It takes two: Bilateral bed nuclei of the stria terminalis mediate the expression of contextual fear, but not of moderate cued fear.

A growing body of research supports a prominent role for the bed nucleus of the stria terminalis (BST) in the expression of adaptive and perhaps even pathological anxiety. The traditional premise that the BST is required for long-duration responses to threats, but not for fear responses to distinct, short-lived cues may, however, be oversimplified. A thorough evaluation of the involvement of the BST in cued and contextual fear is therefore warranted. In a series of preregistered experiments using male Wistar rats, we first addressed the involvement of the BST in cued fear. Following up on earlier work where we found that BST lesions disrupted auditory fear while the animals were in a rather high stress state, we here show that the BST is not required for the expression of more specific fear for the tone under less stressful conditions. In the second part, we corroborate that the same lesion method does attenuate contextual fear. Furthermore, despite prior indications for an asymmetric recruitment of the BST during the expression of anxiety, we found that bilateral lesioning of the BST is required for a significant attenuation of the expression of contextual fear. A functional BST in only one hemisphere resulted in increased variability in the behavioral outcome. We conclude that, in animals that acquired a fear memory with an intact brain, the bilateral BST mediates the expression of contextual fear, but not of unambiguous cued fear.

FAS inhibitor cerulenin reduces food intake and melanocortin receptor gene expression without modulating the other (an)orexigenic neuropeptides in chickens.

Cerulenin, a natural fatty acid synthase (FAS) inhibitor, and its synthetic analog C75 are hypothesized to alter the metabolism of neurons in the hypothalamus that regulate ingestive behavior to cause a profound decrease of food intake and an increase in metabolic rate, leading to body weight loss. The bulk of data exclusively originates from mammals (rodents); however, such effects are currently lacking in nonmammalian species. We have, therefore, addressed this issue in broiler chickens because this species is selected for high growth rate and high food intake and is prone to obesity. First, we demonstrate that FAS messenger and protein are expressed in the hypothalamus of chickens. FAS immunoreactivity was detected in a number of brain regions, including the nucleus paraventricularis magnocellularis and the nucleus infundibuli hypothalami, the avian equivalent of the mammalian arcuate nucleus, suggesting that FAS may be involved in the regulation of food intake. Second, we show that hypothalamic FAS gene expression was significantly (P < 0.05) decreased by overnight fasting similar to that in liver, indicating that hypothalamic FAS gene is regulated by energy status in chickens. Finally, to investigate the physiological consequences of in vivo inhibition of fatty acid synthesis on food intake, we administered cerulenin by intravenous injections (15 mg/kg) to 2-wk-old broiler chickens. Cerulenin administration significantly reduced food intake by 23 to 34% (P < 0.05 to P < 0.0001) and downregulated FAS and melanocortin receptors 1, 4, and 5 gene expression (P < 0.05). However, the known orexigenic (neuropeptide Y, agouti gene-related peptide, orexin, and orexin receptor) and anorexigenic (pro-opiomelanocortin and corticotropin-releasing hormone) neuropeptide mRNA levels remained unchanged after cerulenin treatment. These results suggest that the catabolic effect of cerulenin in chickens may be mediated through the melanocortin system rather than the other neuropeptides known to be involved in food intake regulation.

The combined effect of lead exposure and high or low dietary calcium on health and immunocompetence in the zebra finch (Taeniopygia guttata).

The widespread contamination by lead and the acidification of the environment ask for a better understanding of the effects of the interaction between lead and calcium on various aspects of health, including disease defense, in wildlife. Here, we investigated the effects of chronic exposure to sublethal levels of lead, combined with high or low dietary calcium, on health and several components of immunity in male and female zebra finches (Taeniopygia guttata). Thirty individuals of each sex were randomly assigned to three groups: a control group, a group exposed to lead with an additional calcium source (i.e. grit) and a group exposed to lead without access to an extra calcium source. Lead was administered as lead acetate via the drinking water (20 ppm) for 38 consecutive days. Exposure to lead increased significantly the concentrations of lead in kidney and bone in individuals of the experimental groups. Furthermore, the lack of a calcium supplement significantly enhanced the uptake of lead. Lead did not affect health indices such as hematocrit, spleen mass and body mass, nor the adrenal stress response. Cell-mediated immune responsiveness, assessed by a delayed-type hypersensitivity response to phytohaemagglutinin, was also not affected by lead exposure. On the other hand, lead exposure did significantly suppress the secondary humoral immune response towards sheep red blood cells in females, but only when the additional calcium source was not available. This effect was not found in males, suggesting sexual differences in susceptibility of humoral immunity to lead treatment in zebra finches.