Neonatal interventions differently affect maternal care quality and have sexually dimorphic developmental effects on corticosterone secretion.

Neonatal handling (H) and maternal separation (MS) both induce changes in maternal care, but the contribution of these changes to the behavioral and neurochemical outcomes of the offspring remains unclear, as studies often find opposite results concerning the frequency of maternal behaviors, particularly in the MS paradigm. In this study, behavior displayed by H, MS and non-handled (NH) Wistar rat dams were observed during the first 10days after birth. A tentative assessment of the quality of maternal care was made, using a previously reported score that reflects behavior fragmentation and inconsistency. Central oxytocin levels and hippocampal synaptic plasticity markers were also evaluated in dams, immediately after litter weaning. In adulthood, male and female offspring were subjected to a contextual stress-induced corticosterone challenge to provide further information on the impact of early interventions on neuroendocrine parameters. We found that while both H and MS interventions induced an increase in the amount of pup-directed behavior, MS dams displayed a more fragmented and inconsistent pattern of care, reflecting poorer maternal care quality. Interestingly, an increase in oxytocin levels was observed only in H dams. While H offspring did not differ from NH, MS males and females showed marked differences in corticosterone secretion compared to controls. Our results suggest that briefly removing the pups from the nest alters maternal care quantity but not quality and increases central oxytocin, while long separations appear to increase low quality maternal care and change neuroendocrine responses in adult offspring in a sex-specific manner.

Prenatal stress produces sex differences in nest odor preference.

Prenatal stress (PS) and early postnatal environment may alter maternal care. Infant rats learn to identify their mother through the association between maternal care and familiar odors. Female Wistar rats were exposed to restraint stress for 30 min, 4 sessions per day, in the last 7 days of pregnancy. At birth, pups were cross-fostered and assigned to the following groups: prenatal non-stressed mothers raising non-stressed pups (NS:NS), prenatal stressed mothers raising non-stressed pups (S:NS), prenatal non-stressed mothers raising stressed pups (NS:S), prenatal stressed mothers raising stressed pups (S:S). Maternal behaviors were assessed during 6 postpartum days. On postnatal day (PND) 7, the behavior of male and female pups was analyzed in the odor preference test; and noradrenaline (NA) activity in olfactory bulb (OB) was measured. The results showed that restraint stress increased plasma levels of corticosterone on gestational day 15. After parturition, PS reduced maternal care, decreasing licking the pups and increasing frequency outside the nest. Female pups from the NS:S, S:NS, S:S groups and male pups from the S:S group showed no nest odor preference. Thus, at day 7, female pups that were submitted to perinatal interventions showed more impairment in the nest odor preference test than male pups. No changes were detected in the NA activity in the OB. In conclusion, repeated restraint stress during the last week of gestation reduces maternal care and reduces preference for a familiar odor in rat pups in a sex-specific manner.

Neonatal handling impairs spatial memory and leads to altered nitric oxide production and DNA breaks in a sex specific manner.

Early life events lead to behavioral and neurochemical changes in adulthood. The aim of this study is to verify the effects of neonatal handling on spatial memory, nitric oxide (NO) production, antioxidant enzymatic activities and DNA breaks in the hippocampus of male and female adult rats. Litters of rats were non-handled or handled (10 min/day, days 1-10 after birth). In adulthood they were subjected to a Morris water maze or used for biochemical evaluations. Female handled rats showed impairment in spatial learning. They also showed decreased NO production, while no effects were observed in these parameters in male rats. No effects were observed on the number of hippocampal NADPH diaphorase positive cells. In the Comet Assay, male handled rats showed increased DNA breaks index when compared to non-handled ones. We conclude that neonatal handling impairs learning performance in a sex-specific manner, what may be related to NO decreased levels.

Lithium and methylphenidate: opposite effects on perirenal brown fat / Lítio e metilfenidato: efeitos opostos sobre a gordura perirrenal

OBJECTIVE: To evaluate the effects of the administration of lithium to adult rats on brown (perirenal) and white (inguinal) adipose tissues and to assess whether methylphenidate modulates lithium effects. METHODS: Twenty-five adult male Wistar rats were fed with either regular or lithium-containing chow for 30 days. Between days 15 to 30 of treatment, animals received daily intraperitoneal administrations of either methylphenidate or saline. RESULTS: Lithium significantly reduced perirenal fat, and this effect was minimized by the administration of methylphenidate. There were no significant differences between the groups in terms of the effects of lithium on inguinal fat. CONCLUSION: Our findings suggest that different effects on white and brown tissue distribution may be involved in lithium-induced weight gain.

OBJETIVO: Avaliar como a administração de lítio afeta o tecido adiposo marrom (perirrenal) e branco (inguinal) e se o metilfenidato modula os efeitos do lítio. MÉTODOS: Vinte e cinco ratos Wistar adultos machos foram alimentados com ração normal ou contendo lítio por 30 dias. Entre os dias 15 e 30 de tratamento, os animais receberam doses intraperitoneais diárias de metilfenidato ou solução salina. RESULTADOS: A administração de lítio reduziu significativamente a gordura perirrenal. Esse efeito foi reduzido com a administração de metilfenidato. Não houve diferenças significativas entre os grupos em relação à gordura inguinal. CONCLUSÃO: Os achados sugerem que efeitos diferenciados sobre os tecidos adiposos marrom e branco podem estar envolvidos no ganho de peso induzido pelo tratamento com lítio.

Sex-specific differences on caffeine consumption and chronic stress-induced anxiety-like behavior and DNA breaks in the hippocampus.

