| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2001: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Estrogens are reported to have cardiovascular protective effects, but the mechanisms underlying these effects are not well defined. We investigated the sex difference in stress-induced cardiovascular responses and the effect of estrogen on these responses in free-moving adult rats. Furthermore, we assessed the central role of estrogen on the effect of corticotrophin-releasing hormone (CRH) in stress-induced cardiovascular responses.
Four groups of rats, which consisted of male (M), normal female (NF), ovariectomized+placebo-treated (P) and ovariectomized+estrogen-treated (E) groups, were used in this experiment.
1. Psychological stress was induced by cage-switch stress. After rats were placed in the novel environment, blood pressure and heart rate significantly increased. Blood pressure elevation was attenuated significantly in the NF group compared with the M group. Ovariectomy diminished the sex difference of blood pressure response to the stress.
2. In the M group blood pressure elevat
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ion during cage-switch stress, which was repeated 60 min daily, was weakened on the 2nd and the 3rd days compared with the 1st day, but not in the NF group.
2. The blood pressure responses were suppressed significantly in the E group compared with the P group during cage-switch and restraint stress. The plasma norepinephrine response induced by cage-switch stress was attenuated significantly in the E group.
3. In unstressed NF, P and E group rats, the intracerebroventricular (I.C.V.) injection of CRF-41 (10 μg) increased blood pressure and heart rate. However, there were no significant differences between 3 groups.
4. The I.C.V.injection of a-helical CRH (9-41), a CRH-41 receptor antagonist, did not attenuated the stress-induced hypertension in the 3 groups of female rats.
These results suggest that estrogen may influence blood pressure regulation during stress in suppressing the activation of a sympathetic nervous tone in female rat. The mechanisms responsible for the greater resistance to these stresses in the NF and E group should be investigated further. Less
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