Efectos conductuales y neuroquímicos del consumo de éxtasis y cocaína en ratones adolescentes.

La 3,4-metilendioximetanfetamina (MDMA), una sustancia popularmente conocida como éxtasis, es una droga ilícita consumida habitualmente por adolescentes y adultos jóvenes. Además, el policonsumo es una práctica habitual entre los usuarios de la MDMA, siendo la cocaína una de las drogas más frecuentemente asociadas a esta sustancia. El objetivo del presente trabajo fue evaluar los efectos a corto y largo plazo que se producen tras la administración de la MDMA (5, 10, o 20 mg/kg) sola o en combinación con cocaína (25 mg/kg) en ratones adolescentes. En el estudio sobre el efecto agudo, observamos que ambas drogas administradas individual o simultáneamente incrementan la actividad motora. La dosis alta de MDMA disminuye de los contactos sociales en la prueba de la interacción social afectando igualmente el test de retención de la evitación pasiva. Sin embargo, sólo la co-administración de MDMA en combinación con cocaína produjo un efecto ansiolítico caracterizado por un aumento del tiempo de permanencia en los brazos abiertos del laberinto elevado en cruz. Igualmente, el análisis neuroquímico reveló que los ratones que recibieron MDMA en combinación con cocaína mostraron un incremento en el turnover de DA en el estriado, pero una disminución del de serotonina en la corteza. Los estudios de los efectos a largo plazo, realizados tres semanas después de haber finalizado un tratamiento con MDMA sola o en combinación con cocaína (2 administraciones por día durante 3 días consecutivos), mostraron que los ratones expuestos a la MDMA, sola o más cocaína, incrementaron el tiempo dedicado a las conductas sociales, aunque los que también habían recibido cocaína presentaban además conductas de amenaza. Observamos un efecto neurotóxico en los ratones tratados únicamente con 20 mg/kg de MDMA que mostraron un decremento de la concentración de DA en el estriado, no observándose este deterioro en los tratados además con cocaína. Por otra parte, mediante el condicionamiento de la preferencia de lugar (CPL) confirmamos que la MDMA posee efectos reforzantes y que esta sustancia es capaz de reinstaurar la preferencia de lugar una vez que esta se ha extinguido. La expresión y la reinstauración del CPL inducido por la MDMA dependen de la pauta de condicionamiento que condiciona los efectos neurotóxicos producidos por esta droga. Para finalizar, el tratamiento con MDMA sola o en combinación con cocaína durante la adolescencia favorece los efectos reforzantes de la MDMA durante el periodo adulto. Además, la exposición previa a la cocaína aumenta el tiempo necesario para extinguir la preferencia de lugar inducida por la MDMA.3,4-methylene-dioxy-methamphetamine (MDMA), commonly known as ecstasy, is an illicit recreational drug consumed by teenagers and young adults. The poly-drug pattern is the most common among those observed in MDMA users, with cocaine being a frequently associated drug. The aim of the present study was to evaluate the short- and long-term effects of exposure to MDMA (5, 10, or 20 mg/kg), alone or plus cocaine (25 mg/kg), on adolescent mice. In the acute phase, both drugs produced hyperactivity whether administered alone or concurrently. The highest MDMA dose decreased social contacts and affected the passive avoidance task. However, an anxiolytic effect, studied by means of the elevated plus maze and expressed as an increase in the time spent on the open arms, was observed only in animals treated with both cocaine and MDMA. Neurochemical analyses revealed an increase in striatal DA turnover and a decrease in serotonin cortical turnover in mice treated with MDMA plus cocaine. The studies conducted to establish long-term effects, which were performed 3 weeks after a 3-day treatment of two daily injections of MDMA alone or plus cocaine (6 administrations) during the adolescent period, showed that mice treated with MDMA alone and plus cocaine spent more time engaged in social contact, although those also treated with cocaine exhibited threat behaviors. Furthermore, we observed a neurotoxic effect in mice exposed to 20 mg/kg of MDMA, evident in a decrease in DA levels in the striatum, but this effect was not detected in mice additionally treated with cocaine. On the other hand, using the conditioned place preference (CPP), we have confirmed the rewarding effects of MDMA. In addition, we also show that MDMA can produce reinstatement of place preference after the extinction of this response. The expression and reinstatement of MDMA-induced CPP depend on the conditioning protocol, which conditions the neurotoxic effects produced by this drug. Finally, exposure during adolescence to MDMA alone or plus cocaine facilitates the rewarding effects of MDMA in adulthood. Moreover, previous experience of cocaine increases the time required to extinguish the MDMA-induced CPP

Effect of the CB1 cannabinoid agonist WIN 55212-2 on the acquisition and reinstatement of MDMA-induced conditioned place preference in mice

