Blood serotonin levels in adults, autistic and non-autistic children--with a comparison of different methodologies

Host 5-HT affects Plasmodium transmission in mosquitoes via modulating mosquito mitochondrial homeostasis

Malaria parasites hijack the metabolism of their mammalian host during the blood-stage cycle. Anopheles mosquitoes depend on mammalian blood to lay eggs and to transmit malaria parasites. However, it remains understudied whether changes in host metabolism affect parasite transmission in mosquitoes. In this study, we discovered that Plasmodium infection significantly decreased the levels of the tryptophan metabolite, 5-hydroxytryptamine (5-HT), in both humans and mice. The reduction led to the decrease of 5-HT in mosquitoes. Oral supplementation of 5-HT to Anopheles stephensi enhanced its resistance to Plasmodium berghei infection by promoting the generation of mitochondrial reactive oxygen species. This effect was due to the accumulation of dysfunctional mitochondria caused by 5-HT-mediated inhibition of mitophagy. Elevating 5-HT levels in mouse serum significantly suppressed parasite infection in mosquitoes. In summary, our data highlight the critical role of metabolites in animal blood in determining the capacity of mosquitoes to control parasite infection.

Generation of High-Affinity Aptamers for Indazole Synthetic Cannabinoids

Synthetic cannabinoids are a widely abused class of dangerous psychoactive substances, especially among youths and young adults. Dozens of such drugs have been identified to date, and new ones continue to emerge. The ability to detect these drugs is important for interdiction efforts and the diagnosis of drug overdose, but existing analytical methods lack broad cross-reactivity to diverse members of this drug family. Here, we have utilized library-immobilized SELEX to generate DNA aptamers that can broadly recognize various members of the indazole-3-carboxamide synthetic cannabinoid family. Using two representatives of this family, AB-FUBINACA and 5F-AMB, we identify two aptamers FUB4 and AMB2F with respective dissociation constants (KDs) of 138 ± 15 and 411 ± 20 nM for their targets. These aptamers can recognize many indazole-based synthetic cannabinoids with high affinity and excellent specificity against natural cannabinoids as well as other structurally similar interferents like serotonin and tryptophan. We use these two aptamers to develop fluorescence strand-displacement sensors that successfully detect these synthetic cannabinoids at concentrations as low as 50 nM in human serum. The sensors can also detect up to 14 different drugs from this family─a major improvement over the six recognized by an existing commercial immunoassay.

A Systematic Review on Autism and Hyperserotonemia: State-of-the-Art, Limitations, and Future Directions

Hyperserotonemia is one of the most studied endophenotypes in autism spectrum disorder (ASD), but there are still no unequivocal results about its causes or biological and behavioral outcomes. This systematic review summarizes the studies investigating the relationship between blood serotonin (5-HT) levels and ASD, comparing diagnostic tools, analytical methods, and clinical outcomes. A literature search on peripheral 5-HT levels and ASD was conducted. In total, 1104 publications were screened, of which 113 entered the present systematic review. Of these, 59 articles reported hyperserotonemia in subjects with ASD, and 26 presented correlations between 5-HT levels and ASD-core clinical outcomes. The 5-HT levels are increased in about half, and correlations between hyperserotonemia and clinical outcomes are detected in a quarter of the studies. The present research highlights a large amount of heterogeneity in this field, ranging from the characterization of ASD and control groups to diagnostic and clinical assessments, from blood sampling procedures to analytical methods, allowing us to delineate critical topics for future studies.

Long COVID-19 and Peripheral Serotonin: A Commentary and Reconsideration

We believe there are serious problems with a recently published and highly publicized paper entitled "Serotonin reduction in post-acute sequelae of viral infection." The blood centrifugation procedure reportedly used by Wong et al would produce plasma that is substantially (over 95%) depleted of platelets. Given this, their published mean plasma serotonin values of 1.2 uM and 2.4 uM for the control/contrast groups appear to be at least 30 to 60 times too high and should be disregarded. The plasma serotonin values reported for the long COVID and viremia patients also should be disregarded, as should any comparisons to the control/contrast groups. We also note that the plasma serotonin means for the two control/contrast groups are not in good agreement. In the "Discussion" section, Wong et al state that their results tend to support the use of selective serotonin reuptake inhibitors (SSRIs) for the treatment of COVID-19, and they encourage further clinical trials of SSRIs. While they state that, "Our animal models demonstrate that serotonin levels can be restored and memory impairment reversed by precursor supplementation or SSRI treatment", it should be noted that no data are presented showing an increase or restoration in circulating serotonin with SSRI administration. In fact, one would expect a marked decline in platelet serotonin due to SSRIs' effective inhibition of the platelet serotonin transporter. Wong et al hypothesize that problems of long COVID arise from too little peripheral serotonin. However, given the frequent presence of a hyperaggregation state in long COVID, and the known augmenting effects of platelet serotonin on platelet aggregation, it is plausible to suggest that reductions in platelet serotonin might be associated with a lessening of the cardiovascular sequelae of COVID-19.

