more selective modulators of 5-HT metabolism.

The teratogenic effects of sertraline in mice

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs), which include paroxetine (Paxil), sertraline (Zoloft), fluoxetine (Prozac), citalopram (Celexa), and escitalopram (Lexapro), are the most common antidepressants prescribed to pregnant women. There is considerable debate in the literature regarding the developmental toxicities of SSRIs individually, and as a class.

METHODS

It is considered unethical to perform developmental toxicity studies on pregnant women, but rodent and nonrodent species provide laboratory-controlled experimental models to examine the toxicity of SSRI exposure during pregnancy. The Embryo-Fetal Developmental Toxicity Study was conducted with sertraline in mice, Crl:CD1 (lCR), during the period of organogenesis.

RESULTS

Increased resorption rates, lower fetal weight, and increased percentage of fetuses with visceral and skeletal abnormalities were found in the intermediate and high sertraline dose groups. In addition to incomplete ossification of treated animals, eleven sertraline exposed fetuses, two in group 2 (5 mg/kg), five in group 3 (25 mg/kg), and four in group 4 (60 mg/kg), had cleft palate (CP). This malformation was not observed in any controls. Only the highest dose of sertraline was found to be maternally toxic, as evidenced by significantly lower weight gain during pregnancy.

CONCLUSION

These data indicate that in utero exposure to sertraline at 25 and 60 mg/kg was embryotoxic, teratogenic, and fetotoxic in mice. The incidence of CP observed in groups 3 and 4 (2.99% and 2.5%, respectively) were higher than the maximum range value noted in historical controls and indicate sertraline is a teratogen in ICR mice.

Revisiting the validity of the mouse tail suspension test: Systematic review and meta-analysis of the effects of prototypic antidepressants

Animal models in neuropsychiatric research need validation. One way to address external validity is systematic reviews and meta-analyses. The present study presents a meta-analysis of the effects of antidepressants in the mouse tail suspension test (TST). A PubMed search identified studies that examined imipramine and fluoxetine effects in the TST. Inclusion criteria were testing in the light phase; trial duration was six minutes; immobility time scored 6 or (last) 4 min; adult mice; acute intraperitoneal (IP) administration. Effect sizes (ES) were estimated using Cohen's d, heterogeneity of ES with Cochran's Q test, correlations between dose and ES with Pearson's correlation and differences between strains with Analysis of variance. Results show that antidepressants decrease immobility time in the TST and a correlation between drug dose and ES but no effects of strain. We suggest that the TST is a valid tool to quantitatively, consistently and reproducibly capture the immobility-reducing aspects of fluoxetine and imipramine and that the lack of strain effects is due to small number of experiments in many of the strains.

Postnatal outcomes in lambs exposed antenatally and acutely postnatally to fluoxetine

BACKGROUND

Approximately 1/3 of newborns exposed antenatally to selective serotonin reuptake inhibitors (SSRIs) exhibit poor neonatal adaptation. Although several potential mechanisms have been proposed, the actual mechanism has not been elucidated.

METHODS

We investigated outcomes in neonatal lambs exposed prenatally or postnatally to fluoxetine (FX). Daily FX injections (50 mg) were given intravenously (i.v.) to five pregnant ewes via implanted catheters beginning at 131-132 days gestation (term = 147 days) for 2 weeks. In another group, lambs with implanted vascular catheters had sterile water (n = 9) or FX (1 mg/kg, n = 12) injected i.v. on ~postnatal day (PND) 4.

RESULTS

Prenatal FX-exposed lambs (n = 7) were hyperactive during PND 4 to 14 and their heart rate variability (HRV) was significantly lower than in control lambs (n = 7) on PND 2. In contrast, arterial pressure, heart rate, electrocardiogram, arterial blood gases, pH, glucose, lactate, cortisol, and sleep-activity cycles were not altered following postnatal FX injection.

CONCLUSION

This abnormal postnatal hyperactivity with antenatal FX exposure may reflect increased maturity in terms of locomotory activity. The results suggest that altered brain development may be involved in the poor neonatal adaptation in human infants exposed to FX in utero.

Prenatal Selective Serotonin Reuptake Inhibitor Use and Associated Risk for Gestational Hypertension and Preeclampsia: A Meta-Analysis of Cohort Studies

BACKGROUND

To analyze existing cohort studies and provide evidence for the use of prenatal selective serotonin reuptake inhibitor (SSRI) monotherapy and the associated risk of gestational hypertension and preeclampsia.

METHODS

A comprehensive search of English language articles published before 30th April 2017 was conducted on PubMed, EMBASE, and the Web of Science databases. Using data acquired, we summarized the relative risks (RRs) and 95% confidence intervals (CIs) of gestational hypertension and preeclampsia using the random-effects model. Heterogeneity between studies was also assessed with the I² statistic.

RESULTS

Seven cohort studies with 1,108,261 individuals were included for analysis. Compared with nonusers, those undertaking prenatal SSRI monotherapy were more likely to develop gestational hypertension or preeclampsia (summarized RR = 1.21, 95% CI: 1.05-1.40, I² = 71.3%), gestational hypertension (summarized RR = 1.14, 95% CI: 1.00-1.30, I² = 5.7%), and preeclampsia (summarized RR = 1.32, 95% CI: 0.99-1.78, I² = 83.3%). In addition, although subgroup analyses, which were stratified by study design, number of cases, geographic location, duration of SSRI monotherapy, registry databases, and adjustment for potential confounders and risk factors, were consistent with the main findings, not all of these showed statistical significance. No evidence of publication bias was detected.

CONCLUSIONS

Women who receive SSRI monotherapy during pregnancy are at increased risk of gestational hypertension and preeclampsia.

Application of Aorta-gonad-mesonephros Explant Culture System in Developmental Hematopoiesis

The limitation of using mouse embryos for hematopoiesis studies is the added inconvenience in operations, which is largely due to the intrauterine development of the embryo. Although genetic data from knockout (KO) mice are convincing, it is not realistic to generate KO mice for all genes as needed. In addition, performing in vivo rescue experiments to consolidate the data obtained from KO mice is not convenient. To overcome these limitations, the Aorta-Gonad-Mesonephros (AGM) explant culture was developed as an appropriate system to study hematopoietic stem cell (HSC) development. Especially for rescue experiments, it can be used to recover the impaired hematopoiesis in KO mice. By adding the appropriate chemicals into the medium, the impaired signaling can be reactivated or up-regulated pathways can be inhibited. With the use of this method, many experiments can be performed to identify the critical regulators of HSC development, including HSC related gene expression at mRNA and protein levels, colony formation ability, and reconstitution capacity. This series of experiments would be helpful in defining the underlying mechanisms essential for HSC development in mammals.

5-hydroxytryptamine synthesized in the aorta-gonad-mesonephros regulates hematopoietic stem and progenitor cell survival

Lv et al. show that in mice, 5-HT can be synthesized in the aorta-gonad-mesonephros and acts as a novel endogenous regulator of hematopoietic stem and progenitor cell (HSPC) development. The promoting effect of 5-HT on the survival of HSPCs in the intraaortic hematopoietic cluster is mediated through Htr5a-AKT-Foxo1 signaling.

The in vitro or ex vivo production of transplantable hematopoietic stem cells (HSCs) holds great promise for the treatment of hematological diseases in the clinic. However, HSCs have not been produced from either embryonic or induced pluripotent stem cells. In this study, we report that 5-hydroxytryptamine (5-HT; also called serotonin) can enhance the generation of hematopoietic stem and progenitor cells (HSPCs) in vitro and is essential for the survival of HSPCs in vivo during embryogenesis. In tryptophan hydroxylase 2–deficient embryos, a decrease in 5-HT synthesized in the aorta-gonad-mesonephros leads to apoptosis of nascent HSPCs. Mechanistically, 5-HT inhibits the AKT-Foxo1 signaling cascade to protect the earliest HSPCs in intraaortic hematopoietic clusters from excessive apoptosis. Collectively, our results reveal an unexpected role of 5-HT in HSPC development and suggest that 5-HT signaling may be a potential therapeutic target for promoting HSPC survival.

