Physiology & behavior
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Physiology & behavior · Jan 2007
Chronic restraint or variable stresses differently affect the behavior, corticosterone secretion and body weight in rats.
Organisms are constantly subjected to stressful stimuli that affect numerous physiological processes and activate the hypothalamo-pituitary-adrenal (HPA) axis, increasing the release of glucocorticoids. Exposure to chronic stress is known to alter basic mechanisms of the stress response. The purpose of the present study was to compare the effect of two different stress paradigms (chronic restraint or variable stress) on behavioral and corticosterone release to a subsequent exposure to stressors. ⋯ Exposure to chronic restraint leads to increased novelty-induced locomotor activity. Furthermore, only the exposure to variable stress reduced body weights. In conclusion, the present results provide additional evidence on how chronic stress affects the organism physiology and point to the importance of the chronic paradigm and challenge stress on the behavioral and hormonal adaptations induced by chronic stress.
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Physiology & behavior · Nov 2006
ReviewMetabolic sensing neurons and the control of energy homeostasis.
The brain and periphery carry on a constant conversation; the periphery informs the brain about its metabolic needs and the brain provides for these needs through its control of somatomotor, autonomic and neurohumoral pathways involved in energy intake, expenditure and storage. Metabolic sensing neurons are the integrators of a variety of metabolic, humoral and neural inputs from the periphery. Such neurons, originally called "glucosensing", also respond to fatty acids, hormones and metabolites from the periphery. ⋯ In some obese individuals, the relative sensitivity of metabolic sensing neurons to various peripheral inputs is genetically reduced. This may provide one mechanism underlying their propensity to become obese when exposed to diets high in fat and caloric density. Thus, metabolic sensing neurons may provide a potential therapeutic target for the treatment of obesity.
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Physiology & behavior · Sep 2006
Comparative StudyTasting fat: cephalic phase hormonal responses and food intake in restrained and unrestrained eaters.
Restrained eaters exhibit strict cognitive control over their food intake, primarily by limiting intake of high-fat foods. Earlier studies indicate a relationship between dietary restraint and cephalic phase insulin release, which is hypothesized to influence hunger and food intake. To compare cephalic phase hormonal responses to high- and low-fat stimuli and determine if the sensory experience of tasting fat alters hormonal responses and influences subsequent food intake in restrained and unrestrained eaters, normal weight women classified as unrestrained (n=11) or restrained (n=11) eaters were tested under 3 conditions: (1) fasting, (2) sham-feeding a non-fat cake, and (3) sham-feeding a high-fat cake. ⋯ Cephalic phase PP was significantly greater following oral sensory stimulation by the high-fat food (205.4+/-83.6) compared to the fasting control (11.1+/-38.8, p=0.04). No significant differences in hormonal responses to the food stimuli were found between restrained and unrestrained eaters but the restrained eaters consumed more food after the high-fat condition (p<0.05) relative to the fasted condition and compared to the unrestrained group (p<0.05). In conclusion, the sensory experience of tasting fat increases food intake in restrained eaters and increases vagal efferent activity compared to a non-fat food in both populations.
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Physiology & behavior · Aug 2006
ReviewGhrelin and the short- and long-term regulation of appetite and body weight.
Ghrelin, an acylated upper gastrointestinal peptide, is the only known orexigenic hormone. Considerable evidence implicates ghrelin in mealtime hunger and meal initiation. Circulating levels decrease with feeding and increase before meals, achieving concentrations sufficient to stimulate hunger and food intake. ⋯ Congenital ablation of the ghrelin or ghrelin-receptor gene causes resistance to diet-induced obesity, and pharmacologic ghrelin blockade reduces food intake and body weight. Ghrelin levels are high in Prader-Willi syndrome and low after gastric bypass surgery, possibly contributing to body-weight alterations in these settings. Extant evidence favors roles for ghrelin in both short-term meal initiation and long-term energy homeostasis, making it an attractive target for drugs to treat obesity and/or wasting disorders.
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Physiology & behavior · Jun 2006
Comparative StudyLasting anxiogenic effects of feline predator stress in mice: sex differences in vulnerability to stress and predicting severity of anxiogenic response from the stress experience.
Previous work in male Swiss Webster (CFW) mice demonstrated a long lasting effect of predator stress on risk assessment in the elevated plus maze (EPM). Most severe effects (increases in risk assessment) were seen following a brief unprotected exposure to a cat. Lesser effects were produced by a brief exposure of mice to the cat exposure room without a cat in the room (room stress). ⋯ Finally, factor analysis indicated that different tests of anxiety-like behavior may be measuring different and independent aspects of mouse affect. Moreover, stressors had no lasting effects on sugar solution consumption. Implications of these findings for modeling PTSD and using transgenic strains of mice to study lasting effects of stress on affect are discussed.