Odor-evoked spH responses to retronasal airflow in the dorsal olfactory bulb. A: Resting fluorescence image of the dorsal olfactory bulb showing spH-labeled glomeruli visible through thinned bone. No glomerular responses were observed in the absence of odor stimuli. Scale bar = 200 μm. B: Glomerular response maps to 50% v/v eugenol presented orthonasally or retronasally under different flow rates and stimulus durations. The pseudocolored images show % change in spH fluorescence from resting fluorescence intensity recorded before stimulus onset. Images were obtained from the same animal preparation. The three numbered white arrows indicate the glomeruli for which odor-evoked responses were analyzed in panels C and D. C: The amplitudes of orthonasal and retronasal responses at different flow rates and stimulus durations. Response amplitudes were quantified for glomeruli #1 – #3 corresponding to numbered arrows in panel B. Each value is the mean ± SE of 3 trials. D: Normalized response traces evoked by 10 s (left) and 30 s (right) stimulus pulses in glomerulus #1. The shaded regions indicate the duration of odor pulses. Red lines indicate orthonasal response traces at a flow rate of 150 ml/min. Blue and green lines indicate retronasal response traces at 150 and 300 ml/min, respectively.