Reserpine-induced supersensitivity to the activation of cardiac glycogen phosphorylase by calcium.

Rats receiving reserpine (2.5 mg/kg, 24 h before sacrifice) developed a supersensitivity to the phosphorylase activating effect of both noradrenaline and Ca2+. Supersensitivity to the inotropic and chronotropic effects of the agonists did not develop with this dose of reserpine. It is concluded that reserpine induced supersensitivity, as well as being dose and species dependent, is also dependent on the response measured. It is concluded further that the supersensitivity developed to noradrenaline may be due to an alteration in the responding system (in this case the phosphorylase activating system) to calcium.