Relationship between food intake and metabolic rate in rats treated with beta-adrenoceptor agonists.

The purpose of the present experiment was to clarify the interaction between food intake and activity of the thermogenic component of the sympathetic nervous system by studying the dose response relationships of typical beta 1-, beta 2-, and beta 3-adrenoceptor agonists on oxygen consumption and food intake. The data showed that the ED50 for the effects of Dobutamine (beta 1), Clenbuterol (beta 2) and ICI D7114 (beta 3) agonists on food intake were 8.9, 0.041 and > 1.1 mumol/kg respectively whereas the ED50 values for stimulation of metabolic rate were 7.1, 1.3 and 0.11 mumole/kg respectively. The marked differences in ED50 values for suppression of food intake and stimulation of metabolic rate for both clenbuterol and ICI D7114 suggest that the regulation of feeding and of metabolic rate in response to these agonists are independent of each other. The experiments also identified that Clenbuterol activated a very sensitive beta 2-adrenergic system for the regulation of feeding behavior.