α-Methyl-5-HT, a 5-HT₂ receptor agonist, stimulates β₂-adrenoceptors in guinea pig airway smooth muscle

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• 作者：Patricia Campos-Bedolla ; Mario H. Vargas ; Eduardo Calixto ; Patricia Segura ; Nic ; ro Mendoza-Patiñ ; o ; Alej ; ra Figueroa ; Edgar Flores-Soto ; Carlos Barajas-Ló ; pez ; Luis M. Montañ ; o
• 关键词：α ; -Methyl-5-HT ; α ; -Methyl-serotonin ; Airway smooth muscle ; β ; ₂-Adrenoceptors ; K⁺ currents
• 刊名：Pharmacological Research
• 出版年：2006
• 期刊代码：54_10436618
• 类别：pha
• 出版时间：December 2006
• 卷：54
• 期：6
• 页码：468-473
• 文件大小：512 K

摘要

α-Methyl-5-HT is widely used as a high-affinity 5-HT₂ receptors agonist, though some studies have postulated that this drug also activates other serotonergic receptors. In the present work, we found that a wide range of concentrations of α-methyl-5-HT induced biphasic responses (contraction followed by relaxation) in guinea pig tracheal rings. The relaxing phase caused by 32 μM α-methyl-5-HT was blocked by 0.1 μM propranolol. Furthermore, during an ongoing histamine-induced contraction, α-methyl-5-HT (0.1–100 μM) produced a concentration-dependent relaxation starting at 10 μM. This relaxation was fully abolished by 0.1 μM propranolol or 1 μM ICI 118,551 (a selective β₂-adrenoceptor antagonist). Additionally, in electrophysiological recordings, 32 μM α-methyl-5-HT also enhanced the membrane K⁺ currents of single tracheal myocytes, an effect reverted by propranolol and ICI 118,551, and mimicked by 0.1 μM salbutamol. Thus, we concluded that α-methyl-5-HT activates β₂-adrenoceptors in guinea pig tracheal smooth muscle at concentrations ≥10 μM. This effect must be taken into account when this drug is used in airway smooth muscle and in other tissues expressing β₂-adrenoceptors.