Caffeine is widely consumed in beverages and food, and its consumption in high doses is associated with anxiety increase. Stress situations are often associated to coffee consumption, and have a strong influence on oxidative DNA damage. As there are sex-specific differences in many metabolic, neurochemical and behavioral aspects, the aim of this study is to verify the interaction between chronic consumption of caffeine and chronic stress on anxiety and DNA breaks in the hippocampus on male and female rats. Wistar rats were submitted to restraint stress for at least 50 days. The diet consisted of standard rat chow and caffeine 0.3 or 1 g/L in drinking water "ad libitum" as the only drinking source. Controls received tap water. Anxiety-like behavior and DNA breaks in the hippocampus were evaluated. Caffeine consumption and chronic stress increased anxiety-like behavior as well as DNA breaks in the hippocampus of male rats. No effect on these parameters was observed in females. These results may be related to the presence of estradiol, which may have anxiolytic and neuroprotective properties.

Interactions between chronic stress and chronic consumption of caffeine on the enzymatic antioxidant system.

We studied the effect of chronic caffeine on parameters related to oxidative stress in different brain regions of stressed and non-stressed rats. Wistar rats were divided into three groups: control (receiving water), caffeine 0.3 g/L and caffeine 1.0 g/L (in the drinking water). These groups were subdivided into non-stressed and stressed (repeated restraint stress during 40 days). Lipid peroxide levels and the total radical-trapping potential were assessed, as well as antioxidant enzyme activities superoxide dismutase, gluthatione peroxidase, and catalase in hippocampus, striatum and cerebral cortex. Results showed interactions between stress and caffeine, especially in the cerebral cortex, since caffeine increased the activity of some antioxidant enzymes, but not in stressed animals. We concluded that chronic administration of caffeine led, in some cases, to increased activity of antioxidant enzymes. However, these effects were not observed in the stressed animals.

Effects of chronic restraint stress and estradiol replacement on glutamate release and uptake in the spinal cord from ovariectomized female rats.

Glutamate is an excitatory neurotransmitter involved in neuronal plasticity and neurotoxicity. Chronic stress produces several physiological changes on the spinal cord, many of them presenting sex-specific differences, which probably involve glutamatergic system alterations. The aim of the present study was to verify possible effects of exposure to chronic restraint stress and 17beta-estradiol replacement on [3H]-glutamate release and uptake in spinal cord synaptosomes of ovariectomized (OVX) rats. Female rats were subjected to OVX, and half of the animals received estradiol replacement. Animals were subdivided in controls and chronically stressed. Restraint stress or estradiol had no effect on [3H]-glutamate release. The chronic restraint stress promoted a decrease and 17beta-estradiol induced an increase on [3H]-glutamate uptake, but the uptake observed in the restraint stress +17beta-estradiol group was similar to control. Furthermore, 17beta-estradiol treatment caused a significant increase in the immunocontent of the three glutamate transporters present in spinal cord. Restraint stress had no effect on the expression of these transporters, but prevented the 17beta-estradiol effect. We suggest that changes in the glutamatergic system are likely to take part in the mechanisms involved in spinal cord plasticity following repeated stress exposure, and that 17beta-estradiol levels may affect chronic stress effects in this structure.

Long lasting sex-specific effects upon behavior and S100b levels after maternal separation and exposure to a model of post-traumatic stress disorder in rats.

This study was undertaken to verify if repeated long-term separation from dams would affect the development of parameters related to post-traumatic stress disorder (PTSD) after animals are subjected to inescapable shock when adults. Wistar rats were subjected to repeated maternal separation during post-natal days 1-10. When adults, rats from both sexes were submitted to a PTSD model consisting of exposure to inescapable footshock, followed by situational reminders. We observed long-lasting effects of both interventions. Exposure to shock increased fear conditioning. Anxiety-like behavior was increased and exploratory activity decreased by both treatments, and these effects were more robust in males. Additionally, basal corticosterone in plasma was decreased, paralleling effects observed in PTSD patients. Levels of S100B protein in serum and cerebrospinal fluid (CSF) were measured. Levels in serum correlated with the effects observed in anxiety-like behavior, increasing in males exposed to shock, and presenting no effect in females. S100B in CSF was increased in females submitted to maternal separation during the neonatal period. These results suggest that, in rats, an early stress experience such as maternal separation may aggravate some effects of exposure to a stressor during adult age, and that this effect is sex-specific. Additionally, data suggest that the increased S100B levels, observed in serum, have an extracerebral origin, possibly mediated by an increase in the noradrenergic tonus. Increased S100B in brain could be related to its neurotrophic actions.

Chronic lithium treatment has antioxidant properties but does not prevent oxidative damage induced by chronic variate stress.

This study evaluated the effects of chronic stress and lithium treatments on oxidative stress parameters in hippocampus, hypothalamus, and frontal cortex. Adult male Wistar rats were divided into two groups: control and submitted to chronic variate stress, and subdivided into treated or not with LiCl. After 40 days, rats were killed, and lipoperoxidation, production free radicals, total antioxidant reactivity (TAR) levels, and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were evaluated. The results showed that stress increased lipoperoxidation and that lithium decreased free radicals production in hippocampus; both treatments increased TAR. In hypothalamus, lithium increased TAR and no effect was observed in the frontal cortex. Stress increased SOD activity in hippocampus; while lithium increased GPx in hippocampus and SOD in hypothalamus. We concluded that lithium presented antioxidant properties, but is not able to prevent oxidative damage induced by chronic variate stress.