Characterization of 5-hydroxytryptamine receptors in rabbit isolated iliac artery

YILDIZ O., TUNCER M.

Archives Internationales de Pharmacodynamie et de Therapie, cilt.326, ss.72-83, 1993 (Scopus)

Özet

To characterize the 5-hydroxytryptamine (5-HT) receptors, the contractile effects of both 5-HT and the 5-HT1-like receptor agonist sumatriptan were investigated in isolated open ring preparations of the rabbit common iliac artery. 5-HT induced concentration-dependent contractions. Sumatriptan did not induce any contraction of unstimulated preparations, whereas it elicited concentration-dependent contractions in preparations given a moderate tone with a threshold concentration of prostaglandin F(2α). In vessel segments precontracted with prostaglandin F(2α). E(max) values for 5-HT and sumatriptan reached about 85% and 30% of the phenylephrine maximal effect, respectively. The mean EC50 values for sumatriptan and 5-HT were 3.34 μM and 1.5 μM, respectively. Pargyline, cocaine or normetanephrine were without significant effect on the contractions induced by 5-HT or sumatriptan. The 5- HT3 receptor antagonist tropisetron (1 μM) had no effect on 5-HT- and sumatriptan-induced contractions. The 5-HT2 receptor antagonist ketanserin (0.1-1 μM) produced parallel displacements to the right of the 5-HT and phenylephrine concentration-effect curves, without significant reduction in the maximum responses. The pA2 values were 7.85 ± 0.19 and 7.9 ± 0.16, respectively. Ketanserin had no effect on the sumatriptan concentration- effect curves. The nonselective 5-HT receptor antagonists methysergide (0.3 μM) and methiothepin (0.01 μM) shifted the concentration-response curve to sumatriptan to the right (mean pK(B) values of 6.91 and 8.68, respectively). The pA2 value for prazosin against 5-HT (9.98 ± 0.43) was not significantly different from the value against phenylephrine (9.27 ± 0.20). These results suggest that the sumatriptan-induced contraction is mediated by a 5-HT1- like receptor, whereas an additional mechanism, probably an α1-adrenoceptor stimulation, plays a role in the contraction induced by 5-HT in the rabbit iliac artery.