Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) platelet content in normal subjects

Serotonin metabolism in cluster headache

Despite some evidence of the involvement of the serotonergic system in cluster headache (CH) pathophysiology, the serotonin (5HT) metabolism has so far been poorly studied. The aim of this study was to investigate plasma and platelet levels of 5HT and 5-hydroxyindoleacetic acid (5HIAA) in CH patients in the active period of the disease. Nineteen CH sufferers and 17 sex- and age-matched healthy controls were studied. CH patients showed significantly higher plasma levels of 5HT and 5HIAA compared to controls (5HT: 5.7+/-6.1 ng/ml vs 0.2+/-0.2 ng/ml; p=0.02; 5HIAA: 34.7+/-46.1 ng/ml vs 0.6+/-0.7 ng/ml; p=0.004). In platelet 5HT levels were slightly reduced in CH patients in comparison with those of control subjects (662.4+/-522.3 ng/10(-8) platelets vs 832.4+/-587.9 ng/10(-8) platelets; n.s.) and 5HIAA levels resulted significantly lower in CH sufferers than in control subjects (3.2+/-2.6 ng/10(-8) platelets vs 6.7+/-4.8 ng/10(-8) platelets; p=0.04). Our data suggest that CH is characterized by an increase of plasma serotonergic metabolism that could reflect an involvement of the central serotonergic system in the pathogenesis of CH.

Platelet serotonin pathway in menstrual migraine

In order to understand the possible 5-hydroxytryptamine (5HT) anomalies in migraine, particularly in the period before the headache attack, we compared the levels of 5HT, its stable metabolite 5-hydroxyindoleacetic acid (5HIAA) and platelet monoaminoxidase (MAO) activity in patients with menstrual migraine with those of healthy female controls. In every subject, blood samples were drawn during both follicular and late luteal phases of the menstrual cycle. In controls, platelet 5HT levels remained stable, whereas 5HIAA levels and MAO activity were higher in the luteal than in the follicular phase, suggesting an increased catabolism of 5HT which occurs physiologically just before menses. In menstrual migraine 5HIAA levels and MAO activity showed similar changes with higher values in the luteal than in the follicular phase. The luteal phase values were significantly higher than those of controls. Also, and in contrast to controls, 5HT levels decreased in the luteal phase. These data suggest that 5HT availability is reduced in menstrual migraine, possibly due to an increased catabolism and/or to a reduced synthesis, and hence predisposes patients to migraine attacks.

Platelet secretion from dense and alpha-granules in vitro in migraine with or without aura

Several studies in vivo indicate platelet activation in migraine, as reflected by increased plasma concentrations of platelet secretory products. In vitro data on platelet secretion are scant, which prompted an investigation into agonist-induced platelet aggregation and secretion in platelets from patients with migraine. Sixty two patients with migraine with aura (MA) and 41 with migraine without aura (MwA) were studied during a headache-free phase, together with 26 healthy controls. Platelet aggregation and secretion in platelet-rich plasma were induced by collagen and platelet activating factor (PAF). Serotonin was measured by high performance liquid chromatography and platelet factor 4 (PF4) with an enzyme immunoassay kit. There were no significant aberrations in platelet aggregation in those with migraine compared with healthy controls. The platelet PF4 secretion induced by PAF (1.0 and 0.1 microM) was increased in MwA (p < 0.05, p < 0.0001) compared with controls, and there was a similar trend in MA (NS, p < 0.01). By contrast, the PF4 secretion induced by collagen (0.5 and 2.0 micrograms/ml) was reduced in MA (p < 0.01 and p < 0.05). Further, the MA group exhibited increased basal intraplatelet serotonin concentrations (p < 0.0001) and increased serotonin secretion induced by both concentrations of collagen (p < 0.0001) and PAF (p < 0.001). The data indicate an abnormal platelet a-granule secretion in those with migraine, and focus attention on PAF as a possible factor contributing to the platelet activation associated with migraine. The increased platelet content and secretion of serotonin was specific to MA, and may reflect different serotonin turnover in the two clinical migraine types.

Increased platelet serotonin content and hypersecretion from dense and alpha-granules in vitro in tension-type headache

We investigated platelet aggregation and secretion from dense and alpha-granules in vitro in 28 tension-type headache (TH) patients and 26 healthy controls. We also measured basal platelet serotonin levels. Platelet aggregation was normal in TH, but the secretion of serotonin and platelet factor 4 (PF4) was significantly increased in response to 0.5 and 2.0 micrograms/ml collagen and to 1.0 mumol/l PAF. The basal platelet serotonin levels were also higher in patients than in controls. The mechanisms of platelet hypersecretion remain to be determined, but the increased secretion of serotonin is probably in part related to the increased basal levels. The increased platelet serotonin in TH patients may reflect an enhanced serotonin turnover.

