Effects of separate or combined exposure of nonylphenol and octylphenol on central 5-HT system and related learning and memory in the rats.

This study evaluated toxic effects of nonylphenol (NP) and octylphenol (OP) on central 5-hydroxytryptamine (5-HT) system and related learning and memory in the rats. Male Sprague-Dawley rats were exposed to NP (30, 90, or 270 mg/kg), OP (40, 120, or 360 mg/kg), or a mixture of NP and OP [(mixed with the corresponding NP, OP alone exposed low, medium and high dose according to the natural environment exists NP:OP = 4:1; NOL (24 mg/kg NP+8 mg/kg OP), NOM (72 mg/kg NP+24 mg/kg OP), NOH (216 mg/kg NP+72 mg/kg OP)] by gavage every other day for 30 d. Learning and memory were assessed using a passive-avoidance test. Levels of estrogen receptor ß (ERß), 5-HT, tryptophan hydroxylase 2 (TPH2), monoamine oxidase (MAOA) enzyme, serotonin transporter (SERT), the vesicular monoamine transporter 2 (VMAT2), 5-hydroxytryptamine 1 A (5-HT1A), 5-hydroxytryptamine 3 A (5-HT3A), 5-hydroxytryptamine 3B (5-HT3B), 5-hydroxytryptamine 4 A (5-HT4A) and 5-hydroxytryptamine 6 A (5-HT6A) were measured using ELISA kits. Levels of ERß, MAOA, SERT, VMAT2, 5-HT1A, 5-HT3A, 5-HT3B, 5-HT4A and 5-HT6A in rat hippocampal reduced by a high dose of NP and/or OP. Levels of TPH2 in rat midbrain and 5-HT in rat hippocampal increased by a high dose of NP and/or OP. In addition, latency was significantly shorter and errors were significantly greater in the high dose NP and NP+OP (NO) groups. Taken together, these results suggest that NP and/or OP may affect learning and memory in rats by inhibiting levels of ERß, which could then lead to decreases in levels of 5-HT1A, 5-HT3A, 5-HT3B, 5-HT4A, and 5-HT6A in the rat hippocampus. These findings suggested that separate and combined exposure to NP and OP could produce toxic effects on central 5-HT system and related learning and memory in the rats.

Demystifying serotonin syndrome (or serotonin toxicity).

OBJECTIVE: To review the symptoms of serotonin toxicity (commonly referred to as serotonin syndrome) and the causative drugs and their mechanisms of action, and to equip primary care providers with practical strategies to prevent and identify serotonin toxicity. QUALITY OF EVIDENCE: PubMed and Google Scholar were searched for relevant articles on serotonin toxicity, the causes, and the differential diagnosis using search terms related to serotonin toxicity (serotonin syndrome, serotonin toxicity, serotonin overdose), causes (individual names of drug classes, individual drug names), and diagnosis (differential diagnosis, neuroleptic malignant syndrome, anticholinergic toxicity, discontinuation syndrome, malignant hyperthermia, serotonin symptoms). Experts in psychiatric medicine, psychiatric pharmacy, clinical pharmacology, and medical toxicology were consulted. Evidence is level II and III. MAIN MESSAGE: Serotonin toxicity is a drug-induced condition caused by too much serotonin in synapses in the brain. Cases requiring hospitalization are rare, and mild cases caused by serotonin-mediated side effects are unlikely to be fatal. Patients present with a combination of neuromuscular, autonomic, and mental status symptoms. Serotonin-elevating drugs include monoamine oxidase inhibitors, serotonin reuptake inhibitors, and serotonin releasers. Most cases involve 2 drugs that increase serotonin in different ways; the most concerning combination is a monoamine oxidase inhibitor with a selective serotonin reuptake inhibitor or a serotonin-norepinephrine reuptake inhibitor. CONCLUSION: Family physicians play a key role in identifying and preventing serotonin syndrome by teaching patients to recognize symptoms and monitoring patients throughout therapy.

Innocuous warming enhances peripheral serotonergic itch signaling and evokes enhanced responses in serotonin-responsive dorsal horn neurons in the mouse.

