The mechanism of enriched environment repairing the learning and memory impairment in offspring of prenatal stress by regulating the expression of activity-regulated cytoskeletal-associated and insulin-like growth factor-2 in hippocampus

Background Prenatal stress can cause neurobiological and behavioral defects in offspring; environmental factors play a crucial role in regulating the development of brain and behavioral; this study was designed to test and verify whether an enriched environment can repair learning and memory impairment in offspring rats induced by prenatal stress and to explore its mechanism involving the expression of insulin-like growth factor-2 (IGF-2) and activity-regulated cytoskeletal-associated protein (Arc) in the hippocampus of the offspring. Methods Rats were selected to establish a chronic unpredictable mild stress (CUMS) model during pregnancy. Offspring were weaned on 21st day and housed under either standard or an enriched environment. The learning and memory ability were tested using Morris water maze and Y-maze. The expression of IGF-2 and Arc mRNA and protein were respectively measured by using RT-PCR and Western blotting. Results There was an elevation in the plasma corticosterone level of rat model of maternal chronic stress during pregnancy. Maternal stress’s offspring exposed to an enriched environment could decrease their plasma corticosterone level and improve their weight. The offspring of maternal stress during pregnancy exhibited abnormalities in Morris water maze and Y-maze, which were improved in an enriched environment. The expression of IGF-2, Arc mRNA, and protein in offspring of maternal stress during pregnancy was boosted and some relationships existed between these parameters after being exposed enriched environment. Conclusions The learning and memory impairment in offspring of prenatal stress can be rectified by the enriched environment, the mechanism of which is related to the decreasing plasma corticosterone and increasing hippocampal IGF-2 and Arc of offspring rats following maternal chronic stress during pregnancy.

Bacopa monnieri alleviates aluminium chloride-induced anxiety by regulating plasma corticosterone level in Wistar rats

ObjectivesAluminium is present in food preparations, antacids and many medications. It causes neurodegeneration thereby resulting in a spectrum of neurological disorders such as dementia, Alzheimer’s disease and anxiety. Bacopa monnieri (BM) is widely used in ayurvedic medicine to improve memory functions. Its anxiolytic property was investigated in this study by using elevated plus maze (EPM) and plasma corticosterone level.MethodsThirty rats were assigned into five groups. Control group received distilled water, and 0.5% tween 80, AlCl3 group received Aluminium Chloride (AlCl3), Protective groups (BM100 + AlCl3 group and BM200 + AlCl3 group) received AlCl3 and BM at two different doses, and the BM200 group received BM. The EPM experiment was performed at the end of the 4th week of oral administration of BM and AlCl3 followed by the measurement of plasma corticosterone.ResultsOral administration of AlCl3 to rats increases the levels of anxiety as seen in a decrease in the percentage of entries into the open arms of EPM, an increase in grooming frequency and defecation index. However, the rats in the protective groups shown an increase in the percentage of open arm entries and rearing frequency, and decreased grooming frequency and defecation index. AlCl3 alone treated group showed a significant increase in the plasma corticosterone levels compared to the control group. Whereas the protective groups have shown a significant decrease in the plasma corticosterone levels than the AlCl3 alone treated group.ConclusionsHence the BM has potential role in reverting the anxiogenic effect of AlCl3 in the amygdala as it is evident from the plasma corticosterone levels and the EPM parameters of different groups under study.

ANTIDEPRESSANT ACTIVITY OF THYMOQUINONE POSSIBLY THROUGH INVOLVEMENT OF CORTICOTROPIN RELEASING FACTOR

Objective: Present study aimed to evaluate the antidepressant-like activity of thymoquinone (TQ) in unstressed and stressed condition and to explore the possible underlying mechanism for this activity.Methods: TQ (5, 10, and 20 mg/kg) and fluoxetine per se were administered to the unstressed and stressed mice; immobility periods were observed using forced swim test (FST) and tail suspension test (TST). Effect of corticotropin-releasing factor (CRF)-1 antagonist on antidepressant-like activity was also evaluated. The mechanism of action was also explored by measuring plasma corticosterone levels.Results: TQ (20 mg/kg) and fluoxetine per se significantly decreased immobility periods in stressed mice indicating significant antidepressant-like activity under stress. There was no significant effect on locomotor activity of the mice on treatment with TQ and fluoxetine per se. It significantly decreased plasma corticosterone level. Antalarmin (a CRF-1 receptor antagonist) significantly attenuated TQ induced the antidepressant-like effect in both FST and TST.Conclusion: TQ significantly produced antidepressant-like activity in mice possi‑bly through inhibiting CRF activity and decreasing plasma corticosterone levels.

