Some studies on the 5-hydroxytryptamine receptors in the isolated rat uterus

Selective 5-hydroxytryptamine (5-HT) receptor antagonists were employed to further characterize the receptor subtypes mediating the contractile actions of 5-HT on the isolated uterine preparations of the rat. Increasing concentrations (10(-8)-10(-6) M) of the 5-HT receptor antagonist methysergide produced rightward shifts of the concentration-response curves of the 5-HT-induced contractions (pA2=8.05, slope of A-S plot=1.12 n=7) ketanserin a 5-HT2A receptor antagonist (10(-8)-10(-6) M) competitively antagonized the actions of 5-HT on the preparation (pA2=8.81; slope=1.04; n=7). Both LY53857 (10(-8)-10(-6) M) and ICI169369 (10(-8)-10(-6) M) which are known 5-HT2 receptor blockers also produced concentration-dependent shifts of the curves LY53857 yielded a pA2 of 8.9 (slope=0.82; n=7) while the pA2 for ICI169369 on the preparation was 7.9 (slope=1.29; n=7). ICS205930 a potent 5-HT3 blocker (10(-12)-10(-9) M) also produced concentration-dependent shifts of the curves (pA2=11.3; slope=0.94; n=7). The presence of 5-HT1 receptors could not be established. However both 5-HT2 and 5-HT3 receptors seem to be present on the rat uterine preparation.