Itch is often triggered by warming the skin in patients with itchy dermatitis, but the underlying mechanism is largely unknown. We presently investigated if warming the skin enhances histamine- or serotonin (5-HT)-evoked itch behavior or responses of sensory dorsal root ganglion (DRG) cells, and if responses of superficial dorsal horn neurons to innocuous warming are enhanced by these pruritogens. In a temperature-controlled environmental chamber, mice exhibited greater scratching following intradermal injection of 5-HT, but not histamine, SLIGRL, or BAM8-22, when the skin surface temperature was above 36°C. Calcium imaging of DRG cells in a temperature-controlled bath revealed that responses to 5-HT, but not histamine, were significantly greater at a bath temperature of 35°C vs. lower temperatures. Single-unit recordings revealed a subpopulation of superficial dorsal horn neurons responsive to intradermal injection of 5-HT. Of these, 58% responded to innocuous skin warming (37°C) prior to intradermal injection of 5-HT, while 100% responded to warming following intradermal injection of 5-HT. Warming-evoked responses were superimposed on the 5-HT-evoked elevation in firing and were significantly larger compared with responses pre-5-HT, as long as 30 min after the intradermal injection of 5-HT. Five-HT-insensitive units, and units that either did or did not respond to intradermal histamine, did not exhibit any increase in the incidence of warmth sensitivity or in the mean response to warming following intradermal injection of the pruritogen. The results suggest that 5-HT-evoked responses of pruriceptors are enhanced during skin warming, leading to increased firing of 5-HT-sensitive dorsal horn neurons that signal nonhistaminergic itch. NEW & NOTEWORTHY: Skin warming often exacerbates itch in patients with itchy dermatitis. We demonstrate that warming the skin enhanced serotonin-evoked, but not histamine-evoked, itch behavior and responses of sensory dorsal root ganglion cells. Moreover, serotonin, but not histamine, enhanced responses of superficial dorsal horn neurons to innocuous warming. The results suggest that skin warming selectively enhances the responses of serotonin-sensitive pruriceptors, leading to increased firing of serotonin-sensitive dorsal horn neurons that signal nonhistaminergic itch.

Fenfluramine-Phentermine is Associated with an Increase in Cellular Proliferation Ex Vivo and In Vitro.

BACKGROUND AND AIM OF THE STUDY: Fenfluraminephentermine (FenPhen) has been implicated in accelerated valvular heart disease, characterized by valvular regurgitation and thickening, and resembling the histopathologic lesions found in carcinoid. The study aim was to determine whether cellular proliferation is present in FenPhen-exposed valves, by utilizing an in-vitro model to test whether FenPhen has a direct mitogenic effect on cardiac valvular cells, as compared to serotonin. METHODS: Ex-vivo valves were tested for proliferation in surgically removed FenPhen-exposed valves (n = 10) and compared to proliferation levels in normal human cardiac valves removed at autopsy (n = 10). Immunostaining for a DNA polymerase, proliferating cell nuclear antigen (PCNA), was performed and quantified using digital imaging analysis. In-vitro assays were performed for direct proliferative effects of serotonin and FenPhen (10-6, 10-7 and 10-8 M) on porcine aortic valve subendothelial cells, using a [3H]-thymidine incorporation assay. RESULTS: Ex-vivo PCNA levels in human FenPhenexposed valves were elevated compared to controls (22.8 ± 4.54 versus 1.26 ± 0.47; p <0.001). In vivo, serotonin and FenPhen markedly increased (10-fold) cell proliferation (as measured by [3H]-thymidine incorporation) in subendothelial cells in vitro (p <0.001). This proliferative response was demonstrated by PCNA staining in carcinoid heart valves and FenPhen-exposed valves. Mechanistically, plateletderived growth factor increased cell proliferation in a dose-related manner (p <0.001), the response being inhibited by a MAP kinase inhibitor (determined by monitoring p42/44 levels). CONCLUSIONS: In vitro, FenPhen acts as a powerful mitogen on subendothelial myofibroblast valve cells. Ex vivo, cellular proliferation was significantly elevated in human FenPhen-exposed cells.

Anti-Inflammatory and Analgesic Activities of the Complex of Flavonoids from Lychnis chalcedonica L.

Anti-inflammatory and analgesic activities of the complex of flavonoids from Lychnis chalcedonica L. were studied in the models of acute aseptic inflammation induced by carrageenan, histamine, and serotonin and acetic acid-induced painful chemical stimulation. It is demonstrated that course treatment with flavonoids derived from Lychnis chalcedonica L. produced a stable pharmacological effect comparable with that of the reference anti-inflammatory drug diclofenac.

