Residual effects of ecstasy (3,4-methylenedioxymethamphetamine) on low level visual processes

'Ecstasy' (3,4-methylenedioxymethamphetamine) induces impaired functioning in the serotonergic system, including the occipital lobe. This study employed the 'tilt aftereffect' paradigm to operationalise the function of orientation-selective neurons among ecstasy consumers and controls as a means of investigating the role of reduced serotonin on visual orientation processing. The magnitude of the tilt aftereffect reflects the extent of lateral inhibition between orientation-selective neurons and is elicited to both 'real' contours, processed in visual cortex area V1, and illusory contours, processed in V2. The magnitude of tilt aftereffect to both contour types was examined among 19 ecstasy users (6 ecstasy only; 13 ecstasy-plus-cannabis users) and 23 matched controls (9 cannabis-only users; 14 drug-naive). Ecstasy users had a significantly greater tilt magnitude than non-users for real contours (Hedge's g = 0.63) but not for illusory contours (g = 0.20). These findings provide support for literature suggesting that residual effects of ecstasy (and reduced serotonin) impairs lateral inhibition between orientation-selective neurons in V1, which however suggests that ecstasy may not substantially affect this process in V2. Multiple studies have now demonstrated ecstasy-related deficits on basic visual functions, including orientation and motion processing. Such low-level effects may contribute to the impact of ecstasy use on neuropsychological tests of visuospatial function.     

Short-term and long-term effects of methamphetamine on biogenic amine metabolism in extra-striatal dopaminergic nuclei

The effects of multiple toxic doses of methamphetamine on catecholaminergic, serotonergic and cholinergic metabolism in the neostriatum, nucleus accumbens, olfactory tubercle and median eminence area of the rat brain have been investigated. Methamphetamine (15 mg/kg s.c.) was administered every 6 hr for 5 doses. Thirty-six hours after the first of 5 doses, tyrosine hydroxylase (TH) activity, as well as dopamine and norepinephrine levels, were significantly decreased in the neostriatum and olfactory tubercle but were not altered in the nucleus accumbens or median eminence area. Prior to the 36-hr time point, drug treatment significantly decreased TH activity in the neostriatum and olfactory tubercle, but did not change the enzyme activity in the nucleus accumbens. Neostriatal TH activity in the neostriatum and olfactory tubercle was significantly decreased up to 30 days after methamphetamine. However, only a slight change in TH activity occurred in the nucleus accumbens at 30 days after drug treatment. In contrast, tryptophan hydroxylase (TPH) activity was significantly decreased from 3 hr after the first dose up to 30 days after the fifth dose in all brain regions investigated. Methamphetamine caused a slight decrease in choline acetyltransferase activity only in the olfactory tubercle at the 36-hr time point. This evidence suggests that the serotonergic neurons are more sensitive to the toxic effects of methamphetamine than the dopaminergic neurons, whereas, the cholinergic neurons seem to be essentially unaffected.     

Pulmonary hypertension: therapeutic targets within the serotonin system

Pulmonary arterial hypertension (PAH) is characterized by a sustained and progressive elevation in pulmonary arterial pressure and pulmonary vascular remodelling leading to right heart failure and death. Prognosis is poor and novel therapeutic approaches are needed. The serotonin hypothesis of PAH originated in the 1960s after an outbreak of the disease was reported among patients taking the anorexigenic drugs aminorex and fenfluramine. These are indirect serotonergic agonists and serotonin transporter substrates. Since then many advances have been made in our understanding of the role of serotonin in the pathobiology of PAH. The rate-limiting enzyme in the synthesis of serotonin is tryptophan hydroxylase (Tph). Serotonin is synthesized, through Tph1, in the endothelial cells of the pulmonary artery and can then act on underlying pulmonary arterial smooth muscle cells and pulmonary arterial fibroblasts in a paracrine fashion causing constriction and remodelling. These effects of serotonin can be mediated through both the serotonin transporter and serotonin receptors. This review will discuss our current understanding of 'the serotonin hypothesis' of PAH and highlight possible therapeutic targets within the serotonin system.     

