Gene expression analysis indicates reduced memory and cognitive functions in the hippocampus and increase in synaptic reorganization in the frontal cortex 3 weeks after MDMA administration in Dark Agouti rats.

BACKGROUND: 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") is a widely used entactogenic drug known to impair cognitive functions on the long-run. Both hippocampal and frontal cortical regions have well established roles in behavior, memory formation and other cognitive tasks and damage of these regions is associated with altered behavior and cognitive functions frequently described in otherwise healthy MDMA users. Meanwhile, in post-traumatic stress disorder (PTSD) patients seem to benefit from therapeutic application of the drug, where damage in hippocampal cue extinction may play a role. The aim of this study was to examine the hippocampus, frontal cortex and dorsal raphe of Dark Agouti rats with gene expression arrays (Illumina RatRef bead arrays) looking for possible mechanisms and new candidates contributing to the consequences of a single dose of MDMA (15 mg/kg) 3 weeks earlier. RESULTS: The number of differentially expressed genes in the hippocampus, frontal cortex and the dorsal raphe were 481, 155, and 15, respectively. Gene set enrichment analysis of the microarray data revealed reduced expression of 'memory' and 'cognition', 'dendrite development' and 'regulation of synaptic plasticity' gene sets in the hippocampus, parallel to the downregulation of CaMK II subunits, glutamate-, CB1 cannabinoid- and EphA4, EphA5, EphA6 receptors. Downregulated gene sets in the frontal cortex were related to protein synthesis, chromatin organization, transmembrane transport processes, while 'dendrite development', 'regulation of synaptic plasticity' and 'positive regulation of synapse assembly' gene sets were upregulated besides elevated levels of a CaMK II subunit and NMDA2B glutamate receptor. Changes in the dorsal raphe region were mild and in most cases not significant. CONCLUSION: The present data raise the possibility of new synapse formation / synaptic reorganization in the frontal cortex 3 weeks after a single neurotoxic dose of MDMA. In contrast, a prolonged depression of new neurite formation in the hippocampus is proposed by downregulations of members in long-term potentiation pathway and synaptic plasticity emphasizing the particular vulnerability of this brain region and proposing a mechanism responsible for cognitive problems in healthy individuals. At the same time, these results underpin benefits of MDMA in PTSD, where the drug may help memory extinction.

[Antidepressants, stressors and the serotonin 1A receptor]. / Antidepresszívumok, stresszorok és a szerotonin 1A receptor.

5-HT(1A) receptor is a receptor of surprises. Buspirone, an anxiolytic drug with a then yet unidentified mechanism of action had been marketed for years when it was discovered that it is a 5-HT(1A) partial agonist. Several more years had to pass before it was accepted that this receptor plays the key role in the action mechanism of buspirone. This was followed by further surprises. It was discovered that in spite of its anxiolytic effect buspirone activates the hypothalamic-pituitary-adrenal (HPA) stress axis, furthermore, it increases peripheral noradrenaline and adrenaline concentration via a central mechanism. Thus activation of this receptor leads to ACTH/corticosterone and catecholamine release and also increases beta-endorphine, oxytocin and prolactin secretion while decreasing body temperature, increasing food uptake, eliciting characteristic behavioural responses in rodents and also playing a role in the development of certain types of epilepsy. Human genetic studies revealed the role of 5-HT(1A) receptors in cognitive processes playing a role in the development of depression such as impulsiveness or response to environmental stress. This exceptionally wide spectrum of effects is attributable to the presence of 5-HT1A receptors in serotonergic as well as other, for example glutamatergic, cholinergic, dopaminergic and noradrenergic neurons. The majority of the effects of 5-HT(1A) receptors is manifested via the mediation of Gi proteins through the hyperpolarisation or inhibition of the neuron carrying the receptor. 5-HT(1A) receptors on serotonergic neurons can be found in the somatodendritic area and play a significant role in delaying the effects of antidepressants which is an obvious disadvantage. Therefore the newest serotonergic antidepressants including vilazodone and vortioxetine have been designed to possess 5-HT(1A) receptor partial agonist properties. In the present paper we focus primarily on the role of 5-HT(1A) receptors in stress and antidepressant response.

Transcriptional evidence for the role of chronic venlafaxine treatment in neurotrophic signaling and neuroplasticity including also Glutamatergic [corrected] - and insulin-mediated neuronal processes.