Attenuation of serotonin-induced itch responses by inhibition of endocannabinoid degradative enzymes, fatty acid amide hydrolase and monoacylglycerol lipase.

Itch and pain are two irritating sensations sharing a lot in common. Considering the antinociceptive effects of blockade of endocannabinoid degrading enzymes in pain states, we attempted to reduce scratching behavior by endocannabinoid modulation, i.e. by inhibiting fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), or cellular uptake of endocannabinoids. Scratching behavior was induced by intradermal injection of serotonin to Balb/c mice. URB597 (10 mg/kg, i.p.), a FAAH inhibitor, JZL184 (16 mg/kg, i.p.), a MAGL inhibitor, and AM404 (10 mg/kg, i.p.), an endocannabinoid transport inhibitor, were given to evaluate the effects of endocannabinoid modulation on scratching responses. Then, the CB1 receptor antagonist, AM251 (1 mg/kg, i.p.), and the CB2 receptor antagonist, SR144528 (1 mg/kg, i.p.), were administered to determine whether cannabinoid receptors mediate these effects. URB597 and JZL184, but not AM404, attenuated serotonin-induced scratches. The inhibitory effect of URB597 was reversed by SR144528, but cannabinoid receptor antagonists had no other effects on modulation by the inhibitors. We propose that augmenting the endocannabinoid tonus by inhibition of degradative enzymes, FAAH and MAGL, but not cellular uptake, may be a novel target for the development of antipruritic agents.

Persistence of serotonergic enhancement of airway response in a model of childhood asthma.

The persistence of airway hyperresponsiveness (AHR) and serotonergic enhancement of airway smooth muscle (ASM) contraction induced by ozone (O3) plus allergen has not been evaluated. If this mechanism persists after a prolonged recovery, it would indicate that early-life exposure to O3 plus allergen induces functional changes predisposing allergic individuals to asthma-related symptoms throughout life, even in the absence of environmental insult. A persistent serotonergic mechanism in asthma exacerbations may offer a novel therapeutic target, widening treatment options for patients with asthma. The objective of this study was to determine if previously documented AHR and serotonin-enhanced ASM contraction in allergic monkeys exposed to O3 plus house dust mite allergen (HDMA) persist after prolonged recovery. Infant rhesus monkeys sensitized to HDMA were exposed to filtered air (FA) (n = 6) or HDMA plus O3 (n = 6) for 5 months. Monkeys were then housed in a FA environment for 30 months. At 3 years, airway responsiveness was assessed. Airway rings were then harvested, and ASM contraction was evaluated using electrical field stimulation with and without exogenous serotonin and serotonin-subtype receptor antagonists. Animals exposed to O3 plus HDMA exhibited persistent AHR. Serotonin exacerbated the ASM contraction in the exposure group but not in the FA group. Serotonin subtype receptors 2, 3, and 4 appear to drive the response. Our study shows that AHR and serotonin-dependent exacerbation of cholinergic-mediated ASM contraction induced by early-life exposure to O3 plus allergen persist for at least 2.5 years and may contribute to a persistent asthma phenotype.

Serotonin toxicity from antidepressant overdose and its association with the T102C polymorphism of the 5-HT2A receptor.

Serotonin toxicity results from serotonin excess in the central nervous system from serotonergic drugs. Previous studies suggest an association between T102C polymorphism of the serotonin 2A (5-hydroxytryptamine 2A) receptor gene and serotonergic adverse effects with serotonergic drugs. We aimed to determine whether there is an association between the T102C polymorphism and serotonin toxicity in patients taking serotonergic drug overdoses. Ninety-five patients presenting with serotonergic drug overdoses were examined for serotonin toxicity and had blood collected for DNA analysis. A diagnosis of serotonin toxicity was made in 14 patients (15%) based on the Hunter Serotonin Toxicology Criteria. Four of the 14 patients (29%) with serotonin toxicity had the C/C genotype compared with 20/81 (25%) without serotonin toxicity. There were no differences in age or sex, but the median defined daily dose taken by patients with serotonin toxicity was 27 (14-84) compared with 18 (2-136) in patients without serotonin toxicity (P=0.06). There was no association between serotonin toxicity and the T102C polymorphism in patients taking a serotonergic drug overdose.

