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Shokry IM, DeSuza K, Callanan JJ, Shim G, Ma Z, Tao R. Individuals with Hyperthyroidism are More Susceptible to having a Serious Serotonin Syndrome Following MDMA (Ecstasy) Administration in Rats. ANNALS OF FORENSIC RESEARCH AND ANALYSIS 2018; 5:1052. [PMID: 31172032 PMCID: PMC6548465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In a recreational use of 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy"), some but not all users are stricken with a serious serotonin (5-hydroxytryptamine; 5-HT) syndrome. This raises a question as to whether there exist subpopulations that are more susceptible to MDMA intoxication. The hypothesis was tested with hyperthyroid versus euthyroid rats by measuring changes in body-core temperature (T cor) and 5-HT in the hypothalamus. In the euthyroid rats, injection of MDMA at a recreationally relevant dose had no serious effect on T cor. In contrast, the same dose was sufficient to evoke life-threatening hyperthermia in hyperthyroid rats. Neurochemical studies revealed that there was greater 5-HT efflux in the hyperthyroid than the euthyroid rats. These effects were blocked by pretreatment with M100907, a 5-HT2A receptor antagonist. In summary, our data support the hypothesis that individuals with hyperthyroidism are more susceptible to having a serious serotonin syndrome following MDMA administration.
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Affiliation(s)
- Ibrahim M. Shokry
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
- Ross University School of Veterinary Medicine, West Indies
| | - Kayla DeSuza
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
| | | | - Giselle Shim
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
| | - Zhiyuan Ma
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
| | - Rui Tao
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
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Bello AU, Idrus Z, Meng GY, Narayan EJ, Farjam AS. Dose-response relationship of tryptophan with large neutral amino acids, and its impact on physiological responses in the chick model. Gen Comp Endocrinol 2018; 260:146-150. [PMID: 29339185 DOI: 10.1016/j.ygcen.2018.01.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 12/21/2017] [Accepted: 01/11/2018] [Indexed: 11/20/2022]
Abstract
Tryptophan (Trp) has been associated with the regulation of several behavioral and physiological processes, through stimulation of serotonergic activity. Tryptophan utilization at the metabolic level is influenced by the competitive carrier system it shares with large neutral amino acids (LNAA). This study was carried out using meat-type chicken as a model, to investigate the dose response effects of Trp/LNAA on fear response (tonic immobility; TI) and hormonal responses, including corticosterone (CORT), serotonin (5-HT), triiodothyronine (T3) and thyroxine (T4). A total of 12 cages (48 birds) were assigned to each of the six experimental groups at 29-42 days of age. Experimental diets were formulated to have incremental levels of Trp/LNAA (0.025, 0.030, 0.035, 0.040, 0.045, and 0.050). The results revealed that, Trp/NAA had no significant effect on growth performance and TI of the birds. However, elevation of Trp/LNAA was concurred with a linear reduction in CORT (P < .0001, r2 = 0.819) and linear increases in 5-HT (P < .0001, r2 = 0.945), T3 (P = .0003, r2 = 0.403) and T4 (P < .0001, r2 = 0.937) levels. In conclusion, the results from the current study demonstrated that, although incremental levels of Trp/LNAA did not affect bird growth performance or fearfulness, it increased 5-HT, T3 and T4, and decreased CORT levels in a linear dose-dependent manner. Manipulation of Trp feeding levels could be applied to manage stressful conditions in birds.
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Affiliation(s)
- Alhassan Usman Bello
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Selangor, Malaysia
| | - Zulkifli Idrus
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Selangor, Malaysia; Department of Animal Science, Universiti Putra Malaysia, 43400 Selangor, Malaysia
| | - Goh Yong Meng
- Department of Preclinical Sciences, Universiti Putra Malaysia, 43400 Selangor, Malaysia
| | - Edward J Narayan
- School of Science and Health, Western Sydney University, Penrith, NSW 2751, Australia
| | - Abdoreza Soleimani Farjam
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Selangor, Malaysia.