OBJECTIVES: Venlafaxine (VLX), a serotonine-noradrenaline reuptake inhibitor, is one of the most commonly used antidepressant drugs in clinical practice for the treatment of major depressive disorder (MDD). Despite being more potent than its predecessors, similarly to them, the therapeutical effect of VLX is visible only 3-4 weeks after the beginning of treatment. Furthermore, recent papers show that antidepressants, including also VLX, enhance the motor recovery after stroke even in non depressed persons. In the present, transcriptomic-based study we looked for changes in gene expressions after a long-term VLX administration. METHODS: Osmotic minipumps were implanted subcutaneously into Dark Agouti rats providing a continuous (40 mg/kg/day) VLX delivery for three weeks. Frontal regions of the cerebral cortex were isolated and analyzed using Illumina bead arrays to detect genes showing significant chances in expression. Gene set enrichment analysis was performed to identify specific regulatory networks significantly affected by long term VLX treatment. RESULTS: Chronic VLX administration may have an effect on neurotransmitter release via the regulation of genes involved in vesicular exocytosis and receptor endocytosis (such as Kif proteins, Myo5a, Sv2b, Syn2 or Synj2). Simultaneously, VLX activated the expression of genes involved in neurotrophic signaling (Ntrk2, Ntrk3), glutamatergic transmission (Gria3, Grin2b and Grin2a), neuroplasticity (Camk2g/b, Cd47), synaptogenesis (Epha5a, Gad2) and cognitive processes (Clstn2). Interestingly, VLX increased the expression of genes involved in mitochondrial antioxidant activity (Bcl2 and Prdx1). Additionally, VLX administration also modulated genes related to insulin signaling pathway (Negr1, Ppp3r1, Slc2a4 and Enpp1), a mechanism that has recently been linked to neuroprotection, learning and memory. CONCLUSIONS: Our results strongly suggest that chronic VLX treatment improves functional reorganization and brain plasticity by influencing gene expression in regulatory networks of motor cortical areas. These results are consonant with the synaptic (network) hypothesis of depression and antidepressant-induced motor recovery after stroke.

Advent and recent advances in research on the role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of gonadotropic hormone secretion of female rats.

PACAP (ADCYAP1) was isolated from ovine hypothalami. PACAP activates three distinct receptor types: G-protein coupled PAC1, VPAC1, and VPAC2 with seven transmembrane domains. Eight splice variants of PAC1 receptor are described. A part of the hypothalamic PACAP is released into the hypophyseal portal circulation. Both hypothalamic and pituitary PACAP are involved in the dynamic control of gonadotropic hormone secretion. In female rats, PACAP in the paraventricular nucleus is upregulated in the morning and pituitary PACAP is upregulated in the late evening of the proestrus stage of the reproductive cycle. PACAP mRNA peak in the hypothalamic PVN precedes the LHRH release into the portal circulation. It is supposed that PACAP peak is evoked by the elevated estrogen on proestrous morning. At the beginning of the so-called critical period of the same day, PACAP level starts to decline allowing LHRH release into the portal circulation, resulting in the LH surge that evokes ovulation. Just before the critical period, icv-administered exogenous PACAP blocks the LH surge and ovulation. The blocking effect of PACAP is mediated through CRF and endogenous opioids. The effect of the pituitary-born PACAP depends on the intracellular cross-talk between PACAP and LHRH.

[Anxiogenic and depressogenic side-effects of non-psychiatric drugs]. / Nem pszichiátriai gyógyszerek szorongást és depressziót kiváltó mellékhatásai.

Although medications such as anticancer, antimicrobial, immunomodulatory, neurological or hormonal therapies may have a negative impact on mood, adequate attention was not paid until the withdrawal of rimonabant in 2008. In the present study the authors review full spectrum of currently available medications discussing anxiety and depression as possible adverse effects of treatment. A relatively high risk of depression should always be considered when pharmacotherapy applied, especially if current depressive episodes, positive family history, or neurotic personality traits increasing susceptibility to depressogenic effects. Prior to start of medical treatment, the potential effectiveness of the given drug should be precisely evaluated, and alternative medical and non-medical treatment options should also be carefully considered. In addition, monitoring patients during treatment for signs of depressive or anxious symptoms is necessary.

[The cognitive effects of ecstasy]. / Az ecstasy hatása a kognitív funkciókra.

