High ambient temperature reduces rate of body-weight loss produced by wheel running.
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: La Anorexia Basada en Actividad (ABA) es un fenómeno que resulta de exponer a ratas a un programa de alimentación de entre 1 y 1.5 h al día, concediéndole libre acceso a una rueda de actividad el resto del tiempo. Los efectos reportados son niveles altos de actividad sin una aparente compensación en la ingesta de comida y, en consecuencia, bajo peso corporal. Existen varias interpretaciones sobre las causas de este fenómeno, sin embargo, se reconocen dos principales teorías. Una de ellas afirma que la ABA es producto de un fallo adaptativo al nuevo régimen de alimentación y que la actividad en la rueda interfiere con esta adaptación. La segunda postura teórica afirma que la actividad adquiere propie-dades reforzantes debido a la restricción de los alimentos, y que ella genera pér-dida de peso y a su vez mayor actividad. Hasta el momento, ambas teorías han sido interpretadas contradictoriamente, no obstante, una serie de estudios ha revelado que la temperatura ambiental, y en consecuencia la temperatura corporal de los sujetos, juega un papel esencial en los hallazgos en el área, lo cual da sentido a ambas teorías y pone en evidencia su complementariedad. El objetivo de este documento es revisar la evidencia empírica que apoya la hipótesis de la ABA como un fenómeno de termorregulación.
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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.07/2012; 19(2):89-96.
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ABSTRACT: The potential involvement of the melanocortin system in the beneficial effects of heat application in rats submitted to activity-based anorexia (ABA), an analogous model of anorexia nervosa (AN), was studied. Once ABA rats had lost 20% of body weight, half of the animals were exposed to a high ambient temperature (HAT) of 32 degrees C, whereas the rest were maintained at 21 degrees C. Control sedentary rats yoked to ABA animals received the same treatment. ABA rats (21 degrees C) showed increased Melanocortin 4 (MC4) receptor and Agouti gene Related Peptide (AgRP) expression, and decreased pro-opiomelanocortin (POMC) mRNA levels (Real Time PCR), with respect to controls. Heat application increased weight gain and food intake, and reduced running rate in ABA rats, when compared with ABA rats at 21 degrees C. However, no changes in body weight and food intake were observed in sedentary rats exposed to heat. Moreover, heat application reduced MC4 receptor, AgRP and POMC expression in ABA rats, but no changes were observed in control rats. These results indicate that hypothalamic MC4 receptor overexpression could occur on the basis of the characteristic hyperactivity, weight loss, and self-starvation of ABA rats, and suggest the involvement of hypothalamic melanocortin neural circuits in behavioural changes shown by AN patients. Changes in AgRP and POMC expression could represent an adaptative response to equilibrate energy balance. Moreover, the fact that HAT reversed hypothalamic MC4 receptor overexpression in ABA rats indicates the involvement of brain melanocortin system in the reported beneficial effects of heat application in AN. A combination of MC4 receptor antagonists and heat application could improve the clinical management of AN.Psychoneuroendocrinology 12/2008; 34(3):420-9. DOI:10.1016/j.psyneuen.2008.10.003 · 5.59 Impact Factor