Alpha-Receptor Subsensitivity of Isolated Atria from Rats Following Physical Training or Repeated ACTH-Injections

Abstract
Decreased chronotropic and inotropic sensitivity of isolated atria to phenylephrine but not to isoprenaline was found in rats following repeated physical training by swimming or repeated ACTH-injections. These changes were induced within a week of subjection of animals to these treatments. These effects are apparently mediated by increased adrenergic activity which results in this subsensitivity of .alpha.-receptors.