Procarbazine and antidepressants: a retrospective review of the risk of serotonin toxicity.

BACKGROUND: Procarbazine is an anticancer agent that also inhibits monoamine oxidase, an enzyme responsible for the metabolism of various catecholamines, including serotonin. METHODS: A retrospective chart review of lymphoma patients who were treated with both procarbazine and an antidepressant, as well as procarbazine alone, was performed to determine if signs and symptoms of serotonin toxicity were present. RESULTS: A total of 65 patients received procarbazine between 2004 and 2010 and were eligible to be included in the study. Twenty-six of these patients received an antidepressant in combination with procarbazine, with selective serotonin reuptake inhibitors being the most common type of antidepressant. No patients in the study were diagnosed with serotonin toxicity, nor did any meet Hunter's diagnostic criteria for serotonin toxicity. Diarrhea, tremor, and shivering were the symptoms from Sternbach's criteria that were further analyzed, with diarrhea occurring 8.54% of the time, tremor occurring 5.53% of the time, and shivering occurring 2.51% of the time in patients who received an antidepressant with their procarbazine. Despite these symptoms, the diagnosis of serotonin toxicity according to Sternbach's criteria was determined to be unlikely. CONCLUSIONS: In this small sample of patients treated with procarbazine plus an antidepressant (most typically SSRIs), there were no reports of serotonin toxicity, nor did any patients demonstrate symptoms consistent with serotonin toxicity. The authors urge clinicians to ensure depression is adequately managed in cancer patients who are undergoing procarbazine therapy, starting with typical first-line antidepressant agents.

Increased levels of monoamine-derived potential neurotoxins in fetal rat brain exposed to ethanol.

Pregnant SD rats were exposed to ethanol (25 % (v/v) ethanol at 1.0, 2.0 or 4.0 g/kg body weight from GD8 to GD20) to assess whether ethanol-derived acetaldehyde could interact with endogenous monoamine to generate tetrahydroisoquinoline or tetrahydro-beta-carboline in the fetuses. The fetal brain concentration of acetaldehyde increased remarkably after ethanol administration (2.6 times, 5.3 times and 7.8 times as compared to saline control in 1.0, 2.0 and 4.0 g/kg ethanol-treated groups, respectively) detected by HPLC with 2,4-dinitrophenylhydrazine derivatization. Compared to control, ethanol exposure induced the formation of 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol, Sal), N-methyl-salsolinol (NMSal) and 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline (6-OH-MTHBC) in fetal rat brains. Determined by HPLC with electrochemical detector, the levels of dopamine and 5-hydroxytryptamine in whole fetal brain were not remarkably altered by ethanol treatment, while the levels of homovanillic acid and 5-hydroxyindole acetic acid in high dose (4.0 g/kg) of ethanol-treated rats were significantly decreased compared to that in the control animals. 4.0 g/kg ethanol administration inhibited the activity of mitochondrial monoamine oxidase (51.3 % as compared to control) and reduced the activity of respiratory chain complex I (61.2 % as compared to control). These results suggested that ethanol-induced alteration of monoamine metabolism and the accumulation of dopamine-derived catechol isoquinolines and 5-hydroxytryptamine-derived tetrahydro-beta-carbolines may play roles in the developmental dysfuction of monoaminergic neuronal systems.

Marked and prolonged serotonin toxicity in a tramadol-poisoned patient with a pharmacokinetic study.

BACKGROUND: Tramadol poisoning rarely causes serotonin toxicity, which mechanisms remain poorly understood. We investigated alterations in tramadol pharmacokinetics in a tramadol-poisoned patient who presented with marked and prolonged serotonin toxicity. CASE REPORT: A 21-year-old male self-ingested 750 mg-tramadol, 200 mg-sotalol, 400 mg-propranolol and 6 mg-lorazepam. He was a kidney transplant patient treated with mycophenolate, tacrolimus, prednisone, and paroxetine. He developed transitory cardiovascular failure and prolonged serotonin toxicity requiring sedation, muscle paralysis, and cyproheptadine, with a favorable outcome. METHODS: We measured plasma concentrations of tramadol, M1, M2, and M5 using liquid-chromatography-tandem mass spectrometry, calculated elimination half-lives and metabolic ratios of the compounds, and genotyped cytochromes involved in tramadol metabolism. RESULTS: Elimination half-lives of tramadol (6.1 h) and M1 (7.1 h) were normal while those of M2 (26.5 h) and M5 (16.7 h) prolonged. M1 metabolic ratio (0.12) was 2-fold reduced, M2 metabolic ratio (197) 1000-fold increased and M5 metabolic ratio (0.12) normal. This metabolic profile in a patient with normal CYP2D6-metabolizer status based on genotyping supports CYP2D6 inhibition by paroxetine and propranolol, two strong mechanism-based inhibitors. Only M2 present in sufficient concentrations up to 48 h could explain the prolonged serotonin toxicity. CONCLUSION: Marked and prolonged serotonin toxicity was attributed to increased M2 production due to paroxetine- and propranolol-related CYP2D6 inhibition of tramadol metabolism.