The recreational drug ecstasy is widely used among dance clubbers for its acute euphoric and entactogenic effects. Ecstasy exerts its acute effects by increasing the extracellular concentration of monoamines in the brain by reversing the functions of reuptake mechanisms. These elevations in extracellular monoamine concentrations result in wake promoting effects, body hyperthermia and reductions in local cerebral blood flow. However, on the long-run, ecstasy reduces serotonin concentration and density of serotonergic markers in several brain areas. Functional deficits, like sleep disturbances, anxiogenic- and aggressive behavioral responses and mood disorders also may occur. However, one of the most prominent adverse effects is related to the cognitive functions. Following ecstasy use attenuated retro- and prospective memory and defective higher order cognitive functions can be observed, especially in heavy users. Several studies indicated the involvement of the endocannabinoid system, the sleep regulating centers and the hypothalamic-pituitary-adrenal axis based on or parallel to serotonergic damage in these processes. Recent evidence, however, also showed that changes in one of the latter systems can influence the functions of each other. In this review we summarize the related literature, and propose a complex mechanism for the long-lasting cognitive deficits following heavy ecstasy use.

Gene expression analysis indicates CB1 receptor upregulation in the hippocampus and neurotoxic effects in the frontal cortex 3 weeks after single-dose MDMA administration in Dark Agouti rats.

BACKGROUND: 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") is a widely used recreational drug known to impair cognitive functions on the long-run. Both hippocampal and frontal cortical regions have well established roles in behavior, memory formation and other cognitive tasks and damage of these regions is associated with altered behavior and cognitive functions, impairments frequently described in heavy MDMA users. The aim of this study was to examine the hippocampus, frontal cortex and dorsal raphe of Dark Agouti rats with gene expression arrays (Illumina RatRef bead arrays) looking for possible mechanisms and new candidates contributing to the effects of a single dose of MDMA (15 mg/kg) 3 weeks earlier. RESULTS: The number of differentially expressed genes in the hippocampus, frontal cortex and the dorsal raphe were 481, 155, and 15, respectively. Gene set enrichment analysis of the microarray data revealed reduced expression of 'memory' and 'cognition', 'dendrite development' and 'regulation of synaptic plasticity' gene sets in the hippocampus, parallel to the upregulation of the CB1 cannabinoid- and Epha4, Epha5, Epha6 ephrin receptors. Downregulated gene sets in the frontal cortex were related to protein synthesis, chromatin organization, transmembrane transport processes, while 'dendrite development', 'regulation of synaptic plasticity' and 'positive regulation of synapse assembly' gene sets were upregulated. Changes in the dorsal raphe region were mild and in most cases not significant. CONCLUSION: The present data raise the possibility of new synapse formation/synaptic reorganization in the frontal cortex three weeks after a single neurotoxic dose of MDMA. In contrast, a prolonged depression of new neurite formation in the hippocampus is suggested by the data, which underlines the particular vulnerability of this brain region after the drug treatment. Finally, our results also suggest the substantial contribution of CB1 receptor and endocannabinoid mediated pathways in the hippocampal impairments. Taken together the present study provides evidence for the participation of new molecular candidates in the long-term effects of MDMA.

Long-term neuronal damage and recovery after a single dose of MDMA: expression and distribution of serotonin transporter in the rat brain.

"Ecstasy", 3,4-methylenedioxymethamphetamine (MDMA), an amphetamine analogue is one of the most widely used recreational drugs. In spite of the fact that neurotoxic effects of MDMA has been found in several species from rodents to non-human primates, and results increasingly point to damage also in human MDMA users, data about the sensitivity of different brain areas and the recovery after neuronal damage are scarce. Serotonin transporter (5-HTT) mRNA in the raphe nuclei also has not been examined. Humans with genetic predisposition for the slow metabolism of MDMA, the so-called "poor metabolizers" of debrisoquin are at higher risk. Five- 9% of the Caucasian population is considered to carry this phenotype. These studies were carried out in Dark Agouti rats, a special strain that show decreased microsomal CYP2D1 isoenzyme activity, and thus may serve as a model of vulnerable human users. These works were designed to characterize MDMA-induced damage and recovery of the serotonergic system including sleep and morphological changes within 180 days. In our experiments we investigated the 5-HTT mRNA expression in the brainstem and medullary raphe nuclei, 5-HTT immunoreactive (IR) fibre densities in several brain areas, and 16 functional measures of sleep in response to a single dose of +/- MDMA (15mg\kg). Furthermore, behavioural experiments were performed 21 days after MDMA treatment. We found similar changes in 5-HTT mRNA expression in the examined raphe nuclei, namely transient increases 7 days after MDMA treatment followed by transient decreases at 21 days. Significant (20-40%), widespread reductions in 5-HTT-IR fibre density were detected in most brain areas at 7 and 21 days after MDMA administration. All cortical, but only some brainstem areas were damaged. Parallel to the neuronal damage we observed significant reductions in rapid eye movement (REM) sleep latency, increased fragmentation of sleep and increases in delta power spectra in non-REM sleep. At 180 days almost all functional changes in sleep were normalized together with 5-HTT mRNA expression in the examined raphe nuclei and the recovery of 5-HTT-IR fibre density in most brain areas. Our results also suggest that the acute MDMA administration abolished aggressive behaviour but MDMA pretreatment and the consequent depletion of serotonergic terminals did not affect aggression. Our findings concerning the changes detected in 5-HTT mRNA expression and fibre density indicate lasting impairment of the serotonergic system and suggest that a single use of MDMA may be associated with long-lasting cognitive, learning, memory and mood deficits and sleep disturbances particularly when a constellation of genetic vulnerability and certain environmental factors are present. Our data provide further evidence for the connection between altered serotonergic functions and sleep disturbance.

