Medgett I C, Hicks P E, Langer S Z
J Pharmacol Exp Ther. 1984 Oct;231(1):159-65.
The alpha adrenoceptor-mediated vasoconstriction in isolated perfused tail arteries from spontaneously hypertensive (SHR) and age matched Wistar Kyoto (WKY) normotensive rats has been examined. Responses induced by periarterial field stimulation, exogenous norepinephrine or the selective alpha-1 adrenoceptor agonist methoxamine were preferentially antagonized by prazosin in both SHR or WKY tail arteries. However, in SHR only, the alpha-2 adrenoceptor antagonist idazoxan (RX 781094) at low concentrations, significantly antagonized responses to periarterial field stimulation and to exogenous norepinephrine. Except at rather high concentrations, idazoxan was inactive as an antagonist of responses induced by methoxamine. The alpha-1 adrenoceptor blocking agent prazosin was a very potent antagonist of the responses induced by periarterial field stimulation and by methoxamine. These results indicate that alpha-2 adrenoceptors predominate in both SHR and WKY tail arteries, but a significant subpopulation of smooth muscle alpha-2 adrenoceptors is present in tail arteries of SHR but not of WKY rats. In contrast to WKY normotensive rats, postjunctional alpha-2 adrenoceptors may also be involved in the vasoconstrictor responses to sympathetic nerve stimulation in tail arteries of SHR.
研究了来自自发性高血压大鼠（SHR）和年龄匹配的Wistar Kyoto（WKY）正常血压大鼠的离体灌注尾动脉中α肾上腺素能受体介导的血管收缩作用。在SHR和WKY尾动脉中，动脉周围场刺激、外源性去甲肾上腺素或选择性α-1肾上腺素能受体激动剂甲氧明诱导的反应均优先被哌唑嗪拮抗。然而，仅在SHR中，低浓度的α-2肾上腺素能受体拮抗剂咪唑克生（RX 781094）可显著拮抗动脉周围场刺激和外源性去甲肾上腺素诱导的反应。除了相当高的浓度外，咪唑克生作为甲氧明诱导反应的拮抗剂无活性。α-1肾上腺素能受体阻断剂哌唑嗪是动脉周围场刺激和甲氧明诱导反应的非常有效的拮抗剂。这些结果表明，α-2肾上腺素能受体在SHR和WKY尾动脉中均占主导地位，但SHR尾动脉中存在显著的平滑肌α-2肾上腺素能受体亚群，而WKY大鼠尾动脉中则不存在。与WKY正常血压大鼠相比，节后α-2肾上腺素能受体也可能参与SHR尾动脉对交感神经刺激的血管收缩反应。