Facial injections of pruritogens or algogens elicit distinct behavior responses in rats and excite overlapping populations of primary sensory and trigeminal subnucleus caudalis neurons.

In the present study, we investigated whether intradermal cheek injection of pruritogens or algogens differentially elicits hindlimb scratches or forelimb wipes in Sprague-Dawley rats, as recently reported in mice. We also investigated responses of primary sensory trigeminal ganglion (TG) and dorsal root ganglion (DRG) cells, as well as second-order neurons in trigeminal subnucleus caudalis (Vc), to pruritic and algesic stimuli. 5-HT was the most effective chemical to elicit dose-dependent bouts of hindlimb scratches directed to the cheek, with significantly less forelimb wiping, consistent with itch. Chloroquine also elicited significant scratching but not wiping. Allyl isothiocyanate (AITC; mustard oil) elicited dose-dependent wiping with no significant scratching. Capsaicin elicited equivalent numbers of scratch bouts and wipes, suggesting a mixed itch and pain sensation. By calcium imaging, ∼ 6% of cultured TG and DRG cells responded to 5-HT. The majority of 5-HT-sensitive cells also responded to chloroquine, AITC, and/or capsaicin, and one-third responded to histamine. Using a chemical search strategy, we identified single units in Vc that responded to intradermal cheek injection of 5-HT. Most were wide dynamic range (WDR) or nociceptive specific (NS), and a few were mechanically insensitive. The large majority additionally responded to AITC and/or capsaicin and thus were not pruritogen selective. These results suggest that primary and second-order neurons responsive to pruritogens and algogens may utilize a population coding mechanism to distinguish between itch and pain, sensations that are behaviorally manifested by distinct hindlimb scratching and forelimb wiping responses.

Inhibition of 3,4-methylenedioxymethamphetamine metabolism leads to marked decrease in 3,4-dihydroxymethamphetamine formation but no change in serotonin neurotoxicity: implications for mechanisms of neurotoxicity.

3,4-Methylenedioxymethamphetamine (MDMA)'s O-demethylenated metabolite, 3,4-dihydroxymethamphetamine (HHMA), has been hypothesized to serve as a precursor for the formation of toxic catechol-thioether metabolites (e.g., 5-N-acetylcystein-S-yl-HHMA) that mediate MDMA neurotoxicity. To further test this hypothesis, HHMA formation was blocked with dextromethorphan (DXM), which competitively inhibits cytochrome P450 enzyme-mediated O-demethylenation of MDMA to HHMA. In particular, rats were randomly assigned to one of four treatment groups (n = 9-12 per group): (1) Saline/MDMA; (2) DXM/MDMA; (3) DXM/Saline; (4) Saline/Saline. During drug exposure, time-concentration profiles of MDMA and its metabolites were determined, along with body temperature. One week later, brain serotonin (5-HT) neuronal markers were measured in the same animals. DXM did not significantly alter core temperature in MDMA-treated animals. A large (greater than 70%) decrease in HHMA formation had no effect on the magnitude of MDMA neurotoxicity. These results cast doubt on the role of HHMA-derived catechol-thioether metabolites in the mechanism of MDMA neurotoxicity.

Striatal dopamine D1 and D2 receptors: widespread influences on methamphetamine-induced dopamine and serotonin neurotoxicity.

