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.

Astrocyte-neuron interaction in the substantia gelatinosa of the spinal cord dorsal horn via P2X7 receptor-mediated release of glutamate and reactive oxygen species.

The substantia gelatinosa (SG) of the spinal cord processes incoming painful information to ascending projection neurons. Whole-cell patch clamp recordings from SG spinal cord slices documented that in a low Ca(2+) /no Mg(2+) (low X(2+) ) external medium adenosine triphosphate (ATP)/dibenzoyl-ATP, Bz-ATP) caused inward current responses, much larger in amplitude than those recorded in a normal X(2+) -containing bath medium. The effect of Bz-ATP was antagonized by the selective P2X7 receptor antagonist A-438079. Neuronal, but not astrocytic Bz-ATP currents were strongly inhibited by a combination of the ionotropic glutamate receptor antagonists AP-5 and CNQX. In fact, all neurons and some astrocytes responded to NMDA, AMPA, and muscimol with inward current, demonstrating the presence of the respective receptors. The reactive oxygen species H2 O2 potentiated the effect of Bz-ATP at neurons but not at astrocytes. Hippocampal CA1 neurons exhibited a behavior similar to, but not identical with SG neurons. Although a combination of AP-5 and CNQX almost abolished the effect of Bz-ATP, H2 O2 was inactive. A Bz-ATP-dependent and A-438079-antagonizable reactive oxygen species production in SG slices was proven by a microelectrode biosensor. Immunohistochemical investigations showed the colocalization of P2X7-immunoreactivity with microglial (Iba1), but not astrocytic (GFAP, S100ß) or neuronal (MAP2) markers in the SG. It is concluded that SG astrocytes possess P2X7 receptors; their activation leads to the release of glutamate, which via NMDA- and AMPA receptor stimulation induces cationic current in the neighboring neurons. P2X7 receptors have a very low density under resting conditions but become functionally upregulated under pathological conditions.

Central P2Y12 receptor blockade alleviates inflammatory and neuropathic pain and cytokine production in rodents.

In this study the role of P2Y12 receptors (P2Y12R) was explored in rodent models of inflammatory and neuropathic pain and in acute thermal nociception. In correlation with their activity to block the recombinant human P2Y12R, the majority of P2Y12R antagonists alleviated mechanical hyperalgesia dose-dependently, following intraplantar CFA injection, and after partial ligation of the sciatic nerve in rats. They also caused an increase in thermal nociceptive threshold in the hot plate test. Among the six P2Y12R antagonists evaluated in the pain studies, the selective P2Y12 receptor antagonist PSB-0739 was most potent upon intrathecal application. P2Y12R mRNA and IL-1ß protein were time-dependently overexpressed in the rat hind paw and lumbar spinal cord following intraplantar CFA injection. This was accompanied by the upregulation of TNF-α, IL-6 and IL-10 in the hind paw. PSB-0739 (0.3mg/kg i.t.) attenuated CFA-induced expression of cytokines in the hind paw and of IL-1ß in the spinal cord. Subdiaphragmatic vagotomy and the α7 nicotinic acetylcholine receptor antagonist MLA occluded the effect of PSB-0739 (i.t.) on pain behavior and peripheral cytokine induction. Denervation of sympathetic nerves by 6-OHDA pretreatment did not affect the action of PSB-0739. PSB-0739, in an analgesic dose, did not influence motor coordination and platelet aggregation. Genetic deletion of the P2Y12R in mice reproduced the effect of P2Y12R antagonists on mechanical hyperalgesia in inflammatory and neuropathic pain models, on acute thermal nociception and on the induction of spinal IL-1ß. Here we report the robust involvement of the P2Y12R in inflammatory pain. The anti-hyperalgesic effect of P2Y12R antagonism could be mediated by the inhibition of both central and peripheral cytokine production and involves α7-receptor mediated efferent pathways.

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.

The absence of P2X7 receptors (P2rx7) on non-haematopoietic cells leads to selective alteration in mood-related behaviour with dysregulated gene expression and stress reactivity in mice.

