Reversed effects of RU486 and anisomycin on memory retention of light exposure or corticosterone facilitation in the dark-incubated chicks

Epigenetic Programming Effects of Early Life Stress: A Dual-Activation Hypothesis

Epigenetic processes during early brain development can function as 'developmental switches' that contribute to the stability of long-term effects of early environmental influences by programming central feedback mechanisms of the HPA axis and other neural networks. In this thematic review, we summarize accumulated evidence for a dual-activation of stress-related and sensory networks underlying the epigenetic programming effects of early life stress. We discuss findings indicating epigenetic programming of stress-related genes with impact on HPA axis function, the interaction of epigenetic mechanisms with neural activity in stress-related neural networks, epigenetic effects of glucocorticoid exposure, and the impact of stress on sensory development. Based on these findings, we propose that the combined activation of stress-related neural networks and stressor-specific sensory networks leads to both neural and hormonal priming of the epigenetic machinery, which sensitizes these networks for developmental programming effects. This allows stressor-specific adaptations later in life, but may also lead to functional mal-adaptations, depending on timing and intensity of the stressor. Finally, we discuss methodological and clinical implications of the dual-activation hypothesis. We emphasize that, in addition to modifications in stress-related networks, we need to account for functional modifications in sensory networks and their epigenetic underpinnings to elucidate the long-term effects of early life stress.

Alteration of 11β-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor by ethanol in rat liver and mouse hepatoma cells

Alcohol is a potential risk factor of type 2 diabetes, but its underlying mechanism is unclear. To explore this issue, Wistar rats and mouse hepatoma cells (Hepa 1-6) were exposed to ethanol, 8 g·kg(-1) ·d(-1) for 3 months and 100 mM for 48 h, respectively. Glucose and insulin tolerance tests in vivo were performed, and protein levels of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and glucocorticoid receptor (GR) in liver and Hepa 1-6 cells were measured. Alterations of key enzymes of gluconeogenesis phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase), as well as glycogen synthase kinase 3a (GSK3 α ), were also examined. The results revealed that glucose levels were increased, and insulin sensitivity was impaired accompanied with liver injury in rats exposed to ethanol compared with controls. The 11β-HSD1, GR, PEPCK, G6Pase, and GSK3 α proteins were increased in the liver of rats treated with ethanol compared with controls. Ethanol-exposed Hepa 1-6 cells also showed higher expression of 11β-HSD1, GR, PEPCK, G6Pase, and GSK3 α proteins than control cells. After treatment of Hepa 1-6 cells exposed to ethanol with the GR inhibitor RU486, the expression of 11β-HSD1 and GR was significantly decreased. At the same time the increases in PEPCK, G6Pase, and GSK3 α levels induced by ethanol in Hepa 1-6 cells were also attenuated by RU486. The results indicate that ethanol causes glucose intolerance by increasing hepatic expression of 11β-HSD1 and GR, which leads to increased expression of gluconeogenic and glycogenolytic enzymes.

Effects of lanthanum chloride administration in prenatal stage on one-trial passive avoidance learning in chicks

Lanthanum cations (La 3+) are well known for their inhibitory actions on calcium channels. Prenatal lanthanum exposure may affect the development of embryo and alter the capacity for learning and memory in adults, and the one-trial passive avoidance learning paradigm with day-old chicks is an excellent model to study several mechanisms of memory formation. In the present study, we examined the effects of prenatal lanthanum chloride exposure on memory consolidation using one-trial passive avoidance learning task in day-old chicks. The data suggest that chicks injected with lanthanum chloride (2 mg/kg) daily from E9 to E16 had significantly impaired long-term memory at 120 min after training (p < 0.05) but not the chicks injected with lanthanum chloride (0.1 mg/kg) daily from E9 to E16.

The effect of prenatal morphine exposure on memory consolidation in the chick

The central nervous system exhibits remarkable plasticity in early life and can be altered significantly by prenatal morphine exposure. Previous studies show that prenatal morphine exposure may alter the capacity for learning and memory in post-partum chicks. The one-trial passive avoidance learning paradigm with 1-day-old chicks is an excellent model to study several mechanisms of memory formation, including STM, ITM, and LTM. The following represents our investigation of the effect of prenatal morphine exposure on learning and memory deficits in the chick. In these experiments, morphine was injected into the airspace of eggs (20 mg/kg) and the one-trial passive avoidance learning paradigm was used to test the effect of prenatal morphine exposure on memory consolidation. The data suggest that chicks injected with morphine daily from E12 to E16 had significantly impaired long-term memory at 120 min after training (p<0.001) but not intermediate-term memory at 30 min after training.