Inhibitory Effect of NMDA Receptors in the Ventral Tegmental Area on Hormonal and Eating Behavior Responses to Stress in Rats

Background. Stress and its consequences are among the causes of accidents.Objective. The effects of intraventral tegmental area (I-VTA) memantine on the plasma corticosterone and eating parameters disturbance induced by acute stress were investigated.Methods. Male Wistar rats (W: 250–300 g) were divided into control and experiential groups, each of which received memantine either intra-VTA or peripherally. One week after bilateral cannulation, the rats received memantine (1 and 5 μg/Rat) five min before electroshock stress. The other experimental groups received memantine (1 and 5 mg/kg) intraperitoneally 30 min before stress. The control groups received saline or memantine but did not experience stress. Food and water intake and plasma corticosterone level were recorded.Results. Results showed that stress decreases food intake but does not change water intake and increase in plasma corticosterone level. Intraperitoneal memantine administration slightly inhibits the stress effects on food intake. However, water intake and plasma corticosterone level were increased. Intra-VTA memantine reduces the effects of stress on corticosterone and water intake.Conclusion. It could be concluded that inhibition of glutamate NMDA receptors in the VTA by memantine leads to the inhibition of the eating behavior parameters and plasma corticosterone level disturbance induced by stress in rats.

Inflammatory Pain and Corticosterone Response in Infant Rats: Effect of 5-HT1A Agonist Buspirone Prior to Gestational Stress

Our researches have shown that gestational stress causes exacerbation of inflammatory pain in the offspring; the maternal 5-HT1A agonist buspirone before the stress prevents the adverse effect. The serotonergic system and hypothalamo-pituitary-adrenal (HPA) axis are closely interrelated. However, interrelations between inflammatory pain and the HPA axis during the hyporeactive period of the latter have not been studied. The present research demonstrates that formalin-induced pain causes a gradual and prolonged increase in plasma corticosterone level in 7-day-old male rats; twenty-four hours after injection of formalin, the basal corticosterone level still exceeds the initial basal corticosterone value. Chronic treatments of rat dams with buspirone before restraint stress during gestation normalize in the offspring pain-like behavior and induce during the acute phase in the formalin test the stronger corticosterone increase as compared to the stress hormonal elevation in animals with other prenatal treatments. Negative correlation between plasma corticosterone level and the number of flexes+shakes is revealed in buspirone+stress rats. The new data enhance the idea about relativity of the HPA axis hyporeactive period and suggest that maternal buspirone prior to stress during gestation may enhance an adaptive mechanism of the inflammatory nociceptive system in the infant male offspring through activation of the HPA axis peripheral link.

Blood corticosterone levels in growing geese around feather gathering

Feather production is realised by gathering feathers from geese right as they start their natural moulting. The adequate gathering time coincides with the time of moulting. There is still scarce information as to whether or not gathering causes distress and pain to geese. A series of experiments was carried out by our research group to determine the effect of gathering on plasma corticosterone level in growing geese. In the present experiment, the reactions of five groups (two gathered and three not gathered groups) of 9-week-old Babat Hungarian Upgraded geese were compared regarding gathering. Blood samples were taken right before, during and 5 min, 1 and 3 h after gathering into heparinised tubes from all groups. The plasma concentration of corticosterone was determined by radioimmunoassay (RIA). The results show that the plasma concentration of corticosterone is high in the first sample of all groups but is significantly lower at subsequent blood samplings compared to the first samples, especially in gathered geese. Compared to the first sampling, we observed higher corticosterone levels in samples collected 1 and 3 h after gathering. This was true only for groups which were not gathered, especially for the group which was not given any antistress material. From these results it can be concluded that the handling of geese causes an elevation in plasma corticosterone level and that feather gathering does not result in a higher corticosterone level than the handling or catching of the bird. Therefore, it can be concluded that feather gathering — especially when it is done adequately in time — does not cause more distress than the handling or catching of the bird.