Methamphetamine (mAMPH) is an addictive psychostimulant drug that releases monoamines through nonexocytotic mechanisms. In animals, binge mAMPH dosing regimens deplete markers for monoamine nerve terminals, for example, dopamine and serotonin transporters (DAT and SERT), in striatum and cerebral cortex. Although the precise mechanism of mAMPH-induced damage to monoaminergic nerve terminals is uncertain, both dopamine D1 and D2 receptors are known to be important. Systemic administration of dopamine D1 or D2 receptor antagonists to rodents prevents mAMPH-induced damage to striatal dopamine nerve terminals. Because these studies employed systemic antagonist administration, the specific brain regions involved remain to be elucidated. The present study examined the contribution of dopamine D1 and D2 receptors in striatum to mAMPH-induced DAT and SERT neurotoxicities. In this experiment, either the dopamine D1 antagonist, SCH23390, or the dopamine D2 receptor antagonist, sulpiride, was intrastriatally infused during a binge mAMPH regimen. Striatal DAT and cortical, hippocampal, and amygdalar SERT were assessed as markers of mAMPH-induced neurotoxicity 1 week following binge mAMPH administration. Blockade of striatal dopamine D1 or D2 receptors during an otherwise neurotoxic binge mAMPH regimen produced widespread protection against mAMPH-induced striatal DAT loss and cortical, hippocampal, and amygdalar SERT loss. This study demonstrates that (1) dopamine D1 and D2 receptors in striatum, like nigral D1 receptors, are needed for mAMPH-induced striatal DAT reductions, (2) these same receptors are needed for mAMPH-induced SERT loss, and (3) these widespread influences of striatal dopamine receptor antagonists are likely attributable to circuits connecting basal ganglia to thalamus and cortex.

Sex differences in behavior and expression of CGRP-related genes in a rodent model of chronic migraine.

OBJECTIVE: The objectives of this study were to develop a preclinical rodent model that produces migraine-like behaviors based on International Headache Society diagnostic criteria, to determine whether sex differences are present, and to determine whether expression of calcitonin gene-related peptide (CGRP) and the genes encoding its receptor in trigeminal ganglion or medulla correlates with those behaviors. BACKGROUND: Few animal studies of migraine have tested behaviors associated with migraine diagnostic criteria. In this study, changes in activity and in mechanical sensitivity of facial regions following application of inflammatory soup (IS) or vehicle (phosphate-buffered saline [PBS]) to the dura were measured to model changes in routine activity and allodynia. CGRP, an important mediator of migraine pathogenesis, and the 3 components of its receptor, calcitonin-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and receptor component protein (RCP) mRNAs were quantified in the trigeminal ganglion and medulla to identify baseline sex differences and changes associated with application of IS or PBS to the dura. METHODS: Male and female Sprague-Dawley rats were implanted with a dural cannula. Groups of rats were treated with 10 or 20 µL volumes of IS or PBS. Baseline behavioral testing was conducted prior to surgery and again at 7 days postsurgery, and dural application of IS or PBS was performed repeatedly for a total of 8 applications. Locomotor activity was assessed using force plate actimetry during and following application to provide information on distance traveled, bouts of low mobility, spatial confinement, and focused energy. Periorbital and perimasseter sensory testing was performed 20 minutes post-application to measure allodynia. The rats were sacrificed 30 minutes following the final dural treatment, tissue was dissected and total RNAs were isolated from ipsilateral trigeminal ganglia and ipsilateral medulla. Quantitative real-time polymerase chain reactions were used to measure the expression of amplified constructs using gene-specific primers for CGRP, RAMP1, CLR, and RCP. RESULTS: Both males and females showed behavioral effects of IS application, but there were pronounced sex differences. Females showed effects at the lower dose, and activity changes were present for a longer duration, but males required fewer applications of IS to exhibit behavioral changes. Females showed increased withdrawal responses for periorbital and perimasseter mechanical testing (10 µL IS groups), and males showed increased perimasseter withdrawal responses (20 µL IS group). In the trigeminal ganglion, there were no baseline sex differences in CGRP-encoding mRNA, but females had lower baseline expression of RAMP1, CLR, and RCP-encoding mRNAs. In the medulla, females had higher baseline levels of CGRP-encoding mRNAs and lower baseline levels of RAMP1, CLR, and RCP-encoding mRNAs than males. Both IS and PBS increased expression of mRNAs encoding CGRP, RAMP1, RCP, and CLR in the trigeminal ganglion in males, but in females, only CLR and RCP were increased. In the medulla both IS and PBS increased expression of CGRP, CLR in males and CLR and RCP in females. Thus, expression of CGRP-related genes did not mirror the behavioral differences between IS and PBS groups. Instead, CGRP-related genes were upregulated by both IS and PBS applications. CONCLUSIONS: This study demonstrates significant changes in locomotor activity and facial allodynia associated with application of IS to the dura as well as significant sex differences, demonstrating that International Headache Society diagnostic criteria can be used to design a rodent behavioral model of migraine. In addition, there were prominent baseline sex differences in expression of CGRP and its receptor in both the trigeminal ganglion and medulla, but the majority of changes in expression of CGRP and its receptor were present in both the IS and PBS treated rats. This suggests that the CGRP pathway responds to changes in intracranial pressure or meningeal stretch, while migraine-like behaviors occur after meningeal inflammation.