Study on anti-inflammatory and immunomodulatory effects of fluoxetine in rat models of inflammation

The aim of the present study was to evaluate the anti-inflammatory effect of fluoxetine in carrageenan- and lipoplysaccharide-induced models of inflammation by investigating the changes in serum levels of pro-inflammatory cytokine TNF-α and anti-inflammatory cytokines IL-10 and TGF-β after single and repeated administration of the drug. To study the effect of a single and repeated dose fluoxetine on carrageenan-induced paw edema male Wistar rats were divided into five groups (n = 8): control group; positive control group; and three experimental groups treated with 5, 10, and 20 mg/kg bodyweight (bw) fluoxetine, respectively. To study the effect of a single and repeated dose of fluoxetine on serum cytokine levels, the animals were divided in four groups (n = 8): two control groups treated with saline and two experimental groups treated with fluoxetine 20 mg/kg bw. Carrageenan and LPS were injected immediately after fluoxetine or saline injection. Serum cytokine concentrations were tested by enzyme immunoassay. In single administration only the highest dose used inhibited carrageenan-induced inflammation. Edema inhibition was seen with 10 and 20 mg/kg bw fluoxetine after repeated administration. At 24 h a statistically significant effect on inhibition of carrageenan edema was found only in rats treated with 20 mg/kg bw fluoxetine In carrageenan-induced inflammation, fluoxetine significantly increased Il-10 and decreased TNF-α after repeated administration. Surprisingly, in single-dose treated animals an increase in TNF-α values upon fluoxetine administration was observed in this model of inflammation. In LPS-induced inflammation, fluoxetine significantly decreased TNF-α after single and repeated treatment. Fluoxetine has anti-inflammatory and immunomodulatory effect in the carrageenan-induced model of exudative inflammation. In LPS-induced inflammation it showed an immunomodulatory effect manifested with a decrease in pro-inflammatory cytokine TNF-α.

Morphine-Induced Constipation Develops With Increased Aquaporin-3 Expression in the Colon via Increased Serotonin Secretion

Aquaporin-3 (AQP3) is a water channel that is predominantly expressed in the colon, where it plays a critical role in the regulation of fecal water content. This study investigated the role of AQP3 in the colon in morphine-induced constipation. AQP3 expression levels in the colon were analyzed after oral morphine administration to rats. The degree of constipation was analyzed after the combined administration of HgCl(2) (AQP3 inhibitor) or fluoxetine (5-HT reuptake transporter [SERT] inhibitor) and morphine. The mechanism by which morphine increased AQP3 expression was examined in HT-29 cells. AQP3 expression levels in rat colon were increased during morphine-induced constipation. The combination of HgCl(2) and morphine improved morphine-induced constipation. Treatment with morphine in HT-29 cells did not change AQP3 expression. However, 5-HT treatment significantly increased the AQP3 expression level and the nuclear translocation of peroxisome proliferator-activated receptor gamma (PPARγ) 1 h after treatment. Pretreatment with fluoxetine significantly suppressed these increases. Fluoxetine pretreatment suppressed the development of morphine-induced constipation and the associated increase in AQP3 expression in the colon. The results suggest that morphine increases the AQP3 expression level in the colon, which promotes water absorption from the luminal side to the vascular side and causes constipation. This study also showed that morphine-induced 5-HT secreted from the colon was taken into cells by SERT and activated PPARγ, which subsequently increased AQP3 expression levels.

Effects of antidepressants on alternations in serum cytokines and depressive-like behavior in mice after lipopolysaccharide administration

Accumulating evidence suggests that inflammation may play a role in the pathophysiology of major depressive disorder (MDD). Antidepressants, including selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs), possess anti-inflammatory effects in vitro. Here, we examined the effects of SSRIs and SNRIs on lipopolysaccharide (LPS)-induced inflammation and depressive-like behavior in male mice. A single administration of LPS (0.5mg/kg, i.p.) increased serum levels of the pro-inflammatory cytokine, tumor necrosis factor-α (TNFα) and the anti-inflammatory cytokine, interleukin-10 (IL-10) in mice. Pretreatment with SSRIs (fluoxetine and paroxetine), SNRIs (venlafaxine and duloxetine), or 5-hydroxytryptophan (5-HTP), a precursor of serotonin, attenuated LPS-induced increases in TNFα, whereas it increased serum levels of IL-10, in mice treated with LPS. In the tail suspension test (TST), LPS increased the immobility time without affecting spontaneous locomotor activity, suggesting that LPS induced depressive-like behavior in mice. Treatment with fluoxetine (30 mg/kg) or paroxetine (10mg/kg) significantly shortened LPS-induced increases of immobility time. These results suggested that antidepressants exert anti-inflammatory effects in vivo, and that the serotonergic system may partially mediate these effects. In addition, the anti-inflammatory effects of antidepressants may help alleviate the symptoms of LPS-induced depression in mice.

Antidepressant use during pregnancy and the risk of pregnancy-induced hypertension

AIM

Due to their effect on altering physiological interactions between vasodilator and vasoconstrictor autacoids in normal pregnancies, antidepressants may be associated with the risk of pregnancy-induced hypertension. We evaluated the impact of antidepressant use during pregnancy on the risk of pregnancy-induced hypertension.

METHODS

We conducted a nested case-control study within the Quebec Pregnancy Registry, built by linkage of provincial medical, pharmaceutical, hospital and birth databases. We identified 1216 women with a diagnosis of pregnancy-induced hypertension with or without pre-eclampsia and with no history of hypertension before pregnancy. We randomly selected 10 controls for each case, matched on case index date (date of diagnosis) and gestational age. Odds ratios (OR) were calculated using conditional logistic regression models, adjusting for sociodemographic characteristics, maternal depression, anxiety, other chronic conditions, medication use and health service utilization.

RESULTS

Among cases, 45 (3.7%) had used antidepressants during pregnancy compared with 300 (2.5%) in the control group (OR 1.52, 95% CI 1.10, 2.09). After adjusting for potential confounders, use of antidepressants during pregnancy was significantly associated with increased risk of pregnancy-induced hypertension (OR 1.53, 95% CI 1.01, 2.33). In stratified analyses, use of selective serotonin re-uptake inhibitors (OR 1.60, 95% CI 1.00, 2.55), and more specifically, paroxetine (OR 1.81, 95% CI 1.02, 3.23) was associated with risk of pregnancy-induced hypertension.

CONCLUSIONS

Women who use antidepressants during pregnancy are at increased risk of pregnancy-induced hypertension with or without pre-eclampsia above and beyond the risk that could be attributed to their depression or anxiety disorders.

Third trimester fetal heart rate and Doppler middle cerebral artery blood flow velocity characteristics during prenatal selective serotonin reuptake inhibitor exposure

Prenatal selective serotonin reuptake inhibitor (SSRI) exposure increases the risk for adverse neonatal behavioral outcomes; although it is unknown whether altered brain function is present before birth. We investigated fetal vascular and heart rate changes at 36-wk gestation in SSRI-treated women with mood disorders (n = 29) [exposed (EXP)] and controls (n = 45) [non-EXP (NEXP)]. Fetal middle cerebral artery (MCA) flow parameters and heart rate characteristics were obtained during pre-SSRI dose morning and postdose afternoon sessions. Maternal mood and cord Hb and hematocrit were measured. Basal fetal heart rate (fHR) did not differ between groups or across the day. The fHR short- and long-term variations, accelerations, and duration of high variability episodes remained lower and did not change across the day in EXP, whereas all increased significantly in NEXP. In both groups, MCA flow velocity and volume flow increased significantly across the day. EXP MCA pulsatility index was significantly lower, as was MCA cross-sectional area. EXP cord Hb and hematocrit were significantly increased. Prenatal SSRI exposure reduced fetal MCA flow resistance and fHR variability, before and after an SSRI dose, controlling for maternal mood. These changes and the SSRI-related increased red cell indices suggest possible fetal hypoxia.

