Fig. 4. Blocking of MG neuron migration by enzyme inhibitors of the NO/cGMP/PKG pathway and the cAMP/PKA cascade. Histograms show the distance migrated by the leading MG neuron on the midgut. (A) After 24 hours, normal migration of MG neurons was found in cultured control embryos (n=21). MG neuron migration was significantly reduced in the presence of 500 µM 7NI (n=21), 200 µM ODQ (n=20) and 50 µM RPcGMPS (n=21). (B) ODQ reduced MG neuron migration in a concentration-dependent manner. Normal migration of MG neurons was highly significantly inhibited in embryos that were cultured in the presence of 200 µM ODQ (control, n=21; 200 µM, n=20; 100 µM, n=20; 50 µM, n=24). (C) Histogram shows that incubation in 500 µM 7NI resulted in a significant reduction of the migratory distance (7NI; n=21) when compared with cultured control embryos (control). This disruptive effect of 7NI could be rescued by the addition of 1 mM protoporphyrin IX free acid so that the MG neurons again covered the normal distance (7NI + protoporphyrin; n=20). (D) Incubation in 200 µM ODQ resulted in a significant reduction of the migratory distance (ODQ; n=20) when compared with cultured control embryos (control; n=21). This disruptive effect of ODQ could be rescued by the addition of 8Br-cGMP such that the MG neurons again covered the normal distance (ODQ + 8Br-cGMP; n=20). (E) MG neuron migration was significantly reduced in the presence of 100 µM forskolin (n=20) and 50 µM SPcAMPS (n=21). By contrast, 50 µM RPcAMPS had no significant effect on migration (n=21) when compared with controls (control). ^**P<0.005; ^***P<0.001.

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