Functional consequences of perinatal exposure to 3,4-methylenedioxymethamphetamine in rat brain

1. In this study we have examined methylenedioxymethamphetamine (MDMA)-induced toxicity in perinatal rat brain, related this to normal development of serotonin transporter sites (SERT), and determined whether early exposure to MDMA subsequently alters cerebral function in adults. 2. Perinatal development of SERT was visualized and quantified using [(3)H]-paroxetine binding autoradiography in embryonic and neonatal rat brain from embryonic day 15 (E15) to postnatal day p30 (p30). Cerebral glucose utilization (lCMR(glu)) was measured by 2-deoxyglucose autoradiography in adult rats. 3. [(3)H]-Paroxetine binding was observed in forebrain from E18. From birth (p0), binding was organized into neocortical columns (75% higher at p10 than in adult) which declined toward adult levels between p20 and p25. 4. MDMA treatment (20 mg x kg(-1) s.c. twice daily for four days) commencing at developmental stages from E15 (treatment given to dams) to p20, had no effect upon [(3)H]-paroxetine binding measured at p40. Treatments started on p25 or later resulted in significant decreases in [(3)H]-paroxetine binding (>or=46%). This was coincident with the development of adult patterns of binding in forebrain. 5. Despite the lack of MDMA-induced neurotoxicity, rats treated in utero (E15) showed increased lCMR(glu) in locus coeruleus (+37%), and in areas receiving ascending noradrenergic innervation, such as anterior thalamus (+44%) and septal nucleus (+24%). 6 These studies confirm that the susceptibility of serotonergic terminals to the neurotoxic properties of MDMA is absent in the immediate perinatal period, but also suggests that in utero MDMA exposure produces significant long-term effects on cerebral function by a mechanism as yet unknown.     

The effects of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) on monoaminergic systems in the rat brain

The effects of two amphetamine-like designer drugs, 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA), on dopaminergic and serotonergic systems in the rat brain were investigated and compared to those of methamphetamine (METH). Like METH, single or multiple 10 mg/kg doses of either drug caused marked reductions in both tryptophan hydroxylase (TPH) activity and concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid, in several serotonergic nerve terminal regions. In all regions examined, the reduction in 5-HT content corresponded to the depression of TPH activity. Unlike multiple METH administrations, which induced pronounced deficits in dopaminergic neuronal markers, repeated doses of MDA or MDMA did not alter striatal tyrosine hydroxylase (TH) activities or reduce striatal dopamine concentrations. A single dose of MDA or MDMA significantly elevated striatal dopamine content; however, after repeated drug administrations dopamine concentrations were comparable to control values. At this time, striatal levels of homovanillic acid were significantly elevated suggesting that both drugs influence dopamine turnover. The effects of MDA or MDMA administration in the rat brain are reminiscent of those elicited by p-chloroamphetamine, a presumed serotonergic neurotoxin.     

The development of tryptophan hydroxylase in the chicken brain: effects of p-chloroamphetamine and antagonists of serotonin, noradrenaline and dopamine.

The development of tryptophan hydroxylase in a number of regions of the midbrain and hindbrain of the chicken has been examined. In general, specific activities were low prior to day 14 of incubation of eggs. reaching a plateau around hatching (day 21). The total amount of tryptophan hydroxylase in the hindbrain, but not the midbrain. continued to increase after hatching. The injection of the dopamine antagonists haloperidol, ( + )-butaclamol, fluphenazine and methiothepin into the air sac of chicken eggs incubated for 14 days resulted in elevated levels of tryptophan hydroxylase in the hindbrain I region of 7-day-old chickens. With haloperidol. enzyme levels were higher in most regions of the midbrain and hindbrain, whereas with pimozide, the level of tryptophan hydroxylase decreased in the hindbrain I region, but not in other brain regions. The effect of haloperidol was on the development of tryptophan hydroxylase since it was without effect when injected into 7-day-old chickens and the levels of the enzyme measured 2 weeks later. Treatment of eggs with the dopamine agonists apomorphine. piribedil and S584. the serotonin antagonists methysergide and cyproheptadine, p-chloroamphetamine and dl-propranolol were without significant effect in any brain region examined.     

Toward a better understanding of depression and anxiety: the involvement of stress and tryptophan hydroxylase activation

Tryptophan hydroxylase (TPH) has been implicated as the key enzyme involved in the etiology of the affective disorders, anxiety and depression. In addition to its activation by stress, TPH is also activated by the amino‐acid decarboxylase inhibitor, NSD 1015, which is widely used for the determination of serotonin turnover. The blockade of this activation by the established antidepressants provides a new, distinct concept to account for the beneficial activity of these compounds. The blockade of the stress‐induced activation of TPH by the benzodiazepine, diazepam, is consistent with its anxiolytic activity involving TPH activation inhibition. In support of the concept, a selective TPH activation inhibitor, AGN 2979, has been reported to exert both powerful antidepressant and anxiolytic effects in the clinic, with a notable lack of the side effects associated with transmitter reuptake inhibition and benzodiazepine receptor interactions. Drug Dev. Res. 67:801–805, 2006. © 2007 Wiley‐Liss, Inc.     

