Background Men and women differ in their ability to extinguish fear. Fear extinction requires the activation of brain regions including the ventromedial prefrontal cortex (vmPFC) and amygdala. Could estradiol modulate the activity of these brain regions during fear extinction? Methods All rat experiments were conducted in naturally cycling females. Rats underwent fear conditioning on day 1. On day 2, they underwent extinction training during the metestrus phase of the cycle (low estrogen and progesterone). Extinction recall was assessed on day 3. Systemic injections of estrogen-receptor beta and alpha agonists, and estradiol were administered at different time points to assess their influence on extinction consolidation and c-fos expression in the vmPFC and amygdala. In parallel, healthy naturally cycling women underwent an analogous fear conditioning extinction training while in a 3T fMRI scanner. Measurement of their estradiol levels and skin conductance responses were obtained throughout the experiment. Results In female rats, administration of the estrogen-receptor beta (but not alpha) agonist facilitated extinction recall. Immediate (but not delayed) post-extinction training administration of estradiol facilitated extinction memory consolidation and increased c-fos expression in the vmPFC while reducing it in the amygdala. In parallel, natural variance in estradiol in pre-menopausal cycling women modulated vmPFC and amygdala reactivity and facilitated extinction recall. Conclusion We provide translational evidence that demonstrates the influence of endogenous and exogenous estradiol on the fear extinction network. Our data suggest that women’s endogenous hormonal status should be considered in future neurobiological research related to anxiety and mood disorders.

Drug-induced liver injury (DILI) limits the development and utilization of numerous therapeutic compounds, and consequently presents major challenges to the pharmaceutical industry and clinical medicine1, 2. Acetaminophen (APAP) containing compounds are among the most frequently prescribed drugs, and also the most common cause of DILI3. Here we describe a pharmacological strategy that targets gap junction communication to prevent amplification of fulminant hepatic failure and APAP-induced hepatotoxicity. We report that connexin 32 (Cx32), a key hepatic gap junction protein, is an essential mediator of DILI by showing that mice deficient in Cx32 are protected against liver damage, acute inflammation, and death. We identified a small molecule inhibitor of Cx32 as a novel hepatoprotectant that achieves the same result in wildtype mice when coadministered with known hepatotoxic drugs. These findings demonstrate that gap junction inhibition is an effective therapy for limiting DILI, and suggest a novel pharmaceutical strategy to improve drug safety.

BackgroundEnvironmental enrichment (EE) fosters attachment behavior through its effect on brain oxytocin levels in the hippocampus and other brain regions, which in turn modulate the hypothalamic-pituitary axis (HPA). Social isolation and other stressors negatively impact physical healing through their effect on the HPA. Therefore, we reasoned that: 1) provision of a rat EE (nest building with Nestlets®) would improve wound healing in rats undergoing stress due to isolation rearing and 2) that oxytocin would have a similar beneficial effect on wound healing.Methodology/Principal FindingsIn the first two experiments, we provided isolation reared rats with either EE or oxytocin and compared their wound healing to group reared rats and isolation reared rats that did not receive Nestlets or oxytocin. In the third experiment, we examined the effect of Nestlets on open field locomotion and immediate early gene (IEG) expression. We found that isolation reared rats treated with Nestlets a) healed significantly better than without Nestlets, 2) healed at a similar rate to rats treated with oxytocin, 3) had decreased hyperactivity in the open field test, and 4) had normalized IEG expression in brain hippocampus.Conclusions/SignificanceThis study shows that when an EE strategy or oxytocin is given to isolation reared rats, the peripheral stress response, as measured by burn injury healing, is decreased. The findings indicate an association between the effect of nest making on wound healing and administration of the pro-bonding hormone oxytocin. Further elucidation of this animal model should lead to improved understanding of how EE strategies can ameliorate poor wound healing and other symptoms that result from isolation stress.