High ambient temperature reduces rate of body-weight loss produced by wheel running.

Universidad de Santiago, Santiago de Compostela, Spain.
Quarterly journal of experimental psychology (2006) (Impact Factor: 1.73). 08/2006; 59(7):1196-211. DOI: 10.1080/17470210500417688
Source: PubMed

ABSTRACT This study examined the effect of ambient temperature (AT) on the relationship between activity and weight loss. Compared with a neutral AT of 21 degrees C, high ATs of 27-29 degrees C produced a slower rate of weight loss in rats given 1.5-hr food access and 22.5-hr running-wheel access in a standard activity-based anorexia (ABA) procedure (Experiments 1 and 2). The high AT did not affect food intake or wheel running in Experiment 1, but did reduce running in Experiment 2. Switching from neutral to high AT had only a transient effect on weight loss when wheel access was maintained (Experiment 2) but resulted in less weight loss when wheel access was prevented (Experiment 3). Giving rats only 3 hr of wheel access each day at a neutral AT also produced substantial weight loss, but less if for the rest of each day they were maintained at a high AT (Experiment 4).

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    ABSTRACT: Activity Based Anorexia (ABA) is a phenomenon that results from exposing rats to a feeding program of about 1 to 1.5 h per day, giving them free access to an activity wheel the rest of the time. The reported effects are high levels of activity without a visible compensation in food intake, and in consequence a low body weight. There is a variety of interpretations about the causes of this phenomenon. However, there are two main theories: one of them says that ABA is a product of adaptive failure to the new feeding regime and that the activity in the wheel interferes with such adaptation. The second theoretical position says that the activity acquires reinforcing properties due to feeding restrictions which causes body weight loss and, in turn, more activity. At present, both theories have been interpreted as contradictory. Nevertheless, a series of studies have revealed that the temperature of the environment and in consequence the subjects’ body temperature play an essential role in the findings of the field, giving sense to both theories and evidencing their complementariness. The aim of this paper is to review the empirical evidence that supports the hypothesis of ABA as a thermoregulation phenomenon.
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    ABSTRACT: Anorexia nervosa (AN) is an eating disorder characterized by self-imposed severe starvation and often linked with excessive exercise. Activity-based anorexia (ABA) is an animal model that reproduces some of the behavioral phenotypes of AN, including the paradoxical increase in voluntary exercise following food restriction (FR). Although certain rodents have been used successfully in this animal model, C57BL/6 mice are reported to be less susceptible to ABA. We re-examined the possibility that female C57BL/6 mice might exhibit ABA vulnerability during adolescence, the developmental stage/sex among the human population with particularly high AN vulnerability. After introducing the running wheel to the cage for 3 days, ABA was induced by restricting food access to 1 h per day (ABA1, N = 13) or 2 h per day (ABA2, N = 10). All 23 exhibited increased voluntary wheel running (p < 0.005) and perturbed circadian rhythm within 2 days. Only one out of five survived ABA1 for 3 days, while 10 out of 10 survived ABA2 for 3 days and could subsequently restore their body weight and circadian rhythm. Exposure of recovered animals to a second ABA2 induction revealed a large range of vulnerability, even within littermates. To look for the cellular substrate of differences in vulnerability, we began by examining synaptic patterns in the hippocampus, a brain region that regulates anxiety as well as plasticity throughout life. Quantitative EM analysis revealed that CA1 pyramidal cells of animals vulnerable to the second ABA2 exhibit less GABAergic innervation on cell bodies and dendrites, relative to the animals resilient to the second ABA (p < 0.001) or controls (p < 0.05). These findings reveal that C57BL/6J adolescent females can be used to capture brain changes underlying ABA vulnerability, and that GABAergic innervation of hippocampal pyramidal neurons is one important cellular substrate to consider for understanding the progression of and resilience to AN.
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