The purpose of this study was to explore how genetic deletion and pharmacological antagonism of the P2X7 receptor (P2rx7) alter mood-related behaviour, gene expression and stress reactivity in the brain. The forced swim test (FST), tail suspension test (TST) and amphetamine-induced hyperlocomotion (AH) tests were used in wild-type (P2rx7(+/+)) and P2rx7-deficient (P2rx7(-/-)) mice. Biogenic amine levels were analysed in the amygdala and striatum, adrenocorticotropic hormone (ACTH) and corticosterone levels were measured in the plasma and pituitary after restraint stress. Chimeric mice were generated by bone marrow transplantation. A whole genome microarray analysis with real-time polymerase chain reaction validation was performed on the amygdala. In the absence of P2rx7s decreased behavioural despair in the FST, reduced immobility in the TST and attenuated amphetamine-induced hyperactivity were detected. Basal norepinephrine levels were elevated in the amygdala, whereas stress-induced ACTH and corticosterone responses were alleviated in P2rx7(-/-) mice. Sub-acute treatment with the selective P2rx7 antagonist, Brilliant Blue G, reproduced the effect of genetic deletion in the TST and AH test in P2rx7(+/+) but not P2rx7(-/-) mice. No change in behavioural phenotype was observed in chimeras lacking the P2rx7 in their haematopoietic compartment. Whole genome microarray analysis indicated a widespread up- and down-regulation of genes crucial for synaptic function and neuroplasticity by genetic deletion. Here, we present evidence that the absence of P2rx7s on non-haematopoietic cells leads to a mood-stabilizing phenotype in several behavioural models and suggest a therapeutic potential of P2rx7 antagonists for the treatment of mood disorders.

The role of purinergic signaling in depressive disorders.

The purinergic signaling system consists of transporters, enzymes and receptors responsible for the synthesis, release, action and extracellular inactivation of adenosine 5'-triphosphate (ATP) and its extracellular breakdown product adenosine. The actions of ATP are mediated ionotropic P2X and metabotropic P2Y receptor subfamilies, whilst the actions of adenosine are mediated by P1 adenosine receptors. Purinergic signaling pathways are widely expressed in the central nervous system (CNS) and participate in its normal and pathological functions. Among P2X receptors, the P2X7 receptor (P2rx7) has received considerable interest in both basic and clinical neuropsychiatric research because of its profound effects in animal CNS pathology and its potential involvement as a susceptibility gene in mood disorders. Although genetic findings were not always consistently replicated, several studies demonstrated that single nucleotide polymorphisms (SNPs) in the human P2X7 gene (P2RX7) show significant association with major depressive disorder and bipolar disorder. Animal studies revealed that the genetic knock-down or pharmacological antagonism leads to reduced depressive-like behavior, attenuated response in mania-model and alterations in stress reactivity. A potential mechanism of P2rx7 activation on mood related behavior is increased glutamate release, activation of extrasynaptic NMDA receptors and subsequent enduring changes in neuroplasticity. In addition, dysregulation of monoaminergic transmission and HPA axis reactivity could also contribute to the observed changes in behavior. Besides P2rx7, the inhibition of adenosine A1 and A2A receptors also mediate antidepressant-like effects in animal experiments. In conclusion, despite contradictions between existing data, these findings point to the therapeutic potential of the purinergic signaling system in mood disorders.

Damage of serotonergic axons and immunolocalization of Hsp27, Hsp72, and Hsp90 molecular chaperones after a single dose of MDMA administration in Dark Agouti rat: temporal, spatial, and cellular patterns.

