Effect of intracerebroventricular angiotensin II on body weight and food intake in adult rats

We recently reported that intracerebroventricular infusions of ANG II decreased food intake and increased energy expenditure in young rats. The aim of the present study was to determine if intracerebroventricular ANG II has similar effects in adult rats. The time course of the effect was also investigated with the idea that at earlier time points, a potential role for increased hypothalamic expression of corticotropin-releasing hormone (CRH) in the anorexia could be established. Finally, the contribution of ANG II-induced water drinking to the decrease in food intake was directly investigated. Rats received intracerebroventricular saline or ANG II using osmotic minipumps. Food intake, water intake, and body weight were measured daily. Experiments were terminated 2, 5, or 11 days after the beginning of the infusions. ANG II (similar to32 ng.kg(-1).min(-1)) produced a transient decrease in food intake that lasted for 4-5 days although body weight continued to be decreased for the entire experiment most likely due to increased energy expenditure as evidenced by increased uncoupling protein-1 mRNA expression in brown adipose tissue. At 11 and 5 days, the expression of CRH mRNA was decreased. At 2 days, CRH expression was not suppressed even though body weight was decreased. The decrease in food intake and body weight was identical whether or not rats were allowed to increase water consumption. These data suggest that in adult rats ANG II acts within the brain to affect food intake and energy expenditure in a manner that is not related to water intake.