Figure 8. Autoradiographs of 125I-VIP binding on E14 rat embryos. Autoradiography was performed as previously described (71). a: Sagittal section, total binding showing relatively even and dense VIP binding throughout the brainstem and spinal cord, dense binding in the posterior commissure and low to moderate binding in the forebrain. Low levels of binding can also be seen in the gut. b: Stained section adjacent to ‘a' to show morphological detail. c: Stained section, enlargement of the posterior commissure showing fasciculation. d: Sagittal section of spinal cord, total binding. e: Coronal section, total binding. f: Coronal section, total binding. g: Sagittal section of spinal cord adjacent to ‘d', binding in the presence of stable GTP analogue showing dense GTP-insensitive binding in the ventral midline, including the floor plate region. h: Coronal section, adjacent to ‘e', binding in the presence of stable GTP analogue showing dense GTP-insensitive binding in the posterior commissure. I: Coronal section, adjacent to ‘f', binding in the presence of stable GTP analogue showing dense GTP-insensitive binding in dorsal midline structures. PC, posterior commissure. Bar in ‘c' = 0.24 mm, bar in ‘a' = 2.0 mm and applies to all sections but ‘c'. (Taken, with permission, from ref. 71)