3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") causes long-term disturbance of the serotonergic system. We examined the temporal, spatial, and cellular distribution of three molecular chaperones, Hsp27, Hsp72, and Hsp90, 3 and 7 days after treatment with 7.5, 15, and 30 mg/kg single intraperitoneal (i.p.) doses of MDMA in Dark Agouti rat brains. Furthermore, we compared the immunostaining patterns of molecular chaperones with serotonergic axonal-vulnerability evaluated by tryptophan-hydroxylase (TryOH) immunoreactivity and with astroglial-activation detected by GFAP-immunostaining. There was a marked reduction in TryOH-immunoreactive axon density after MDMA treatment in all examined areas at both time points. Three days after treatment, a significant dose-dependent increase in Hsp27-immunoreactive protoplasmic astrocytes was found in the cingulate, frontal, occipital, and pyriform cortex, and in the hippocampus CA1. However, there was no increase in astroglial Hsp27-immunoreactivity in the caudate putamen, lateral septal nucleus, or anterior hypothalamus. A significant increase in the GFAP immunostaining density of protoplasmic astrocytes was found only in the hippocampus CA1. In addition, numerous strong Hsp72-immunopositive neurons were found in some brain areas only 3 days after treatment with 30 mg/kg MDMA. Increased Hsp27-immunoreactivity exclusively in the examined cortical areas reveals that Hsp27 is a sensitive marker of astroglial response to the effects of MDMA in these regions of Dark Agouti rat brain and suggests differential responses in astroglial Hsp27-expression between distinct brain areas. The co-occurrence of Hsp27 and GFAP response exclusively in the hippocampus CA1 may suggest the particular vulnerability of this region. The presence of strong Hsp72-immunopositive neurons in certain brain areas may reflect additional effects of MDMA on nonserotonergic neurons.

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.

Effect of two noncompetitive AMPA receptor antagonists GYKI 52466 and GYKI 53405 on vigilance, behavior and spike-wave discharges in a genetic rat model of absence epilepsy.

The present study was conducted to investigate the effects of two noncompetitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists, GYKI 52466 and GYKI 53405 (the racemate of talampanel) on the generation of spike-wave discharges (SWD) parallel with the vigilance and behavioral changes in the genetic absence epilepsy model of WAG/Rij rats. Intraperitoneal (i.p.) administration of GYKI 52466 (1-[4-aminophenyl]-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine; 3, 10 and 30 mg/kg, i.p.), the prototypic compound of the 2,3-benzodiazepine family, caused a fast dose-dependent increase in the number and cumulative duration of SWD. These changes were accompanied by dose-dependent increase in duration of light slow wave sleep (SWS1) and passive awake, vigilance states associated with the presence of SWD. In addition a short, transient behavioral activation occurred that was followed by strong ataxia and immobility, decrease of active wakefulness and increase in deep slow wave sleep. GYKI 53405 (7-acetyl-5-(4-aminophenyl)-8-methyl-8,9-dihydro-7H-1,3-dioxolo[4,5-b][2,3]benzodiazepine, the racemate of talampanel, 16 mg/kg, i.p.) failed to affect any measure of SWD and vigilance. When used as a pretreatment, GYKI 52466 (10 mg/kg) slightly attenuated SWD-promoting effects of the 5-HT1A receptor agonist 8-OH-DPAT, it decreased cumulative duration and average time of paroxysms. In conclusion, AMPA receptors play moderate role in regulation of epileptic activity, and some of these effects are connected to their effects on vigilance in this model.

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.

The role of glutamate release mediated by extrasynaptic P2X7 receptors in animal models of neuropathic pain.