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U. Bello A, Idrus Z, Yong Meng G, Awad EA, Soleimani Farjam A. Gut microbiota and transportation stress response affected by tryptophan supplementation in broiler chickens. ITALIAN JOURNAL OF ANIMAL SCIENCE 2017. [DOI: 10.1080/1828051x.2017.1340814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Alhassan U. Bello
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, Selangor, Malaysia
| | - Zulkifli Idrus
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, Selangor, Malaysia
- Department of Animal Science, Universiti Putra Malaysia, Selangor, Malaysia
| | - Goh Yong Meng
- Department of Preclinical Sciences, Universiti Putra Malaysia, Selangor, Malaysia
| | - Elmutaz Atta Awad
- Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, Selangor, Malaysia
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Tao R, Shokry IM, Callanan JJ. Environment Influencing Serotonin Syndrome Induced by Ecstasy Abuse. ANNALS OF FORENSIC RESEARCH AND ANALYSIS 2017; 4:1039. [PMID: 29732414 PMCID: PMC5931730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Ecstasy is a recreational drug containing 3,4-methylenedioxymethamphetamine (MDMA). In the U.S., there are several millions of lifetime users, and millions each year added to the list as new users. Only several thousand every year show signs of severe toxicity and require emergency intervention. The illness is known as serotonin (5-HT) syndrome, which can be mild, moderate or severe. The relationship between mild, moderate and severe syndromes appears to be interchangeable, but the severe syndrome is life-threatening. The serotonergic mechanisms of how the mild or moderate syndrome becomes severe and life-threatening have attracted considerable attention in the last few years as an effort to explore new treatments potentially to manage illness and prevent death of patients. High levels of extracellular 5-HT in the brain produced by large doses of MDMA are not always necessary to cause a severe serotonin syndrome. Additional mechanisms may be more important. Recent research has demonstrated that environmental conditions (i.e., non-drug factors) are more critical in determining the severity of MDMA-induced serotonin syndrome than the drug dose. The purpose of the current article was to review available evidence regarding the effect of non-drug factors on serotonergic extrasynaptic receptor responsivity and the severity of MDMA-induced serotonin syndrome.
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Affiliation(s)
- Rui Tao
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
| | - Ibrahim M. Shokry
- Charles E. Schmidt College of Medicine, Florida Atlantic University, USA
- Ross University School of Veterinary Medicine, West Indies
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Fukushima A, Sekiguchi W, Mamada K, Tohma Y, Ono H. Serotonergic System Does Not Contribute to the Hypothermic Action of Acetaminophen. Biol Pharm Bull 2016; 40:227-233. [PMID: 27916764 DOI: 10.1248/bpb.b16-00728] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acetaminophen (AcAP), a widely-used antipyretic and analgesic drug, has been considered to exert its effects via central mechanisms, and many studies have demonstrated that the analgesic action of AcAP involves activation of the serotonergic system. Although the serotonergic system also plays an important role in thermoregulation, the contribution of serotonergic activity to the hypothermic effect of AcAP has remained unclear. In the present study, we examined whether the serotonergic system is involved in AcAP-induced hypothermia. In normal mice, AcAP (300 mg/kg, intraperitoneally (i.p.)) induced marked hypothermia (ca. -4°C). The same dose of AcAP reduced pain response behavior in the formalin test. Pretreatment with the serotonin synthesis inhibitor DL-p-chlorophenylalanine (PCPA, 300 mg/kg/d, i.p., 5 consecutive days) substantially decreased serotonin in the brain by 70% and significantly inhibited the analgesic, but not the hypothermic action of AcAP. The same PCPA treatment significantly inhibited the hypothermia induced by the selective serotonin reuptake inhibitor fluoxetine hydrochloride (20 mg/kg, i.p.) and the serotonin 5-HT2 receptor antagonist cyproheptadine hydrochloride (3 mg/kg, i.p.). The lower doses of fluoxetine hydrochloride (3 mg/kg, i.p.) and cyproheptadine hydrochloride (0.3 mg/kg, i.p.) did not affect the AcAP-induced hypothermia. These results suggest that, in comparison with its analgesic effect, the hypothermic effect of AcAP is not mediated by the serotonergic system.