Acute SSRI-induced anxiogenic and brain metabolic effects are attenuated 6 months after initial MDMA-induced depletion.

To assess the functional state of the serotonergic system, the acute behavioural and brain metabolic effect of SSRI antidepressants were studied during the recovery period after MDMA-induced neuronal damage. The effects of the SSRI fluoxetine and the serotonin receptor agonist meta-chloro-phenylpiperazine (m-CPP) were investigated in the social interaction test in Dark Agouti rats, 6 months after treatment with a single dose of MDMA (15 or 30 mg kg(-1), i.p.). At earlier time points these doses of MDMA have been shown to cause 30-60% loss in axonal densities in several brain regions. Densities of the serotonergic axons were assessed using serotonin-transporter and tryptophan-hydroxylase immunohistochemistry. In a parallel group of animals, brain function was examined following an acute challenge with either fluoxetine or citalopram, using 2-deoxyglucose autoradiographic imaging. Six months after MDMA treatment the densities of serotonergic axons were decreased in only a few brain areas including hippocampus and thalamus. Basal anxiety was unaltered in MDMA-treated animals. However, the acute anxiogenic effects of fluoxetine, but not m-CPP, were attenuated in animals pretreated with MDMA. The metabolic response to both citalopram and fluoxetine was normal in most of the brain areas examined with the exception of ventromedial thalamus and hippocampal sub-fields where the response was attenuated. These data provide evidence that 6 months after MDMA-induced damage serotonergic axons show recovery in most brain areas, but serotonergic functions to challenges with SSRIs including anxiety and aggression remain altered.

MDMA treatment 6 months earlier attenuates the effects of CP-94,253, a 5-HT1B receptor agonist, on motor control but not sleep inhibition.

The possible long-term effects of the recreational drug "ecstasy" (3,4-methylenedioxymethamphetamine, MDMA) on the function of 5-hydroxytryptamine-1B (5-HT(1B)) receptor in sleep and motor control were investigated using a selective 5-HT(1B) receptor agonist, 5-propoxy-3-(1,2,3,6-tetrahydro-4-pyrinzidyl)-1H-pyrrolo([3,2-b])pyridine hydrochloride (CP-94,253; 5 mg/kg). CP-94,253 or vehicle was administered to freely moving rats pre-treated with MDMA (15 mg/kg) or vehicle 6 months earlier, and polygraphic recording for 24 h and motor activity measurements were performed. Active wake (AW), passive wake (PW), light slow wave sleep (SWS-1), deep slow wave sleep (SWS-2), paradoxical sleep (PS), and diurnal rhythm were analyzed for the whole period. In additional, the EEG power spectrum was calculated for the second hour after the acute treatment for AW, PW, SWS-1, and SWS-2. 5-HT transporter (5-HTT) immunohistochemistry was measured in brain areas related to sleep and motor control 6 months after MDMA treatment. CP-94,253 increased AW and PW, decreased SWS-2 and PS, and altered parameters of diurnal rhythm in control animals. CP-94,253 decreased the EEG power spectra at higher frequencies. The effects of CP-94,253 on AW and diurnal rhythm were reduced or eliminated in MDMA-treated animals. MDMA treatment decreased 5-HTT fibre density in posterior hypothalamus, tuberomammillary nucleus, caudate putamen and ventrolateral striatum. These data suggest that long-term changes in 5-HT(1B) receptor function occur after serotonergic damage caused by a single dose of MDMA.

