Background
In mammals, detection of ambient temperatures is mainly mediated by thermosensory neurons residing in the dorsal root ganglion (DRG) and trigeminal ganglion (TG) [1–3]. Recently, neurons in the Grueneberg ganglion (GG) of the murine nasal vestibule have been found to be activated by cool temperatures [4, 5]. Unlike coolness-sensitive cells in the DRG and TG, neurons in the GG lack the TRPM8 channel [6] which is considered as a principal detector of cold [1–3]. Therefore, GG neurons are supposedly endowed with a so far unknown thermosensor. Interestingly, coolness-sensitive GG neurons express signaling elements associated with cyclic guanosine monophosphate (cGMP), including the cGMP-activated ion channel CNGA3 and receptor guanylyl cyclase-G (GC-G) [6–8]. Recent observations suggest that cGMP signaling is crucial for thermotransduction in the GG [8]. However, whether GC-G directly acts as a temperature sensor remains elusive.