去甲肾上腺素和脑室内注射甲氧明引起的小鼠排便抑制

去甲肾上腺素（ＮＥ）５ｍｇ·ｋｇ￣（－１）ｉｐ和赛拉嗪１－２ｍｇ·ｋｇ￣（－１）ｓｃ可抑制小鼠排便，而甲氧明（Ｍｅｔ）１５ｍｇ·ｋｇ￣（－１）ｓｃ，异丙肾上腺素１０ｍｇ·ｋｇ￣（－１）ｓｃ多巴酚丁胺２０ｍｇ·ｋｇ￣（－１）ｓｃ和沙丁胺醇５ｍｇ·ｋｇ￣（－１）ｓｃ无效、Ｍｅｔ１５０μｇｉｃｖ也抑制排便。咪唑克生１ｍｇ·ｋｇ￣（－１）ｓｃ可拮抗ＮＥ，赛拉嗪和ｉｃｖＭｅｔ引起的排便抑制，哌唑嗪１ｍｇ·ｋｇ￣（－１）ｓｃ和普萘洛尔１０ｍｇ·ｋｇ￣（－１）ｓｃ则无效。这提示ＮＥ和ｉｃｖＭｅｔ抑制小鼠排便是作用于肠α＿２肾上腺素受体所致。

Inhibition of defecation caused by norepinephrine andintracerebroventricular injection of methoxamine in mice

When a small rubber tube(14mm×2mm)iS insertedinto rectum through anus of a mousefor a distance of 10 mm,generally it will be evacuatedwithin 1 min by defecation reflex. The effect of drugson defecation was estimated by recording the evacua-tion time of the small tube. Inhibition of defecationwas defined as the time was longer than 5 min.Defecation was inhibited by norepinephrine(NE,5mg·kg￣(-1),ip)and α2 agonist xylazine(1-2 mg·kg￣(-1),sc), but not by α_1 agonist methoxamine(Met, 15 mg·kg￣(-1) sc)mixed β_1,β_2 agonist isoprenaline (10mg·kg￣(-1),sc)β_1 agonist dobutamine(20 mg·kg￣(-1),sc) and β_2 agonist salbutamol( 5 mg· kg￣(-1),sc),whileintracerebroventricular injection of Met(150 μg)al-so inhibited defecation.The inhibitory effect ondefecation by NE, xylazine or icv Met was antago-nized by α_2 antagonist idazoxan(1 mg· kg￣(-1), sc),but not affected by α_1 antagonist prazosin(1 mg·kg￣(-1), sc) and βantagonist propranolol(10 mg· kg￣(-1)sc).These results suggested that the inhibition ofdefecation caused by NE or icv Met was mediatedvia α_2 adrenoceptors.