Figure 6. Effects of 3, 4, 5-trimethoxybenzoic acid 8-(diethylamino) octyl ester hydrochloride (TMB-8, 10 sup -5 M) on the relaxation responses to isoproterenol (a) and acetylcholine (b) of aortic rings precontracted with norepinephrine. (open circle) denotes the rings without TMB-8 (control). (closed circle) denotes the rings treated with TMB-8. All rings represent mean +/- standard errors of the means of seven separate experiments. **P < 0.001 versus control.