Fig. 13. Mean external contraction ratios in response to the membrane permeable guanylate cyclase inhibitor ODQ. Treatment demibranchs (numerator) were exposed to 10^-6 mol l^-1 DEANO and varying concentrations of ODQ and then to 2x10^-5 mol l^-1 5HT, while the control demibranchs (denominator) were only exposed to 2x10^-5 mol l^-1 5HT. Values are means ± 1 S.E.M., N=6-4 at each concentration of ODQ.