Relationship Between The Level Of Stress And Supersensitivity To Norepinephrine In Female Rats At Proestrus [relação Entre Nível De Estresse E Supersensibilidade à Norepinefrina Em Ratas No Proestro]

We studied the relationship between the level of stress and the sensitivity to norepinephrine (NE) in female rats submitted to swimming stress. Female rats at estrus or proestrus were submitted to one 50-min-swimming session. The experiments were recorded and the level of stress was evaluated by the scape try time (active swimming, close to the boards of the tank as if the animal was looking for exit) and by the time of immobility (floating). Immediately after the stress session, the animal was sacrificed and its right atria set up for isometric recording of spontaneous beating. Concentration-effect curves to NE were obtained in tissues from stressed and control rats. Scape try time at proestrus was higher than at estrus. The immobility time was significantly lower at proestrus compared to estrus. Swimming stress induced supersensitivity to NE in right atria from rats at proestrus, without changes at estrus. 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