Figure 6.

Influence of cumulatively administered increasing concentrations of 5-HT and the 5-HT₄ receptor agonists prucalopride, tegaserod, R149402 and R199715 on the contraction force in IBMX-treated left atrial pectinate muscles (a) and the beating rate of right atrium (b) of young pigs. The experiments in (b) were carried out in the absence of IBMX. The vertically averaged experimental data points were expressed as mean percentage of the contraction caused by 0.1 mM isoprenaline. The curves shown superimposed on the vertically averaged data points represent the population mean obtained from an iterative fitting procedure to the Hill equation in a nonlinear mixed-effect model.