Figure 2. Effect of 4-AP (300 μm) on ACh-evoked relaxation of segments of rat basilar artery precontracted with 5-HT.

A, representative recording showing oscillatory increase in basal tension induced by 4-AP in some tissues. B, representative recording showing ACh (1 nm to 3 μm)-evoked relaxations of 5-HT (0.1 μm)-induced tone in the absence and presence of 4-AP. C, cumulative concentration-relaxation curves for ACh in the absence and presence of 4-AP and clofilium (3 μm). Data are the average of 11 and 5 experiments ± s.e.m. with 4-AP and clofilium, respectively,