RESUMO
PURPOSE: Sex differences play a crucial role in understanding vulnerability to opioid addiction, yet there have been limited preclinical investigations of this effect during the transition from adolescence to adulthood. The present study compared the behaviors of male and female rodents in response to fentanyl treatment and targeted molecular correlates in the striatum and medial prefrontal cortex. MATERIALS AND METHODS: Thirty adolescent C57BL/6J mice underwent a 1-week fentanyl treatment with an escalating dose. In addition to evaluating locomotor activity and anxiety-related parameters, we also assessed naloxone-induced fentanyl acute withdrawal jumps. We employed real-time quantitative PCR (qPCR) to assess overall gene expression of dopaminergic receptors (Drd1, Drd2, Drd4 and Drd5) and the µ-opioid receptor Oprm1. The levels of epigenetic base modifications including 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) were assessed on CpG islands of relevant genes. RESULTS: Females had higher locomotor activity than males after chronic fentanyl treatment, and they exhibited higher fentanyl withdrawal jumping behavior induced by naloxone. Females also presented lower Drd4 gene expression and DNA methylation (5mC + 5hmC) in the striatum. We found that locomotor activity and fentanyl withdrawal jumps were negatively correlated with Drd4 methylation and gene expression in the striatum, respectively. CONCLUSIONS: The findings suggested that female mice displayed heightened sensitivity to the effects of fentanyl treatment during the transition from adolescence to adulthood. This effect may be associated with molecular alterations related to the Drd4 gene.
Assuntos
Fentanila , Camundongos Endogâmicos C57BL , Receptores Opioides mu , Caracteres Sexuais , Animais , Fentanila/farmacologia , Masculino , Feminino , Receptores Opioides mu/genética , Receptores Opioides mu/metabolismo , Camundongos , Metilação de DNA/efeitos dos fármacos , Analgésicos Opioides/farmacologia , Corpo Estriado/metabolismo , Corpo Estriado/efeitos dos fármacos , Locomoção/efeitos dos fármacos , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Receptores Dopaminérgicos/genética , Receptores Dopaminérgicos/metabolismo , Naloxona/farmacologia , Comportamento Animal/efeitos dos fármacos , Síndrome de Abstinência a Substâncias/genética , Síndrome de Abstinência a Substâncias/metabolismo , Epigênese Genética/efeitos dos fármacosRESUMO
Early life stress (ELS) is considered a risk factor for the development of psychiatric conditions, including depression and anxiety disorder. Individuals that live in adverse environments are usually exposed to multiple stressors simultaneously, such as maternal neglect, maltreatment, and limited resources. Nevertheless, most pre-clinical ELS models are designed to explore the impact of these events separately. For this reason, this study aims to investigate the effects of a combined model of ELS on anxiety-like behavior and hypothalamic-pituitary-adrenal (HPA) axis related targets. From PND 2 to PND 15 BALB/cJ mice were exposed simultaneously to maternal separation (MS; 3 h per day) and limited bedding (LB; ELS group) or left undisturbed (CT group). Maternal behavior was recorded in intercalated days, from PND 1 to PND 9. Male offspring were tested for anxiety-like behavior from PND 53 to PND 55 in the open field test (OF), elevated plus-maze (EPM), and light/dark test (LD). After behavioral testing, animals were euthanized, and glucocorticoid receptor (Nr3c1), corticotrophin-releasing hormone (Crh), and its receptor type 1 (Crhr1) gene expression in the hypothalamus were measured. Moreover, plasma corticosterone levels were analyzed. We observed that ELS dams presented altered quality of maternal care, characterized by a decrease in arched-back nursing, and an increase in passive nursing. Stressed dams also showed an increase in the number of exits from the nest when compared to CT dams. Furthermore, ELS animals showed increased anxiety-like behavior in the OF, EPM, and LD. Regarding gene expression, we identified an increase in hypothalamus Crh levels of ELS group when compared to CT animals, while no differences in Nr3c1 and Crhr1 expression were observed. Finally, stressed animals showed decreased levels of plasma corticosterone when compared to the CT group. In conclusion, we observed an alteration in maternal behavior in ELS dams. Later in life, animals exposed to the combined model of ELS showed increased levels of anxiety-like behavior. Moreover, the central and peripheral HPA measures observed could indicate a dysregulation in HPA function provoked by ELS exposure.
