Influencia do ciclo estral e do estresse sobre a sensibilidade as catecolamidas em atrios de ratas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

This study was performed to analyse the alterations in sensitivity to catecholamines in right atria isolated (AD) from rats submitted to footshock stress and sacrificed at estrus or diestrus. Adult Wistar female rats exhibiting regular 4-day estrous cycles were submitted to three footshock sessions at estrus, metestrus and diestrus or at diestrus, proestrus and estrus. Each rat received during 30 min, 120 electric shocks (1. 0 mA, 1.0 s) at variable intervals of 5 to 25 s. After the last session, the animals were sacrificed and its right atria set up for isometric recording of spontaneous beating. Dose-response curves to noradrenaline (NA), adrenaline (ADR) and soterenol (SQ) were obtained before "in vitro" treatment. To analyse the mechanisms of the alterations in sensitivity one or more of the following "in vitro" treatment were used: sympathetic denervation, inhibition of the extraneuronal uptake and neuronal reuptake and blockade of alpha adrenoceptors and muscarine receptors. Data were compared by using analysis of variance followed by Scheffé test and student t-test. Differences were considered significant at p <0,05. Right atria from rats submitted to footshock stress and sacrificed at diestrus compared to those from control rats showed subsensitivity to ADR (pD2 = 7.38 ` + or -´ 0,09 vs. 6.63 ` + or -´ 0,08), NA (pD2 = 7.67 ` + or -´ 0.11 vs. 6.95 ` + or -´ 0,13) and SQ (pD2 = 6.80 ` + or -´ 0.13 vs. 6.36 ` + or -´ 0.07). The inhibition of neuronal reuptake canceled the subsensitivity to NA (pD2 = 7.88 ` + or -´ 0.06 vs. 7.73 ` + or -´ 0.08). After complete "in vitro" treatment AD from stressed rats showed subsensitivity to NA (pD2 = 8.10 ` + or -´ 0.11 vs 7.68 ` + or -´ 0.14) however the subsensitivity to ADR was canceled (pD2 = 7.67 ` + or -´ 0.13 vs. 7.49 ` + or -´ 0.08) but returned afier addition of butoxamine (pD2 = 7.51` + or -´ 0.05 vs. 7.15` + or -´ 0.13). Right atria from stressed rats sacrificed at estrus were also subsensitive to ADR afier addition of butoxamine (pD2 = 7.59 ` + or -´ 0.05 vs. 7.17 ` + or -´ 0.07). These results demonstrat that footshock stress, induces an increase in the efficiency of the neuronal reuptake process, desensitization of `beta 1´adrenoceptors and increase in `beta 2´-adrenoceptor-mediated response in right atria from female rats sacrificed at diestrus. During estrus it seems that those adaptive responses of the chronotropic control of the heart by catecholamines do not occur with the exception of the increase in `beta 2´-adrenoceptor-mediated response

ASSUNTO(S)

stress (fisiologia) estro receptores de substancias endogenas adrenalina

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