Ingested histamine and serotonin interact to alter Anopheles stephensi feeding and flight behavior and infection with Plasmodium parasites

Blood levels of histamine and serotonin (5-HT) are altered in human malaria, and, at these levels, we have shown they have broad, independent effects on Anopheles stephensi following ingestion by this invasive mosquito. Given that histamine and 5-HT are ingested together under natural conditions and that histaminergic and serotonergic signaling are networked in other organisms, we examined effects of combinations of these biogenic amines provisioned to A. stephensi at healthy human levels (high 5-HT, low histamine) or levels associated with severe malaria (low 5-HT, high histamine). Treatments were delivered in water (priming) before feeding A. stephensi on Plasmodium yoelii-infected mice or via artificial blood meal. Relative to effects of histamine and 5-HT alone, effects of biogenic amine combinations were complex. Biogenic amine treatments had the greatest impact on the first oviposition cycle, with high histamine moderating low 5-HT effects in combination. In contrast, clutch sizes were similar across combination and individual treatments. While high histamine alone increased uninfected A. stephensi weekly lifetime blood feeding, neither combination altered this tendency relative to controls. The tendency to re-feed 2 weeks after the first blood meal was altered by combination treatments, but this depended on mode of delivery. For blood delivery, malaria-associated treatments yielded higher percentages of fed females relative to healthy-associated treatments, but the converse was true for priming. Female mosquitoes treated with the malaria-associated combination exhibited enhanced flight behavior and object inspection relative to controls and healthy combination treatment. Mosquitoes primed with the malaria-associated combination exhibited higher mean oocysts and sporozoite infection prevalence relative to the healthy combination, with high histamine having a dominant effect on these patterns. Compared with uninfected A. stephensi, the tendency of infected mosquitoes to take a second blood meal revealed an interaction of biogenic amines with infection. We used a mathematical model to project the impacts of different levels of biogenic amines and associated changes on outbreaks in human populations. While not all outbreak parameters were impacted the same, the sum of effects suggests that histamine and 5-HT alter the likelihood of transmission by mosquitoes that feed on hosts with symptomatic malaria versus a healthy host.

Sex-Specific Effects of Blood Serotonin on Reproductive Effort in a Small Passerine

AbstractLaboratory animal models have shown that blood serotonin levels reflect consistent individual differences in behavioral decision-making and maternal behavior. Serotonin could also help to understand intraspecific variation in reproductive strategies, although the mechanisms are poorly understood. In this study, the relationships of plasma serotonin with breeding parameters and parental behavior were examined in wild great tits (Parus major). Females who laid eggs earlier had higher levels of serotonin in the second half of the nestling period, while no significant relationship of serotonin with clutch size, brood size, and body size was detected. In males, serotonin levels were negatively related to clutch size and brood size and positively related to body size. The association of serotonin with provisioning behavior was sex specific, and acute fear stress induced by a predator presentation did not change this relationship. Food provisioning was positively related to size-corrected serotonin levels in females and negatively related to size-corrected serotonin levels in males. These results suggest that peripheral serotonin is a sensitive marker of parental behavior and reproductive effort in wild birds, while the mechanisms linking this neurotransmitter to reproduction are probably mediated by interplay between the serotonergic system, sex hormones, and other neurotransmitters.

