RESUMEN
Adrenalectomized female rats with lesions of the ventromedial hypothalamus or sham lesions were given SC implants of wax pellets or a fused mixture of corticosterone-cholesterol (40, 75, or 130% by weight). In animals with sham lesions, high dosages of corticosterone proved to be catabolic (r = -0.61 between plasma corticosterone and weight change). In marked contrast, animals with VMH lesions displayed substantial weight gains at all circulating levels of corticosterone, with a significant positive correlation (r = +0.48) between these two variables. It is concluded that: a) damage to the basomedial hypothalamus alters an organism's response to corticosterone at both ends of the dose-response curve, and b) both Type I and Type II corticosterone receptors in the brain play a role in hypothalamic obesity.
Asunto(s)
Glándulas Suprarrenales/fisiología , Corticosterona/sangre , Núcleo Hipotalámico Ventromedial/fisiología , Aumento de Peso/fisiología , Adrenalectomía , Hormona Adrenocorticotrópica/sangre , Animales , Glucemia/metabolismo , Mapeo Encefálico , Corticosterona/administración & dosificación , Ingestión de Alimentos/fisiología , Femenino , Insulina/sangre , Ratas , Receptores de Esteroides/efectos de los fármacos , Receptores de Esteroides/fisiología , Núcleo Hipotalámico Ventromedial/efectos de los fármacos , Aumento de Peso/efectos de los fármacosRESUMEN
Marked weight gain was observed in female rats given small electrolytic lesions in the dorsal posterior portion of the amygdala. With a standard lab pellet diet, weight gains typically ranged between 20-30 g during the first 3 postoperative days, and between 60-100 g over the first 20 days. Rats with sham lesions generally gained only 5-15 g in 20 days. The results are consistent with much older studies that reported obesity in cats, dogs, and primates with lesions of the amygdala.
Asunto(s)
Amígdala del Cerebelo/fisiología , Aumento de Peso/fisiología , Animales , Mapeo Encefálico , Dominancia Cerebral/fisiología , Femenino , RatasRESUMEN
The role of adrenal glucocorticoid hormones in the weight gain produced by lesions of the paraventricular nuclei was explored in two experiments. In the first experiment, female rats with PVN lesions were found to have normal a.m. plasma corticosterone concentrations and blunted, albeit still elevated, p.m. concentrations. Nighttime corticosterone levels were moderately correlated with plasma insulin levels. In the second experiment, adrenalectomy markedly suppressed weight gain in animals with very large PVN lesions (mean weight gain of 33.0 g/20 days compared to 137.6 g/20 days for PVN rats with sham adrenalectomies). In the ADX-PVN group, there was a +0.90 correlation between plasma corticosterone levels and weight gain. Administration of corticosterone restored the abnormal weight gain in ADX-PVN animals. It is concluded that the steroid receptors mediating this effect of corticosterone lie outside the hypothalamus.
Asunto(s)
Corticosterona/fisiología , Obesidad/fisiopatología , Núcleo Hipotalámico Paraventricular/fisiología , Adrenalectomía , Animales , Glucemia/metabolismo , Peso Corporal , Corticosterona/sangre , Femenino , Histocitoquímica , Insulina/sangre , Núcleo Hipotalámico Paraventricular/anatomía & histología , RatasRESUMEN
Radio-frequency and anodal electrolytic lesions of the paraventricular nucleus (PVN) were found to produce equal and dramatic increases in body weight in female rats. Neither of the groups with lesions had significantly elevated plasma insulin levels during a period of food restriction, but individual values varied greatly. Both groups displayed marked basal hyperinsulinemia after 30 days of food ad lib. It is concluded that radio-frequency and electrolytic PVN lesions produce similar obesity syndromes.
Asunto(s)
Núcleo Hipotalámico Paraventricular/fisiología , Proyectos de Investigación , Aumento de Peso/fisiología , Animales , Glucemia/análisis , Femenino , Insulina/sangre , Núcleo Hipotalámico Paraventricular/patología , Distribución Aleatoria , RatasRESUMEN
Female rats were subjected to radio-frequency or anodal electrolytic lesions of the ventromedial hypothalamus (VMH) when 28 days old. Blood samples for determination of basal plasma insulin and glucose levels were taken on postoperative day 30 (Experiment 1) and on day 10 (Experiment 2). Body weight and daily food intake of rats with either type of lesion did not differ from unoperated animals during the first 10 days, but rats with electrolytic lesions, unlike radio-frequency lesioned animals, displayed excess food intake and weight gain starting in the third postoperative week. Both types of lesions produced stunted linear growth and a higher than normal Lee Obesity Index. Only the rats with electrolytic VMH lesions were significantly hyperinsulinemic on postoperative day 30, with a mean plasma insulin level that was at least double that observed in unoperated or radio-frequency lesioned animals. On day 10, however, the animals with electrolytic lesions had markedly lower plasma insulin and glucose levels compared to the other two groups, which did not differ from one another. There was no apparent difference in the size of the lesions produced by the two techniques, and it is therefore concluded that some of the endocrine dysfunctions resulting from electrolytic VMH lesions are due to metallic ion deposits (stimulating adjacent tissue) rather than to tissue ablation.