FIGURE 2.

Effects of CB₁R inhibition on agonist-induced responses of gracilis arterioles. A and B, shown are the effects of the CB₁R antagonist O2050 (1 μm) on the relaxations induced by the CB₁R agonist WIN 55212 (1 μm) and by the endothelial relaxant Ach (10 μm) in rat gracilis arteriole segments (A, n = 4) and in mouse gracilis arteriole segments (B, n = 4). Values were calculated as percent change of diameter from control. Mean ± S.E. values are shown. The asterisk indicates significant change of agonist-induced tone in response to inhibitor treatment (p < 0.05). C and D, cumulative log-concentration-effect curves for Ang II were taken by pressure arteriography in rat (C, n = 5–6) and mouse (D, n = 4) gracilis arterioles. Effects of the CB₁R antagonist O2050 (1 μm) are shown. E and F, shown are cumulative log-concentration-effect curves induced by WIN 55212 (0.1 nm–1 μm) and by sodium nitroprusside (0.1 nm--10 μm) in rat gracilis arterioles (n = 4–7). Effects of the CB₁R antagonist O2050 (1 μm) are shown. Values were calculated as percent change of diameter from the incubated control. Mean ± S.E. values are shown. The asterisk indicates significant change of vasoconstrictor-induced contraction in response to inhibitor treatment (p < 0.05). Data obtained with curve fitting method showed that in rat gracilis arterioles E_max values were 30.3 ± 4.4 and 47.5 ± 4.5% (p < 0.05, n = 5–6) in the absence and in the presence of O2050, respectively. Log EC₅₀ values were −8.8 ± 0.2 and −9.7 ± 0.29 in the absence and presence of O2050, respectively. In mouse arterioles E_max values were 24.3 ± 1.5 and 42.1 ± 6.1% in the absence and presence of O2050, respectively (p < 0.05, n = 4). Log EC₅₀ values were −9.2 ± 0.2 and −10.0 ± 3.4 in the absence and presence of O2050. Changes in EC₅₀ values were not significant.