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Affiliation(s)
- Akihiro Fukushima
- Laboratory of Clinical Pharmacy and Pharmacology, Faculty of Pharmacy, Musashino University
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Nguyen CT, Zhou S, Shanahan W, Fain R. Lorcaserin in Obese and Overweight Patients Taking Prohibited Serotonergic Agents: A Retrospective Analysis. Clin Ther 2016; 38:1498-1509. [DOI: 10.1016/j.clinthera.2016.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 04/11/2016] [Accepted: 04/14/2016] [Indexed: 01/21/2023]
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Shokry IM, Callanan JJ, Sousa J, Tao R. New Insights on Different Response of MDMA-Elicited Serotonin Syndrome to Systemic and Intracranial Administrations in the Rat Brain. PLoS One 2016; 11:e0155551. [PMID: 27192423 PMCID: PMC4871448 DOI: 10.1371/journal.pone.0155551] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 04/29/2016] [Indexed: 11/19/2022] Open
Abstract
In spite of the fact that systemic administration of MDMA elicits serotonin syndrome, direct intracranial administration fails to reproduce the effect. To reconcile these findings, it has been suggested that the cause of serotonin syndrome is attributed mainly to MDMA hepatic metabolites, and less likely to MDMA itself. Recently, however, this explanation has been challenged, and alternative hypotheses need to be explored. Here, we tested the hypothesis that serotonin syndrome is the result of excessive 5HT simultaneously in many brain areas, while MDMA administered intracranially fails to cause serotonin syndrome because it produces only a localized effect at the delivery site and not to other parts of the brain. This hypothesis was examined using adult male Sprague Dawley rats by comparing 5HT responses in the right and left hemispheric frontal cortices, right and left hemispheric diencephalons, and medullar raphe nucleus. Occurrence of serotonin syndrome was confirmed by measuring change in body temperature. Administration routes included intraperitoneal (IP), intracerebroventricular (ICV) and reverse microdialysis. First, we found that IP administration caused excessive 5HT in all five sites investigated and induced hypothermia, suggesting the development of the serotonin syndrome. In contrast, ICV and reverse microdialysis caused excessive 5HT only in regions of delivery sites without changes in body-core temperature, suggesting the absence of the syndrome. Next, chemical dyes were used to trace differences in distribution and diffusion patterns between administration routes. After systemic administration, the dyes were found to be evenly distributed in the brain. However, the dyes administered through ICV or reverse microdialysis injection still remained in the delivery sites, poorly diffusing to the brain. In conclusion, intracranial MDMA administration in one area has no or little effect on other areas, which must be considered a plausible reason for the difference in MDMA-elicited serotonin syndrome between systemic and intracranial administrations.
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Affiliation(s)
- Ibrahim M Shokry
- Ross University School of Veterinary Medicine, St. Kitts, West Indies
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - John J Callanan
- Ross University School of Veterinary Medicine, St. Kitts, West Indies
| | - John Sousa
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Rui Tao
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, United States of America
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Tao R, Shokry IM, Callanan JJ, Adams HD, Ma Z. Mechanisms and environmental factors that underlying the intensification of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy)-induced serotonin syndrome in rats. Psychopharmacology (Berl) 2015; 232:1245-60. [PMID: 25300903 PMCID: PMC4361258 DOI: 10.1007/s00213-014-3759-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 09/23/2014] [Indexed: 01/08/2023]
Abstract
RATIONALE Illicit use of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) may cause a mild or severe form of the serotonin syndrome. The syndrome intensity is not just influenced by drug doses but also by environmental factors. OBJECTIVES Warm environmental temperatures and physical activity are features of raves. The purpose of this study was to assess how these two factors can potentially intensify the syndrome. METHODS Rats were administered MDMA at doses of 0.3, 1, or 3 mg/kg and examined in the absence or presence of warm temperature and physical activity. The syndrome intensity was estimated by visual scoring for behavioral syndrome and also instrumentally measuring changes in symptoms of the syndrome. RESULTS Our results showed that MDMA at 3 mg/kg, but not 0.3 or 1 mg/kg, caused a mild serotonin syndrome in rats. Each environmental factor alone moderately intensified the syndrome. When the two factors were combined, the intensification became more severe than each factor alone highlighting a synergistic effect. This intensification was blocked by the 5-HT2A receptor antagonist M100907, competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist CGS19755, autonomic ganglionic blocker hexamethonium, and the benzodiazepine-GABAA receptor agonist midazolam but not by the 5-HT1A receptor antagonist WAY100635 or nicotinic receptor antagonist methyllycaconitine. CONCLUSIONS Our data suggest that, in the absence of environmental factors, the MDMA-induced syndrome is mainly mediated through the serotonergic transmission (5-hydroxytryptamine (5HT)-dependent mechanism) and therefore is relatively mild. Warm temperature and physical activity facilitate serotonergic and other neural systems such as glutamatergic and autonomic transmissions, resulting in intensification of the syndrome (non-5HT mechanisms).
