Influencia do sexo e das fases do ciclo estral sobre a reação de estresse em ratos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

We studied the influence of sex and estrous cyc1e on the response of rats to swimming stress, at 30°C. The sensitivity to cathecolamines of isolated right atria and corticosterone plasma levels on male rats and female rats at estrus or diestrus were analysed after one swimming session of 5, 15, 30 or 50 min (single stress) or after three sessions of 5, 15 and 30 mino In female rats, repeated swimming sessions were applied during diestrus, metestrus and estrus (estrus group), or during estrus, metestrus and diestrus (diestrus group). Dose-response curves to isoprenaline, noradrenaline and adrenaline were obtained in right atria isolated from rats after a 30 min or 50 min session, or after the last swimming session of repeated stress. Blood was withdrawn from the left renal vein under pentobarbital anestesy, and corticosterone plasma levels were determined fluorimetrically. Right atria isolated from male rats submitted to swimming stress at 30°C did not present any alteration on sensitivity to catecholamines. Tissue isolated from rats at estrus exhibited subsensitivity to isop_enaline after a 50 min swimming session. Right atria isolated from rats at diestrus showed subsensitivity to noradrenaline and to adrenaline after a single 50 min swimming session or after repeated stress. Corticosterone plasma levels of mal e rats showed an increase after 5, 15 and 30 min of swimming, but not after a 50 min session compared to the control group. In female rats at estrus, corticosterone plasma levels were increased in all experimental groups. However the variation profile was different comparing male with female rats. There was a large variation ofthe hormonal response to swimming stress within each group. After repeated stress, corticosterone plasma levels of male and female rats increased. However, in the third session, whereas mal e rats exhibited a higher plasma corticosterone leves, female rats showed lower increase than those observed after the two previous sessions. Our results demonstrated that sex and estrous cyc1e have an important influence on the stress response to swimmming in rats. Significant increase on corticosterone plasma levels are necessary, but not sufficient, to induce changes on sensitivity to catecholamines. There is also a large individual variation on the hormonal response to swimming stress

ASSUNTO(S)

estro natação corticosterona ciclo sexual adrenalina receptores de substancias endogenas

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