Walland A
Eur J Pharmacol. 1978 Jan 15;47(2):211-21. doi: 10.1016/0014-2999(78)90392-8.
In cats anaesthetized with chloralose--urethane (70/100 mg/kg) a somato-sympathetic reflex increase of blood pressure and heart rate was evoked by electrical stimulation of sensory fibres running within the tibial nerve. I.V. injection of 30 microgram/kg of the alpha-adrenoceptor agonist clonidine caused a reflex inhibition in intact and vagotomized animals. In contrast, injection of 2 microgram/kg clonidine into the vertebral artery elicited hypotension but no reflux inhibition. In small doses, phenylephrine which is known from in vitro experiments to prefer the postsynaptic alpha-adrenoceptor, potentiated the reflex increase in blood pressure by an additive effect on the vascular alpha-adrenoceptor, while oxymetazoline and tramazoline, which preferentially activate the presynaptic receptor, were inhibitory. The inhibitory effect of tramazoline on the reflex increase in blood pressure and heart rate was antagonized by the presynaptic alpha-adrenolytic drug yohimbine. The results suggest that peripheral presynaptic alpha-adrenoceptors are responsible for somato-sympathetic reflex inhibition. The importance of peripheral presynaptic alpha-adrenoceptors in the in vivo regulation of blood pressure is discussed.
在用氯醛糖-乌拉坦（70/100毫克/千克）麻醉的猫中，通过电刺激胫神经内走行的感觉纤维可诱发血压和心率的躯体-交感反射性升高。静脉注射30微克/千克的α-肾上腺素能受体激动剂可乐定，在完整动物和迷走神经切断的动物中均可引起反射性抑制。相比之下，向椎动脉内注射2微克/千克可乐定可引起低血压，但无反射性抑制。小剂量时，体外实验表明优先作用于突触后α-肾上腺素能受体的去氧肾上腺素，通过对血管α-肾上腺素能受体的相加作用增强了血压的反射性升高，而优先激活突触前受体的羟甲唑啉和曲马唑啉则具有抑制作用。曲马唑啉对血压和心率反射性升高的抑制作用被突触前α-肾上腺素能阻断药育亨宾所拮抗。结果提示，外周突触前α-肾上腺素能受体参与了躯体-交感反射抑制。本文讨论了外周突触前α-肾上腺素能受体在体内血压调节中的重要性。