<p>Abstract</p> <p>Background</p> <p>Numerous reports indicate that MDMA users consume other psychoactive drugs, among which cannabis is one of the most common. The aim of the present study was to evaluate, using the conditioned place preference, the effect of the cannabinoid agonist WIN 55,212-2 on the rewarding effects of MDMA in mice.</p> <p>Methods</p> <p>In the first experiment adolescent mice were initially conditioned with 1.25, 2.5 or 5 mg/kg of MDMA or 0.1 or 0.5 mg/kg of WIN and subsequently with both drugs. Reinstatement of the extinguished preference by priming doses was performed in the groups that showed CPP. In the second experiment, animals were conditioned with 2.5 or 5 mg/kg of MDMA and, after extinction, reinstatement of the preference was induced by 0.5 or 0.1 mg/kg of WIN.</p> <p>Results</p> <p>A low dose of WIN 55212-2 (0.1 mg/kg) increased the rewarding effects of low doses of MDMA (1.25 mg/kg), although a decrease in the preference induced by MDMA (5 and 2.5 mg/kg) was observed when the dose of WIN 55212-2 was raised (0.5 mg/kg). The CB1 antagonist SR 141716 also increased the rewarding effects of the lowest MDMA dose and did not block the effects of WIN. Animals treated with the highest WIN dose plus a non-neurotoxic dose of MDMA exhibited decreases of striatal DA and serotonin in the cortex. On the other hand, WIN 55212-2-induced CPP was reinstated by priming injections of MDMA, although WIN did not reinstate the MDMA-induced CPP.</p> <p>Conclusions</p> <p>These results confirm that the cannabinoid system plays a role in the rewarding effects of MDMA and highlights the risks that sporadic drug use can pose in terms of relapse to dependence. Finally, the potential neuroprotective action of cannabinoids is not supported by our data; on the contrary, they are evidence of the potential neurotoxic effect of said drugs when administered with MDMA.</p

A Methanol Extract of Brugmansia arborea Affects the Reinforcing and Motor Effects of Morphine and Cocaine in Mice

Previous reports have shown that several of the effects of morphine, including the development of tolerance and physical withdrawal symptoms, are reduced by extracts of Brugmansia arborea (L.) Lagerheim (Solanaceae) (B. arborea). In the present study we evaluate the action of the methanol extract of B. arborea (7.5–60 mg/kg) on the motor and reinforcing effects of morphine (20 and 40 mg/kg) and cocaine (25 mg/kg) using the conditioned place preference (CPP) procedure. At the doses employed, B. arborea did not affect motor activity or induce any effect on CPP. The extract partially counteracted morphine-induced motor activity and completely blocked the CPP induced by 20 mg/kg morphine. On the other hand, B. arborea blocked cocaine-induced hyperactivity but did not block cocaine-induced CPP. Reinstatement of extinguished preference with a priming dose of morphine or cocaine was also inhibited by B. arborea. The complex mechanism of action of B. arborea, which affects the dopaminergic and the cholinergic systems, seems to provide a neurobiological substrate for the effects observed. Considered as a whole, these results point to B. arborea as a useful tool for the treatment of morphine or cocaine abuse

Role of the dopaminergic system in the acquisition, expression and reinstatement of MDMA-induced conditioned place preference in adolescent mice.

BACKGROUND: The rewarding effects of 3,4-methylenedioxy-metamphetamine (MDMA) have been demonstrated in conditioned place preference (CPP) procedures, but the involvement of the dopaminergic system in MDMA-induced CPP and reinstatement is poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: In this study, the effects of the DA D1 antagonist SCH 23390 (0.125 and 0.250 mg/kg), the DA D2 antagonist Haloperidol (0.1 and 0.2 mg/kg), the D2 antagonist Raclopride (0.3 and 0.6 mg/kg) and the dopamine release inhibitor CGS 10746B (3 and 10 mg/kg) on the acquisition, expression and reinstatement of a CPP induced by 10 mg/kg of MDMA were evaluated in adolescent mice. As expected, MDMA significantly increased the time spent in the drug-paired compartment during the post-conditioning (Post-C) test, and a priming dose of 5 mg/kg reinstated the extinguished preference. The higher doses of Haloperidol, Raclopride and CGS 10746B and both doses of SCH 23390 blocked acquisition of the MDMA-induced CPP. However, only Haloperidol blocked expression of the CPP. Reinstatement of the extinguished preference was not affected by any of the drugs studied. Analysis of brain monoamines revealed that the blockade of CPP acquisition was accompanied by an increase in DA concentration in the striatum, with a concomitant decrease in DOPAC and HVA levels. Administration of haloperidol during the Post-C test produced increases in striatal serotonin, DOPAC and HVA concentrations. In mice treated with the higher doses of haloperidol and CGS an increase in SERT concentration in the striatum was detected during acquisition of the CPP, but no changes in DAT were observed. CONCLUSIONS/SIGNIFICANCE: These results demonstrate that, in adolescent mice, the dopaminergic system is involved in the acquisition and expression of MDMA-induced CPP, but not in its reinstatement

The novelty-seeking phenotype modulates the long-lasting effects of intermittent ethanol administration during adolescence.

