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Comparative Study
. 2000 Mar 15;20(6):2383-90.
doi: 10.1523/JNEUROSCI.20-06-02383.2000.

Peripheral odor coding in the rat and frog: quality and intensity specification

P Duchamp-Viret  1 , A Duchamp, M A Chaput
Affiliations
Comparative Study

Peripheral odor coding in the rat and frog: quality and intensity specification

P Duchamp-Viret et al. J Neurosci. .

Abstract

In mammals, two recent studies have shown recently that one odor molecule can be recognized by several molecular olfactory receptors (ORs), and a single OR can recognize multiple odor molecules. In addition, one olfactory receptor neuron (ORN) may respond to different stimuli chosen as representative of distinct odor qualities. The aim of the present study was to analyze quality and intensity coding abilities of rat single ORNs, comparing them with previous extensive data gathered in the frog to get insight into the generality of olfactory coding mechanisms over vertebrates. Response properties of 90 rat ORNs to different odors or to one odor at different concentrations were analyzed. In the rat and the frog, odor quality appears to be specified through the identity of activated ORNs. However, rat ORNs have higher response thresholds. This lower sensitivity may be interpreted as an increase in selectivity of rat ORNs for low or medium odor intensities. In these conditions, the lower proportion of activated ORNs could be counterbalanced by their number, as well as by their higher glomerular convergence ratio in the olfactory bulb. From amphibians to mammals, the olfactory system appears to use universal mechanisms based on a combinatorial-coding mode that may allow quasi-infinite possibilities of adaptation to various olfactory environments.

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Figures

Fig. 1.
Fig. 1.
Distribution of spontaneous ORN firing frequencies in the rat (n = 90) and the frog (n = 99) (Revial et al., 1982).
Fig. 2.
Fig. 2.
Spontaneous activity (top trace) and response profile (bottom traces) of ORN13 (raw data). This ORN was tested with all odors except CIT. It did not respond to CAM, CIN, VAN, d-CAR, andl-CAR, and to CYM, CDN, HEP, and HEX (data not shown). All its thresholds corresponded to SV/5.62, i.e., 3.5 × 10−6m/l for ACE, 1.9 × 10−5m/l for LIM, 3.5 × 10−5m/l for ANI and MAC, and 5.2 × 10−5m/l for ISO.
Fig. 3.
Fig. 3.
Percentages of excitatory (hatchedand dotted bars) and suppressive (black bars) responses elicited by six odors commonly tested in the rat and frog.
Fig. 4.
Fig. 4.
Distribution of response types in single ORNs response profiles. Black bars represent ORNs that were simulated with the six odors of the first subset (ACE, ANI, CAM, LIM, ISO, and MAC). Hatched bars represent ORNs that were tested with 2 of the 16 odors of our set. Bars represent response profiles of ORNs containing no response to all the tested odors (N), excitatory responses only (E), both excitatory and suppressive responses (E/S), both excitatory and no responses (E/N), both suppressive and no responses (S/N), and excitatory, suppressive, and no responses (E/S/N).
Fig. 5.
Fig. 5.
Selectivity of ORNs for ISO, LIM, ANI, and CAM. Distribution of the percentages of cells as a function of the number of odors to which they responded by excitation. Hatched bar, Rat (n = 51); line with symbols, frog (n = 60).
Fig. 6.
Fig. 6.
Percentages of successful discrimination of odor pairs by rat ORNs. On the right are indicated the number of pairs used for each comparison. Only pairs presented to at least 15 cells are shown.
Fig. 7.
Fig. 7.
Percentages of successful discrimination of odor pairs in the rat and frog for ANI, ISO, LIM, and MAK.
Fig. 8.
Fig. 8.
Spontaneous (top trace) and odor-evoked single-unit responses and EOGs (pairs of bottom traces) of rat ORN50 (raw data) to increasing concentrations of ANI. Recordings obtained for two presentations at 1.98 × 10−5m/l (SV/10) illustrate the reproducibility of the response. Firing frequencies in the initial response burst and amplitudes of the EOG are given between the respective recordings. Concentrations (molar) are on theleft and right, respectively.Asterisks below single-unit recordings indicate the artifact at the beginning of the stimulation. This ORN had a mean spontaneous firing frequency of ∼1 spike/sec.
Fig. 9.
Fig. 9.
Detail of Figure 8. Initial decremental response bursts of ORN50 (indicated by arrowheads in Fig. 8) elicited at high concentrations.
Fig. 10.
Fig. 10.
Concentration–response curves of ORN50 spike frequency and EOG amplitude, and their corresponding latency curves (inset).
Fig. 11.
Fig. 11.
Concentration–response curves of ORN55 spike frequency and EOG amplitude, and their corresponding latency curves (inset).
Fig. 12.
Fig. 12.
Distribution of rat ORNs response thresholds (n = 55) over the concentrations ranges for the six odors of the first subset. For each odor, the diameters of thefilled circles are proportional to the number of thresholds determined for a given concentration.
Fig. 13.
Fig. 13.
Dynamics of ORNs recruitment for ANI, CAM, ISO, and LIM in the rat and frog. The cumulative number of excited cells is represented as a function of concentration. One hundred percent of excited cells correspond to 53.5 and 59% of the total number of stimulation performed in the rat and frog, respectively. We had observed in preliminary experiments the low sensitivity of rat ORNs compared with the frog. This led us to shift the concentration range available toward higher values. Thus, concentrations lower than SV/1000 were not tested in the rat.
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References

    1. Breer H, Boekhoff I, Tareilus E. Rapid kinetics of second messenger formation in olfactory transduction. Nature. 1990;345:65–68. - PubMed
    1. Bronstein AA. Olfactory receptors of vertebrates (in Russian) (Setchenova IM, ed), pp 1–159. Sciences Editions; Leningrad: 1977.
    1. Buck L. Identification and analysis of a multigene family encoding odorant receptors: implications for mechanisms underlying olfactory information processing. Chem Senses. 1993;18:203–208.
    1. Buck L, Axel R. A novel multigene family may encode odorant receptors: a molecular basis for odor recognition. Cell. 1991;65:175–187. - PubMed
    1. Byrd CA, Burd GD. Development of the olfactory bulb in the clawed frog, Xenopus laevis: a morphological and quantitative analysis. J Comp Neurol. 1991;314:79–90. - PubMed

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