EFFECTS OF CLENBUTEROL, A BETA(2)-ADRENOCEPTOR AGONIST, ON MACRONUTRIENT SELECTION IN RATS

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