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Obesity is a world problem that requires a better understanding of its physiological and genetic basis, as well as the mechanisms by which the hypothalamus controls feeding behavior. The volcano mouse Neotomodon alstoni develops obesity in captivity when fed with regular chow diet, providing a novel model for the study of obesity. Females develop obesity more often than males; therefore, in this study, we analysed in females, in proestrous lean and obese, the differences in hypothalamus expression of receptors for leptin, ghrelin (growth hormone secretagogue receptor GHS-R), and VPAC, and correlates for plasma levels of total ghrelin. The main comparisons are between mice fed ad libitum and mice after 24 hours of fasting. Mice above 65 g body weight were considered obese, based on behavioral and physiological parameters such as food intake, plasma free fatty acids, and glucose tolerance. Hypothalamic tissue from obese and lean mice was analysed by western blot. Our results indicate that after ad libitum food access, obese mice show no significant differences in hypothalamic leptin receptors, but a significant increase of 60% in the GHS-R, and a nearly 62% decrease in VPAC2 was noted. After a 24-hour fast, plasma ghrelin increased nearly two fold in both lean and obese mice; increases of hypothalamic leptin receptors and GHS-R were also noted, while VPAC2 did not change significantly; levels of plasma free fatty acids were 50% less after fasting in obese than in lean animals. Our results indicate that in obese N. alstoni mice, the levels of orexigenic receptors in the hypothalamus correlate with overfeeding, and the fact that lean and obese females respond in different ways to a metabolic demand such as a 24-hour fast.

Some Mexican volcano mice (Neotomodon alstoni), when in captivity and fed regularly on a laboratory rodents' diet, develop obesity. The aims of the present work are to compare lean and obese mice with regard to the main characteristics of the sleep-wake cycle in 12:12 LD, and to investigate if there is a correlation with changes in metabolic-related blood parameters (leptin, insulin, triacylglycerides, corticosterone and the glucose tolerance test). The analysis of the sleep-wake cycle evaluated the temporal distribution of vigilance states and indicated a polyphasic architecture. Trends were observed in obese mice to have increased percentages of slow wave sleep and decreased wakefulness, but the percentage of rapid eye movement sleep was not different. Obese mice had higher concentrations of leptin and insulin, and showed a slower glucose removal from blood at noon than at midnight, indicating a possible resistance to these hormones. We propose that volcano mice are a good model for studying daily rhythms and metabolic disorders related to obesity.