STRESS-INDUCED SUBSENSITIVITY TO CATECHOLAMINES DEPENDS ON THE ESTROUS-CYCLE

In this article we compare how sensitivity to the chronotropic effect of noradrenaline and adrenaline of right atria isolated from female ra ts is modified after repeated swimming or foot-shock stress, under the influence of the estrous cycle. Right atria from stressed female rats sacrificed at diestrus were subsensitive to both catecholamines, irre spective of the stressor agent. However, although subsensitivity to no radrenaline was of similar intensity, subsensitivity to adrenaline was more pronounced in right atria from foot shock stressed rats as oppos ed to swimming-stressed rats. Identical stress protocols did not induc e any alteration in atrial sensitivity to catecholamines when the stre ssed female rats were sacrificed at estrus. We conclude that the stres s reaction concerning the mediation of cardiac chronotropism by catech olamines is related to the severity of the stressor agent and is stron gly influenced by the estrous cycle.