Purinergic signaling represents a major non-synaptic signaling mechanism in the normal and pathological nervous system. The expression of the purinergic ligand gated ion channel P2X7 receptor (P2rx7) has been described on nerve terminals as well as in non-neuronal cells, such as astrocytes and microglia. The activation of P2rx7s results in Ca(2+) influx and increased transmitter release in the brain. P2rx7s previously suggested having a pivotal role in different pain modalities, including neuropathic pain. Here we investigated whether the activation of P2rx7 leads to increased glutamate release from the spinal cord in an experimental model of neuropathic pain (partial nerve ligation of the sciatic nerve, PNL). One week after surgery, we studied the effects of PNL on tactile allodynia using aesthesiometry, in parallel with the in vitro release of [(3)H]glutamate from lumbar spinal cord slices. The observed allodynia in wild-type (P2rx7+/+) mice one week after PNL surgery was lower that was observed in P2rx7 deficient (P2rx7-/-) animals. Perfusion of spinal cord slices with ATP (10mM) elicited [(3)H]glutamate release in both sham operated and neuropathic P2rx7+/+ animals. The ATP-induced [(3)H]glutamate release was absent in P2rx7-/- mice. Electrically evoked release of [(3)H]glutamate from spinal cord slices was not significantly altered in PNL animals and in P2rx7-/- mice. The results suggest that activation of P2rx7 by ATP releases glutamate in the spinal cord, which might contribute to mechanical allodynia following PNL. On the other hand, this release does not contribute to glutamate efflux evoked by conventional neuronal activity, which is consistent with the idea that P2X7 receptors are either extrasynaptic or expressed on non-neuronal cells. This article is part of a Special Issue entitled 'Extrasynaptic ionotropic receptors'.

The inhibitory action of exo- and endocannabinoids on [³H]GABA release are mediated by both CB1and CB2receptors in the mouse hippocampus.

Exogenous and endogenous cannabinoids play an important role in modulating the release of neurotransmitters in hippocampal excitatory and inhibitory networks, thus having profound effect on higher cognitive and emotional functions such as learning and memory. In this study we have studied the effect of cannabinoid agonists on the potassium depolarization-evoked [(3)H]GABA release from hippocampal synaptosomes in the wild-type (WT) and cannabinoid 1 receptor (CB(1)R)-null mutant mice. All tested cannabinoid agonists (WIN55,212-2, CP55,940, HU-210, 2-arachidonoyl-glycerol, 2-AG; delta-9-tetra-hydrocannabinol, THC) inhibited [(3)H]GABA release in WT mice with the following rank order of agonist potency: HU-210>CP55,490>WIN55,212-2>>2-AG>THC. By contrast, 2-AG and THC displayed the greatest efficacy eliciting almost complete inhibition of evoked [(3)H]GABA efflux, whereas the maximal inhibition obtained by HU-210, CP55,490, and WIN55,212-2 were less, eliciting not more than 40% inhibition. The inhibitory effect of WIN55,212-2, THC and 2-AG on evoked [(3)H]GABA efflux was antagonized by the CB(1) receptor inverse agonist AM251 (0.5 µM) in the WT mice. In the CB(1)R knockout mice the inhibitory effects of all three agonists were attenuated. In these mice, AM251 did not antagonize, but further reduced the [(3)H]GABA release in the presence of the synthetic agonist WIN55,212-2. By contrast, the concentration-dependent inhibitory effects of THC and 2-AG were partially antagonized by AM251 in the absence of CB(1) receptors. Finally, the inhibition of evoked [(3)H]GABA efflux by THC and 2-AG was also partially attenuated by AM630 (1 µM), the CB(2) receptor-selective antagonist, both in WT and CB(1) knockout mice. Our data prove the involvement of CB(1) receptors in the effect of exo- and endocannabinoids on GABA efflux from hippocampal nerve terminals. In addition, in the effect of the exocannabinoid THC and the endocannabinoid 2-AG, non-CB(1), probably CB(2)-like receptors are also involved.

Recovery and aging of serotonergic fibers after single and intermittent MDMA treatment in Dark Agouti rat.

