Fig. 8. A model for the development of IT and DA neurons. (A) Regulatory network underlying isotocinergic (IT, purple oval) and dopaminergic (DA, brown hexagon) neurons in the zebrafish hypothalamus (see text). Regulation of Otp by the proneural gene product Neurogenin1 (Neurog1) are yet to be determined (dashed arrow, see Discussion). (B) Expression of pac1, fezl and otp in either IT neurons that reside in the neurosecretory preoptic nucleus (NPO) or DA neurons that reside in the posterior tuberculum (PT) are schematically shown.