Anopheles stephensi Feeding, Flight Behavior, and Infection With Malaria Parasites are Altered by Ingestion of Serotonin

Approximately 3.4 billion people are at risk of malaria, a disease caused by infection with Plasmodium spp. parasites, which are transmitted by Anopheles mosquitoes. Individuals with severe falciparum malaria often exhibit changes in circulating blood levels of biogenic amines, including reduced serotonin or 5-hydroxytryptamine (5-HT), and these changes are associated with disease pathology. In insects, 5-HT functions as an important neurotransmitter for many behaviors and biological functions. In Anopheles stephensi, we show that 5-HT is localized to innervation in the head, thorax, and midgut, suggesting a gut-to-brain signaling axis that could support the effects of ingested 5-HT on mosquito biology and behavioral responses. Given the changes in blood levels of 5-HT associated with severe malaria and the key roles that 5-HT plays in insect neurophysiology, we investigated the impact of ingesting blood with healthy levels of 5-HT (1.5 µM) or malaria-associated levels of 5-HT (0.15 µM) on various aspects of A. stephensi biology. In these studies, we provisioned 5-HT and monitored fecundity, lifespan, flight behavior, and blood feeding of A. stephensi. We also assessed the impact of 5-HT ingestion on infection of A. stephensi with the mouse malaria parasite Plasmodium yoelii yoelii 17XNL and the human malaria parasite Plasmodium falciparum. Our data show that ingestion of 5-HT associated with severe malaria increased mosquito flight velocity and investigation of visual objects in response to host odor (CO2). 5-HT ingestion in blood at levels associated with severe malaria also increased the tendency to take a second blood meal 4 days later in uninfected A. stephensi. In mosquitoes infected with P. y. yoelii 17XNL, feeding tendency was decreased when midgut oocysts were present but increased when sporozoites were present. In addition to these effects, treatment of A. stephensi with 5-HT associated with severe malaria increased infection success with P. y. yoelii 17XNL compared to control, while treatment with healthy levels of 5-HT decreased infection success with P. falciparum. These changes in mosquito behavior and infection success could be used as a basis to manipulate 5-HT signaling in vector mosquitoes for improved control of malaria parasite transmission.

Biological Timing and Neurodevelopmental Disorders: A Role for Circadian Dysfunction in Autism Spectrum Disorders

Autism spectrum disorders (ASDs) are a spectrum of neurodevelopmental disorders characterized by impaired social interaction and communication, as well as stereotyped and repetitive behaviors. ASDs affect nearly 2% of the United States child population and the worldwide prevalence has dramatically increased in recent years. The etiology is not clear but ASD is thought to be caused by a combination of intrinsic and extrinsic factors. Circadian rhythms are the ∼24 h rhythms driven by the endogenous biological clock, and they are found in a variety of physiological processes. Growing evidence from basic and clinical studies suggest that the dysfunction of the circadian timing system may be associated with ASD and its pathogenesis. Here we review the findings that link circadian dysfunctions to ASD in both experimental and clinical studies. We first introduce the organization of the circadian system and ASD. Next, we review physiological indicators of circadian rhythms that are found disrupted in ASD individuals, including sleep-wake cycles, melatonin, cortisol, and serotonin. Finally, we review evidence in epidemiology, human genetics, and biochemistry that indicates underlying associations between circadian regulation and the pathogenesis of ASD. In conclusion, we propose that understanding the functional importance of the circadian clock in normal and aberrant neurodevelopmental processes may provide a novel perspective to tackle ASD, and clinical treatments for ASD individuals should comprise an integrative approach considering the dynamics of daily rhythms in physical, mental, and social processes.

The study protocol: Neuroendocrinology and (epi-) genetics of female reproductive transition phase mood disorder - an observational, longitudinal study from pregnancy to postpartum

BACKGROUND

Postpartum depression is considered to be one of the most common health threats during pregnancy and postpartum, affecting not only the woman herself but also the offspring and the whole family system. Evidence for a conclusive etiopathological model with distinct risk and resilience factors is still broadly lacking. Therefore, the aim of the present study is to investigate numerous health-related markers to obtain greater insight into which biopsychosocial profiles render women more vulnerable to PPD or facilitate a healthy transition from pregnancy to postpartum.

METHODS

The observational, longitudinal study aims to include a total of 288 physically healthy women, aged 20-45 years. A multitude of relevant parameters, of an (epi-) genetic, endocrinological, physiological and psychological nature, will be assessed over a period of 5 months, following the participants from the 3rd trimester until three months postpartum.

