(A) Experimental design. (B) The number of TH and GFP neurons in the RVLM (N = 4). Cell count was obtained in six coronary brain sections (40 μm with 240 μm intervals between slices) from each rat. (C, C’) Single case showing that the C1 neurons are transfected by the lentivirus PRSX8-ChR2-eYFP. (D, E) Schematic drawing of a coronal brain section showing the distribution of GFP terminals in the pFRG region in three rats (bregma level: −11.36 mm in accordance with Paxinos and Watson, 2007). (E’) Photomicrography showing terminals into the pFRG region of the R#03. (F–H) Photomicrography showing fibers and terminals expressing lentivirus (GFP, green) and glutamate (VGlut2, red) in the pFRG region. Abbreviations: Fn, facial nerve; GFP, green fluorescent protein; pFRG, parafacial respiratory group; NTS, nucleus of the solitary tract; py, pyramid tract; RPa, raphe pallidus; RVLM, rostral ventrolateral medulla; Sp5, spinal trigeminal tract; TH, tyrosine hydroxylase; VGlut2, vesicular glutamate transporter 2; VII, facial motor nucleus. Scale bars in panels (C) and (E–H) = 50 μm, (C’), (E’) and (H’) = 20 μm, (D) = 1 mm.