Locomotor stimulation produced by 3,4-methylenedioxymethamphetamine (MDMA) is correlated with dialysate levels of serotonin and dopamine in rat brain

(+/-)-3,4-Methylenedioxymethamphetamine (MDMA, or Ecstasy) is an illicit drug that evokes transporter-mediated release of monoamines, including serotonin (5-HT) and dopamine (DA). Here we monitored the effects of MDMA on neurochemistry and motor activity in rats, as a means to evaluate relationships between 5-HT, DA, and behavior. Male rats undergoing in vivo microdialysis were housed in chambers equipped with photobeams for measurement of ambulation (i.e., forward locomotion) and stereotypy (i.e., head weaving and forepaw treading). Microdialysis probes were placed into the n. accumbens, striatum or prefrontal cortex in separate groups of rats. Dialysate samples were assayed for 5-HT and DA by microbore HPLC-ECD. Rats received two i.v. injections of MDMA, 1 mg/kg followed by 3 mg/kg 60 min later; neurochemical and locomotor parameters were measured concurrently. MDMA produced dose-related elevations in extracellular 5-HT and DA in all regions, with the magnitude of 5-HT release always exceeding that of DA release. MDMA-induced ambulation was positively correlated with dialysate DA levels in all regions (P<0.05-0.0001) and with dialysate 5-HT in striatum and cortex (P<0.001-0.0001). Stereotypy was strongly correlated with dialysate 5-HT in all areas (P<0.001-0.0001) and with dialysate DA in accumbens and striatum (P<0.001-0.0001). These data support previous work and suggest the complex spectrum of behaviors produced by MDMA involves 5-HT and DA in a region- and modality-specific manner.     

A pharmacokinetic analysis of 3,4-methylenedioxymethamphetamine effects on monoamine concentrations in brain dialysates.

Interpretation of the in vivo actions of 3,4-methylenedioxymethamphetamine (MDMA) is complicated by the formation of the active metabolite, 3,4-methylenedioxyamphetamine (MDA). This study evaluates the role of MDA in the dopamine releasing actions of (+)-MDMA. In the study, rats were given subcutaneous doses of (+)-MDMA and concentrations of monoamines and their metabolites in striatal dialysate were measured at 15 min intervals. In parallel experiments, plasma concentrations of (+)- and (-)-MDMA and MDA were determined by GC/MS procedures. The time course of MDMA levels was comparable for the two isomers as were their bioavailabilities. In contrast, the plasma levels of MDA were about three times higher after (+)-MDMA. (+)-MDMA caused a rapid increase in striatal dialysate levels of dopamine and decreased extracellular levels of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). There was a significant correlation between dopamine concentration in striatal dialysate and plasma MDMA concentration, but not with plasma MDA. These results indicate that MDMA itself has stereoselective actions on dopamine neurons. However, the higher plasma MDA levels after (+)-MDMA may account for part of the enantiomeric differences in the behavioral and neurotoxicological effects of MDMA.     

Glycyrrhizin treatment ameliorates post-traumatic stress disorder-like behaviours and restores circadian oscillation of intracranial serotonin

Post-traumatic stress disorder (PTSD) has become a major disease that threatens human health. Neurotransmitters and the amygdala are found to be critical in the development and maintenance of PTSD. We aim to investigate the role of glycyrrhizin in treating PTSD. Contextual fear extinction and elevated plus maze test were applied to evaluate the anxiety and fear memory. Microdialysis and high-performance liquid chromatography were used to analyze the expression of amygdala neurotransmitters in PTSD animal models and to verify the effects of glycyrrhizin on major neurotransmitters. The protein levels of tryptophan hydroxylase 2 (TPH2) were examined by western bolt. Glycyrrhizin treatment significantly reduced anxiety and fear memory after 1 and 7 days of PTSD modelling. In addition, glycyrrhizin treatment restored the circadian rhythm changes of serotonin and TPH2. The present study found a significant circadian rhythm change of serotonin in the amygdala in PTSD rats. Besides, glycyrrhizin treatment restored the altered serotonin diurnal fluctuations, which raises important implications for PTSD treatment.     

Possible role of brain serotonin in the central effects of ketamine.

Ketamine increased serotonin turnover in the rat brain. This effect persisted for several hours after the anaesthetic effect of ketamine had terminated. Pretreatment with para-chlorophenyl-alanine, an inhibitor of serotonin synthesis, or with methergoline, a serotonin receptor blocker, potentiated the anaesthetic and analgesic effect of ketamine.     