Serotonin Toxicity in Children and Adolescents: A Systematic Review and Meta-Analysis of Cases.

Objectives: Serotonin toxicity is a state of central nervous system (CNS) excitation classically featuring altered mental status, neuromuscular excitation, and autonomic instability. While retrospective studies and reviews have characterized serotonin toxicity in adults, there have been no systematic reviews of serotonin toxicity in pediatric populations. The goal of this review was to use published case reports to describe serotonin toxicity in pediatric patients and to consider the impact of age on clinical presentation. Methods: A search for case reports of serotonin toxicity in patients younger than 18 years was conducted. Cases were systematically screened for inclusion using serotonin toxicity diagnostic tools, and a meta-analysis of case characteristics was conducted. Results: Sixty-six cases of serotonin toxicity in pediatric patients were reviewed. Only 56.1% met diagnostic criteria for serotonin toxicity on all three of the most commonly used diagnostic tools. Antidepressants were found to be the most common trigger of toxicity, implicated in 78.8% of cases. While onset of toxicity was rapid following overdose, toxicity was more likely to be delayed in the setting of medication titration (71.8% vs. 0%, p < 0.0001). Signs of neuromuscular excitation were prevalent, occurring in 92.4% of cases with 81.8% showing the full triad of neuromuscular symptoms, altered mental status, and autonomic instability. The only age-related differences occurred in relation to activation symptoms (more likely to be reported in children than in adolescents) and seizures (less likely to be reported in children than in adolescents or toddlers). Treatment was primarily supportive in nature, although 25.8% of patients received cyproheptadine. In all but one reviewed case, the patient survived. Conclusions: The presentation of serotonin toxicity in the pediatric population is similar to that seen in adults. Treatment is supportive with most patients achieving full recovery. Further exploration of the age-related differences in serotonin activity within the CNS is needed.

Pharmacological studies on aqueous extract of Launaea arborescens from southwest Algeria.

ETHNOPHARMACOLOGICAL RELEVANCE: Launaea arborescens, its vernacular name is Mol-albina belonging to asteracaea family origin of the southwest of Algeria. This plant is used in folk medicines to treat gastroenteritis, diabetes, child aliment and other diseases; it is taken macerated or boiled. AIM: This study aims to evaluate the anti-inflammation an analgesic activity of the aqueous extract of Launaea arborescens (AqELA) and its pathway of action. METHODS: the investigation of anti-inflammatory and analgesic effects were done using formalin test, acetic acid test. For mechanism investigation, it was used hot plate test to induce opioid receptors, a histamine and serotonin test to induce edema paw, finally, for the TRPV1 receptor, it was used the capsaicin test. RESULTS: The aqueous extract of Launaea arborescens showed a significant inhibition of abdominal writhing test 95% and 100% inhibition of licking paw using acid acetic test and formalin test respectively (EC: 47 mg/kg and 104 mg/kg). The analgesic effect of the aqueous extract of Launaea arborescens showed inhibition of sensation of pain after 120 min compared to morphine effect. The aqueous extract of Launaea arborescens reduced paw volume after 180 min and 120 min for histamine and serotonin respectively with dose-dependent. Concerning of TRPV1 receptors, the inhibition was showed at doses 100 mg and 300 mg. CONCLUSION: Our results contribute towards validation of the traditional use of Launaea arborescens for inflammation ailment.

Delayed pre-conditioning by 3-nitropropionic acid prevents 3,4-methylenedioxymetamphetamine-induced 5-HT deficits.

