On the characterization of dopamine-induced contractile response of rat anococcygeus muscle preparation.
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.
Sharma
A
A
Department of Pharmaceutical Sciences, Panjab University, Chandigarh, India.
Kulkarni
S K
SK
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D019329:Idazoxan; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects; D011954:Receptors, Dopamine / Q000145:classification / Q000187:drug effects* / Q000502:physiology; D012110:Reserpine / Q000494:pharmacology; D013469:Sulpiride / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D001381:Azepines; D001552:Benzazepines; D004146:Dioxanes; D011941:Receptors, Adrenergic; D011954:Receptors, Dopamine; D015016:Yohimbine; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; C024763:talipexole; D013469:Sulpiride; D012110:Reserpine; D006220:Haloperidol; D003891:Desipramine; D004298:Dopamine; D011224:Prazosin; D019329:Idazoxan