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Affiliation(s)
- Rui Tao
- Charles E. Schmidt College of Medicine, Florida Atlantic University, 777 Glades Road, Boca Raton, FL, 33431, USA,
| | - Ibrahim M. Shokry
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, USA, School of Veterinary Medicine, Ross University, St. Kitts, West Indies
| | - John J. Callanan
- School of Veterinary Medicine, Ross University, St. Kitts, West Indies
| | - H. Daniel Adams
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, USA
| | - Zhiyuan Ma
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida, USA
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Changes in intensity of serotonin syndrome caused by adverse interaction between monoamine oxidase inhibitors and serotonin reuptake blockers. Neuropsychopharmacology 2014; 39:1996-2007. [PMID: 24577320 PMCID: PMC4059910 DOI: 10.1038/npp.2014.49] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/15/2014] [Accepted: 02/17/2014] [Indexed: 11/08/2022]
Abstract
Drug interaction between inhibitors of monoamine oxidase (MAOIs) and selective serotonin (5-hydroxytryptamine, 5-HT) reuptake (SSRIs) induces serotonin syndrome, which is usually mild but occasionally severe in intensity. However, little is known about neural mechanisms responsible for the syndrome induction and intensification. In this study, we hypothesized that the syndrome induction and intensity utilize two different but inter-related mechanisms. Serotonin syndrome is elicited by excessive 5-HT in the brain (presynaptic mechanism), whereas syndrome intensity is attributed to neural circuits involving 5-HT2A and NMDA receptors (postsynaptic mechanism). To test this hypothesis, basal 5-HT efflux and postsynaptic circuits were pharmacologically altered in rats by once daily pretreatment of the MAOI clorgyline for 3, 6, or 13 days. Syndrome intensity was estimated by measuring 5-HT efflux, neuromuscular activity, and body-core temperature in response to challenge injection of clorgyline combined with the SSRI paroxetine. Results showed that the onset of serotonin syndrome is caused by 5-HT efflux exceeding 10-fold above baseline, confirming the presynaptic hypothesis. The neuromuscular and body-core temperature abnormalities, which were otherwise mild in drug-naive rats, were significantly intensified to a severe level in rats pretreated with daily clorgyline for 3 and 6 days but not in rats pretreated for 13 days. The intensified effect was blocked by M100907 and MK-801, suggesting that variation in syndrome intensity was mediated through a 5-HT2A and NMDA receptor-engaged circuit. Therefore, we concluded that pretreatments of MAOI pharmacologically alter the activity of postsynaptic circuits, which is responsible for changes in syndrome intensity.
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Fox MA, Panessiti MG, Moya PR, Tolliver TJ, Chen K, Shih JC, Murphy DL. Mutations in monoamine oxidase (MAO) genes in mice lead to hypersensitivity to serotonin-enhancing drugs: implications for drug side effects in humans. THE PHARMACOGENOMICS JOURNAL 2013; 13:551-7. [PMID: 22964922 PMCID: PMC3562558 DOI: 10.1038/tpj.2012.35] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 07/18/2012] [Accepted: 07/23/2012] [Indexed: 12/16/2022]
Abstract
A possible side effect of serotonin-enhancing drugs is the serotonin syndrome, which can be lethal. Here we examined possible hypersensitivity to two such drugs, the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP) and the atypical opioid tramadol, in mice lacking the genes for both monoamine oxidase A (MAOA) and MAOB. MAOA/B-knockout (KO) mice displayed baseline serotonin syndrome behaviors, and these behavioral responses were highly exaggerated following 5-HTP or tramadol versus baseline and wild-type (WT) littermates. Compared with MAOA/B-WT mice, baseline tissue serotonin levels were increased ∼2.6-3.9-fold in MAOA/B-KO mice. Following 5-HTP, serotonin levels were further increased ∼4.5-6.2-fold in MAOA/B-KO mice. These exaggerated responses are in line with the exaggerated responses following serotonin-enhancing drugs that we previously observed in mice lacking the serotonin transporter (SERT). These findings provide a second genetic mouse model suggestive of possible human vulnerability to the serotonin syndrome in individuals with lesser-expressing MAO or SERT polymorphisms that confer serotonergic system changes.
