Figure 5.

The negative inotropic effects of isoprenaline in TG4 left atrial strips are sensitive to B. pertussis toxin treatment. Controls were treated with vehicle (water). Mean data points are shown (s.e.mean indicated by error bars) with curves generated by nonlinear regression, using a five parameter logistic (see text for equations, Table 1 for mean best-fit data). The units of the ordinate axis are change in force of contraction, expressed in milligram; zero was set as the F_c immediately prior to isoprenaline administration. The point labelled ‘NECA' is the mean response of each group to 10 μM NECA, administered after the highest dose of isoprenaline.