Figure 4.
Differential Ca2+ signaling mechanisms underlie the effects of cGMP- and cold stimulation in GGNs. A, B, CNGA3 immunoreactivity (red) is present in ciliary structures of GGNs in OMP-GFP+/− mice (A) but absent in GGNs of Cnga3−/− OMP-GFP+/− mice (B). Endogenous GFP expression (green) is observed in GGNs of both strains (A, B). Images shown are reconstructed Z-projections of 11 (A) or 19 (B) individual confocal sections, each 0.5 μm thick. Scale bar, 5 μm. Results are representative of the analysis of 6 mice per strain. C, D, Examples of Ca2+ responses in Cnga3−/− OMP-GFP+/− GGNs to stimulation with 60 mm K+, 100 μm IBMX, 2 mm 8-bromo-cGMP, or cooling to 12°C. E, Comparison of stimulus-evoked Ca2+ peak responses in GGNs of OMP-GFP+/− and Cnga3−/− OMP-GFP+/− mice. Number of cells is indicated above each bar. *p < 0.0001, unpaired t test; n.s., not significant. F, G, Ca2+ responses to a range of temperature stimuli (F) and analyzed stimulus-response curves (G) in Cnga3−/− OMP-GFP+/− GGNs. H–J, Differential effect of tetrodotoxin (1 μm) on Ca2+ responses to cooling or IBMX in OMP-GFP+/− GGNs. Number of cells is indicated above each bar (J). *p < 0.0001, paired t test; n.s., not significant. Analysis of Cnga3−/− OMP-GFP+/− GGNs gave the same results (data not shown). Basal temperature, 22°C.