Effects of clenbuterol, a beta 2-adrenoceptor agonist, on macronutrient selection in rats

In these studies, clenbuterol, a beta 2-adrenergic agonist, was injected into male rats and the intake of a three-choice macronutrient diet was measured. The intakes of fat and protein were selectively inhibited by clenbuterol in both overnight-fasted and freely fed rats. There was no effect of clenbuterol on carbohydrate intake. Prior administration of nadolol, a beta-adrenergic antagonist, which does not easily pass the blood-brain barrier, completely antagonized the anorectic effect of clenbuterol. However, section of the hepatic branch of the vagus nerve did not abolish the nadolol effect. These results suggest that the anorectic effect of clenbuterol is mediated by peripheral beta 2-adrenergic receptors rather than central beta 2-adrenoceptors, and is not related to information transmitted from the liver via the vagus nerve.