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Marin J, Salaices M, Marco EJ, Gómez B, Lluch S. 
“Analysis of the contractile effect of 5-hydroxytryptamine on the isolated posterior communicating artery of the cat”. 
J. Pharm. Pharmacol. 1979;31:456-459.
5-Hydroxytryptamine (5-HT) induced dose-dependent increases in tension on the isolated posterior communicating artery (PCA) of the cat were significantly antagonized by lysergic acid diethylamide (LSD, 6 x IO-9 M). In the presence of phentolamine (10-6 M) the contraction induced by the two lowest doses of 5-HT was significantly reduced. Pretreatment of the animals with reserpine (3 mcg kg-l, i.p., total dose) did not modify the dose-response curve to 5-HT except for the lowest dose. Removal of both superior cervical sympathetic ganglia 15 days before the experiment brought about a significant increase in the vasoconstriction induced by 5-HT at all the doses compared with the control. Cocaine (10-6 M) induced a significant shift to the left of the dose-response curve to 5-HT but the maximum response was the same as in the control. The augmented response to 5-HT after denervation was partially antagonized by LSD (6 x 10-9 M) but not by phentolamine (10-6 M). These results show that the vasoconstriction elicited by 5-HT in the PCA of the cat is mainly due to direct stimulation of tryptaminergic receptors. The participation of an indirect adrenergic component in the contractile effects of 5-HT seems to be negligible.
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