Serotonin (5-HT) transporter ligands affect plasma 5-HT in rats

Dual dopamine (DA)/serotonin (5-HT)-releasing agents are promising candidate medications for stimulant addiction and other disorders. However, certain 5-HT transporter (SERT) substrates are associated with development of idiopathic pulmonary arterial hypertension (IPAH) and valvular heart disease (VHD). According to the "5-HT hypothesis," SERT substrates increase the risk for developing IPAH and VHD by increasing plasma 5-HT. To test this hypothesis directly, we determined the effects of acute and chronic fenfluramine, and other SERT ligands, on plasma 5-HT in male rats. For acute treatments, rats received i.v. vehicle or test drug (0.3 and 1.0 mg/kg), and serial blood samples were withdrawn. For chronic treatments, vehicle or test drug was infused via osmotic minipump (3 and 10 mg/kg/d) for 2 weeks. On the last day of infusion, rats received i.v. fenfluramine challenge (1 mg/kg), and serial blood samples were withdrawn. Plasma 5-HT was measured using ex vivo microdialysis in whole-blood samples. Baseline plasma 5-HT was <1.0 nM. Acute injection of fenfluramine or other SERT substrates caused large (up to 24-fold) dose-dependent increases in plasma 5-HT. Chronic fenfluramine at 3 and 10 mg/kg/d produced 1.7- and 3.5-fold increases in baseline plasma 5-HT, while chronic fluoxetine had no effect. Chronic infusions of fenfluramine or fluoxetine diminished the ability of acute fenfluramine to elevate dialysate 5-HT, and both drugs markedly reduced whole-blood 5-HT. Acute fenfluramine increases plasma 5-HT to concentrations that are below the micromolar levels necessary to produce adverse cardiovascular effects. Chronic fenfluramine and fluoxetine have minimal effects on plasma 5-HT, suggesting that the increased risk for IPAH associated with fenfluramine does not depend upon elevations in plasma 5-HT.

Fetal and neonatal effects of maternal drug treatment for depression

Depression has a female sex predilection with 2 to 3% of the pregnant women population presently requiring treatment with selective serotonin reuptake inhibitors (SSRI). Exposure to SSRIs in late gestation leads to clinical manifestations in as much as 30% of the neonates. These include neurobehavioral, respiratory, gastrointestinal, and somatic symptoms. Among the respiratory manifestations, persistent pulmonary hypertension syndrome is a newly recognized and concerning side effect of SSRI exposure in utero. This causal association has been reproduced in an animal model where fluoxetine administration to pregnant rats induces fetal pulmonary hypertension. The pharmacological effects of SSRI on the fetus and newborn, available treatment, and prevention strategies are discussed in this review.

Morphological and functional determinants of fluoxetine (Prozac)-induced pulmonary disease in an experimental model

Fluoxetine treatment effects were determined by evaluating respiratory mechanics (elastance/resistance) and exhaled nitric oxide, as well as mononuclear and polymorphonuclear cell recruitment into the lungs, in an experimental guinea pig model. Guinea pigs were divided into four groups: Fl (fluoxetine only, n=7); Fl+Sw (fluoxetine and forced swimming, n=7); Ns+Sw (normal saline and forced swimming, n=8); and Ns (normal saline only, n=8). Treated animals received oral fluoxetine (10 mg/(kg day)) for 30 consecutive days. On day 31, all animals were anesthetized and mechanically ventilated so that respiratory system elastance and resistance, as well exhaled nitric oxide, could be determined. The lungs were then excised en bloc for histological and immunohistochemical evaluation. Forced swimming induced bronchodilation in untreated animals and bronchoconstriction in fluoxetine-treated animals. Fluoxetine treatment was also associated with mononuclear infiltration (predominantly into alveolar walls) and neutrophil recruitment. In addition, levels of exhaled nitric oxide, an inflammatory marker, were higher in fluoxetine-treated animals. Swimming-induced stress also amplified mononuclear cell recruitment to the lungs. These results show that, in this experimental model, fluoxetine treatment reproduces the pathology of chronic interstitial pneumonia in humans.

Fluoxetine during pregnancy: impact on fetal development

Women are at greatest risk of suffering from depression during the childbearing years and thus may either become pregnant while taking an antidepressant or may require a prescription for one during pregnancy. The antidepressant fluoxetine (FX) is a selective serotonin reuptake inhibitor (SSRI), which increases serotonin neurotransmission. Serotonin is involved in the regulation of a variety of physiological systems, including the sleep–wake cycle, circadian rhythms and the hypothalamic–pituitary–adrenal axis. Each of these systems also plays an important role in fetal development. Compared with other antidepressant drugs, the SSRIs, such as FX, have fewer side effects. Because of this, they are now frequently prescribed, especially during pregnancy. Clinical studies suggest poor neonatal outcome after exposure to FX in utero. Recent studies in the sheep fetus describe the physiological effects of in utero exposure to FX with an 8 day infusion during late gestation in the sheep. This is a useful model for determining the effects of FX on fetal physiology. The fetus can be studied for weeks in its normal intrauterine environment with serial sampling of blood, thus permitting detailed studies of drug disposition in both mother and fetus combined with monitoring of fetal behavioural state and cardiovascular function. Fluoxetine causes an acute increase in plasma serotonin levels, leading to a transient reduction in uterine blood flow. This, in turn, reduces the delivery of oxygen and nutrients to the fetus, thereby presenting a mechanism for reducing growth and/or eliciting preterm delivery. Moreover, because FX crosses the placenta, the fetus is exposed directly to FX, as well as to the effects of the drug on the mother. Fluoxetine increases high-voltage/non-rapid eye movement behavioural state in the fetus after both acute and chronic exposure and, thus, may interfere with normal fetal neurodevelopment. Fluoxetine also alters hypothalamic function in the adult and increases the magnitude of the prepartum rise in fetal cortisol concentrations in sheep. Fetal FX exposure does not alter fetal circadian rhythms in melatonin or prolactin. Studies of the effects of FX exposure on fetal development in the sheep are important in defining possible physiological mechanisms that explain human clinical studies of birth outcomes after FX exposure. To date, there have been insufficient longer-term follow-up studies in any precocial species of offspring exposed to SSRIs in utero. Thus, further investigation of the long-term consequences of in utero exposure to FX and other SSRIs, as well as the mechanisms involved, are required for a complete understanding of the impact of these agents on development. This should involve studies in both humans and appropriate animal models.

Increased release of serotonin from rat ileum due to dexfenfluramine

Plasma levels of serotonin are elevated in primary pulmonary hypertension even after bilateral lung transplantation, suggesting a possible etiologic role. Serotonin is released primarily from the small intestine. Anorectic agents, such as dexfenfluramine, which can cause pulmonary hypertension, are known to inhibit potassium channels in vascular smooth muscle cells. We examined the hypothesis that dexfenfluramine may stimulate release of serotonin from the ileum by inhibition of K+ channels. In an isolated loop of rat ileum perfused with a physiological salt solution, the administration of dexfenfluramine, its major metabolite d-norfenfluramine, the potassium channel blocker 4-aminopyridine (5 mM), and caffeine (30 mM) increased serotonin levels in the venous effluent. Potassium chloride (60 mM) tended to increase serotonin levels. In genetically susceptible individuals, dexfenfluramine may induce pulmonary hypertension by increasing cytosolic calcium in enterochromaffin cells of the small intestine, thus releasing serotonin and causing vasoconstriction. This work indicates that dexfenfluramine and its major metabolite d-norfenfluramine can increase serotonin release from the small intestine.