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is a popular party drug known to cause selective serotonergic damage. Here we examined the long-term recovery and aging of serotonergic fibers and levels of brain-derived neurotrophic factor (BDNF) after intermittent MDMA administration (15 mg kg(-1) i.p. every 7th day for 4 weeks, MDMA ×4) and a single-dose treatment (15 mg kg(-1) i.p., MDMA ×1) in adolescent/young adult male Dark Agouti rats. After MDMA treatment, tryptophan hydroxylase-immunoreactive fiber density decreased and then recovered in all brain regions. Recovery was more pronounced in the MDMA ×4 group compared with the MDMA ×1 group, but similar long-term BDNF responses were found after both treatments. Twenty-two months after treatment, there were fewer clusters of aberrant serotonergic fibers in the parietal cortex in the MDMA ×4 group compared with the MDMA ×1 group. There was no difference in the density of microglial cells or astrocytes in treated groups versus the control 22 months after the treatments. These results indicate that recovery of serotonergic fibers is faster after intermittent MDMA treatment than after single-dose administration, and differences in BDNF levels per se are unlikely to account for this difference. Moreover, it seems that intermittent MDMA treatment attenuates the morphological signs of aging in serotonergic fibers. In addition, neither intermittent nor single-dose MDMA exposition of young animals induces accelerated aging processes or neurodegeneration in senescence, as indicated by the unaltered densities of microglial cells and astrocytes in the treated groups compared with the control.

Low ambient temperature reveals distinct mechanisms for MDMA-induced serotonergic toxicity and astroglial Hsp27 heat shock response in rat brain.

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is a widely used recreational drug known to cause selective long-term serotonergic damage. In our recent paper we described region-specific, dose-dependent increase in the protein expression of astroglial Hsp27 and neuronal Hsp72 molecular chaperones after MDMA administration of rats. Here, we examined the possible interaction of elevated Hsp27 protein level to hyperthermic responses after MDMA administration and its separation from drug-induced serotonergic neurotoxicity. For this, 7-8 week old male Dark Agouti rats were treated with 15 mg/kg i.p. MDMA. Treatment at an ambient temperature of 22 ± 1°C caused a significant elevation of the rectal temperature, an increase of Hsp27 immunoreactive protoplasmic astrocytes in the hippocampus, the parietal and cingulate cortices, and a significant decrease in the density of tryptophan hydroxylase immunoreactive fibers in the same brain regions, 8h as well as 24h after drug administrations. In addition, serotonergic axons exhibited numerous swollen varicosities and fragmented morphology. MDMA treatment at low ambient temperature (10 ± 2°C) almost completely abolished the elevation of body temperature and the increased astroglial Hsp27 expression but failed to alter - or just slightly attenuated - the depletion in the density of tryptophan hydroxylase immunoreactive fibers. These results suggest that the increased astroglial Hsp27 protein expression is rather related to the hyperthermic response after the drug administration and it could be separated from the serotonergic neurotoxicity caused by MDMA. In addition, the induction of Hsp27 per se is uneffective to protect serotonergic fibers after MDMA administration. Our results also suggest that Tph immunohistochemistry is an early and sensitive method to demonstrate MDMA-caused vulnerability.

Ultrastructural characterization of tryptophan hydroxylase 2-specific cortical serotonergic fibers and dorsal raphe neuronal cell bodies after MDMA treatment in rat.

RATIONALE: 3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a widely used recreational drug known to cause selective long-term serotonergic damage. OBJECTIVES: The aim of this study was to characterize the ultrastructure of serotonergic pericarya and proximal neurites in the dorsal raphe nucleus as well as the ultrastructure of serotonergic axons in the frontal cortex of adolescent Dark Agouti rats 3 days after treatment with 15 mg/kg i.p. MDMA. METHODS: Light microscopic immunohistochemistry and pre-embedding immunoelectron microscopy with a novel tryptophan hydroxylase-2 (Tph2) specific antibody, as a marker of serotonergic structures. RESULTS: Light microscopic analysis showed reduced serotonergic axon density and aberrant swollen varicosities in the frontal cortex of MDMA-treated animals. According to the electron microscopic analysis, Tph2 exhibited diffuse cytoplasmic immunolocalization in dorsal raphe neuronal cell bodies. The ultrastructural-morphometric analysis of these cell bodies did not indicate pathological changes or significant alteration in the cross-sectional areal density of any examined organelles. Proximal serotonergic neurites in the dorsal raphe exhibited no ultrastructural alteration. However, in the frontal cortex among intact fibers, numerous serotonergic axons with destructed microtubules were found. Most of their mitochondria were intact, albeit some injured axons also contained degenerating mitochondria; moreover, a few of them comprised confluent membrane whorls only. CONCLUSIONS: Our treatment protocol does not lead to ultrastructural alteration in the serotonergic dorsal raphe cell bodies and in their proximal neurites but causes impairment in cortical serotonergic axons. In these, the main ultrastructural alteration is the destruction of microtubules although a smaller portion of these axons probably undergo an irreversible damage.