The antinociceptive effects of 3,4-methylenedioxymethamphetamine (MDMA) in the rat

The antinociceptive effects of MDMA and morphine were examined in rats using the tail-flick and hot-plate analgesiometric tests. MDMA, in the dose range of 1.5-6.0 mg/kg IP, produced a dose-dependent elevation in hot-plate latency, but did not elevate tail-flick latency. In contrast, morphine (2-8 mg/kg, IP) produced analgesia on both the tail-flick and hot-plate tests in a dose-dependent manner. Neither the opiate antagonist naltrexone nor the adrenoceptor antagonist phentolamine effectively attenuated MDMA-induced analgesia. Conversely, the serotonin antagonist methysergide significantly reversed the analgesic effects of MDMA on the hot-plate test. These findings suggest that the antinociceptive effects of MDMA are serotonergically mediated. Furthermore, the results verify earlier findings describing the test-specific effects of serotonin-induced pain modulation.     

Acute effects of 3,4-methylenedioxymethamphetamine (MDMA) on monoamines in rat caudate.

Extracellular levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and serotonin (5-HT) were assayed in the caudate of freely moving rats using microdialysis and high performance liquid chromatography with electrochemical detection (HPLC-EC) to detect changes in their release. Dialysates were assayed at 20-minute intervals for four hours after an intraperitoneal (IP) injection of MDMA (10 mg/kg). In a separate study to determine MDMA effects on total caudate levels of the above neurochemicals, animals were injected IP with MDMA (10 mg/kg) and then sacrificed at 20, 60, 120 and 180 minutes after treatment. Brains were quickly removed, and caudate nuclei were dissected for neurochemical analysis using HPLC-EC. MDMA elicited an amphetamine-like increase in DA release, followed by an increase in DA content. DOPAC and HVA were both reduced in homogenate. 5-HT release was also increased, followed by a drop in caudate homogenate levels by three hours. DA extracellular content was 686% of control at 80 minutes; caudate homogenate levels were 122% at 120 minutes. 5-HT extracellular release was 123% at 20 minutes, then decreased thereafter. It is concluded that the acute effect of MDMA on caudate is at least as great on the DA as it is on the 5-HT system.     

Subjective effects of 3,4-methylenedioxymethamphetamine in recreational users

3,4-Methylenedioxymethamphetamine (MDMA; Ecstasy) is a serotonergic neurotoxin in laboratory animals that has been used for recreational purposes by humans. The subjective effects of this drug were determined in recreational users at a university campus. Of individuals who had admitted to using MDMA recreationally, 100 of 143 agreed to complete a detailed questionnaire concerning the subjective effects of this Schedule I compound. The most common effect of MDMA was a heightened sense of "closeness" with other people (90% of subjects). Tachycardia, dry mouth, bruxism and/or trismus were reported by the majority of users. These effects probably result from the amphetaminelike properties of the drug. Visual hallucinations were reported by 20% of users. Untoward side effects were most common on the day following the use of MDMA, with complaints of muscle aches, fatiguability, depression, and difficulty concentrating noted by 21% to 36% of subjects. Sixty-seven percent of frequent users of the drug (six or more separate doses) reported that the "positive" effects of the drug decreased with successive doses while the "negative" effects increased. Although these observations should be considered preliminary, they represent the first documentation of the subjective effects of MDMA in recreational users and confirm previous reports obtained from patients treated with this drug.     

Effects of chronic monoamine oxidase inhibitor treatment on biogenic amine metabolism in rat brain.

The effects of acute and chronic administration of phenelzine and tranylcypromine on rat brain monoamine metabolism have been examined. Peak increases in norepinephrine, dopamine and 5-hydroxytryptamine occurred between 1 and 7 days with monoamine oxidase inhibitor treatments followed by a gradual decline in brain monoamines towards control levels with continued chronic drug administration. There was an associated adaptive increase in tryptophan hydroxylase but no change in tyrosine hydroxylase activity with chronic phenelzine treatment. Tranylcypromine did not affect tryptophan hydroxylase or tyrosine hydroxylase activities but was associated with a significant increase in aromatic amino acid decarboxylase activity after 14 and 21 days of treatment.     

