Figure 1 A-F.

Distribution of PVH neurons that project to the NTS as determined by retrograde neuronal labeling. CTb was injected in the medial NTS (insert panel A′), with some spread into the dorsal vagal nucleus (DMX) and area postrema (AP). This pattern of retrograde labeling is relevant to the present study because, among all target sites in the brainstem, this region of the NTS receives the most extensive input from the PVH. Most of the neurons that project to the NTS (red dots) are concentrated in a ventral region of the medial parvicellular PVH (PVH-mp, panel C), but other regions including the dorsal, lateral, and perifornical parvicellular subdivisions (PVH-dp, PVH-lp, and PVH-f, respectively) contribute to this projection. These projection neurons are not restricted to any one of PVH subdivision, but originate from all of regions, including the dorsal parvicellular subnucleus, which supplies the highest number of PVH neurons that project to the spinal cord (Hosoya and Matsushita, 1979). Weaker projections from contralateral PVH subnuclei were found as well. Very few CTb-labeled cells were located in surrounding regions of the diencephalon, other than a group of neurons lying dorsal to the fornix in the LHA (panel F), which is anatomically continuous with and morphologically similar to those in the PVH. Case #8148 was used in a previous publication (Geerling and Loewy, 2006a). Inset scale bar is 500 μm.