Reinforcing properties of alcohol in rats: Progressive ratio licking performance reinforced with 66% alcohol.

Rodents are generally reluctant to consume high concentrations of alcohol. However, few experiments have reported the behavior of rats when they are given access to high alcohol concentrations. Four experiments with food-deprived Wistar rats were designed to determine whether 66% alcohol could be used as a positive reinforcer for operant responses. In Experiment 1, animals learned to lick an empty sipper to gain access to 66% alcohol in a second tube; licking extinguished after it if provided a only access to water (operant licking task, OL). Experiment 2 used the OL task combined with a progressive ratio (PR) schedule in a within-subject design with the order of alcohol concentrations counterbalanced across subjects. The breakpoint (the last completed ratio in the PR schedule) was higher for 10% and 66% alcohol concentrations than for water. In Experiment 3, animals trained in the same PR task gained access to water, 10%, or 66% alcohol in a between-subject design. Breakpoints were higher for 66% alcohol than for water, but not for 10% alcohol relative to water. Experiment 4 tested the effects of the orexin-1 receptor antagonist SB-334,867 on licking reinforced with access to 66% alcohol in the PR task. The antagonist reduced the breakpoint at 1- and 5-mg/kg doses, but not at 10 mg/kg. These results suggest that 66% alcohol can be used to reinforce operant behavior. Although the effects were modest, they were reliable. The estimated amount of alcohol consumed in the OL task suggests that these reinforcing effects were not dependent on the pharmacological effects of 66% alcohol, but could perhaps reflect a sensation-seeking effect.

Sex differences in the impact of childhood socioeconomic status on immune function.

Early life stress increases one's risk for health problems later in life, and many studies find that these effects are sex-differentiated. Here, we examined relationships between multiple sources of early life stress and adult immune function in humans across several functional assays. Adult participants provided retrospective information about their childhood (a) socioeconomic status, (b) household unpredictability, and (c) exposure to adverse experiences. Participants' peripheral blood mononuclear cells (PBMCs) were then isolated for use in functional assays of immune performance: (a) tumor cell lysis by natural killer cells, (b) phagocytosis of Escherichia coli bioparticles, and (c) mitogen-induced leukocyte proliferation and cytokine release. In men, lower childhood socioeconomic status predicted decrements in immunological performance across functional assays, along with greater spontaneous cytokine release from PBMCs. These changes co-occurred with elevations in plasma testosterone levels. Similar effects were not observed for other sources of stress, nor were they found in women (with the exception of spontaneous cytokine release). These findings provide evidence that low childhood socioeconomic status has a lasting negative impact on multiple aspects of immune function, particularly in men.

Chronic sleep restriction increases soluble hippocampal Aß-42 and impairs cognitive performance.

Currently, over 44 million people worldwide suffer from Alzheimer's disease (AD). A common feature of AD is disrupted sleep. Sleep is essential for many psychological and physiological functions, though 35.3% of adults report getting less than 7 hours per night. The present research examined whether chronic sleep restriction would elevate hippocampal amyloid-beta1-42 expression or alter cognitive ability in adult C57BL/6 mice. Chronic sleep restriction was associated with cognitive impairment and increased hippocampal amyloid-beta. Thus, chronic sleep loss may have a detrimental effect upon cognitive function, in part, via increasing amyloid-beta levels in the hippocampus, even in non-genetically modified mice.

Inflammation Predicts Decision-Making Characterized by Impulsivity, Present Focus, and an Inability to Delay Gratification.

Here, we propose a novel theoretical model linking present-focused decision-making to the activities of the immune system. We tested our model by examining the relationship between inflammatory activity - in vivo and in vitro - and decision-making characterized by impulsivity, present focus, and an inability to delay gratification. Results support our model, revealing that inflammation predicts these outcomes even after controlling for factors that may contribute to a spurious linkage between them. Moreover, subsequent analyses revealed that our model was a better fit for the data than alternative models using present-focused decision-making and its health-harming behavioural sequelae (e.g., smoking, risky sexual behaviour) to predict inflammation, lending support for the proposed directionality of this relationship. Together, these results suggest that inflammation may contribute to decision-making patterns that can result in undesirable personal and societal outcomes.

Day length predicts investment in human immune function: Shorter days yield greater investment.

Winter is characterized by stressful conditions which compromise health and render animals more vulnerable to infection and illness than during other times of the year. Organisms are hypothesized to adapt to these seasonal stressors by increasing investment in immune function in response to diminished photoperiod duration. Here, we examined this hypothesis in a sample of healthy human participants. Using several functional immune assays in vitro, as well as by utilizing measures of in vivo proinflammatory cytokine levels, we predicted that shorter day length would be associated with greater investment in immunological function. Results revealed that shorter days predicted significant upregulation of several facets of immune function, including natural killer cell cytotoxicity, peripheral blood mononuclear cell proliferation (in response to, and in the absence of stimulation), and plasma levels of interleukin-6, as well as lower rates of Staphylococcus aureus growth in serum ex vivo. Further, consistent with the hypothesis that these trade-offs would be offset by decreased investment in mating effort, shorter day length also predicted lower levels of total testosterone in men. These results suggest that ambient photoperiod may be a powerful regulator of human immunological activity, providing some of the first evidence of seasonal changes in multiple facets of human immune function.

Behavioral immune system activity predicts downregulation of chronic basal inflammation.

Here, we present a mechanistically grounded theory detailing a novel function of the behavioral immune system (BIS), the psychological system that prompts pathogen avoidance behaviors. We propose that BIS activity allows the body to downregulate basal inflammation, preventing resultant oxidative damage to DNA and promoting longevity. Study 1 investigated the relationship between a trait measure of pathogen avoidance motivation and in vitro and in vivo proinflammatory cytokine production. Study 2 examined the relationship between this same predictor and DNA damage often associated with prolonged inflammation. Results revealed that greater trait pathogen avoidance motivation predicts a) lower levels of spontaneous (but not stimulated) proinflammatory cytokine release by peripheral blood mononuclear cells (PBMCs), b) lower plasma levels of the proinflammatory cytokine interleukin-6 (IL-6), and c) lower levels of oxidative DNA damage. Thus, the BIS may promote health by protecting the body from the deleterious effects of inflammation and oxidative stress.