The co-expression of VR1 and VRL-1 in the rat vagal sensory ganglia

Immunohistochemistry for two nociceptive transducers, the vanilloid receptor 1 (VR1) and vanilloid receptor 1-like receptor (VRL-1), was performed on the vagal sensory ganglia. In the jugular ganglion, VR1-immunoreactive (IR) neurons were small to medium-sized (range 49.7–1125.6 μm², mean±S.D. 407.7±219.7 μm²), whereas VRL-1-IR neurons were medium-sized to large (range 223.6–1341.1 μm², mean±S.D. 584.3±253.5 μm²). In the nodose ganglion, VR1- and VRL-1-IR neurons were mostly small to medium-sized (VR1: range 148.5–1464.4 μm², mean±S.D. 554.3±207.4 μm²; VRL-1: range 161.7–1166.2 μm², mean±S.D. 541.9±186.2 μm²). The double immunofluorescence method revealed that co-expression of VR1-immunoreactivity among VRL-1-IR neurons was more abundant in the nodose ganglion (63%) than in the jugular ganglion (4%). The present study suggests that co-expression of VR1 and VRL-1 may be more common in visceral sensory neurons than in somatic sensory neurons.