DISCUSSION

The ultimate goal of the present study is to ameliorate mental health care during pregnancy and postpartum, by gaining a better understanding of the underlying biopsychosocial mechanisms that women undergo during the transition from pregnancy to postpartum.

Blood serotonin levels in autism spectrum disorder: a systematic review and meta-analysis

Elevated blood serotonin (5-HT) levels were the first biomarker identified in autism research. Many studies have contrasted blood 5-HT levels in autistic patients and controls, but different measurement protocols, technologies, and biomaterials have been used through the years. We performed a systematic review and meta-analysis to provide an overall estimate of effect size and between-study heterogeneity, while verifying whether and to what extent different methodological approaches influence the strength of this association. Our literature search strategy identified 551 papers, from which 22 studies providing patient and control blood 5-HT values were selected for meta-analysis. Significantly higher 5-HT levels in autistic patients compared to controls were recorded both in whole blood (WB) [O.R.=4.6; (3.1-5.2); P=1.0×10(-12]), and in platelet-rich plasma (PRP) [O.R.=2.6 (1.8-3.9); P=2.7×10(-7)]. Predictably, studies measuring 5-HT levels in platelet-poor plasma (PPP) yielded no significant group difference [O.R.=0.54 (0.2-2-0); P=0.36]. Altogether, elevated 5-HT blood levels were recorded in 28.3% in WB and 22.5% in PRP samples of autistic individuals, as reported in 15 and 4 studies, respectively. Studies employing HPLC vs fluorometric assays yield similar cumulative effect sizes, but the former display much lower variability. In summary, despite some limitations mainly due to small study sample sizes, our results significantly reinforce the reliability of elevated 5-HT blood levels as a biomarker in ASD, providing practical indications potentially useful for its inclusion in multi-marker diagnostic panels for clinical use.

Relations between peripheral and brain serotonin measures and behavioural responses in a novelty test in pigs

Pigs differ in their behavioural responses towards environmental challenges. Individual variation in maladaptive responses such as tail biting, may partly originate from underlying biological characteristics related to (emotional) reactivity to challenges and serotonergic system functioning. Assessing relations between behavioural responses and brain and blood serotonin parameters may help in understanding susceptibility to the development of maladaptive responses. The objective of the current study was, therefore, to assess the relationship between the pigs' serotonergic parameters measured in both blood and brain, and the behaviour of pigs during a novelty test. Pigs (n=31) were subjected to a novelty test at 11weeks of age, consisting of 5-min novel environment exposure after which a novel object (a bucket) was introduced for 5min. Whole blood serotonin, platelet serotonin level, and platelet serotonin uptake were determined at 13weeks of age. Levels of serotonin, its metabolite and serotonin turnover were determined at 19weeks of age in the frontal cortex, hypothalamus and hippocampus. The behaviour of the pigs was different during exposure to a novel object compared to the novel environment only, with more fear-related behaviours exhibited during novel object exposure. Platelet serotonin level and brain serotonergic parameters in the hippocampus were interrelated. Notably, the time spent exploring the test arena was significantly correlated with both platelet serotonin level and right hippocampal serotonin activity (turnover and concentration). In conclusion, the existence of an underlying biological trait - possibly fearfulness - may be involved in the pig's behavioural responses toward environmental challenges, and this is also reflected in serotonergic parameters.

Plasma serotonin levels in young violent offenders: Aggressive responding and personality correlates

70 young male violent offenders and 30 normal controls in Hunan, China were interviewed and assessed by the Minnesota Multiphasic Personality Inventory (MMPI), Point Subtraction Aggression Paradigm (PSAP) and plasma serotonin (5-HT) level. Compared to the normal controls, the violent offenders had significantly higher plasma 5-HT levels; higher scores on the MMPI subscale Pd (P < 0.01), Pa (P < 0.05); and higher PSAP-B responding and lower PSAP-C responding (P < 0.05). There was a positive correlation between the MMPI Pd score and the PSAP B response, but no significant correlation was found between Pd score and plasma 5-HT level, or between PSAP B response and plasma 5-HT level. Our data suggest that the young violent offenders are more aggressive than the normal control. But this study did not demonstrate that the plasma 5-HT level had a correlation with the PSAP aggressive response. The relationship between the aggressiveness and impulsivity in the violent behavior needs further study.

