although the selective down-regulation of alpha 1- and beta 1-adrenergic receptors may reflect a response to the preponderance of norepinephrine in these animals , the results indicate that different tissues and different adrenergic receptor subtypes may have varying susceptibility to down-regulation in response to increased circulating catecholamines in vivo .
C0001642
beta 1-adrenergic receptors
C0034783
adrenergic receptor