The subtype of serotonin (5-HT) receptors in the rat pulmonary artery.
Serotonin (5-HT) and some alpha-agonists induced a marked contraction of ring segments of the rat pulmonary artery. Phenylephrine and 5-HT caused maximum contractions in the artery amounting to 91% and 66%, respectively, of the maximum effect of noradrenaline. Clonidine failed to induce contractions in the artery. The alpha 1-adrenoceptor blocker prazosin (1 X 10(-6)M) and alpha 2-adrenoceptor blocker yohimbine (5 X 10(-7)M) did not antagonize 5-HT-induced contractions. However 5-HT2 receptor antagonists ketanserin (3 X 10(-9)-1 X 10(-7)M), mianserin (3 X 10(-9)-1 X 10(-7)M) and pizotifen (3 X 10(-9)-1 X 10(-7)M) competitively antagonized 5-HT-induced contractions in the tissue studied, whereas the antagonist methysergide (5 X 10(-10)-1 X 10(-7)M) caused a noncompetitive antagonism. The pA2 values for ketanserin (8.98), mianserin (9.1) and pizotifen (9.14) against 5-HT were not different from the values obtained in other tissues which were shown to contain 5-HT2 receptors. The results suggest that 5-HT receptors in rat main pulmonary artery are of the 5-HT2 subtype.
Uma
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S
Department of Pharmacology, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey.
Tuncer
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M
Kayaalp
S O
SO
D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D008803:Mianserin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010918:Pizotyline / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology
D011985:Receptors, Serotonin; D010918:Pizotyline; D010656:Phenylephrine; D008803:Mianserin; D007650:Ketanserin; D009638:Norepinephrine; D011224:Prazosin; D008784:Methysergide