Platelet serotonin levels in pervasive developmental disorders and mental retardation: diagnostic group differences, within-group distribution, and behavioral correlates

OBJECTIVE

To investigate group differences, the within-group distributions, and the clinical correlates of platelet serotonin (5-HT) levels in pervasive developmental disorders (PDD).

METHOD

Platelet 5-HT levels were measured in Dutch children and young adults, recruited from 2001 through 2003, with PDD (autism, Asperger's, and PDD-not otherwise specified [PDD-NOS]; n = 81) or with mental retardation (MR; n = 54) but without PDD, and in normal controls (n = 60). The distribution of platelet 5-HT levels was assessed using mixture-modeling analyses. Relationships between platelet 5-HT levels and a full range of demographic, clinical, and behavioral variables were examined.

RESULTS

Group mean (+/- SD) platelet 5-HT levels (nmol/10 platelets) were significantly higher in the autistic (4.51 +/- 1.61, n = 33) and PDD-NOS (4.90 +/- 1.54, n = 43) groups compared to the MR (3.48 +/- 1.33, n = 54) or the normal control (3.58 +/- 1.08, n = 60) groups (F4,190 = 9.35, p <.001). Platelet 5-HT values in the combined PDD group showed a bimodal distribution, and an empirical cutpoint for hyperserotonemia was determined. None of the behavioral variables examined was significantly associated with platelet 5-HT levels.

CONCLUSIONS

The platelet hyperserotonemia of autism was replicated in Dutch subjects. Platelet 5-HT levels were also increased in PDD-NOS, while no elevation was seen in MR. Platelet 5-HT levels appeared to be bimodally distributed in the PDD group, with an apparent hyperserotonemic subgroup.

Physiological characteristics of platelet/circulatory serotonin: study on a large human population

The aim of this work was the study of platelet/circulatory serotonin (5-hydroxytryptamine, 5-HT), specifically alternative ways of its measurement and main physiological characteristics. The study was performed on a large human population (N=500) of blood donors of both sexes over the course of a longer time period (17 months). Owing to the heterogeneity in measurement of circulatory serotonin encountered in the literature, three ways of expression were comparatively studied: per unit number of platelets, per unit mass of platelet protein and per unit volume of whole blood. Results demonstrated unimodal distribution of individual frequencies of platelet/circulatory serotonin in the human population with the mean values of 579+/-169 ng 5-HT/10(9) platelets; 332+/-89.9 ng 5-HT/mg protein and 130+/-42.3 ng 5-HT/ml blood (mean+/-S.D.). A progressive decrease of serotonin level with age (18-65 years) was demonstrated, reaching statistical significance between the extreme age groups. No significant differences in the serotonin level between the sexes were observed. No seasonal oscillations in platelet/circulatory serotonin were found. Platelet serotonin demonstrated intra-individual stability over time. Finally, regarding the methodology of measurement, our results demonstrated a good correlation among the above-mentioned ways of expression of platelet/circulatory serotonin. This indicates the possibility of intercomparison of the literature reports expressing this physiological parameter either as 5-HT concentration in platelets or as 5-HT level in the circulation.

Whole blood serotonin relates to violence in an epidemiological study

BACKGROUND

Clinical and animal studies suggest that brain serotonergic systems may regulate aggressive behavior; however, the serotonin/violence hypothesis has not been assessed at the epidemiological level. For study of an epidemiological sample we examined blood serotonin, because certain physiological and behavioral findings suggested that it might serve as an analog marker for serotonergic function.

METHODS

Whole blood serotonin was measured in a representative birth cohort of 781 21-year-old women (47%) and men (53%). Violence was measured using cumulative court conviction records and participants' self-reports. Potential intervening factors addressed were: gender, age, diurnal variation, diet, psychiatric medications, illicit drug history, season of phlebotomy, plasma tryptophan, platelet count, body mass, suicide attempts, psychiatric diagnoses, alcohol, tobacco, socioeconomic status, IQ, and overall criminal offending.

RESULTS

Whole blood serotonin related to violence among men but not women. Violent men's mean blood serotonin level was 0.48 SD above the male population norm and 0.56 SD above the mean of nonviolent men. The finding was specific to violence, as opposed to general crime, and it was robust across two different methods of measuring violence. Together, the intervening variables accounted for 25% of the relation between blood serotonin and violence.