Decrease in REM latency and changes in sleep quality parallel serotonergic damage and recovery after MDMA: a longitudinal study over 180 days.

The recreational drug ecstasy [3,4-methylenedioxymethamphetamine (MDMA)], has been found to selectively damage brain serotonin neurons in experimental animals, and probably in human MDMA users, but detailed morphometric analyses and parallel functional measures during damage and recovery are missing. Since there is evidence that serotonin regulates sleep, we have compared serotonergic markers parallel with detailed analysis of sleep patterns at three time-points within 180 d after a single dose of 15 mg/kg MDMA in male Dark Agouti rats. At 7 d and 21 d after MDMA treatment, significant(30-40%), widespread reductions in serotonin transporter (5-HTT) density were detected in the cerebral cortex, hippocampus, most parts of the hypothalamus, and some of the brainstem nuclei. With the exception of the hippocampus, general recovery was observed in the brain 180 d after treatment. Transient increases followed by decreases were detected in 5-HTT mRNA expression of dorsal and median raphe nuclei at 7 d and 21 d after the treatment. Significant reductions in rapid eye movement (REM) sleep latency, increases in delta power spectra in non-rapid eye movement sleep and increased fragmentation of sleep were also detected, but all these alterations disappeared by the 180th day. The present data provide evidence for long-term, albeit, except for the hippocampus, transient changes in the terminal and cellular regions of the serotonergic system after this drug. Reduced REM latency and increased sleep fragmentation are the most characteristic alterations of sleep consistently described in depression using EEG sleep polygraphy.

PACAP is transiently expressed in anterior pituitary gland of rats: in situ hybridization and cell immunoblot assay studies.

In this work the expression of PACAP (pituitary adenylate cyclase activating polypeptide) in rat anterior pituitary was demonstrated for the first time using in situ hybridization. The number of cells showing PACAP signal in intact male rats was negligible similarly to that of diestrous rats. In proestrous rats sacrificed at 10h there was a moderate increase in the expression and after a decrease at 16 h and 18 h, there was a transient peak at 20 h and then the number of labeled cells was declined again (22 h). In the cell immunoblot assay study it was observed that the number of PACAP blot forming (PACAP releasing) cells in an anterior pituitary cell culture changed according to a similar pattern as the number of PACAP expressing cells. The number of blots was also the highest when the animals were sacrificed in the evening of proestrus at 20h. The results obtained by in situ hybridization and cell immunoblot assay well correlate with each other. The above-mentioned results support our hypothesis that the enhanced expression and secretion of PACAP in the pituitary gland may be involved in ceasing the LH surge.

Chronic repeated restraint stress increases prolactin-releasing peptide/tyrosine-hydroxylase ratio with gender-related differences in the rat brain.

In this study, we investigated the effect of chronic repeated restraint (RR) on prolactin-releasing peptide (PrRP) expression. In the brainstem, where PrRP colocalize with norepinephrine in neurons of the A1 and A2 catecholaminergic cell groups, the expression of tyrosine hydroxylase (TH) has also been examined. In the brainstem, but not in the hypothalamus, the basal PrRP expression in female rats was higher than that in the males that was abolished by ovariectomy. RR evoked an elevation of PrRP expression in all areas investigated, with smaller reaction in the brainstems of females. There was no gender-related difference in the RR-evoked TH expression. Elevation of PrRP was relatively higher than elevation of TH, causing a shift in PrRP/TH ratio in the brainstem after RR. Estrogen alpha receptors were found in the PrRP neurons of the A1 and A2 cell groups, but not in the hypothalamus. Bilateral lesions of the hypothalamic paraventricular nucleus did not prevent RR-evoked changes. Elevated PrRP production parallel with increased PrRP/TH ratio in A1/A2 neurons indicate that: (i) there is a clear difference in the regulation of TH and PrRP expression after RR, and (ii) among other factors this may also contribute to the changed sensitivity of the hypothalamo-pituitary-adrenal axis during chronic stress.

Persistent cerebrovascular effects of MDMA and acute responses to the drug.

