1. The effects of three daily sessions of inescapable footshock on the sensitivity of rat isolated right atria to the chronotropic effect of norepinephrine, tyramine and soterenol were studied. 2. Inescapable footshock induces subsensitivity to norepinephrine and tyramine. The maximum response to the partial agonist soterenol was reduced. 3. In vitro denervation and addition of cocaine prevented the demonstration of inescapable footshock-induced subsensitivity to norepinephrine. 4. It is concluded that repeated inescapable footshock stress reduces the number of atrial beta 1-adrenoceptors and increases the efficiency of the neuronal reuptake process.18473-7