Possible involvement of peripheral serotonin 5-HT3 receptors in fluvoxamine-induced emesis in Suncus murinus

Selective serotonin reuptake inhibitors fluvoxamine and fluoxetine, as well as serotonin (5-HT), induced vomiting in Suncus murinus (a house musk shrew). Fluvoxamine- and fluoxetine-induced vomiting gradually decreased with their repeated administration. Vomiting induced by serotonin also decreased with repeated treatment with serotonin. In these shrews, fluvoxamine-induced vomiting was partially inhibited. Fluvoxamine might induce vomiting, at least partially, by indirectly activating peripheral 5-HT(3) receptors, since serotonin has been reported to induce vomiting by activating peripheral 5-HT(3) receptors and granisetron, a 5-HT(3) antagonist, partially suppressed fluvoxamine-induced vomiting in our previous finding. In addition, fluvoxamine-induced vomiting was impaired more effectively using a step-wise dose-up schedule of fluvoxamine than a fixed high-dose schedule. Therefore, a careful dosing strategy starting with a low dose might be effective for avoiding emesis associated with the clinical use of fluvoxamine.

Spotlight on fluvoxamine in anxiety disorders in children and adolescents

Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI) which may be used for the management of anxiety disorders in children and adolescents. Absorption of fluvoxamine was similar in adolescents to that in adults, which suggests that the maximum dosage of the drug for patients aged between 12 and 17 years can be as high as 300 mg/day. However, steady-state plasma fluvoxamine concentrations were 2 to 3 times higher in children (aged between 6 and 11 years) than in adolescents; thus, the maximum fluvoxamine dosage recommended for children is 200 mg/day. Fluvoxamine (50 to 300 mg/day) for 8 to 16 weeks significantly reduced symptoms of obsessive-compulsive disorder (OCD) [measured across multiple assessment scales] compared with placebo in a well controlled trial in paediatric patients (n = 120) or from baseline in noncomparative trials in adolescent (n = 20) or paediatric (n = 16) patients. Improvements with fluvoxamine (up to 200 mg/day) were observed for up to 1 year in 98 patients with OCD in a noncomparative trial. The drug (up to 250 or 300 mg/day) also improved symptoms of anxiety compared with placebo in an 8-week well controlled trial in 128 paediatric patients with social phobia, separation anxiety disorder or generalised anxiety disorder (GAD). Fluvoxamine (50 to 300 mg/day) appears to be well tolerated in paediatric patients, with most adverse events with the drug (except abdominal discomfort, which occurred more often in patients receiving fluvoxamine) occurring with a similar incidence to those with placebo. The most common adverse events involved the CNS or gastrointestinal system. Most adverse events reported by paediatric patients with OCD were similar to those reported by adults. In conclusion, fluvoxamine is generally well tolerated and has demonstrated short-term efficacy compared with placebo in the treatment of OCD, and social phobia, separation anxiety disorder or GAD in well controlled trials in paediatric patients. Reductions in symptoms of anxiety with fluvoxamine have been observed for up to 1 year in children and adolescents with OCD. However, there are currently no comparative trials of fluvoxamine with other pharmacological agents. In the absence of such trials, current consensus opinion recommends that when pharmacotherapy is indicated, fluvoxamine, like other SSRIs, can be used as first-line treatment for anxiety disorders, particularly OCD, in paediatric patients. However, direct comparisons are required to assess the relative efficacy and tolerability of pharmacological agents in order to make firm recommendations for the treatment of anxiety disorders in this patient group.

Fluvoxamine: a review of its therapeutic potential in the management of anxiety disorders in children and adolescents

Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI) which may be used for the management of anxiety disorders in children and adolescents. Absorption of fluvoxamine was similar in adolescents to that in adults, which suggests that the maximum dosage of the drug for patients aged between 12 and 17 years can be as high as 300 mg/day. However, steady-state plasma fluvoxamine [corrected] concentrations were 2 to 3 times higher in children (aged between 6 and 11 years) than in adolescents; thus, the maximum fluvoxamine dosage recommended for children is 200 mg/day. Fluvoxamine (50 to 300 mg/day) for 8 to 16 weeks significantly reduced symptoms of obsessive-compulsive disorder (OCD) [measured across multiple assessment scales] compared with placebo in a well controlled trial in paediatric patients (n = 120) or from baseline in noncomparative trials in adolescent (n = 20) or paediatric (n = 16) patients. Improvements with fluvoxamine (up to 200 mg/day) were observed for up to 1 year in 98 patients with OCD in a noncomparative trial. The drug (up to 250 or 300 mg/day) also improved symptoms of anxiety compared with placebo in an 8-week well controlled trial in 128 paediatric patients with social phobia, separation anxiety disorder or generalised anxiety disorder (GAD). Fluvoxamine (50 to 300 mg/day) appears to be well tolerated in paediatric patients, with most adverse events with the drug (except abdominal discomfort, which occurred more often in patients receiving fluvoxamine) occurring with a similar incidence to those with placebo. The most common adverse events involved the central nervous system or gastrointestinal system. Most adverse events reported by paediatric patients with OCD were similar to those reported by adults. In conclusion, fluvoxamine is generally well tolerated and has demonstrated short-term efficacy compared with placebo in the treatment of OCD, and social phobia, separation anxiety disorder or GAD in well controlled trials in paediatric patients. Reductions in symptoms of anxiety with fluvoxamine have been observed for up to 1 year in children and adolescents with OCD. However, there are currently no comparative trials of fluvoxamine with other pharmacological agents. In the absence of such trials, current consensus opinion recommends that when pharmacotherapy is indicated, fluvoxamine, like other SSRIs, can be used as first-line treatment for anxiety disorders, particularly OCD, in paediatric patients. However, direct comparisons are required to assess the relative efficacy and tolerability of pharmacological agents in order to make firm recommendations for the treatment of anxiety disorders in this patient group.

A novel immunocytochemical assay for the detection of serotonin in platelets

A method for the rapid, inexpensive and easy detection of platelet serotonin (5-hydroxytryptamine, 5-HT) is not currently available. Consequently, many patients suffering from unresolved platelet-related bleeding disorders are not examined for a possible platelet 5-HT deficiency. The direct measurement of 5-HT concentration with high-performance liquid chromatography (HPLC) or serotonin enzyme-linked immunosorbent assay (ELISA) is costly and highly demanding. Indirect methods, which determine the content of ATP or calcium with lumi-aggregometry or electron microscopy, rely upon the assumption that the ATP or calcium concentration is equivalent to that of 5-HT. We have developed a fluorescence-based assay for 5-HT that can be performed within 2 h on fresh or frozen samples using a fluorescence microscope or a flow cytometer. The assay requires only 0.2 ml of platelet-rich plasma and might therefore be of particular interest for paediatric patients. Samples from control and patient donors were analysed for 5-HT with the new immunocytochemical assay in comparison with HPLC and/or 5-HT ELISA. Patients with Hermansky-Pudlak syndrome were readily identified. The new assay was also reliable in cases where the 5-HT content of dense granules was not correlated with the calcium or ATP content, such as in calcium deficiency or in the presence of selective serotonin reuptake inhibitors.

Effects of repeated fluoxetine and citalopram administration on cytokine release in C57BL/6 mice

This study examines the effects of repeated administration of the selective serotonin reuptake inhibitors (SSRIs), fluoxetine and citalopram (10 mg/kg, i.p.), on immunoreactivity in C57BL/6 mice. Immune functions were evaluated by the ability of splenocytes to reduce a tetrazolium salt to formazan (MTT test), to proliferate, and to produce cytokines, including interleukin (IL)-1, IL-2, IL-4, IL-6, IL-10 and interferon gamma (IFN gamma). Citalopram administered for 1, 2 and 4 weeks stimulates the proliferative activity of splenocytes and suppresses their ability to secrete the anti-inflammatory cytokine IL-4. Fluoxetine administration for 1 and 2 weeks, but not 4 weeks, stimulates the proliferative activity of splenocytes, whereas a 4-week administration of fluoxetine suppresses the secretion of IL-4. Four weeks of prolonged administration of citalopram and fluoxetine induces a significant increase in the production of IL-6 and IL-10, a cytokine with immunosuppressive and anti-inflammatory activities. The results show that, in C57BL/6 mice, the immunomodulatory effects of SSRIs depend on the SSRI used and the duration of administration.

