Lefebvre R A, Guenaneche F, De Beurme F A
Heymans Institute of Pharmacology, University of Gent Medical School, Belgium.
Eur J Pharmacol. 1990 Aug 21;185(1):69-79. doi: 10.1016/0014-2999(90)90212-o.
The effects of the DA1-receptor agonist, fenoldopam, and the DA2-receptor agonist, quinpirole, were studied with the longitudinal muscle of rat gastric fundus and circular muscle of rat gastric corpus, as there are contrasting reports about the receptors involved in the inhibitory effect of dopamine in these tissues. Quinpirole had no effect on basal tone in the longitudinal muscle of the rat gastric fundus and did not inhibit the sustained contractions induced by electrical field stimulation or by methacholine. Fenoldopam had no effect on the tone increased by methacholine but slightly potentiated the electrically induced contraction at the highest concentrations; it concentration dependently (10(-7)-3 X 10(-5) M) increased the basal tone. The contractile effect of fenoldopam was clearly antagonized by rauwolscine 10(-6) M, yohimbine 10(-6) M and phentolamine 3 X 10(-6) M plus propranolol 10(-5) M. The 5-HT receptor antagonist, methysergide, antagonized the fenoldopam-induced contractions in a non-competitive way. Fenoldopam and quinpirole had no effect on contractions induced in the circular muscle of the rat gastric corpus by methacholine or electrical field stimulation. They induced some contraction at basal tone, at their highest concentrations. As fenoldopam and quinpirole did not mimic the inhibitory effect observed with dopamine in the same models, no evidence was found for the presence of inhibitory dopamine receptors in rat gastric muscle. The contractile effect of fenoldopam in the longitudinal muscle of the fundus is probably due to an interaction with 5-HT receptors.
由于关于多巴胺在这些组织中的抑制作用所涉及的受体存在相互矛盾的报道，因此使用大鼠胃底纵行肌和大鼠胃体环行肌研究了DA1受体激动剂非诺多泮和DA2受体激动剂喹吡罗的作用。喹吡罗对大鼠胃底纵行肌的基础张力无影响，也不抑制电场刺激或乙酰甲胆碱诱导的持续性收缩。非诺多泮对乙酰甲胆碱引起的张力无影响，但在最高浓度时可轻微增强电诱导的收缩；它呈浓度依赖性（10^(-7)-3×10^(-5)M）增加基础张力。非诺多泮的收缩作用明显被10^(-6)M的萝芙木碱、10^(-6)M的育亨宾和3×10^(-6)M的酚妥拉明加10^(-5)M的普萘洛尔所拮抗。5-羟色胺受体拮抗剂麦角新碱以非竞争性方式拮抗非诺多泮诱导的收缩。非诺多泮和喹吡罗对乙酰甲胆碱或电场刺激在大鼠胃体环行肌中诱导的收缩无影响。它们在最高浓度时，对基础张力诱导了一些收缩。由于非诺多泮和喹吡罗在相同模型中未模拟多巴胺观察到的抑制作用，因此未发现大鼠胃肌中存在抑制性多巴胺受体的证据。非诺多泮在胃底纵行肌中的收缩作用可能是由于与5-羟色胺受体相互作用所致。
