RESUMEN
Defective brain extracellular matrix (ECM) is a factor of vulnerability in various psychiatric diseases such as schizophrenia, depression and autism. The glycoprotein reelin is an essential building block of the brain ECM that modulates neuronal development and participates to the functions of adult central synapses. The reelin gene (RELN) is a strong candidate in psychiatric diseases of early onset, but its synaptic and behavioral functions in juvenile brain circuits remain unresolved. Here, we found that in juvenile reelin-haploinsufficient heterozygous reeler mice (HRM), abnormal fear memory erasure is concomitant to reduced dendritic spine density and anomalous long-term potentiation in the prefrontal cortex. In juvenile HRM, a single in vivo injection with ketamine or Ro25-6981 to inhibit GluN2B-N-methyl-D-aspartate receptors (NMDARs) restored normal spine density, synaptic plasticity and converted fear memory to an erasure-resilient state typical of adult rodents. The functional and behavioral rescue by ketamine was prevented by rapamycin, an inhibitor of the mammalian target of rapamycin pathway. Finally, we show that fear memory erasure persists until adolescence in HRM and that a single exposure to ketamine during the juvenile period reinstates normal fear memory in adolescent mice. Our results show that reelin is essential for successful structural, functional and behavioral development of juvenile prefrontal circuits and that this developmental period provides a critical window for therapeutic rehabilitation with GluN2B-NMDAR antagonists.
Asunto(s)
Moléculas de Adhesión Celular Neuronal/genética , Proteínas de la Matriz Extracelular/genética , Proteínas del Tejido Nervioso/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Serina Endopeptidasas/genética , Transducción de Señal/fisiología , Serina-Treonina Quinasas TOR/metabolismo , Análisis de Varianza , Animales , Animales Recién Nacidos , Moléculas de Adhesión Celular Neuronal/deficiencia , Condicionamiento Clásico/efectos de los fármacos , Condicionamiento Clásico/fisiología , Espinas Dendríticas/efectos de los fármacos , Espinas Dendríticas/genética , Relación Dosis-Respuesta a Droga , Fármacos actuantes sobre Aminoácidos Excitadores/farmacología , Extinción Psicológica/efectos de los fármacos , Extinción Psicológica/fisiología , Proteínas de la Matriz Extracelular/deficiencia , Miedo/efectos de los fármacos , Miedo/fisiología , Femenino , Técnicas In Vitro , Ketamina/farmacología , Potenciación a Largo Plazo/efectos de los fármacos , Potenciación a Largo Plazo/genética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas del Tejido Nervioso/deficiencia , Técnicas de Placa-Clamp , Fenoles , Piperidinas/farmacología , Corteza Prefrontal/citología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/crecimiento & desarrollo , Proteína Reelina , Serina Endopeptidasas/deficiencia , Transducción de Señal/efectos de los fármacos , SirolimusRESUMEN
3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is a recreational drug widely used by adolescents and young adults. Although its rewarding effects are well established, there is controversy on its addictive potential. We aimed to compare the consequences of active and passive MDMA administration on gene expression in the mouse brain since all previous studies were based on passive MDMA administration. We used a yoked-control operant intravenous self-administration paradigm combined with microarray technology. Transcriptomic profiles of ventral striatum, frontal cortex, dorsal raphe nucleus and hippocampus were analysed in mice divided in contingent MDMA, yoked MDMA and yoked saline groups, and several changes were validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The comparison of contingent MDMA and yoked MDMA vs. yoked saline mice allowed the identification of differential expression in several genes, most of them with immunological and inflammatory functions, but others being involved in neuroadaptation. In the comparison of contingent MDMA vs. yoked MDMA administration, hippocampus and the dorsal raphe nucleus showed statistically significant changes. The altered expression of several genes involved in neuroadaptative changes and synapse function, which may be related to learning self-administration behaviour, could be validated in these two brain structures. In conclusion, our study shows a strong effect of MDMA administration on the expression of immunological and inflammatory genes in all the four brain regions studied. In addition, experiments on MDMA self-administration suggest that the dorsal raphe nucleus and hippocampus may be involved in active MDMA-seeking behaviour, and show specific alterations on gene expression that support the addictive potential of this drug.
Asunto(s)
Encéfalo/efectos de los fármacos , Comportamiento de Búsqueda de Drogas/fisiología , Regulación de la Expresión Génica/efectos de los fármacos , Alucinógenos/farmacología , N-Metil-3,4-metilenodioxianfetamina/farmacología , Adaptación Fisiológica , Factores de Edad , Animales , Ganglios Basales/efectos de los fármacos , Ganglios Basales/metabolismo , Encéfalo/metabolismo , Condicionamiento Operante , Lóbulo Frontal/efectos de los fármacos , Lóbulo Frontal/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Análisis por Micromatrices , Proteínas del Tejido Nervioso/efectos de los fármacos , Proteínas del Tejido Nervioso/metabolismo , Núcleos del Rafe/efectos de los fármacos , Núcleos del Rafe/metabolismo , Recompensa , Autoadministración , Distribución Tisular , Transcriptoma/efectos de los fármacosRESUMEN
The elevated plus-maze is an animal model used to study anxiety. In a second session, rats show a reduction in the exploratory behavior even when the two sessions are separated by intervals as large as 7 days. The aim of the present study was to investigate whether the reduction in the exploratory behavior is maintained after intervals larger than 7 days. Additionally, we aimed at investigating eventual correlations between behaviors in the plus-maze and activation of limbic structures as measured by Fos protein expression after the second session. Rats were tested for 5 min in the elevated plus-maze and re-tested 3, 9 or 33 days later. Other groups were tested only once. The rat brains were processed for immunohistochemical detection of Fos protein. The results show a decrease in the open arms exploration in the second trial with intervals of 3, 9 and 33 days. The expression of Fos protein in the piriform cortex, septal nucleus and paraventricular hypothalamic nucleus in the groups tested with intervals of 9 and 33 days were statistically different from the other groups. The alterations observed in exploratory behavior in the second session in the plus-maze did not correlate with Fos expression. In conclusion, although the specific test conditions were sufficient to evoke behavioral alterations in exploration in the elevated plus-maze, they were enough to induce significant Fos protein expression in piriform cortex, septal nucleus and thalamic and hypothalamic paraventricular nuclei but not in other areas such as dorsomedial nucleus of the hypothalamus and amygdala nuclei, known to be also active participants in circuits controlling fear and anxiety.