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Affiliation(s)
- MA Fox
- Laboratory of Clinical Science (LCS), National Institute of Mental Health, NIH, Bethesda, MD, USA
| | - MG Panessiti
- Laboratory of Clinical Science (LCS), National Institute of Mental Health, NIH, Bethesda, MD, USA
| | - PR Moya
- Laboratory of Clinical Science (LCS), National Institute of Mental Health, NIH, Bethesda, MD, USA
| | - TJ Tolliver
- Laboratory of Clinical Science (LCS), National Institute of Mental Health, NIH, Bethesda, MD, USA
| | - K Chen
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, USA
| | - JC Shih
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, USA
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - DL Murphy
- Laboratory of Clinical Science (LCS), National Institute of Mental Health, NIH, Bethesda, MD, USA
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Haberzettl R, Bert B, Fink H, Fox MA. Animal models of the serotonin syndrome: a systematic review. Behav Brain Res 2013; 256:328-45. [PMID: 24004848 DOI: 10.1016/j.bbr.2013.08.045] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/26/2013] [Accepted: 08/28/2013] [Indexed: 11/16/2022]
Abstract
The serotonin syndrome (SS) is a potentially life-threatening disorder in humans which is induced by ingestion of an overdose or by combination of two or more serotonin (5-HT)-enhancing drugs. In animals, acute administration of direct and indirect 5-HT agonists also leads to a set of behavioral and autonomic responses. In the current review, we provide an overview of the existing versions of the animal model of the SS. With a focus on studies in rats and mice, we analyze the frequency of behavioral and autonomic responses following administration of 5-HT-enhancing drugs and direct 5-HT agonists administered alone or in combination, and we briefly discuss the receptor mediation of these responses. Considering species differences, we identify a distinct set of behavioral and autonomic responses that are consistently observed following administration of direct and indirect 5-HT agonists. Finally, we discuss the importance of a standardized assessment of SS responses in rodents and the utility of animal models of the SS in translational studies, and provide suggestions for future research.
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Affiliation(s)
- Robert Haberzettl
- Institute of Pharmacology and Toxicology, School of Veterinary Medicine, Freie Universität Berlin, Koserstrasse 20, 14195 Berlin, Germany
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Ma Z, Rudacille M, Prentice HM, Tao R. Characterization of electroencephalographic and biochemical responses at 5-HT promoting drug-induced onset of serotonin syndrome in rats. J Neurochem 2013; 125:774-89. [PMID: 23286698 DOI: 10.1111/jnc.12141] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 12/20/2012] [Accepted: 01/02/2013] [Indexed: 12/22/2022]
Abstract
Many psychotropic substances used either for medications or illicit recreational purposes are able to produce an increase in extracellular serotonin (5HT) in the CNS. 5HT is well known to improve mood; however, only when the levels of its release are in an appropriate range. Excessive 5HT is harmful, and will generally result in serotonin syndrome. To date, clinical diagnosis of serotonin syndrome relies exclusively on observation of symptoms because of a lack of available laboratory tests. The goal of this study was to characterize the onset of the syndrome using laboratory settings to determine excessive 5HT-evoked neurological abnormalities. Experiments were carried out in rats with the syndrome being elicited by three groups of 5HT-promoting drugs: (i) (±)-3,4-methylenedioxymethamphetamine (MDMA); (ii) a combination of the monoamine oxidase inhibitor clorgyline with the 5HT precursor 5-hydroxytryptophan; (iii) clorgyline combined with the serotonin-selective reuptake inhibitor paroxetine. The onset of the syndrome was characterized by electroencephalography (EEG), tremor, and brain/plasma 5HT tests. We found that a mild syndrome was associated with reduced EEG amplitudes while a severe syndrome strongly with seizure-like EEG activity and increased tremor activity. The occurrence of the syndrome was confirmed with microdialysis, showing excessive 5HT efflux in brain dialysate and the increased concentration of unbound 5HT in the plasma. Our findings suggest that the syndrome onset can be revealed with EEG recording, measurements of tremor activity and changes of unbound 5HT concentration in the plasma.
