Figure 3.

Effects of suramin plus PPADS, apamin and L-NAME on the concentration-dependent action of ATP (a), ADPβS (b) and α,β-meATP (c) to increase the peristaltic pressure threshold (PPT). The concentration-response curves were recorded in a cumulative manner, and the graph shows peak changes in PPT which occurred within 15 min after exposure to each purine concentration. Vehicle, suramin (300 μM) plus PPADS (150 μM), apamin (0.5 μM) and L-NAME (300 μM) were administered 30 min before exposure to the purinoceptor agonists. The values represent means±s.e.mean, n⩾6. ^*P<0.05 versus vehicle (one way analysis of variance).