抄録
We examined the effect of estrogen (E2) replacement in ovariectomized rats on body fluid regulatory responses to plasma hyperosmolality and central angiotensin II (ANGII), and on the systemic and central ANGII-induced pressor responses. E2 replacement attenuated fluid intake and c-Fos expression of arginine vasopressin (AVP) neurons at the PVN and SON in response to both iv hypertonic saline infusion and icv ANGII injection. E2 replacemnet, however, did not influence the c-Fos expression at the osmosensitive regions, such as OVLT, SFO or MnPO during systemic osmotic challenge, suggesting that E2 does not modify osmoreceptor sensitivity. The c-Fos expression at the ANGII sensitive sites such as SFO and MnPO induced by central ANGII injection were attenuated by E2 replacement, indicating that the central sensitivity to ANGII is attenuated by E2 replacement. Thus, the attenuated osmoregulatory responses by E2 replacement might be due to the reduced central sensitivity to ANGII, because it has been reported that central ANGII is involved in the osmoregulatory thirst and AVP release. The pressor response to iv and icv ANGII was not affected by E2 replacement, while the decrease in heart rate induced by iv ANGII was attenuated by E2 replacement, suggesting that vasoconstrictor response and baroreflex response controlling heart rate are attenuated by E2 replacement. The central ANGII-induced pressor response was not affected by E2, suggesting that E2 differentially affect the central ANGII-induced body fluid and blood pressure regulations. [J Physiol Sci. 2007;57 Suppl:S53]