MUCOSAL INHERENT ACTIVITY PATTERNS IN THE RAT - EVIDENCE FROM VOLTAGE-SENSITIVE DYES

1. Fluorescence changes in the dye di-4-ANEPPS were monitored on the r at's nasal septum and medial surface of the turbinates in response to odorant stimuli. For each mucosal surface a 6.0 x 6.0-mm area was samp led at 100 contiguous sites with a 10 x 10 photodiode array. The odora nts were-propyl acetate, 2-propanol, citral, L-carvone and ethylacetoa cetate, each presented at a low and high concentration. 2. Like previo us work using optical recording techniques and potential-sensitive dye s on the amphibian epithelium, the fluorescence signals elicited by od orant stimuli in the rat preparation were nearly identical in shape, t ime course, and response characteristics as the electroolfactogram (EG G). As with the EGG, a response could only be recorded in the presence of odorant stimuli (that is, no response was detected when nonodorize d, humidified air was presented as the stimulus); the amplitude depend ed on odorant concentration, and the response was abolished both by et her and Triton X-100. 3. Although the entire expanse of each sampled t issue (i.e., septum and medial surface of the turbinates) responded to stimulation with each odorant, each stimulus induced a distinct spati al pattern of activity that was independent of odorant concentration a nd consistent from animal to animal. Furthermore, the spatial activity patterns recorded for the septum were mirror images of those recorded from the medial surface of the turbinates. 4. Formal statistical anal ysis of the loci of maximal activity or ''hot spot'' indicated highly significant effects of the odorants for both the septum and medial sur face of the turbinates. 5. The results of these studies give further s upport to the hypothesis that odorant quality is encoded by differenti al spatial activity patterns in the olfactory epithelium that are char acteristic of differ ent odorants.