Evidence that serotonin affects female sexual functioning via peripheral mechanisms

A review of the literature indicates that serotonin is active in several peripheral mechanisms that are likely to affect female sexual functioning. Serotonin has been found in several regions of the female genital tract in both animals and humans. In the central nervous system (CNS), serotonin acts primarily as a neurotransmitter, but in the periphery, serotonin acts primarily as a vasoconstrictor and vasodilator. Since, in the periphery, the principal component of sexual arousal is vasocongestion of the genital tissue, it is likely that serotonin participates in producing normal sexual arousal. In addition, serotonin administration produces contraction of the smooth muscles of the genito-urinary system and is found in nerves innervating the sexual organs. Taken together, this evidence suggests that peripheral serotonergic activity may be involved in the normal sexual response cycle. In addition, exogenous substances that alter serotonin activity, such as selective serotonin uptake inhibitors (SSRIs) and the atypical antipsychotics, can produce sexual dysfunction. It is possible that sexual side effects seen with these drugs may result, at least in part, from their action on peripheral mechanisms.

Endotoxin and dietary amines may increase plasma 5-hydroxytryptamine in the horse

Uptake of 5-hydroxytryptamine (5-HT) into platelets is an important mechanism by which low plasma concentrations are maintained, and platelet activation may therefore result in significant release of this vasoconstrictor. The present study examined the kinetics of active uptake of radiolabelled [3H]5-HT by washed equine platelets in vitro, and investigated the effects on this process of 4 other naturally occurring monoamines which may be released from the caecum in conditions of carbohydrate overload. The release of [3H]5-HT by platelets was also studied, since platelet accumulation and activation has been associated with acute laminitis. Release of [3H]5-HT was measured in response to platelet activating factor (PAF), unlabelled 5-HT and the indirect activation of platelets by endotoxin in the presence of blood leucocytes. Km value for the uptake of 5-HT by equine platelets was 2.4 +/- 0.6 micromol/l and the Vmax was 8.3 +/- 0.6 pmol [3H]5-HT/10(7) platelets/min. The rate of uptake of 5 micromol/l [3H]5-HT was significantly decreased by the uptake inhibitors fluvoxamine and clomipramine. The 4 other monoamines examined all inhibited the uptake of [3H]5-HT in a noncompetitive manner, decreasing Vmax by between 17 and 82%. Incubation of platelets with LPS (0.1 mg/ml) in the absence of leucocytes did not result in significant release of [3H]5-HT; however, in the presence of leucocytes 3.8 +/- 1.7 pmol [3H]5-HT/10(7) platelets (mean +/- s.e.) were released. This release was significantly inhibited by parthenolide and WEB2086, but not by aspirin. This suggests that PAF from activated leucocytes was responsible for the 5-HT release. These data show that 5-HT uptake by equine platelets is a saturable process operating most efficiently at substrate concentrations in the low micromolar range. The noncompetitive inhibition of 5-HT uptake by other naturally occurring monoamines may result in increased plasma concentrations of 5-HT, as would its release by endotoxin. Such a rise in plasma 5-HT concentrations may contribute to selective vasoconstriction in the equine digital circulation.

Fluvoxamine. An updated review of its use in the management of adults with anxiety disorders

Fluvoxamine is a potent and selective serotonin reuptake inhibitor (SSRI) that has little or no effect on other monoamine reuptake mechanisms. Relative to other SSRIs, fluvoxamine is a weak inhibitor of cytochrome P450 (CYP) 2D6, a moderate inhibitor of CYP2C19 and CYP3A4 and a potent inhibitor of CYP1A2. In randomised, double-blind trials. fluvoxamine 100 to 300 mg/day for 6 to 10 weeks significantly reduced symptoms of obsessive-compulsive disorder (OCD) compared with placebo. Response rates of 38 to 52% have been reported with fluvoxamine, compared with response rates of 0 to 18% with placebo. In patients with OCD, fluvoxamine had similar efficacy to that of clomipramine and, in smaller trials, the SSRIs paroxetine and citalopram and was significantly more effective than desipramine. Maintenance therapy with fluvoxamine may reduce the likelihood of relapses in up to 67% of patients with OCD. Fluvoxamine < or = 300 mg/day for 6 to 8 weeks was as effective as imipramine in patients with panic disorder, and significantly more effective than placebo. In addition, treatment with fluvoxamine < or = 300 mg/day for > or = 8 weeks improved symptoms of social phobia (social anxiety disorder), post-traumatic stress disorder (PTSD), pathological gambling, compulsive buying, trichotillomania, kleptomania, body dysmorphic disorder, eating disorders and autistic disorder. Large trials comparing the efficacy of fluvoxamine and other SSRIs in patients with anxiety disorders are warranted. Fluvoxamine is generally well tolerated; in postmarketing studies, nausea was the only adverse event occurring in >10% of patients with less commonly reported events including somnolence, asthenia, headache, dry mouth and insomnia. Fluvoxamine is associated with a low risk of suicidal behaviour, sexual dysfunction and withdrawal syndrome. Fewer anticholinergic or cardiovascular events are associated with fluvoxamine than tricyclic antidepressants. Although comparative data are lacking, the tolerability profile of fluvoxamine appears to be broadly similar to those of other SSRIs.

CONCLUSION

Fluvoxamine has demonstrated short term efficacy in the treatment of OCD, panic disorder, social phobia, PTSD and in a range of obsessive-compulsive spectrum disorders. The drug is as effective as clomipramine in patients with OCD but appears to have a better tolerability profile. On the basis of current treatment guidelines, fluvoxamine, like other SSRIs, is recommended as first-line treatment for a number of anxiety disorders. It appears to offer some pharmacokinetic advantages and a different drug interaction profile to the other SSRIs with a broadly similar spectrum of adverse events. However, direct comparisons are required to assess the relative efficacy and tolerability of the different agents of this drug class.

[Hemorrhagic syndromes related to selective serotonin reuptake inhibitor (SSRI) antidepressants. Seven case reports and review of the literature]

PURPOSE

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed. Since their release unexpected adverse effects such as bleeding disorders have been described.

METHODS

Thirty patients with either hematoma or muco-cutaneous bleeding have been selected from case reports of the Saint-Etienne Pharmacovigilance center and from a literature review.

RESULTS

The female/male sex-ratio was 3:4 and the mean age 42 years. Two newborns who had been exposed in utero to SSRIs were also included in the study. Eleven patients presented an underlying disease or were at risk. Various adverse effects such as bruising, hematoma, petechiae or purpura, epistaxis, and more rarely intestinal hemorrhage, ocular bleeding or cerebral hemorrhage were encountered. Symptoms were sometimes associated with prolonged bleeding time and platelet aggregation disorders and usually resolved within two days to four months after treatment discontinuation.

CONCLUSION

Hematoma and muco-cutaneous bleeding would therefore be related to treatment, including selective serotonin reuptake inhibitors. However, these adverse effects are still poorly known and rarely reported. The main mechanism suggested would be a decrease in serotonin platelet leading to a defect in platelet aggregation. However, an increase in capillary fragility or susceptibility related to the patient's condition might be involved. Study of hemostasis history in patients requiring treatment with SSRIs might be of value.

