The neuropeptide, relaxin-3 (RLN3) is part of the insulin-relaxin superfamily, is primarily expressed by neurons in the brainstem nucleus incertus (NI) and is implicated in motivated behaviours and stress responses. The present study was designed to investigate the effects of RLN3 mRNA knockdown in NI RLN3-positive neurons of female rats on body weight, food intake and anxiety-like behaviour. Female rats received a bilateral infusion into the NI of adeno-associated virus encoding microRNA against RLN3 (knockdown) or control. Three weeks after viral injections, food intake and body weight were measured every 24 h. At week 7, rats were subjected to the behavioural tests light/dark box (L/D), elevated plus maze (EPM) and large open-field (LOF) test followed. During week 8, rats were sacrificed, and intra-cardiac blood samples and brains were collected. The targeting and specificity of RLN3 knockdown in NI neurons was assessed using in situ hybridization. The c-fos mRNA expression was analysed in regions involved in stress and feeding. RLN3 mRNA expression in the NI of knockdown rats was significantly suppressed compared to control. Two-way ANOVA revealed significant difference on body weight. Bonferroni’s multiple comparison tests revealed a decrease in body weight of RLN3 knockdown rats from week 2 which persisted until week 7. Food intake was decreased in knockdown group compared to control during week 4. In addition, RLN3 knockdown rats displayed significantly higher anxiety-like behaviour in the LOF, but not in the EPM and L/D compared with virus control rats. After behavioural tests, corticosterone levels were not different between groups for all tests, however basal levels of corticosterone were significantly decreased in knockdown group compared to control. Moreover, c-fos mRNA expression significantly decreased in the paraventricular nucleus of the hypothalamus, bed nucleus of the stria terminalis, and in the lateral hypothalamus area in knockdown rats compared to control, at the basal level. Reduced RLN3 expression in NI neurons induced weight loss associated with an imbalance on food intake, elevated anxiety in environment with no escape, and disrupted the hypothalamic-pituitary adrenal axis in female rats.
Effects of silencing relaxin-3 production in nucleus incertus neurons on food intake, body weight, anxiety-like behaviour and limbic brain activity in female rats
C. CIFANI;
2019-01-01
Abstract
The neuropeptide, relaxin-3 (RLN3) is part of the insulin-relaxin superfamily, is primarily expressed by neurons in the brainstem nucleus incertus (NI) and is implicated in motivated behaviours and stress responses. The present study was designed to investigate the effects of RLN3 mRNA knockdown in NI RLN3-positive neurons of female rats on body weight, food intake and anxiety-like behaviour. Female rats received a bilateral infusion into the NI of adeno-associated virus encoding microRNA against RLN3 (knockdown) or control. Three weeks after viral injections, food intake and body weight were measured every 24 h. At week 7, rats were subjected to the behavioural tests light/dark box (L/D), elevated plus maze (EPM) and large open-field (LOF) test followed. During week 8, rats were sacrificed, and intra-cardiac blood samples and brains were collected. The targeting and specificity of RLN3 knockdown in NI neurons was assessed using in situ hybridization. The c-fos mRNA expression was analysed in regions involved in stress and feeding. RLN3 mRNA expression in the NI of knockdown rats was significantly suppressed compared to control. Two-way ANOVA revealed significant difference on body weight. Bonferroni’s multiple comparison tests revealed a decrease in body weight of RLN3 knockdown rats from week 2 which persisted until week 7. Food intake was decreased in knockdown group compared to control during week 4. In addition, RLN3 knockdown rats displayed significantly higher anxiety-like behaviour in the LOF, but not in the EPM and L/D compared with virus control rats. After behavioural tests, corticosterone levels were not different between groups for all tests, however basal levels of corticosterone were significantly decreased in knockdown group compared to control. Moreover, c-fos mRNA expression significantly decreased in the paraventricular nucleus of the hypothalamus, bed nucleus of the stria terminalis, and in the lateral hypothalamus area in knockdown rats compared to control, at the basal level. Reduced RLN3 expression in NI neurons induced weight loss associated with an imbalance on food intake, elevated anxiety in environment with no escape, and disrupted the hypothalamic-pituitary adrenal axis in female rats.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
