Retrograde labeling of PVN-RVLM neurons. A, RVLM injection site was verified with serial medulla slices including RVLM (100 μm thickness). The representative image shows that a fluorescent spot was confined to the triangular frame defined as RVLM . Amb, nucleus ambiguus; sp, the spinal trigeminal nucleus; py, pyramidal tracts; scale bar = 1 mm. B, the fluorescent image illustrates that the labeled PVN-RVLM neurons were located in the medial region (a) and in the posterior region (b) of the PVN in the hypothalamic brain slices (300 μm thickness). The PVN-RVLM neurons are evident primarily in the dorsal cap (DC), the ventral parvocellular (PaV), and the posterior parvocellular (PaPo) subdivisions. 3 V, the third ventricle; scale bar = 200 μm.