The aim of the present study was to investigate if a novelty-seeking phenotype mediates the long-lasting consequences of intermittent EtOH intoxication during adolescence. The hole board test was employed to classify adolescent mice as High- or Low-Novelty Seekers. Subsequently, animals were administered ethanol (1.25 or 2.5 g/kg) on two consecutive days at 48-h intervals over a 14-day period. Anxiety levels--measured using the elevated plus maze- spontaneous motor activity and social interaction test were studied 3 weeks later. A different set of mice underwent the same procedure, but received only the 2.5 g/kg dose of ethanol. Three weeks later, in order to induce CPP, the same animals were administered 1 or 6 mg/kg of cocaine or 1 or 2.5 mg/kg MDMA. The results revealed a decrease in aggressive behaviors and an anxiolytic profile in HNS mice and longer latency to explore the novel object by LNS mice. Ethanol exposure enhanced the reinforcing effects of cocaine and MDMA in both groups when CPP was induced with a sub-threshold dose of the drugs. The extinguished cocaine-induced CPP (1 and 6 mg/kg) was reinstated after a priming dose in HNS animals only. Our results confirm that intermittent EtOH administration during adolescence induces long-lasting effects that are manifested in adult life, and that there is an association between these effects and the novelty-seeking phenotype

CB1 cannabinoid receptor-mediated aggressive behavior

This study examined the role of cannabinoid CB1 receptors (CB1r) in aggressive behavior. Social encounters took place in grouped and isolated mice lacking CB1r (CB1KO) and in wild-type (WT) littermates. Cognitive impulsivity was evaluated in the delayed reinforcement task (DRT). Gene expression analyses of monoaminooxidase-A (MAO-A), catechol-o-methyl-transferase (COMT), 5-hydroxytriptamine transporter (5-HTT) and 5-HT1B serotonergic receptor (5HT1Br) in the median and dorsal raphe nuclei (MnR and DR, respectively) and in the amygdala (AMY) were performed by real time-PCR. Double immunohistochemistry studies evaluated COMT and CB1r co-localization in the raphe nuclei and in the cortical (ACo), basomedian (BMA) and basolateral (BLA) amygdaloid nuclei. The behavioral effects of the CB1r agonist ACEA (1 and 2 mg/kg) on aggression were also evaluated in isolated OF1 mice. CB1KO mice housed in groups showed higher levels of offensive aggression. Isolation increased aggressive behavior only in WT. In grouped CB1KO mice COMT gene expression was significantly higher in the MnR and DR, while MAO-A gene expression was lower in the MnR. Gene expression of 5HT1Br, COMT and MAO-A was higher in the amygdala of CB1KO mice. CB1r double-immunohistochemistry revealed cytoplasmic-labeled COMT-ir cells in the raphe nuclei and in the ACo, BMA and BLA. CB1r immunolabeling was observed only in ACo, BMA and BLA, where it was localized in axons and buttons. The density of labeled processes increased in BLA. Acute administration of the CB1 agonist ACEA (2 mg/kg) significantly decreased the aggression levels of OF1 mice. These results suggest that CB1r plays an important role in social interaction and aggressive behavior.This work was supported by the following research grants: Ministerio de Ciencia e Innovación, (SAF2011-23420 to Jorge Manzanares and SAF2009-10689 to Pere Berbel); Ministerio de Economía y Competitividad, Dirección General de Investigación (PSI2011-24762) to Jose Miñarro; Generalidad Valenciana, Consejería de Educación (PROMETEO/2009/072) to Jose Miñarro; and Instituto de Salud ‘Carlos III’ (FIS), Redes Telemáticas de Investigación Cooperativa en Salud (RETICS), Red de Trastornos Adictivos (RTA), fondos FEDER (RD06/0001/1004, RD12/0028/0019 to Jorge Manzanares; and RD06/001/0016, RD12/0028/005 to Jose Miñarro).Peer reviewe

Effects of DA antagonists on the reinstatement of MDMA-induced CPP.

<p>(3a for the DA release inhibitor CGS 10746B; 3b for the D2 DA antagonist Haloperidol; 3c for the D2 Da antagonist Raclopride; and 3d for the D1 DA antagonist SCH 23390). The bars represent the time in seconds spent in the drug-paired compartment before conditioning sessions during the pre-conditioning test (white bars), the post-conditioning test (black bars), the extinction test (light gray) and the reinstatement test (dark gray). *** p>0.001; * p<0.05; significant difference in the time spent in the drug-paired compartment in pre-conditioning vs post-conditioning tests.</p

Concentration of brain monoamines (expression of the CPP).

<p>Mice were treated on the test day of the CPP with saline (Sal), MDMA 10 mg/kg + saline (M10), MDMA 10 mg/kg + Haloperidol 0.1 mg/kg (M10+HAL 0.1 Acq), and MDMA 10 mg/kg + Haloperidol 0.2 mg/kg (M10+HAL 0.2 Acq). Data are presented as means with ±S.E.M. Differences with respect to the saline group.</p>*<p>p<0.01,</p>**<p>p<0.001.</p