Elevated BDNF protein level in cortex but not in hippocampus of MDMA-treated Dark Agouti rats: a potential link to the long-term recovery of serotonergic axons.

3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a widely used recreational drug known to cause selective long-term serotonergic damage. In this study, we examined the pattern of BDNF protein expression 1 day, 3, 8, 12 and 24 weeks after a single 15mg/kg i.p. dose of MDMA to adolescent Dark Agouti rats. In parallel, we measured either tryptophan-hydroxylase immunoreactive (TpH IR) axon density, or [(3)H]-paroxetine-binding in parietal cortex and hippocampus, two brain areas known to have different recovery capacity after MDMA, to test whether BDNF-levels were associated with the long-term recovery of serotonergic fibers after a neurotoxic dose of MDMA. Both TpH IR axon density and [(3)H]-paroxetine-binding were significantly decreased 3 weeks after the treatment in both brain areas but while normalization in both parameters was found in parietal cortex 24 weeks after treatment, significant decreases remained evident in the hippocampus. In the parietal cortex, a significant reduction in BDNF protein levels was found in the acute phase after treatment (1 day), which was followed by a robust increase 8 weeks later and a return to control levels by 12 weeks. In contrast, no significant alteration of BDNF protein level was found in the hippocampus at any time points. This absence of any significant increase in BDNF protein levels in the hippocampus, and the persistence in this region of decreases in TpH IR axon density and [(3)H]-paroxetine-binding, raises the possibility that BDNF has an important role in the long-term recovery of serotonergic axons after MDMA treatment.

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.

Neurochemical evidence that stimulation of CB1 cannabinoid receptors on GABAergic nerve terminals activates the dopaminergic reward system by increasing dopamine release in the rat nucleus accumbens.

We examined the effect of cannabinoid receptor activation on basal and electrical field simulation-evoked (25 V, 2 Hz, 240 shocks) [(3)H]dopamine efflux in the isolated rat nucleus accumbens in a preparation, in which any effect on the dendrites or somata of ventral tegmental projection neurons was excluded. The cannabinoid agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN55,212-2, 100 nM) significantly enhanced stimulation-evoked [(3)H]dopamine release in the presence of the selective dopamine transporter inhibitor 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine dihydrochloride (GBR12909, 100 nM). GBR12909 (100 nM-1 microM), when added alone, increased the evoked [(3)H]dopamine efflux in a concentration-dependent manner. The stimulatory effect of WIN55,212-2 on the evoked tritium efflux was inhibited by the selective CB1 cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251, 100 nM) and by the GABA(A) receptor antagonist bicuculline (10 microM). Repeated application of N-methyl-d aspartate (1 mM) under Mg(2+)-free conditions, which directly acts on dopaminergic terminals, reversibly increased the tritium efflux, but WIN55,212-2 did not affect N-methyl-d aspartate-evoked [(3)H]dopamine efflux, indicating that WIN55,212-2 has no direct action on dopaminergic nerve terminals. AM251 (100 nM) alone also did not have an effect on electrical stimulation-evoked [(3)H]dopamine efflux. Likewise, the selective CB2 receptor antagonist 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone (AM630, 0.3 microM) and the anandamide transport inhibitor (5Z,8Z,11Z,14Z)-N-(4-hydroxy-2-methylphenyl)-5,8,11,14-eicosatetraenamide (VDM11, 10 microM) had no significant effect on electrically evoked [(3)H]dopamine release. This is the first neurochemical evidence that the activation of CB1 cannabinoid receptors leads to the augmentation of [(3)H]dopamine efflux via a local GABA(A) receptor-mediated disinhibitory mechanism in the rat nucleus accumbens.

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.