Differential changes in brain and platelet 5-HT concentrations after steady-state achievement and repeated administration of antidepressant drugs in mice

The aim of the study was to compare in male NMRI mice the simultaneous evolution of blood serotonin (5-HT) concentrations, which correspond to 99% of platelet 5-HT content, and 5-HT parameters in the dorsal raphe, caudate nucleus and frontal cortex after clomipramine, fluoxetine and moclobemide treatments. After steady-state concentrations of the three compounds were reached, the 5-HT levels were significantly enhanced vs. saline-treated mice in the three brain areas studied. Tryptophan (TRP) levels in the three brain areas were significantly increased with clomipramine and fluoxetine but not with moclobemide. A significant decrease in the metabolite 5-hydroxyindoleacetic acid (5-HIAA) levels was observed only with moclobemide. After 14 days of treatment, 5-HT levels in all areas studied were found to be enhanced only with moclobemide while TRP and 5-HIAA levels were not different under the three drug regimes from those of controls. After 21 days of treatment, 5-HT levels were found enhanced only with moclobemide in the nerve terminal regions. An important depletion in platelet 5-HT content was observed after clomipramine and fluoxetine treatments at day 14 and day 21 and a significant increase was observed after moclobemide treatment at day 14 with a return to initial values after 21 days. Our results show significantly different effects between central and peripheral indices of 5-HT metabolism according to time and to the antidepressant assessed: (i) an enhancement of total tissue 5-HT levels in the three brain areas studied after steady-state achievement of the 3 antidepressants, (ii) the return to initial values of brain 5-HT levels after repeated administration of the two 5-HT re-uptake inhibitors, consistent with the presence of brain adaptative mechanisms, with a concomitant dramatic decrease of platelet 5-HT content and (iii) an apparent gradual attenuation of the brain and periphery MAOI-A effect induced by moclobemide with 5-HT levels remaining elevated only in 5-HT nerve terminal regions.

[3H]Paroxetine binding to human peripheral lymphocyte membranes of patients with major depression before and after treatment with fluoxetine

Serotonin has been involved in major depression and is also related to central and peripheral mechanisms of neuroimmunomodulation. Recently, the uptake of [3H]serotonin into human peripheral blood lymphocytes has been reported. We determined the density of serotonin uptake sites by the binding of [3H]paroxetine to blood peripheral lymphocyte membrane preparations of controls and of patients with major depression before and after treatment with fluoxetine for six weeks. The severity of depression was assessed by the use of Hamilton Rating Scale for Depression and of Beck Depression Inventory. There was a reduction in the number of sites for [3H]paroxetine in patients before administration of the antidepressant respecting controls, and a recovery after the treatment. Affinity was unchanged. No correlation was obtained between the severity of symptoms determined by Hamilton Rating Scale for Depression or by Beck Depression Inventory, and the number of binding sites for [3H]paroxetine. The levels of the plasma serotonin metabolite, 5-hydroxyindoleacetic acid, did not differ between the three groups of subjects, but serotonin was lower in patients after treatment respecting controls and in patients before treatment. The significant correlation between specific binding of [3H]paroxetine and plasma serotonin levels in controls was not present in the patients. Lymphocyte serotonin transporter is decreased in major depressed patients and is modulated by antidepressant treatment. In addition of counting with a peripheral marker in depression, the study of serotonin system in lymphocytes might contribute to understand the bi-directional interaction between the nervous and the immune systems.

Peripheral antinociceptive actions of desipramine and fluoxetine in an inflammatory and neuropathic pain test in the rat

Amitriptyline, a non-selective noradrenaline (NA) and 5-hydroxytryptamine (5-HT) reuptake inhibitor, has recently been demonstrated to produce a peripheral antinociceptive action in an inflammatory (formalin test) and a neuropathic pain model (spinal nerve ligation). In the present study, we determined whether desipramine, a selective NA reuptake inhibitor, and fluoxetine, a selective 5-HT reuptake inhibitor, could produce peripheral antinociceptive actions in these same tests. Effects on paw volume also were determined. In the 2.5% formalin test, desipramine and fluoxetine 10-300 nmol produced a dose-related reduction in phase 2 (16-60 min) flinching and biting/licking behaviours when coadministered with the formalin. Phase 1 flinch behaviours (0-12 min) were significantly reduced at the highest dose. These actions are peripherally mediated, as they were not seen when desipramine or fluoxetine (100, 300 nmol) were injected into the contralateral hindpaw. The peripheral action of desipramine and fluoxetine was not altered by coadministration of caffeine 1500 nmol. In the spinal nerve ligation model, desipramine 100 nmol, but not fluoxetine 100 nmol, produced a peripheral anti-hyperalgesic action in the hindpaw corresponding to the ligated side when thresholds were determined using a thermal paw stimulator. In paw volume experiments, desipramine, at doses which are maximally effective in behavioural tests, produced only a slight increase in paw volume, but fluoxetine (10-300 nmol) produced a robust and sustained dose-related increase in paw volume. Amitriptyline also produced minimal effects on paw volume. When coinjected with formalin, no agent significantly altered the degree of paw swelling produced by formalin. The increase in paw volume produced by fluoxetine was inhibited by ketanserin (5-HT2 receptor antagonist), mepyramine (histamine H1 receptor antagonist) and phentolamine (alpha-adrenergic receptor antagonist), but not by the other selective 5-HT receptor antagonists tested or caffeine. The pronounced peripheral pain alleviating actions in the absence of marked changes in paw volume produced by desipramine and amitriptyline, but not fluoxetine, in the formalin test and the spinal nerve ligation model suggest that these agents could be developed as cream or gel formulations to recruit a peripheral antinociceptive action in inflammatory and neuropathic pain states. Such a formulation might permit the attainment of higher and more efficacious concentrations in the region of the sensory nerve terminal, with limited systemic side effects.

Plasma serotonin monitoring by blood microdialysis coupled to high-performance liquid chromatography with electrochemical detection in humans

Plasma serotonin (5-HT) active pool was monitored in male volunteers by intravenous microdialysis coupled to HPLC-EC with 98.6% efficient probes. 5-HT was monitored from 60 min before to 360 min after an oral dose of fluoxetine, a 5-HT uptake inhibitor, or vehicle. The basal values were within nanomolar range (0.55 to 4.6 ng/ml). After administration of fluoxetine, there was a significant increment of 5-HT with respect to controls. These results showed that intravenous microdialysis is an alternative efficient technique to monitor endogenous unbound 5-HT changes in plasma without extracting blood or sample pretreatment procedures before the chemical analysis.

Relationship between blood serotonergic variables, melancholic traits, and response to antidepressant treatments

The relationship between peripheral serotonergic variables, melancholic traits, and clinical improvement after antidepressant treatment was examined in 83 drug-free major depressive patients. Plasma serotonin (5-HT) concentrations was lower in untreated melancholic patients (1.00 +/- 0.11 vs. 1.84 +/- 0.28 ng/mL, p < 0.008; N = 40 and 43, respectively). A tendency was observed for plasma 5-hydroxyindoleacetic acid (p < 0.06), whereas platelet 5-HT and plasma tryptophan did not differ between groups. After blood sampling and clinical ratings, treatment began with fixed doses of 5-HT uptake inhibitors (clomipramine or fluvoxamine), monoamine oxidase inhibitors, or tianeptine, a 5-HT uptake enhancer. There was no significant difference in response rates between patients with and without melancholic traits. The relationship between the clinical response at 6 weeks (>50% reduction of baseline Hamilton score) and the pretreatment values of biochemical variables was examined. Responders had a lower pretreatment platelet 5-HT (530 +/- 36 vs. 664 +/- 50 ng/10(9) platelets, p < 0.03; N = 44 and 39, respectively). Patients with a platelet 5-HT concentration above 800 ng/10(9) platelets had a lower response rate than those below this value (p < 0.003). This difference was maximal in the subgroup of patients treated with 5-HT uptake inhibitors (N = 49). In this subgroup, the response rates of patients with 5-HT concentrations below and above the cutoff point were, respectively, 70% and 17% (p < 0.001). A pretreatment platelet 5-HT value above 800 ng/10(9) platelets had a predictive value for a negative response of 92%. These results suggest the presence of biochemical differences in the peripheral serotonergic system between melancholic and nonmelancholic patients. The inverse relationship between the pretreatment platelet 5-HT content and clinical response may be useful in the investigation of the relationship between the 5-HT system and antidepressant response.