Simultaneous observation of catecholamine, serotonin and their metabolites in incised skin wounds of guinea pig

In order to examine the vital reaction in wounds, catecholamines, serotonin (5-HT) and their metabolites in the incised skin wounds of guinea pigs were analyzed simultaneously by high-performance liquid chromatography (HPLC) using electrochemical detection (ECD). The principal changes in the levels of these compounds in vital wounds were as follows: a considerable decrease in norepinephrine (NE) content was observed 12-24 h after injury which persisted to at least 7 days. 3,4-Dihydroxyphenylacetic acid (DOPAC) decreased slightly for up to 30 min and then showed no significant difference compared with postmortem levels. Epinephrine and dopamine were barely detected by the HPLC-ECD method employed. 5-HT concentrations which showed an increase up to 24 h showed maximum levels 800 microns from the wound edge at 10 and 30 min after injury. 5-Hydroxyindoleacetic acid (5-HIAA) was significantly higher than the postmortem level over almost the entire period of these experiments. A 5-HIAA content of at least twice the postmortem level was observed 800 microns from the wound edge of a 10-min-old vital wound. Therefore, 5-HIAA is a likely candidate as a new marker for evaluating the vital reaction in wounds. The vital characteristics of NE, DOPAC, 5-HIAA and 5-HT in 10-min-old wounds persisted for up to 12 h at room temperature after death. These results suggest that the HPLC-ECD method used here is very useful for simultaneous examination of the vital reaction in wounds from the earliest to the later stages of the wound-healing period.

Autism: review of neurochemical investigation

The neurochemistry of autism, the most well-validated childhood neuropsychiatric disorder, has been studied extensively over the past three decades. Autism is of interest neurochemically because it represents a relatively homogeneous disorder with a triad of social, communicative, and intellectual developmental disturbance. Because a sufficient animal model has been lacking and relatively few diagnosed people with autism have died, most investigation has been of peripheral fluids and tissues. The most consistent finding has been that over 25% of autistic children and adolescents are hyperserotonemic. However, after 29 years of investigation, the mechanism of hyperserotonemia has not been determined. Hyperserotonemia has been found to be familial. Elevated plasma norepinephrine has also been a replicated finding. Cerebrospinal fluid (CSF) opiate activity has been found to be elevated in two studies. Plasma cyclic adenosine monophosphate (cAMP) has been found to be elevated in autistic children. A high rate of nonsuppression after dexamethasone and blunted or delayed growth hormone response to L-dopa have been found. Abnormal cell-mediated immunity has been replicated consistently in autism. Although several pharmacological trials have been conducted and shown promise in initial open trials, only "typical" antipsychotic drugs have shown replicable chronic ameliorating effects in double-blind trials. However, chronic neurotoxicity (tardive dyskinesia) has also been revealed. Findings of morphological changes in the cerebellum have been replicated. Findings in need of replication include diminished platelet function, increased baseline CSF homovanillic acid, decreased nerve cell adhesion molecule serum fragment, blunted prolactin response to fenfluramine, amelioration of symptoms by naltrexone and bromocriptine, reduced electroretinographic (ERG) b-wave amplitude, and morphological changes in the hippocampus, amygdala, and septal nuclei. In addition to refining and replicating past findings, future directions that may be fruitful include investigation of neurochemical aspects of platelet function, of interactions between monoaminergic systems, of phosphatidylinositides, and of pharmacological response to "atypical" antipsychotic agents and relatively selective serotonin receptor subtype agonists or antagonists.

A plasmatic factor may cause platelet activation in acute ischemic stroke

To study the pathogenesis of platelet activation in ischemic stroke, ionized calcium ([Cai2+]) was measured in aequorin-loaded gel-filtered platelets in the basal and stimulated state. Basal [Cai2+] was increased in stroke patients maximally 36-72 hours after onset. The increase in [Cai2+] after stimulation with thrombin, collagen, and platelet-activating factor were also greater in stroke patients, but the profiles of these [Cai2+] changes were parallel to control. Cross incubation of control platelets with plasma from stroke patients resulted in raised basal [Cai2+] and caused the release of serotonin from platelets. These results indicate that the higher platelet basal [Cai2+] in stroke patients represents a lowered threshold for activation and that this may be due to a plasmatic factor rather than a primary platelet defect.