Serotonin-induced contraction of canine saphenous vein: mediation by 5-HT1 receptors.
The action of serotonin (5-HT) on alpha 1- and alpha 2-adrenoceptors was investigated on the isolated dog saphenous vein strip. Prazosin (1 X 10(-6) and 1 X 10(-5) M), an alpha 1-adrenoceptor blocker, did not alter 5-HT-induced contractions. However, yohimbine (1 X 10(-6) and 1 X 10(-5) M), an alpha 2-adrenoceptor blocker, shifted the concentration-response curve of 5-HT to the right without any reduction in the maximum response. The pA2 value for yohimbine against 5-HT (7.61 +/- 0.28, mean +/- S.E.M.) is different from the value for yohimbine against clonidine (8.35 +/- 0.08) or M-7 (8.58 +/- 0.07), a substance which stimulates postsynaptic alpha 2-adrenoceptors. Mianserin (1 X 10(-8)-1 X 10(-6) M) and ketanserin (1 X 10(-7)-1 X 10(-5) M) antagonized 5-HT-induced contractions noncompetitively. The results suggest that yohimbine competitively antagonizes 5-HT action by blocking probably 5-HT1 receptors, independently from its alpha 2-adrenoceptor blocking effect.
Tuncer
M
M
Doğan
N
N
Ilhan
M
M
Kayaalp
S O
SO
D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004285:Dogs; D004347:Drug Interactions; D004639:Emetics / Q000494:pharmacology; D066298:In Vitro Techniques; D007650:Ketanserin; D008803:Mianserin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009284:Naphthols / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects*; D012501:Saphenous Vein / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D004639:Emetics; D009284:Naphthols; D010880:Piperidines; D011985:Receptors, Serotonin; D008803:Mianserin; D015016:Yohimbine; D012701:Serotonin; C009957:5,6-dihydroxy-2-dimethylaminotetralin; D007650:Ketanserin; D003000:Clonidine