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ObjectiveTo study the effects of olmesartan on the central pressor response to exogenous angiotensinⅡ(AngⅡ) and its relationship with the AT1 receptor in the rostral ventrolater medulla (RVLM) of the spontaneously hypertensive rat (SHR).MethodsSixty rats were divided into SHR control group (n=20, normal drinking), SHR-Olme group [n=20, olmesartan 30 mg/(kg·day)], and Wistar-Kyoto rats(WKY) group (n=20, normal drinking) randomly. Four weeks later, these rats were intraperitoneally anesthetized and removed some cranial bones to orientate the RVLM, then, tubes were inseted into the femoral artery and vein. Finally, microinjected AngⅡinto the RVLM and observed the changs of the arterial pressure and the heart rate. AT1 receptor mRNA and protein level in RVLM was measured by RT-PCR and Western blot,then analyzed with optic density.ResultsThe blood pressure of all SHR-olme rats reach normal level during breeding period. The mean arterial pressures (MAP) of the three groups were all increased. The magnitude of arterial pressure of SHR-olme group was much lower than that of SHR group [(26.3±0.75) vs (47.2±1.41) mmHg, P<0.01], but still higher than that of WKY group [(26.3±0.75) vs (21.5±0.72) mmHg, P<0.05]. The heart rate (HR) of the three groups was all increased, but there wes no statistical significance among groups. The mean optic density (MOD) of AT1 receptor mRNA in RVLM of SHR-olme was much reduced compared with SHR group [(0.94±0.41) vs (2.41±0.37), P<0.01], but higher than that of WKY group [(0.94±0.41) vs (0.81±0.22), P<0.05]. The mean optic density (MOD) of AT1 receptor protein in RVLM of SHR-olme was much reduced compared with SHR group (0.51±0.09比0.93±0.07, P<0.01), but higher than that of WKY group (0.51±0.09比0.43±0.03, P<0.05)ConclusionChronic oral adiministration of olmesartan could obviously attenuate the pressure response caused by microinjecting AngⅡinto the RVLM by reduceing the level of AT1 receptor in this region of SHR.
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