乙醇对大鼠胃不同区域环行肌M受体和5-HT受体介导收缩反应的选择性抑制作用

Selective inhibition of ethanol on muscarinic receptor-or 5-HT receptor-mediated contraction in circular smooth muscle of rat stomach

目的利用大鼠胃不同区域环行肌标本,研究乙醇对M受体和5-HT受体介导的收缩反应是否具有选择性抑制作用。方法制备大鼠离体胃底、胃体、贲门和幽门环行肌标本,观察卡巴胆碱（carbachol,CCh）或5-羟色胺（5-hydroxytryptamine,5-HT）诱发的收缩反应及乙醇的作用。结果体积分数为0.000 05~0.000 5的乙醇不影响CCh诱发的胃底和贲门环行肌收缩反应以及5-HT诱发的胃底和胃体环行肌收缩反应（P〉0.05）。但是0.000 1和0.000 5乙醇明显抑制了CCh诱发的胃体环行肌收缩,Emax值（g）由对照组的12.18±0.33降至10.88±0.41,-lg EC_（50）值由对照组的6.33±0.05降至6.12±0.06（P〈0.05）。同浓度乙醇明显抑制了CCh诱发的幽门环行肌收缩,Emax值（g）由对照组的2.87±0.15降至2.2±0.13,-lg EC_（50）值由对照组的6.49±0.10降至6.05±0.09（P〈0.01）。乙醇预处理贲门环行肌前,5-HT诱发贲门环行肌收缩的E_（max）值（g）是2.93±0.35,-lg EC_（50）值是6.17±0.21;体积分数为0.000 1和0.000 5的乙醇明显抑制了5-HT诱发的贲门环行肌收缩（P〈0.05）,其Emax值（g）降至2.1±0.30（P〈0.05）,-lg EC_（50）值未发生明显改变。结论乙醇对大鼠胃不同区域环行肌收缩功能的抑制强度是：乙醇仅抑制5-HT诱发的贲门收缩,对CCh诱发收缩的抑制强度为幽门大于胃体。在受体激动剂诱发环行肌收缩反应的抑制特点方面,乙醇对CCh的活性及其与受体的亲和力均有抑制作用,但是乙醇仅抑制5-HT的活性。

Aim To investigate the selective inhibition of ethanol on muscarinic receptor-or 5-HT receptor-mediated contractile responses in the circular smooth muscle strips isolated from the different regions of rat stomach. Methods Circular muscle strips isolated from the rat gastric fundus,body,cardia and pylorus were prepared,and the contractile responses to carbachol（ CCh） or 5-HT were recorded. Results Ethanol（ 0. 000 05 ~ 0. 000 5,V/V） did not affect the contractile response to CCh in circular muscle strips from the rat gastric fundus and cardia,and that to 5-HT in the strips from rat gastric fundus and body（ P 0. 05）.However,ethanol（ 0. 000 1 and 0. 000 5） significantly inhibited the Emaxvalue of the contraction by CCh from（ 12. 18 ± 0. 33） g of control level to（ 10. 88 ± 0. 41）g and- lg EC_（50） value from（ 6. 33 ± 0. 05） of control level to（ 6. 12 ± 0. 06）（ P 0. 05） in the strips from rat gastric body. Ethanol（ 0. 000 1 and 0. 000 5） also significantly inhibited the Emaxvalue of the contraction by CCh from（ 2. 87 ± 0. 15） g of control level to（ 2. 2± 0. 13） g and- lg EC_（50） value from（ 6. 49 ± 0. 10） of control level to（ 6. 05 ± 0. 09）（ P 0. 01） in the strips from rat gastric pylorus. Moreover,ethanol（ 0. 000 1and 0. 000 5） significantly inhibited the Emaxvalue of the contraction by 5-HT from（ 2. 93 ± 0. 35） g of control level to（ 2. 1 ± 0. 30） g（ P 0. 05）,but did not affect the- lg EC_（50）value in the strips from rat gastric cardia. Conclusions Ethanol inhibits the contractile responses to 5-HT only in the circular muscle strips of rat gastric cardia,and it inhibits the contractile responses to CCh more strongly in the circular muscle strips of gastric pylorus than gastric body. In those gastric circular muscle strips,ethanol decreases both the activity and affinity of CCh to muscarinic receptors,but decreases only the activity of 5-HT to its receptors.