RESUMO
The peripartum period is accompanied by numerous physiological and behavioural adaptations organised by the maternal brain. These changes are essential for adequate expression of maternal behaviour, thereby ensuring proper development of the offspring. The corticotropin-releasing factor (CRF) plays a key role in a variety of behaviours accompanying stress, anxiety, and depression. There is also evidence that CRF contributes to maladaptations during the peripartum period. We investigated the effects of CRF in the bed nucleus of the stria terminalis (BNST) of lactating mice during maternal care and analysed locomotor activity and anxiety-like behaviour in the offspring. The BNST has been implicated in anxiety behaviour and regulation of the stress response. The effects of intra-BNST CRF administration were compared with those induced by the limited bedding (LB) procedure, a model that produces altered maternal behaviour. BALB/cJ dams were exposed to five infusions of CRF or saline into the BNST in the first weeks after birth while the LB dams were exposed to limited nesting material from postnatal days (P) 2-9. Maternal behaviour was recorded in intercalated days, from P1-9. Offspring anxiety-like behaviour was assessed during adulthood using the open-field, elevated plus-maze, and light/dark tests. Both intra-BNST CRF and LB exposure produced altered maternal care, represented by decreased arched-back nursing and increased frequency of exits from the nest. These changes in maternal care resulted in robust sex-based differences in the offspring's behavioural responses during adulthood. Females raised by CRF-infused dams exhibited increased anxiety-like behaviour, whereas males presented a significant decrease in anxiety. On the other hand, both males and females raised by dams exposed to LB showed higher locomotor activity. Our study demonstrates that maternal care is impaired by intra-BNST CRF administrations, and these maladaptations are similar to exposure to adverse early environments. These procedures, however, produce distinct phenotypes in mice during young adulthood and suggest sex-based differences in the susceptibility to poor maternal care.
Assuntos
Hormônio Liberador da Corticotropina/metabolismo , Lactação/metabolismo , Comportamento Materno/fisiologia , Núcleos Septais/metabolismo , Animais , Ansiedade/metabolismo , Transtornos de Ansiedade/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Fenótipo , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Caracteres SexuaisRESUMO
Toll-like Receptors (TLRs) are implicated with the pathogenesis of cognitive impairment induced by inflammation. Early life stress is associated with altered trajectories of neuroimmune signaling with implications for cognitive development. However, effects of TLR-3 activation on early life stress-related cognitive outcomes are understudied. We investigated the effects of maternal separation (MS) during postnatal development and a viral immune challenge during adolescence on working memory performance. BALB/c mice exposed to MS were separated from their dams daily for 180-min from postnatal day (PND) 2 to 15. At PND 45, animals were challenged with a single i.p. injection of either Poly (I:C) or sterile saline, and then subjected to a spatial working memory test in a Y-maze apparatus. Gene expression was determined by qPCR. Protein levels of oxidative stress markers were also assessed. A single peripheral administration of a TLR-3 agonist was able to induce working memory impairments in adolescent mice exposed to MS. At a molecular level, exposure to MS was associated with lower mRNA levels of Tlr3 in the medial prefrontal cortex (mPFC). However, when MS animals were exposed to Poly (I:C), a more robust activation of Tlr3, Il6 and Nfkb1 gene transcription was observed in these mice compared with control animals. These modifications did not result in oxidative stress. Finally, higher mRNA levels of Nfkb1 in the mPFC were correlated with lower working memory performance, suggesting that altered NF-κB signaling might be related with poor cognitive functioning. These results have implications for how ELS affects neuroimmune signaling in the mPFC.
Assuntos
Disfunção Cognitiva/fisiopatologia , Memória de Curto Prazo/fisiologia , Receptor 3 Toll-Like/metabolismo , Animais , Animais Recém-Nascidos , Encéfalo/metabolismo , Cognição , Disfunção Cognitiva/metabolismo , Hipocampo/metabolismo , Inflamação/metabolismo , Masculino , Privação Materna , Camundongos , Camundongos Endogâmicos BALB C , Neuroimunomodulação/fisiologia , Poli I-C/farmacologia , Córtex Pré-Frontal/metabolismo , RNA Mensageiro/metabolismo , Memória Espacial/fisiologia , Estresse Psicológico/fisiopatologia , Receptor 3 Toll-Like/fisiologiaRESUMO
While increasing evidence posits poor decision-making as a central feature of mental disorders, very few studies investigated the effects of early-life stress (ELS) on specific components of reward-related choice behaviors. Risk-taking (RT) involves the exposure to some danger, or negative consequences, in order to achieve a goal-directed behavior. Such behaviors are likely to be preceded by risk-assessment (RA), which is a dynamic cognitive process involving the acquisition of information in potentially dangerous situations. Here, we investigated the effects of being raised in impoverished housing conditions during early life (P2-P9) on RT, RA and dopaminergic and corticotrophinergic gene expression of adolescent male and female mice. Phenotypes were assessed by two protocols: the elevated plus-maze (EPM) and the predator-odor risk-taking (PORT). We found decreased RA in mice exposed to impoverished housing in the absence of a reward (EPM), with a more pronounced effect among females. Moreover, when exposed to a predatory olfactory cue, increased RT was observed in these females in a reward-related task (PORT), as well as decreased HPA axis responsivity. This sex-specific behavioral effect was associated with increased Crfr1 mRNA expression in the medial prefrontal cortex (mPFC) and higher levels of the histone mark H3R2me2s, a histone modification known to be involved in transcriptional activation, within the promoter of the Crfr1 gene. These findings revealed that ELS exposure can impair the acquisition of environmental information in dangerous situations and increase RT in reward-related scenarios among females, with an important role regarding epigenetic regulation of the Crfr1 gene.