The aim of the present study was to investigate whether late pre-conditioning using 3-nitropropionic acid (3NP) prevents the 5-hydroxytryptamine (5-HT) deficits caused by the amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) in the rat. For this purpose we administered 3NP 24 h before MDMA (3 x 5 mg/kg i.p., every 2 h) and rats were killed 7 days later. Pre-treatment of 3NP afforded complete protection against MDMA-induced 5-HT deficits independent of any effect on MDMA-induced hyperthermia or 5-HT transporter activity. To identify the transductional mechanisms responsible for the neuroprotective effect of 3NP, we first examined the involvement of nitric oxide (NO) by using selective inhibitors of all three nitric oxide synthase isoforms. Inhibition of endothelial and neuronal nitric oxide synthase, but not inducible nitric oxide synthase, reversed 3NP-induced pre-conditioning. The NO donor S-Nitroso-N-acetylpenicilamine mimicked 3NP effects further suggesting the involvement of NO in mediating 3NP protection. To investigate the involvement of NOS/soluble guanylate cyclase (sGC)/protein kinase G/mitochondrial ATP-sensitive potassium channels (mitoK(ATP)) signaling pathway we examined the effect of 5-hydroxydecanoate (5-HD), a selective mitoK(ATP) blocker, and 1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one, a potent inhibitor of sGC, on 3NP-induced tolerance. 5-hydroxydecanoate, but not 1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one, suppressed 3NP-mediated protection suggesting that mitoK(ATP) opening, but not NO-mediated activation of sGC, participates in the mechanism underlying tolerance to MDMA. Our data also showed that the protective effect of 3NP was abolished by cycloheximide, supporting the involvement of de novo protein synthesis. In conclusion, 3NP-induced delayed tolerance against 5-HT deficits caused by MDMA occurs via NO production.

The use of in situ perfusion of the rat mesentery as a model to investigate vascular injury directly induced by drugs.

Exposure of the vasculature to vasodilators, pharmaceuticals and industrial chemicals may lead to injury of the blood vessel wall in animals. Vascular injury may begin with changes in the permeability of vascular endothelial cell and vessels, resulting in possible hemorrhage and edema leading subsequently to immune cell infiltration. The present study was undertaken to determine if the direct exposure of the Sprague Dawley rat mesenteric vasculature through the perfusion of aminophylline, fenoldopam, compound 48/80, histamine or serotonin has any such effects on the blood vessels, and if the two vital dyes Monastral blue B and Evans blue can be used to enhance the visualization of the vascular damage. Microscopic visualization was enhanced by the use of dyes and a variety of alterations of the perfused mesenteric vessels were detected, including varying degrees of mast cell degranulation, microvascular vasodilatation and increased vascular permeability. Macroscopic evidence of vascular damage was minimal. This study demonstrates that in situ perfusion of the rat mesentery is a simple and useful method to eliminate the influence of a variety of physiologic influences or homeostatic responses and can be used to further investigate drug-induced vascular damage.

Monoamine oxidase A inhibition by toxic concentrations of metaxalone.

Context: Serotonin toxicity is a reported complication associated with both therapeutic use and overdose of metaxalone while on therapeutic doses of serotonergic drugs such as serotonin reuptake inhibitors. Monoamine oxidase A (MAO-A) inhibition by metaxalone has been proposed as the etiology of this toxicity. Metaxalone concentrations reported with cases of serotonin toxicity range from 31 to 61 mcg/ml (140-276 µM). We investigated the effect of metaxalone on MAO-A activity using an in vitro model.Methods: Metaxalone at concentrations ranging from 1.56 to 400 µM were incubated with a proprietary MAO substrate and recombinant human MAO-A for 1 h. After that, an esterase and luciferase were added and luminescence measured. Clorgyline, a known MAO-A inhibitor, was used as a positive control. Luminescence was measured using a Biotek Synergy HT microplate reader.Results: Metaxalone demonstrated significant dose-related inhibition of MAO-A activity. Four-parameter logistic regression analysis demonstrated a strong dose-response relationship at increasing concentrations.Conclusions: Our in vitro model shows that at toxic concentrations similar to those reported in case reports metaxalone shows significant MAO-A inhibition. Clinicians should be aware of this mechanism and understand the potentially lethal interactions metaxalone can have when prescribed with other serotonergic drugs and consider this as a potential cause of serotonin toxicity, especially in overdose scenarios.