Cyclic nucleotide-gated ion channels, not PKA or PKG signalling, mediates Sema3A-induced growth cone collapse in sympathetic neurones. (A, B) Inhibition of PKG with KT-5823 (A) or Rp-8-Br-cGMPS (B) did not significantly alter Sema3A-induced growth cone collapse in sympathetic neurones, but both inhibitors caused growth cone collapse on their own. (C, D) Similarly, inhibition of PKA (C, KT-5720; D, Rp-cAMPS) did not alter Sema3A-collapse, but both of these inhibitors caused growth cone collapse. (E,F) However, inhibition of CNGCs (E, DCB; F, LCD) prevented Sema3A-collapse in sympathetic neurones. Furthermore, Sema3A prevented the collapse caused by DCB and LCD on their own. Tukey's test: *P < 0.05, **P < 0.01, ***P < 0.001 versus control (n= 3–5 for all experiments). **P < 0.01, ***P < 0.001 versus control; ##P < 0.01 versus Sema3A; +P < 0.05, ++P < 0.01 versus DCB or LCD. DCB, 2′,4′-dichlorobenzamil; KT-5720, (9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid, hexyl ester; KT-5823, (9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid, methyl ester; LCD, L-cis-diltiazem; Rp-cAMPS, Rp-adenosine-3′,5′-cyclic monophosphorothioate; Rp-8-Br-cGMPS, Rp-8-bromoguanosine-3′,5′-cyclic monophosphorothioate; Sema3A, semaphorin 3A.