Lithium and chlorimipramine differentially alter bilateral asymmetry in mesostriatal serotonin metabolites and kinetic conformations of midbrain tryptophan hydroxylase with respect to tetrahydrobiopterin cofactor

Lithium decreased and the tricyclic drug chlorimipramine (CMI) differentially altered hemispheric asymmetries in striatal and hippocampal concentrations of tryptophan, serotonin and 5-hydroxyindoleacetic acid (5-HIAA) in the rat. The kinetic functions of tryptophan hydroxylase from the two halves of the midbrain, demonstrated by pteridine cofactor (BH₄) kinetic functions, also changed differentially in response to the two drugs. Bilateral asymmetries in 5-HIAA and kinetic functions with regard to BH₄ after CMI administration suggest that this drug may alter the neurophysiological activity (5-HT cell discharge rate) of the 5-HT system in one hemisphere relative to the other. In contrast, lithium evoked similar tryptophan hydroxylase kinetic functions with regard to BH₄ from both hemispheres and reduced asymmetries in metabolites, which is more suggestive of a bilaterally simultaneous biochemical “field” mechanism.     

Ethanol, 3,4-methylenedioxymethamphetamine (ecstasy) and their combination: long-term behavioral, neurochemical and neuropharmacological effects in the rat.

This study investigated long-term behavioral, neurochemical, and neuropharmacological effects of ethanol-(+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) combinations. Over 4 consecutive days, male Long-Evans rats received 1.5 g/kg ethanol and/or 10 mg/kg MDMA, or saline. Rectal temperatures were taken in some rats. Starting 4 days after the last injection, we tested working memory, sensory-motor coordination, and anxiety. Subsequently, we measured cortical, striatal, septal, and hippocampal monoamines (last MDMA injection-euthanasia delay: 20 days), or electrically evoked release of serotonin (5-HT) in cortical and hippocampal slices, and its modulation in the presence of CP 93,129 (3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrollo[3,2-b]pyrid-5-one) or methiotepin (last MDMA injection-euthanasia delays: 3-6 weeks). Ethanol attenuated the MDMA-induced hyperthermia, but only on the first day. In the long-term, MDMA reduced 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) content in most brain regions. The behavioral and neurochemical effects of the ethanol-MDMA combination were comparable to those of MDMA alone; sensory-motor coordination was altered after ethanol and/or MDMA. In hippocampal slices from rats given ethanol and MDMA, the CP 93,129-induced inhibition and methiotepin-induced facilitation of 5-HT release were stronger and weaker, respectively, than in the other groups. This is the first study addressing long-term effects of repeated MDMA and EtOH combined treatments in experimental animals. Whereas the drug combination produced the same behavioral and neurochemical effects as MDMA alone, our neuropharmacological results suggest that MDMA-EtOH interactions may have specific long-term consequences on presynaptic modulation of hippocampal 5-HT release, but not necessarily related to MDMA-induced depletion of 5-HT. Thus, it is likely that the psycho(patho)logical problems reported by ecstasy users drinking alcohol are not solely due to the consumption of MDMA.     

Fluoxetine pretreatment effects pharmacokinetics of 3,4-methylenedioxymethamphetamine (MDMA, ECSTASY) in rat

Fluoxetine has been shown to provide protection from MDMA induced long term neurotoxicity. The purpose of this investigation is to evaluate the pharmacokinetic drug interaction between MDMA and fluoxetine and also to determine the role of P-glycoprotein (P-gp) on mediating drug-drug interactions with MDMA. Bi-directional transport studies were conducted across MDCK-MDR1 and Caco-2 monolayers. MDMA brain and plasma levels were measured in P-gp deficient [mdr1a(-/-)] and normal [mdr1a(+/+)] mice after a 5 mg/kg i.p. dose of MDMA. Sprague-Dawley rats were pretreated with fluoxetine (4 days, 10 mg/kg, i.p.) or saline followed by MDMA (10 mg/kg, p.o.) and brain and plasma samples were collected over 10 h. MDMA and its active metabolite MDA were quantified using a HPLC method with fluorescence detection. In transport studies MDMA exhibited high permeability with essentially unpolarized transport. No significant difference in MDMA and MDA brain levels were seen in P-gp deficient versus normal mice. Pretreatment of rats with fluoxetine resulted in an increase in MDMA (1.4-fold) and MDA (1.5-fold) exposure in both brain and plasma. Elimination half-life was increased for MDMA (2.4 vs. 4.9 h) and MDA (1.8 vs. 8.2 h) with fluoxetine pretreatment. P-gp does not play a physiologically relevant role in absorption and distribution of MDMA, hence this transporter may not have a role in drug-drug interactions with MDMA. Fluoxetine pretreatment to provide protection from MDMA induced long term neurotoxicity decreases elimination of MDMA and MDA and may lead to enhanced risk of MDMA acute toxic effects. Overall, our results indicate that caution need to be practiced when recommending fluoxetine as an agent to provide protection from MDMA induced long term neurotoxicity.