兔眼虹膜睫状体促乙酰胆硷分泌的突触前5-HT受体的研究

Study on prejunctional 5-HT receptor modulation of acetylcholine release in the rabbit iris-ciliary body

目的：确定离体灌注状态下，兔眼虹膜睫状体的突触前５－ＨＴ受体对３Ｈ－乙酰胆硷释放的调节作用．方法：给体外灌注培养虹膜睫状体加入３Ｈ－胆硷，电刺激四次（Ｓ１，Ｓ２，Ｓ３，Ｓ４），刺激强度为３Ｈｚ，５０ｍＡ，１ｍｉｎ．在Ｓ２，Ｓ３，Ｓ４前加入试剂．电刺激诱导的３Ｈ－乙酰胆硷释放的水平通过计算（Ｓｘ／Ｓ１）刺激比率来确定．离子交换色谱法分离灌注液样品中３Ｈ－乙酰胆硷．液内计数仪测定标本中３Ｈ－乙酰胆硷的含量．结果：５－ＨＴ（１ｎｍｏｌ／Ｌ～１０ｍｏｌ／Ｌ）诱导的虹膜睫状体３Ｈ－乙酰胆硷释放的剂量反应曲线呈浓度依赖性（ＥＣ５０＝５８ｎｍｏｌ／Ｌ）．浓度为１ｍｏｌ／Ｌ时，５－ＨＴ诱导的３Ｈ－Ａｃｈ释放量最大，增加了（４５．１４±７．４０）％（ｎ＝６）．给组织灌注５－ＨＴ３拮抗剂Ｔｒｏｐｉｓｅｔｒｏｎ（１ｎｍｏｌ／Ｌ）及５－ＨＴ１拮抗剂Ｍｅｔｈｉｏｔｈｅｐｉｎ（０．１μｍｏｌ／Ｌ），５－ＨＴ（１μｍｏｌ／Ｌ）诱导的３Ｈ－Ａｃｈ释放分别为对照组的８９．９６％及８８．７８％；而加入非选择性５－ＨＴ拮抗剂Ｍｉ－ａｎｓｅｒｉｎ（１０μｍｏｌ／Ｌ）及５－ＨＴ４拮抗剂ＳＤＺ－２０５５５７（０．１μｍｏｌ／Ｌ）时，５－ＨＴ（１μｍｏ?

AIM:To characterize pejunctional 5-HT het-eroreceptorswhich modulate 3H-acetylcholing(3H-Ach)re-lease in isolated rsbbit iris-ciliary bodies(ICBs).METHODS:ICB tissue segments were incubated with 3H-choline,srper-fused and electrically stimulated four times (S1,S2,S3 andS4)at 3 Hzfor 1 min to elicit3H-Ach secretion.Test agents(5-HT agonists and antagonists )were added before S2,S3 andS4 and their effects determined by thestimulation ration(Sx/tions was isolated by ion exchange chromatogeraphy and ana-lyzed for radioactivity by liquid scintillation spectrometry.RESULTS:In rabbit ICBs,the evoked 3H-Ach release wasenhanced in a concentration-dependent manner by 5-HT(1nmol/l^10μmol/L,EC50=58 nmol/L).Themaximum ef-fect of 5-HT(1μmol/L)corresponded to a(45.14+7.40)%(n=6)increase in 3H-Ach release.Highe concenntrations of 5-HT((0.1mmol/L)induced desensitization.The responseto 5-HT(iμmol/L)in thepresence of the 5-HT1 antagonistMethiothepin(0.1μmol/L),equatedto 89.96% and 88.78%respectivelyof control value,in theprd\esense of the non-selective 5-HTantagonist Mianserin (10μmol/L),5-HT4 ntagonist SDZ-205557(0.1μmol/L)was-15.20% and 32.84% of control.The 5-HT response was mimcked by the selective the 5-HT4 ago-nist 5-MOT(5-Medthoxytryptamine,5-MOT)(10nmol/L^100μmol/L,EC50=70nmol/L),wherease the 5-HT3 agonistM-CPBG [(1-m-chlorophenyl)-biguanide]and Phenyl-biguanide,the 5-HT1agonist 5-carboxamidotryptamine,5-HT1A agonist(+)-8-OH-DPAT and 5-HT3 agonist a-methyl-5-HT were ineffective.CONCLUSION:Our results indicatethat cholinergic terminals in thehuman Icb contains facilita-tory 5-HT heteroreceptorsthat belong to the 5-HT4 subtype.Their role in modulation of intraocular pressure remains beclucidated.