Fig. 7. The effect of L-NAME on dose-dependent muscle contraction (as a percentage of resting length) in response to 5HT. Treatment demibranchs (solid circles/solid line) were exposed to 1x10^-5 mol l^-1L-NAME for 15 min, and then both treatment and control demibranchs (open circle/broken line) were exposed to increasing concentrations of 5HT. Data were recorded using ultrasound, which allowed a single demibranch to be used for an entire dose-response curve. Data consist of paired demibranchs (three treatments, three controls) from three clams.