CONCLUSIONS

To our knowledge, this is the first demonstration that an index of serotonergic function is related to violence in the general population.

Initial increase of plasma serotonin: a biological predictor for the antidepressant response to clomipramine?

Hypofunction of the serotonin (5-HT) system might be involved in depression. Initial effects of the 5-HT reuptake inhibitor clomipramine (CMI) on plasma 5-HT have never been assessed. On Day 1, 27 depressed patients received either a 25-mg CMI slow infusion or a 25-mg CMI tablet in a randomized, double-blind, double-dummy design. The daily dose was subsequently titrated up to 75 mg i.v. or 150 mg orally. The Montgomery-Asberg Depression Rating Scale (MADRS) was rated on Days 1, 4, 7 and 14. High-performance liquid chromatography (HPLC-EC) assays of plasma 5-HT, platelet 5-HT, and CMI were performed on Day 1 before and after the infusion. On Day 1, both groups experienced a mean (nonsignificant) plasma 5-HT increase; in the i.v. group this initial increase correlated with MADRS decrease over 14 days (r = 0.76, p = .0025). Correlations between platelet 5-HT and MADRS decrease were not significant. These preliminary data show that: i) CMI administration results in initial changes in plasma 5-HT; and ii) i.v. CMI-induced initial plasma 5-HT increase is consistent with the CMI 5-HT profile, and might predict the clinical response to CMI.

Brief report: circadian melatonin, thyroid-stimulating hormone, prolactin, and cortisol levels in serum of young adults with autism

An abnormal circadian pattern of melatonin was found in a group of young adults with an extreme autism syndrome. Although not out of phase, the serum melatonin levels differed from normal in amplitude and mesor. Marginal changes in diurnal rhythms of serum TSH and possibly prolactin were also recorded. Subjects with seizures tended to have an abnormal pattern of melatonin correlated with EEG changes. In others, a parallel was evidenced between thyroid function and impairment in verbal communication. There appears to be a tendency for various types of neuroendocrinological abnormalities in autistics, and melatonin, as well as possibly TSH and perhaps prolactin, could serve as biochemical variables of the biological parameters of the disease.

Whole blood serotonin and disruptive behaviors in juvenile obsessive-compulsive disorder

OBJECTIVE

The study was conducted with children and adolescents with obsessive-compulsive disorder (OCD) to assess the relationship of whole blood serotonin (5-HT) content to a concurrent diagnosis of a disruptive behavior disorder (DBD) and to severity ratings of aggressive behavior.

METHOD

Eighteen children and adolescents who met DSM-III-R criteria for OCD were evaluated with a structured interview, clinician rating scales, and the Child Behavior Checklist (CBCL). Blood 5-HT concentration was assayed with a fluorometric procedure. Relationships among categorical diagnoses, dimensional ratings, and blood 5-HT content were analyzed with bivariate and multivariate techniques.

RESULTS

OCD subjects with a DBD (n = 6) had significantly higher scores than those without a DBD (n = 12) on the Total Problem scale, the Externalizing Problem scale, and several of the behavioral syndrome scales of the CBCL. Blood 5-HT concentrations were significantly lower in those with a DBD than in those without a DBD, and blood 5-HT concentrations had significant negative correlations with the Total score, the Externalizing score, and the Aggressive Behavior score of the CBCL.

CONCLUSIONS

The results provide further evidence of a significant relationship between aggressive behavior and serotonergic functioning.

Measurement of plasma serotonin by high-performance liquid chromatography with electrochemical detection as an index of the in vivo activity of fluvoxamine

A reversed-phase high-performance liquid chromatographic method is described for the measurement of plasma serotonin concentrations. Sample preparation is by a simple solid-phase extraction using C18 columns. An isocratic separation is used with electrochemical detection. The application of the method to the measurement of plasma serotonin concentrations following the administration of fluvoxamine (a serotonin re-uptake inhibitor), maprotiline (a noradrenaline re-uptake inhibitor) and placebo to normal subjects for a seven-day period is reported. Fluvoxamine significantly decreases plasma serotonin over this time period in a linear fashion. No effect on plasma serotonin was seen for maprotiline or placebo. Plasma serotonin concentrations can be used to monitor compliance with fluvoxamine therapy.

