Body weight regulation over the estrous cycle of the rat: Basal insulin levels and effect of vagotomy

In the first of two experiments basal insulin levels were measured over the estrous cycle of the adult, female rat. Insulin levels were found to be significantly depressed at diestrus compared to both proestrus and estrus. In the second experiment it was found that neither this insulin depression nor the weight gain normally observed during diestrus was affected by bilateral subdiaphragmatic vagotomy. Thus, the rhythm of diestrual weight gain-insulin depression observed in the rat does not parallel other forms of obesity which are dependent upon elevated insulin levels and/or the integrity of the vagus for their expression.