Rat airways express the Tas1R3 receptor and the G-protein α-gustducin. A. A PCR product for the α-gustducin gene is present in taste, respiratory and gastrointestinal tissue samples. B-G. Antisense probe (AS) for α-gustducin hybridizes with taste cells (B-D), as well as taste buds in the epiglottis (red arrows; F) and SCCs in the rhinopharynx and trachea (green arrows; E and G). H. The Tas1R3 gene PCR product is present in taste and airway tissue, but is not detectable in bronchi and lung. In contrast PCR for α-gustducin is positive in rat bronchi and lungs. Testis are positive for α-gustducin, but not for Tas1R3 I-N. The Tas1R3 AS probe hybridizes to taste tissue (I-K), laryngeal epithelium (red arrows indicate location of the taste buds; L-M) and a few SCCs in the trachea (green arrow; N). None of the negative control tissue (heart, spleen, liver and brain) showed expression of these two genes in PCR. Likewise, sense-control in situ probes showed no signal in any epithelium (Additional file 3). CV = circumvallate papillae; Fol = foliate papillae; Fung = fungiform papillae.