Digital infarction in a patient with Raynaud's phenomenon associated with treatment with a specific serotonin reuptake inhibitor. A case report

The authors report the worsening of preexisting Raynaud's phenomenon during treatment of depression with a selective serotonin reuptake inhibitor, fluvoxamine.

Pathophysiology and management of the serotonin syndrome

OBJECTIVE

To review the symptoms, pathophysiology, and treatment of the serotonin syndrome (SS).

DATA SOURCES

A MEDLINE search (1957-1995) of the English-language literature pertaining to the SS was performed. Additional literature was obtained from reference lists of pertinent articles identified through the search.

STUDY SELECTION AND DATA EXTRACTION

All articles were considered for possible inclusion in the review. Pertinent information, as judged by the authors, was selected for discussion.

DATA SYNTHESIS

The SS, an occasionally fatal disorder, is characterized by symptoms such as mental status changes, seizures, myoclonus, and blood dyscrasias. Both the central and peripheral serotonergic systems and several serotonin receptor types are involved in the symptomatology of the SS. The pathogenesis of SS may be due to endogenous as well as iatrogenic deficits in peripheral serotonin metabolism, a stimulus for release of serotonin, and interactions with other neurotransmitter systems. Lorazepam, serotonin-blockers, and nitroglycerin have been used successfully to treat SS.

CONCLUSIONS

The SS is increasingly recognized and reported in the literature. Clinical and basic science research have increased our understanding of the pathophysiology, conditions, and agents that may predispose to the development of the syndrome. Newer treatment strategies are discussed.

Simultaneous brain and blood microdialysis study with a new removable venous probe. Serotonin and 5-hydroxyindolacetic acid changes after D-norfenfluramine or fluoxetine

A removable intravenous microdialysis probe was developed and simultaneously used with a removable microdialysis probe placed in the lateral hypothalamus (LH). Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) changes in blood and brain dialysates were measured by HPLC-EC after an i.p. injection of 5 mg/kg d-norfenfluramine (dNF) or 10 mg/kg fluoxetine (FLU) in freely moving rats. 5-HT in the LH significantly increased after both drugs, but the rise was larger and faster with dNF [F(7,28)=4.0 p<0.05] than with FLU [F(5,20)=5.0 p<0.01]. By contrast, in venous blood 5-HT increased after FLU [F(5,20)=2.96 p<0.05] but not after dNF. 5-HIAA after both drugs continued decreasing significantly in the LH [dNF F(7,28)=11.4 p<0.01; FLU F(5,20)=22.8 p<0.01], but it did not change in blood. Simultaneous dialysis in brain and blood allowed evaluation of the differential effects of dNF and FLU on 5-HT and 5-HIAA in the two places. Removable venous probes prevented the inflammatory reaction that may occur around permanently implanted probes, and the dialysis could be more efficient and with less risk of clogging.

Potential vascular and bleeding complications of treatment with selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) alter peripheral handling of serotonin, leading to potential side effects. Further, the majority of the body's serotonin is found outside the central nervous system. Peripheral serotonin is important in platelet aggregation and the modulation of vascular tone. SSRIs block platelet uptake and pulmonary endothelial metabolism of serotonin, and use of these agents may conceivably result in bleeding and vasospastic complications.

Regional 5-hydroxyindoleacetic acid production in humans

Veno-arterial plasma concentration differences and regional organ plasma flows were used to quantify the relative amounts of 5-hydroxyindoleacetic acid (5-HIAA) contributed by various sites into the peripheral circulation. Positive venoarterial concentration gradients were found in the hepatosplanchnic, forearm, cardiac and jugular vessels in the healthy subjects. The renal circulation was determined to be the principal site of 5-HIAA clearance, extracting 18 +/- 2 nmol/min. The gut was the greatest contributor to the total 5-HIAA plasma pool with the relative contributions of the various organs being as follows: hepatosplanchnic organs 58%, skeletal muscle 26%, brain 6% and the heart 3%. The source of 5-HIAA stemming from these regional beds remains unknown, it may derive from serotonin taken up by and deaminated in ubiquitous endothelial cells, enterochromaffin cells of the gut, peripheral serotonergic nerves, serotonin turnover in platelets or perhaps the metabolism of serotonin taken up by sympathetic nerves. To test the latter hypothesis we examined 23 patients with chronic congestive heart failure and 9 patients with pure autonomic failure to investigate the possible effects of sympathetic nervous system overactivity and underactivity on peripheral 5-HIAA production and plasma 5-HIAA concentration. The resting arterial plasma 5-HIAA concentration in the heart failure patients was increased three-fold. This elevated plasma 5-HIAA concentration was attributable to an increased rate of whole body 5-HIAA production. The arterial 5-HIAA plasma concentration in the autonomic failure patients was paradoxically elevated, being 70% greater than that of the healthy subjects. The increased 5-HIAA plasma concentration in these patients was accounted for by a reduction in 5-HIAA plasma clearance. In all subjects studied there was a weak relationship only between total body norepinephrine spillover to plasma and the arterial 5-HIAA plasma concentration. We found that in healthy subjects the overflow of 5-HIAA into the hepatic vein was significantly related to the underlying degree of sympathetic activity. It can be concluded that 5-HIAA is produced at a number of sites throughout the body with the arterial plasma concentration being dependent on both the level of production and plasma clearance. By far the majority of 5-HIAA in plasma is derived from the gut with only minimal contribution from the brain.

Corticosterone secretion in response to serotonin and ACTH by perfused adrenal of normal and athymic nude mice

Adrenocortical secretory responses to chemical mediators and ACTH in CD1 ICR nu/nu (athymic) mice were compared with those in CD1 ICR (normal) mice. The bilateral adrenals of normal or athymic mice were perfused in situ with artificial medium equilibrated by 95% O2 + 5% CO2. Infusion of serotonin induced the secretory response of corticosterone significantly at 10 nM and markedly at 100 nM and the response at 1000 or 10000 nM declined as compared with that at 100nM in normal mice. Total corticosterone secretion in response to 100 or 1000 nM serotonin in athymic mice was about one fourth that in normal mice, respectively. Corticosterone responses to ACTH at the range of 10 to 300 pg/ml in athymic mice were comparable to those in normal mice. Infusion of histamine, platelet activating factor(PAF), or compound 48/80 did not induce significant corticosterone response in both normal and athymic mice. The data suggest that the congenital defect of the thymus and/or hair causes the hyporesponsiveness of adrenocortical cells to serotonin although the adrenal cortex of athymic mice is able to perform its function in response to ACTH.

The 5-HT3 antagonist ondansetron reduces gastrointestinal side effects induced by a specific serotonin re-uptake inhibitor in man

The selective serotonin re-uptake inhibitors (SSRIs) are increasingly being used to treat depression and anxiety disorders. Gastrointestinal (GI) symptoms are the main side effects, probably resulting from the stimulation of central or peripheral 5-HT receptors. The present double-blind, placebo-controlled study was undertaken to see if the GI side effects of fluvoxamine could be attenuated by the co-administration of the 5-HT(3) antagonist ondansetron. The results demonstrate that, in volunteers, a single 100 mg oral dose of fluvoxamine can produce GI symptoms. Co-administration of ondansetron significantly reduced peak nausea and GI side effects, compared with placebo.