Whole blood serotonin in juvenile obsessive-compulsive disorder

Whole blood serotonin (5-HT) concentration was assessed in 16 children and adolescents with severe obsessive-compulsive disorder (OCD) and in 14 normal adolescent controls. There was no difference in blood 5-HT content between the OCD patients and the normal controls. However, the OCD patients with a family history of OCD had significantly higher blood 5-HT levels than did either the OCD patients without a family history of OCD or the normal controls. Blood 5-HT content was not associated with a history of major depressive disorder or chronic tic disorder. These preliminary results suggest that studies of serotonergic functioning in OCD may need to control for family history of OCD and that blood 5-HT may be a useful biochemical measure in family-genetic studies of OCD.

The hyperserotonemia of autism

The planned and ongoing studies of platelet function and composition should allow us to better define the alteration which we presume to be present in platelets of autistic subjects. Although much of the research focuses on serotonergic aspects, the more general research should permit a better delineation of the extent of the alteration and will protect against a premature narrowing of the inquiry. The methodological development which has been a necessary aspect of the work should contribute to an improved understanding of platelet function and composition, as well as result in improved clinical tools for the assessment of platelet functioning in neuropsychiatric disorders and hematology. As an example, improvements in short-term in vitro storage conditions to stabilize aggregation and shape change responses over time were found to be necessary, and are probably critical to an optimal comparison of these phenomena across groups. The identification of the platelet alteration which is responsible for the hyperserotonemia of autism should prove useful in several ways. It would be expected that assessment of the altered function would provide a marker with less overlap with the normal population than the multidetermined measure of blood 5-HT. Determination of the specific protein(s) involved in the altered platelet should lead directly to gene probes and chromosomal location. These, in turn, should prove useful for neonatal screening, subtyping, and more powerful genetic and family studies. Work of this sort might also allow early intervention and improved treatment. Finally, characterization of the physiological alteration would provide a basis for focusing studies of brain neurochemistry and should, as well, suggest modes of neuropharmacological intervention. The confidence that one can have in the basic finding of hyperserotonemia in autism and the potential benefits to be derived from its explication make further research in this area of great interest.

A controlled crossover trial of fenfluramine in autism

We report a 12 month double-blind randomized crossover trial of fenfluramine in 20 children with the syndrome of autism. On active drug most of the children lost weight and blood serotonin levels fell by an average of 60%. There was a fall in urinary dopamine (DA) and noradrenaline (NA) levels and increased excretion of homovanillic acid (HVA). Some of the children showed improvement in tests of cognitive and language function, although the results did not achieve overall statistical significance. Event-related brain potentials (ERPs) were obtained in seven subjects on an auditory choice reaction time task. Side effects of the drug included irritability and lethargy. Fenfluramine may have a limited place in the management of some patients with autistic disorder.

Event-related potentials and monoamines in autistic children on a clinical trial of fenfluramine

In a double blind, crossover study of the response of autistic subjects to fenfluramine, event-related potentials (ERPs) were recorded from 7 subjects on an attention-demanding auditory choice reaction time task (ACRT). ACRT, IQ and biochemical measures were taken after 5 months placebo and 5 months fenfluramine treatment. After fenfluramine treatment blood serotonin levels fell, urinary catecholamine levels fell and the HVA/DA ratio rose. IQ and ACRT performance improved. On the ACRT subjects were asked to press a button to a rare target (500 Hz, P = 0.14) and to ignore higher pitched rare (2,000 Hz, P = 0.14) and frequent non-targets (1,000 Hz). After fenfluramine treatment N1 latencies increased. The scalp distribution of ERP maxima changes slightly with treatment. P3 maxima elicited by rare non-targets were recorded more rostrally after fenfluramine treatment. After rare non-targets N1 amplitudes at Fz decreased but P3 amplitudes at Pz increased. Early negativity after the rare non-target (particularly on the right side) was negatively correlated with the HVA/DA ratio. Subtraction of the P3 component elicited in a passive condition where no response was required from the active condition showed that P3 positivity to targets was halved with treatment. (In contrast Nd increased on fenfluramine treatment). Overall, N1 and P3 components showed greatest responsiveness to rare non-targets on fenfluramine. N1 but not P3 changes may represent slight improvement of attention-related function with treatment. Small changes in ERP latency and distribution, associated with the neuroleptic action of fenfluramine may be partly responsible for a mild improvement of IQ and ACRT performance on medication.