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Affiliation(s)
- Zhiyuan Ma
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida 33431, USA
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Decision time and perseveration of adolescent rats in the T-maze are affected differentially by buspirone and independent of 5-HT-1A expression. Pharmacol Biochem Behav 2012; 102:58-63. [PMID: 22494991 DOI: 10.1016/j.pbb.2012.03.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 03/19/2012] [Accepted: 03/25/2012] [Indexed: 12/22/2022]
Abstract
Disruption of spontaneous alternation behavior (SAB) by the serotonin 1A (5-HT-1A) receptor agonist, 8-hydroxy-dipropylaminotetraline (8-OH-DPAT), results in repetitive behaviors that have been used to model the perseveration and indecisiveness of human obsessive-compulsive disorder (OCD). In the present study, we compared the effects of buspirone to those of 8-OH-DPAT in two strains of adolescent rats and analyzed repetitive choices of arms of the maze and prolonged apparent decision time due to induction of vicarious trial and error (VTE) behavior. In adolescent Sprague-Dawley (SD) rats, 8-OH-DPAT induced repetitive choices of arms of the maze (perseveration) and increased the apparent decision time. Buspirone induced VTE behavior and increased apparent decision time without perseveration. This distinct effect of buspirone was seen in SD adolescents but not in Long-Evans (LE) adolescents which appeared to be insensitive to buspirone. Lack of responsiveness to buspirone was dependent on the developmental stage because buspirone induced VTE behavior and prolonged decision time in LE adults. Western blotting of brain 5-HT-1A receptors showed expression of receptor protein in adolescent LE brain was comparable to that of adolescent SD and adult LE. The 5-HT-1A antagonist WAY 100365 blocked the effect 8-OH-DPAT on repetitive choice of arms but not the effect of buspirone on VTE behavior. We conclude that the adolescent LE rat has normal levels of 5-HT-1A receptor and that the effect of buspirone on VTE behavior is not mediated by the 5-HT-1A receptor. The LE strain may provide a useful system for further study of the adolescent brain and potential genetic differences in induction of repetitive behaviors.
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Implication of 5-HT2B receptors in the serotonin syndrome. Neuropharmacology 2011; 61:495-502. [DOI: 10.1016/j.neuropharm.2011.01.025] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 11/18/2010] [Accepted: 01/17/2011] [Indexed: 11/17/2022]
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Krishnamoorthy S, Ma Z, Zhang G, Wei J, Auerbach SB, Tao R. Involvement of 5-HT2A receptors in the serotonin (5-HT) syndrome caused by excessive 5-HT efflux in rat brain. Basic Clin Pharmacol Toxicol 2011; 107:830-41. [PMID: 20456331 DOI: 10.1111/j.1742-7843.2010.00586.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies have demonstrated that serotonin (5-HT) syndromes, particularly for the malignant cases, can be alleviated by ice water mists, cooling blankets and many other external cooling measures. In this study, we tested the hypothesis that external cooling measures reduce the responsivity of 5-HT(2A) receptors to excessive 5-HT efflux, which may be a possible mechanism underlying the treatment of serotonin syndrome. To test this, rat experiments were carried out in the standard and cool ambient temperature (T(amb) ) by administration of the 5-HT precursor 5-hydroxy-L-tryptophan combined with the monoamine oxidase inhibitor clorgyline. The first set of experiments was to assess severity of the syndromes by measuring body temperature responses. Consistent with the hypothesis, we found that the syndrome was malignant at the standard T(amb) of 22°C but alleviated at 12 or 6°C, these results being similar to those in rats pre-treated with the 5-HT(2A) receptor antagonist ketanserin. The second set of experiments was to utilize microdialysis to determine the relationship between the syndrome severity and 5-HT levels at the above-mentioned T(amb) . We found that excessive 5-HT efflux consisted of primary and secondary components through two distinct mechanisms. Furthermore, the secondary component efflux, which can be ascribed to 5-HT(2A) receptor activation, was proportionally reduced at the cool T(amb) of 12 and 6°C. In conclusion, results of this study support the hypothesis that cooling T(amb) reduces the functional activity of 5-HT(2A) receptors, thus alleviating the malignant syndrome.
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Affiliation(s)
- Swapna Krishnamoorthy
- Charles E. Schmidt College of Biomedical Science, Florida Atlantic University, Boca Raton, FL, USA
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