Hu J R, Qian J Q
Department of Pharmacology, Tongji Medical University, Hubei, The People's Republic of China.
J Cardiovasc Pharmacol. 1987;10 Suppl 12:S248-50.
The effects of the selective alpha 1-adrenoceptor agonist, phenylephrine, and the alpha 2-adrenoceptor agonist, B-HT933, on the contractility, excitability, automaticity, and functional refractory period in the isolated rat left atria were investigated. For the depletion of catecholamine in rat left atria and the blockade of intra- and extraneuronal uptake of catecholamine, reserpine (10 mg/kg, i.p.) was given to rat 16-18 h before the experiment; cocaine (30 microM) and hydrocortisone (30 microM) were continuously present in the bath. The positive inotropic effect of phenylephrine was competitively antagonized by prazosin with a pA2 value of 9.29. The excitability of rat left atria was not affected by phenylephrine, whereas the automaticity of left atria induced by adrenaline was enhanced and the functional refractory period of left atria was prolonged by phenylephrine. The prolongation of functional refractory period caused by phenylephrine was competitively inhibited by prazosin with a pA2 value of 8.15. B-HT933 was not able to induce any change in the contractility, excitability, automaticity, and functional refractory period of rat left atria under the same conditions. The results indicated that the cardiophysiological effects on rat left atria caused by stimulation of postsynaptic alpha-adrenoceptor was mediated by alpha 1-type receptors while postsynaptic alpha 2-type receptors are not of functional importance on rat left atria.
研究了选择性α1 -肾上腺素能受体激动剂去氧肾上腺素和α2 -肾上腺素能受体激动剂B - HT933对离体大鼠左心房收缩性、兴奋性、自律性和功能不应期的影响。为了耗竭大鼠左心房中的儿茶酚胺并阻断儿茶酚胺的神经元内和神经元外摄取，在实验前16 - 18小时给大鼠腹腔注射利血平（10毫克/千克）；浴槽中持续存在可卡因（30微摩尔）和氢化可的松（30微摩尔）。哌唑嗪以9.29的pA2值竞争性拮抗去氧肾上腺素的正性肌力作用。去氧肾上腺素不影响大鼠左心房的兴奋性，而肾上腺素诱导的左心房自律性增强，去氧肾上腺素使左心房的功能不应期延长。哌唑嗪以8.15的pA2值竞争性抑制去氧肾上腺素引起的功能不应期延长。在相同条件下，B - HT933不能引起大鼠左心房的收缩性、兴奋性、自律性和功能不应期发生任何变化。结果表明，刺激突触后α -肾上腺素能受体对大鼠左心房产生的心脏生理效应由α1型受体介导，而突触后α2型受体对大鼠左心房无功能重要性。
