Figure 1. Location of Arch-transduced neurons and fiber optic tips. A1, Coronal section through the medulla (level ∼11.4 mm caudal to bregma) illustrating the selective expression of ArchT-EYFP by RTN neurons. RTN is identified by the line of strongly Phox2b-ir nuclei close to the ventral medullary surface (Takakura et al., 2006). A2, Higher-power photograph of an ArchT-transduced RTN neuron. This neuron had a Phox2b-immunoreactive (ir) nucleus, was negative for TH, but had close appositions from TH-ir synaptic boutons. A3, Coronal section (level ∼11.7 mm caudal to bregma) showing transduced RTN neurons (on the ventral medullary surface) and catecholamine (CA, presumably C1) cells dorsal to the latter. A4, Example of a transduced CA neuron containing EYFP and TH immunoreactivity plus a Phox2b-ir nucleus. A5, GFAP-ir cells (astrocytes, glia) are not ArchT-EYFP-ir. Arrows point to ArchT-EYFP-expressing neurons that are Phox2b-ir. Arrowhead indicates a nontransduced cell with a Phox2b-ir nucleus. A6, Higher-power photograph of an ArchT-transduced neuron. The GFAP-ir cells and processes are in very close proximity and do not contain EYFP. Scale bars: A1, A5, 100 μm; A3, 200 μm; A2, A4, A6, 20 μm. FN, Facial motor nucleus; vms, ventral medullary surface. B, Rostrocaudal distribution of transduced RTN and CA neurons following bilateral injections of PRSx8-ArchT-EYFP lentiviral vector under the caudal end of the facial motor nucleus (30-μm-thick sections, 180 μm apart). 8n, Eighth nerve root; Cb, cerebellum; DC, dorsal cochlear nucleus; FN, facial motor nucleus; g7, genu of the seventh nerve; py, pyramidal tract; sp5, spinal trigeminal tract; vsc, ventral spinocerebellar tract. The FN extends from −12.0 to −10 mm caudal to bregma. C, Location of the bilateral fiber optic tips identified in 10 rats. These sites are plotted on two transverse brain sections closest to their location; unique colors represent unique subjects. The exact transverse plane in which the fiber optic tips were found is also represented in B (triangles, same color code as in C). Stereotaxic coordinates (transverse planes posterior to bregma) correspond to the atlas of Paxinos and Watson (2005).