Regional Distribution of Rat Electroolfactogram (EOG).
Ezeh, Patrick I., Lisa M. Davis, and John W. Scott.
Department of Anatomy and Cell Biology, Emory University School of Medicine
Atlanta, Georgia 30322-3030, U.S.A.
APStracts 2:0009N, 1995.
SUMMARY AND CONCLUSIONS
1. Electroolfactorgram (EOG) recordings were made from different regions of
the rat olfactory epithelium to test for spatial distribution of odor
responses. 2. The EOG recordings showed spatial distribution of the odor
responses in the olfactory epithelium. While some odorants (amyl acetate,
anisole, and ethyl butyrate) were more effective in evoking responses in the
dorsal recess near the septum, other odorants (including limonene, cineole,
cyclooctane, and hexane) were more effective in at the lateral recesses among
the turbinate bones. These differences were seen as statistically significant
odorant-by-position interactions in analysis of variance. 3. Comparisons of
recordings along the anterior-posterior dimension of the epithelium produced
smaller differences between the odor responses. These were not significant for
3 mm distances, but were statistically significant for 5-6 mm distances along
the dorsomedial epithelium. 4. The latencies were significantly longer in the
lateral recesses than in the medial region. This probably reflects a more
tortuous air path along the turbinate bones to the lateral recesses. 5. The
olfactory receptor cells were activated by antidromic stimulation via the
nerve layer of the olfactory bulb. The population spikes evoked from the
olfactory receptor cells could be suppressed by prior stimulation with
odorants that evoked strong EOG responses. This collision of the antidromic
action potentials with the odor evoked action potentials indicates that the
same population of receptor cells were activated in both cases. 6. The flow
rate and duration of the artificial sniff were varied systematically in some
experiments. The differential distribution of response sizes was present at
all flow rates and sniff durations. Some odors (eg. amyl acetate and anisole)
produced increased responses in the epithelium of the lateral recesses when
flow rates or sniff durations were high. We suggest that these changes may
reflect the sorptive properties of the nasal membranes on these odors. The
responses to other odors (eg. hexane or limonene) were not greatly affected by
flow rate or sniff duration. 7. Taken with existing anatomical data, the
results indicate that the primary olfactory neurons that project axons to
glomeruli in different parts of the olfactory bulb are responsive to different
odors. The latency differences between responses at medial and lateral sites
are large enough to be physiologically significant in the generation of the
patterned responses of olfactory bulb neurons.
Received 30 August; accepted in final form 8 February 1995.
APS Manuscript Number J543-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.