Sharma A, Kulkarni S K
Department of Pharmaceutical Sciences, Panjab University, Chandigarh, India.
Indian J Exp Biol. 1994 Mar;32(3):176-9.
Presence of specific dopamine (DA) receptors and their characterization was attempted in rat anococcygeus muscle preparation. Dopamine (10(-6) M) and B-HT 920 (10(-6) M) produced concentration dependent contractions of the rat anococcygeus muscle preparation. The response of DA was shifted towards right in presence of haloperidol (10(-6) M; pA2 = 6.8) and sulpiride (10(-4) M) in a competitive manner. Alpha 2 antagonists yohimbine (10(-5) M) and idazoxan (10(-5) M) blocked the response to DA in a competitive manner, while alpha 1 antagonist prazosin (10(-5) M) completely blocked the response to DA. SCH 23390 (10(-5) M), a D1 DA antagonist potentiated the response to DA. Reserpinization (5 mg/kg, 24 hr prior) brought about a shift towards the right, and this response was similarly blocked by haloperidol, sulpiride and yohimbine without affecting the maximum response. Desipramine (10(-5) M) blocked the response of DA in a non-competitive manner. Pretreatment of animals with desipramine (10 mg/kg) followed by reserpine, brought about a reversal of action of reserpine. The response to B-HT 920 (10(-6) M), was blocked similarly by haloperidol and yohimbine. However, the effect of desipramine was more pronounced when compared to DA per se. SKF 38393, a D1 DA agonist, potentiated the response to B-HT 920. The findings suggest the presence of both D1 and D2 DA receptors in rat anococcygeus muscle and that DA also acts on adrenergic receptors to produce a contractile response of this muscle preparation.
研究人员尝试在大鼠肛门尾骨肌标本中确定特定多巴胺（DA）受体的存在及其特性。多巴胺（10⁻⁶ M）和B-HT 920（10⁻⁶ M）可使大鼠肛门尾骨肌标本产生浓度依赖性收缩。在存在氟哌啶醇（10⁻⁶ M；pA2 = 6.8）和舒必利（10⁻⁴ M）的情况下，DA的反应以竞争性方式向右偏移。α₂拮抗剂育亨宾（10⁻⁵ M）和咪唑克生（10⁻⁵ M）以竞争性方式阻断对DA的反应，而α₁拮抗剂哌唑嗪（10⁻⁵ M）则完全阻断对DA的反应。D₁ DA拮抗剂SCH 23390（10⁻⁵ M）增强了对DA的反应。利血平化（5 mg/kg，提前24小时）使反应向右偏移，这种反应同样被氟哌啶醇、舒必利和育亨宾阻断，且不影响最大反应。地昔帕明（10⁻⁵ M）以非竞争性方式阻断DA的反应。用去甲丙咪嗪（10 mg/kg）预处理动物后再给予利血平，可使利血平的作用逆转。对B-HT 920（10⁻⁶ M）的反应同样被氟哌啶醇和育亨宾阻断。然而，与DA本身相比，地昔帕明的作用更为明显。D₁ DA激动剂SKF 38393增强了对B-HT 920的反应。这些发现表明大鼠肛门尾骨肌中存在D₁和D₂ DA受体，并且DA也作用于肾上腺素能受体以产生该肌肉标本的收缩反应。
