Fig. 5. Immunohistochemical demonstration of the innervation of the gut of developing zebrafish, showing NKA-like immunoreactivity at 3 d.p.f. (A) and 7 d.p.f. (B; arrows indicate nerve fibres and arrowheads indicate endocrine cells), and PACAP-like immunoreactivity in nerves at 2 d.p.f. (C; arrows), and 7 d.p.f. (D). Bars, 50 µm.