Acutely, 3,4,-methylenedioxymethamphetamine (MDMA) induces cerebrovascular dysfunction [Quate et al., (2004)Psychopharmacol., 173, 287-295]. In the longer term the same single dose results in depletion of 5-hydroxytrptamine (5-HT) nerve terminals. In this study we examined the cerebrovascular consequences of this persistent neurodegeneration, and the acute effects of subsequent MDMA exposure, upon the relationship that normally exists between local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu). Dark agouti (DA) rats were pre-treated with 15 mg/kg i.p. MDMA or saline. Three weeks later, rats from each pre-treatment group were treated with an acute dose of MDMA (15 mg/kg i.p.) or saline. Quantitative autoradiographic imaging was used to measure LCBF or LCMRglu with [(14)C]-iodoantipyrine and [(14)C]-2-deoxyglucose, respectively. Serotonergic terminal depletion was assessed using radioligand binding with [(3)H]-paroxetine and immunohistochemistry. Three weeks after MDMA pre-treatment there were significant reductions in densities of 5-HT transporter (SERT)-positive fibres (-46%) and [(3)H]-paroxetine binding (-47%). In animals pre-treated with MDMA there were widespread significant decreases in LCMRglu, but no change in LCBF indicating a persistent loss of cerebrovascular constrictor tone. In both pre-treatment groups, acute MDMA produced significant increases in LCMRglu, while LCBF was significantly decreased. In 50% of MDMA-pre-treated rats, random areas of focal hyperaemia indicated a loss of autoregulatory capacity in response to MDMA-induced hypertension. These results suggest that cerebrovascular regulatory dysfunction resulting from acute exposure to MDMA is not diminished by previous exposure, despite a significant depletion in 5-HT terminals. However, there may be a sub-population, or individual circumstances, in which this dysfunction develops into a condition that might predispose to stroke.

Partial lesion of the serotonergic system by a single dose of MDMA results in behavioural disinhibition and enhances acute MDMA-induced social behaviour on the social interaction test.

The acute effects of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) on anxiety-related behaviours were studied using indices of social interaction in Dark Agouti (DA) both drug naive rats and those pretreated with MDMA (15 mg/kg i.p.) 3 weeks earlier. The functional neuroanatomy of these MDMA effects was visualised using 2-deoxyglucose imaging of local cerebral glucose use (LCMRglu), whilst MDMA-induced serotonergic neurotoxicity was measured by radioligand binding with [3H]paroxetine. Acute MDMA alone markedly decreased most typical elements of social interaction but increased adjacent lying, a behaviour that also contains social elements. In animals pre-exposed to MDMA, decreased [3H]paroxetine binding indicated serotonergic terminal depletion, and in these animals significant increases in locomotor activity, exploratory behaviour and aggressive behaviour were found. Both behavioural effects and also the metabolic activation induced by acute MDMA were potentiated in rats previously exposed to the drug. In conclusion, a single dose of MDMA caused marked changes in social behaviour acutely that might be interpreted either as a decrease or increase in anxiety. Three weeks after MDMA a behavioural disinhibition similar to psychomotor agitation, a symptom connected to depression or mania, and a sensitization to the acute effects of MDMA are apparent in both the behavioural and brain metabolic effects of the drug.

Acute and long-term effects of a single dose of MDMA on aggression in Dark Agouti rats.

MDMA causes selective depletion of serotonergic terminals in experimental animals and the consequent decrease in synaptic 5-HT may, inter alia, increase impulsivity. To study the effects of MDMA upon brain function, the behaviour of male Dark Agouti rats exposed to MDMA (15 mg/kg i.p.), two 5-HT1B agonists (CGS-12066A and CP-94,253, both 5 mg/kg i.p.) or saline were investigated in the resident-intruder test. Studies were performed in drug-naive rats and also in rats exposed to MDMA (15 mg/kg i.p.) 21 d earlier. In parallel experiments the functional neuroanatomy of MDMA effects were assessed using 2-deoxyglucose imaging of local cerebral metabolic rate of glucose utilization (LCMRGlu) and neurotoxicity was assessed by measuring [3H]paroxetine binding. There was no significant difference in aggressive behaviour (biting, boxing, wrestling and their latencies) between drug-naive rats and rats previously exposed to MDMA 21 d earlier, despite reduced social behaviour, decreased LCMRGlu in several brain areas involved in aggression, and reductions in paroxetine binding by 30-60% in the forebrain. CGS-12066A, CP-94,253 and acute MDMA produced marked decreases in aggressive behaviours, especially in biting, boxing and kicking found in drug-naive rats. In animals previously exposed to the drug, acute anti-aggressive effects of MDMA were, in general, preserved as were MDMA-induced increases in LCMRGlu. Our studies provide evidence that in the resident-intruder test, where social isolation is a requirement, aggressive behaviour and acute anti-aggressive effects of MDMA and 5-HT1B receptor agonists remain intact 3 wk after a single dose of the drug despite significant damage to the serotonergic system.