Fig. 1. Sensory neurones expressing Robo and Slit RNA are intermingled in the VNO at P1. Coronal sections through the VNO outline the sensory epithelia (se, broken line) located underneath the nasal septum (s). (A,B) Cell bodies expressing Robo1 (A) or Robo2 (B) are scattered throughout the sensory epithelia of the VNO in newborn mice. (C) Sections stained with Robo2 sense riboprobes are negative. (D,F) Slit1-(D) and Slit3 (F)-expressing cells are distributed all over the entire area of the sensory epithelia. (E) Slit2 is not expressed on the sensory epithelia, but marks the lateral margins of the VNO sensory epithelia. (G,H) Higher magnifications of B and D, indicating that individual neurones expressing Slit1 (G) and Robo2 (H) RNA are distributed in patches in the VNO sensory epithelium. D, dorsal; l, lumen; se, sensory epithelium; s, nasal septum; V, ventral; vv, vomeronasal vein. Scale-bar: 100 µm in A-F; 50 µm in G,H.