Fig. 6. The timing of the onset of ecdysis-triggering hormone (ETH)-induced ecdysis in larvae injected with the cGMP-specific phosphodiesterase inhibitor Zaprinast. (A) Animals were injected with Zaprinast 10 min prior to injection with 200 pmol of ETH (at 0 min), at the amounts listed on the y-axis. Controls (C) were injected with the Zaprinast solubilizing agent, 100% dimethylsulfoxide (DMSO), before injection of ETH. The timing of ecdysis was not significantly different in these controls from that in untreated controls (data not shown). The bars represent mean times + S.E.M. Letters represent significant differences from the control and from each other, as determined by analysis of variance (P<0.001) using the Tukey test for differences (=0.05). (B) Representative micrographs of cGMP immunoreactivity in abdominal ganglion 3 in DMSO- (C) and Zaprinast-treated (Z) animals 60 min after injection with ETH. Scale bar, 100 µm.