An effort toward molecular biology of food deprivation induced food hoarding in gonadectomized NMRI mouse model: focus on neural oxidative status.

BACKGROUND: Environmental uncertainty, such as food deprivation, may alter internal milieu of nervous system through various mechanisms. In combination with circumstances of stress or aging, high consumption of unsaturated fatty acids and oxygen can make neural tissues sensitive to oxidative stress (OS). For adult rats, diminished level of gonadal steroid hormones accelerates OS and may result in special behavioral manifestations. This study was aimed to partially answer the question whether OS mediates trade-off between food hoarding and food intake (fat hoarding) in environmental uncertainty (e.g., fluctuations in food resource) within gonadectomized mouse model in the presence of food deprivation-induced food hoarding behavior. RESULTS: Hoarding behavior was not uniformly expressed in all male mice that exposed to food deprivation. Extended phenotypes including hoarder and non-hoarder mice stored higher and lower amounts of food respectively as compared to that of low-hoarder mice (normal phenotype) after food deprivation. Results showed that neural oxidative status was not changed in the presence of hoarding behavior in gonadectomized mice regardless of tissue type, however, glutathione levels of brain tissues were increased in the presence of hoarding behavior. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde in brain tissues of gonadectomized mice were also seen. CONCLUSIONS: Although, food deprivation-induced hoarding behavior is a strategic response to food shortage in mice, it did not induce the same amount of hoarding across all colony mates. Hoarding behavior, in this case, is a response to the environmental uncertainty of food shortage, therefore is not an abnormal behavior. Hoarding behavior induced neural OS with regard to an increase in brain glutathione levels but failed to show other markers of neural OS. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde levels in brain tissues of gonadectomized mice could be a hallmark of debilitated antioxidative defense and more lipid peroxidation due to reduced amount of gonadal steroid hormones during aging.

An effort toward molecular neuroeconomics of food deprivation induced food hoarding in mice: focus on xanthine oxidoreductase gene expression and xanthine oxidase activity.

The crucial role of xanthine oxidoreductase (XOR) gene and its active isoform, xanthine oxidase (XO), in purine metabolism and cellular oxidative status led us to investigative their fluctuations in food deprivation induced food hoarding in mice. After, 10 h food deprivation, mice that hoarded lesser than 5 g were considered as 'low-hoarders' while mice that hoarded higher than 20 g were considered as 'high-hoarders'. Mice who hoarded between 5 to 20 g of food were excluded from study. An increase (1.133-fold) in encephalic XOR expression has been found in high-hoarders compared with low-hoarders without sex consideration. An increase (~ 50-fold) in encephalic XOR in female high-hoarders vs. female low-hoarders while a decrease (0.026-fold) in encephalic XOR in male high-hoarders vs. male low-hoarders demonstrated that food deprivation is associated with sex-dependent alteration in XOR expression. The encephalic and hepatic XO activities were not different in male high-hoarders vs. male low-hoarders while encephalic XO activity has been also increased significantly in female high-hoarders (~ 4 times) compared to female low-hoarders. The plasma and hepatic XO activities tended to be increased in female high-hoarders as compared to female low-hoarders, however the uric acid levels in plasma, liver and brain tissues were not altered in female high-hoarders as compared to female low-hoarders. In sum, this study generally proposed that different gene expression space is behind of hoarding behavior in a food-deprived mouse model. Specifically, this is the first study that examined the levels of encephalic XO activity and XOR expression in hoarding behavior, although additional studies are requested.

Neurobehavioral toxicity of carbon nanotubes in mice.

OBJECTIVES: The aim of this study was to evaluate neurobehavioral toxicity of single-walled (SWNTs) and multiwalled carbon nanotubes (MWNTs) in mice. METHODS: Male NMRI mice were randomized into 5 groups ( n = 10 each): Normal control (NC) group was injected intraperitoneally (i.p.) with phosphate-buffered saline (PBS) solution (pH 7.8; ca. 1 mL), MW80 and MW800 groups were injected with either i.p. 80 or 800 mg kg-1 MWNTs suspended in 1 mL of PBS and SW80 and SW800 groups were injected with either i.p. 80 or 800 mg kg-1 SWNTs suspended in 1 mL of PBS. After 2 weeks, five mice from each group were evaluated for brain-derived neurotrophic factor (BDNF) messenger RNA expression and protein content of brain tissues. Locomotion, anxiety, learning and memory, and depression were measured by open field test (OFT), elevated plus-maze (EPM), object recognition test (ORT), and forced swimming test (FST), respectively. RESULTS: Ambulation time and center arena time in the OFT did not change among groups. In the EPM paradigm, SWNTs (800 mg kg-1) and MWNTs (80 and 800 mg kg-1) showed an anxiogenic effect. In ORT, MWNTs (80 mg kg-1) increased the discrimination ratio while in FST, MWNTs showed a depressant effect as compared to vehicle. The BDNF gene expression in mice treated with 80 and 800 mg kg-1 SWNTs or 80 mg kg-1 MWNTs decreased as compared to NC mice although BDNF gene expression increased in mice that were treated with 800 mg kg-1 MWNTs. The whole brain BDNF protein content did not change among groups. CONCLUSION: Our study showed that i.p. exposure to carbon nanotubes (CNTs) may result in behavioral toxicity linked with expression of depression or anxiety that depends on the type of CNTs. In addition, exposure to CNTs changed BDNF gene expression.

The effects of Cannabis sativa L. seed (hemp seed) on reproductive and neurobehavioral end points in rats.

This study determined the effects of maternal dietary intake of hemp seed on reproductive and neurobehavioral end points of Wistar rats. Time-mated rats were fed 100% hemp seed (n = 15), 50% hemp seed (n = 15) or basal diet (n = 15) once a day. The amount of food made available was based on control feed consumption records. All dams remained on their respective diets from premating (14 days) throughout gestation and lactation. After weaning, all pups were given their maternal diet until puberty. Mating and delivery weights of dams in all groups did not show significant changes. Number of pregnancies, number and post-natal survival rate of total rat pups, litter size and milk yield were lower in the group that received 100% hemp seed. Offspring that received 50% hemp seed diet expressed reproductive and neurobehavioral end points from a modified Fox battery earlier than rats on 100% hemp seed or basal diet, except acoustic startle results where no differences appeared. In conclusion, this study shows that hemp seed supplementation does not improve the reproductive and neurobehavioral performances of rats. Pregnant women and nursing mothers should be cautious about the using of Cannabis sativa L. byproducts in their diets.

Effects of dietary phytoestrogen exposure during perinatal period.

Developmental effects of phytoestrogens were studied in offspring from pregnant rats who received a free-feeding diet of either rat chow that was very low in phytoestrogens (low phyto), rat chow low in phytoestrogens and given a genistein and diadzein supplement tablet (high phyto), or normal rat chow (normal) from the second week of pregnancy to weaning (postnatal day 21). Measurements of anogenital distance, daily weights, righting reflex and ultrasonic vocalizations were made on neonatal pups and plasma testosterone and corticosterone were assessed in adult males. There was a significant effect of phytoestrogen treatment on USV for all male and female offspring. Differences between groups in daily weights and anogenital distance were attributed to the micronutrient levels of the two rat chow types employed in this study. No differences in righting reflex test, corticosterone levels or testosterone levels were found among treatment conditions. These results are the first demonstration of phytoestrogens affecting USVs and underscore the complexity of the effects of these substances on biobehavioral development.