Effects of chronic treatment with dexfenfluramine on serotonin in rat blood, brain and lung tissue

We have examined the effects of continuous treatment (0.5, 1, 2.5 and 5 mg.kg-1.day-1 for 14 days, using minipumps) with dexfenfluramine (dF) on the concentration of serotonin (5-hydroxytryptamine, 5-HT) in blood, lungs and brain frontal cortex. 5-HT concentration was decreased in whole blood and tissues by the two higher doses (2.5 and 5 mg.kg-1.day-1). The concentration of dF in plasma was above detection limit only in these two treatment groups. The concentration of 5-HT in plasma (extracellular) was not modified dose-dependently, although values higher than controls were noted in the 2.5 mg.kg-1 group. Significant correlations were observed between the concentration of 5-HT in whole blood and that of 5-HT (and 5-HT + 5-HIAA) in frontal cortex. Both correlated inversely with the plasma concentration of dF. These results show that treatment with dF for two weeks reduces the concentration of intracellular 5-HT in peripheral stores (platelets, lung endothelial cells) without a concurrent increase of the extracellular 5-HT pool in blood. Correlation data suggest that whole blood 5-HT content may have a predictive value of dF-induced reductions of 5-HT in brain tissue after long-term treatment.

Plasma 5-hydroxyindoleacetic acid as an indicator of monoamine oxidase-A inhibition in rat brain and peripheral tissues

We have examined the changes induced by the monoamine oxidase (MAO; EC 1.4.3.4) inhibitors tranylcypromine, clorgyline, and deprenyl on MAO activity and 5-hydroxytryptamine (serotonin, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) content in rat brain and blood (plasma and whole blood). The decreases of MAO-A activity observed in the liver and lungs after different doses of clorgyline or tranylcypromine correlated significantly (r > 0.80 in all cases) with the decline of plasma 5-HIAA. This was unaffected by 0.25 and 5 mg kg-1 of deprenyl, indicating that 5-HT was deaminated exclusively in the periphery by MAO-A. It is interesting that very potent and significant correlations (r > 0.75) were found between plasma 5-HIAA and MAO-A activity, 5-HIAA and 5-HT content in brain tissue. These results suggest that plasma 5-HIAA can be used confidently as a peripheral indicator of the inhibition of MAO-A in brain. This may represent a favorable alternative to the analysis of 5-HIAA in CSF in psychiatric patients undergoing antidepressant treatment with nonspecific MAO inhibitors or with the new selective MAO-A inhibitors.

Effects of the antidepressant drug tianeptine on plasma and platelet serotonin of depressive patients and healthy controls

We have examined the effects of a single 12.5 mg dose and of 12 weeks treatment up to 37.5 mg daily with tianeptine, a new antidepressant drug that potentiates in vivo the uptake of serotonin (5-HT). On day 0, tianeptine reduced plasma 5-HT concentration. This acute effect occurred also on subsequent examination days. However, long-term treatment tended (P < 0.06) to increase basal plasma 5-HT concentrations, in covariation with decreases of MADRS (Montgomery-Asberg Depression Rating Scale) and HARS (Hamilton Anxiety Rating Scale). Platelet 5-HT increased only in elderly patients, probably due to the higher plasma concentration of the drug in this group than in younger patients. These results show that the acute effects of therapeutic doses of tianeptine are consistent with an enhancement of the 5-HT uptake. However, long-term treatment does not result in a decreased plasma 5-HT, as might be expected from the acute effects of the drug.

Fluvoxamine. An updated review of its pharmacology, and therapeutic use in depressive illness

Fluvoxamine facilitates serotoninergic neurotransmission via potent and selective inhibition of serotonin (5-hydroxytryptamine; 5-HT) reuptake into presynaptic neurones. The overall antidepressant efficacy of fluvoxamine 100 to 300 mg/day for 4 to 6 weeks in once daily or divided dosage regimens appears to be at least comparable to that of imipramine and similar to that of clomipramine, dothiepin, desipramine, amitriptyline, lofepramine, maprotiline, mianserin and moclobemide. The efficacy of fluvoxamine has been maintained for up to 1 year, but long term data are limited, and there are no comparative studies of fluvoxamine with other selective serotonin reuptake inhibitors. In some studies, fluvoxamine appeared to have an earlier beneficial effect on suicidal ideation and/or anxiety or somatic complaints compared with imipramine, dothiepin and maprotiline. Gastrointestinal adverse effects, especially nausea, are commonly reported with fluvoxamine but are generally mild to moderate in severity. The tolerability profile of fluvoxamine appears to be more favourable than that of tricyclic antidepressants in terms of cardiotoxic and anticholinergic adverse effects, sedation, weight gain and death from overdosage. Thus, fluvoxamine is an effective and well tolerated antidepressant agent that is becoming established as an alternative to older agents in patients with mild, moderate or severe depression. Fluvoxamine may be particularly beneficial in potentially suicidal patients with severe depression, in those with an underlying compulsive personality or cardiovascular disorder, in patients with coexistent anxiety or agitation, and in the elderly.

Fluvoxamine preferentially increases extracellular 5-hydroxytryptamine in the raphe nuclei: an in vivo microdialysis study

The effects of systemic administration of fluvoxamine on extracellular serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the frontal cortex and raphe nuclei of freely moving rats were examined. Fluvoxamine significantly increased extracellular 5-HT concentrations in both regions at the two doses used (1 and 10 mg/kg i.p.). However, the increase in the raphe nuclei was several-fold that in the frontal cortex. Dialysate 5-HIAA concentrations decreased after treatment with fluvoxamine. These results confirm that 5-HT uptake inhibitors preferentially increase extracellular concentrations of 5-HT in the vicinity of cell bodies and dendrites of serotonergic neurones.

Simultaneous effects of p-chloroamphetamine, d-fenfluramine, and reserpine on free and stored 5-hydroxytryptamine in brain and blood

The effects of acute treatment with p-chloramphetamine, d-fenfluramine, and reserpine on intracellular (brain tissue and whole blood) and extracellular (CSF and platelet-free plasma) compartments of 5-hydroxytryptamine (5-HT) in the brain and blood of the same rats have been examined. These treatments affected 5-HT in brain tissue and whole blood similarly (r = 0.823). Reserpine significantly reduced both intracellular pools at 2 and 24 h. p-Chloroamphetamine and d-fenfluramine were more effective on brain tissue 5-HT. The concentration of 5-HT in CSF was significantly increased by all treatments. p-Chloroamphetamine induced a dramatic 70-fold increase of CSF 5-HT, paralleling a 42% decrease in brain tissue. d-Fenfluramine significantly increased CSF 5-HT to 212% of controls and reduced whole brain 5-HT (-23%). The effects of p-chloroamphetamine and d-fenfluramine on 5-HIAA in brain, CSF, and plasma were nonsignificant. Individual values of 5-hydroxyindoleacetic acid (5-HIAA) in CSF and brain were highly correlated (r = 0.855), indicating that CSF 5-HIAA reflects well the concentration of 5-HIAA in brain tissue. Yet the intra- and extracellular concentrations of 5-HIAA were unrelated to the 5-HT changes. This indicates that CSF 5-HIAA does not reflect the active (extracellular) compartment of 5-HT in brain.

Effects of acute and chronic treatment with fluvoxamine on extracellular and platelet serotonin in the blood of major depressive patients. Relationship to clinical improvement

The effects of the treatment with fluvoxamine (FVX) on platelet and plasma serotonin (5-HT) have been examined in eleven drug-free major depressive patients. Acute FVX was without effect, whereas the repeated oral treatment (100-150 mg daily, 12 weeks) reduced platelet 5-HT (-89%, P less than 0.001) and plasma 5-HT (-60%, P less than 0.02). Patients who responded to the treatment at 6 weeks (Hamilton score less than or equal to 10) had significantly lower (-39%, P less than 0.02) pretreatment values of platelet 5-HT than the rest. This suggests that 'low 5-HT' patients may have a more rapid improvement after fluvoxamine. Platelet 5-HT and HDRS correlated significantly along the treatment (r = 0.679, P less than 0.01). These data demonstrate a marked action of fluvoxamine as 5-HT uptake inhibitor at therapeutic doses and confirm that this mechanism is relevant for its efficacy as antidepressant drug.