HASEGAWA, Masami

YAMADA, Minoru

YOMOSA, Shigeo

Kyoto University Research Information Repository

TitleA Model for Odor Coding at the ReceptorsAuthor(s)YAMADA, Minoru; YOMOSA, Shigeo; HASEGAWA,MasamiCitation防虫科学 (1970), 35(3): 69-72Issue Date1970-08-31URL http://hdl.handle.net/2433/158626RightType Departmental Bulletin PaperTextversionpublisherKyoto University',''JmA Model for Odor Coding at the Receptors. Minoru YAMADA (Fisheries Laboratory, Facultyof Agriculture, Nagoya University, Nagoya, Japan) Shigeo YOMOSA (Department of Physics,Faculty of Science, Nagoya University, Nagoya, Japan) Masami HASEGAWA (Department ofBiophysics and Biochemistry, Faculty of Science, University of Tokyo, Tokyo, Japan) ReceivedJuly 3, 1970, Boiyu-kagaku 35, 69, 1970.8. I\Ut~~~n~I:t.>I:t {,1:]' '~$51~mtf.o.H:T JI- 11~[I] ~ (i;tiill*~ n~$ 7l<~~£l(~[)t=ijliJP~{£mm. (~~ill*~llI1~$J.II1ifuU1:~~llI1tx!li) !HtJIli&~ Otu.!,(*~llI1~Jlil1::~{~~£l('?i[)45. 7. 3 ~J.II11:;J~ 'O)~5JUI:tP;lJ>lt It-Cf1bn -CP;;';/), c P ? F&lm l:t, 1!i'*J:!> fRnv ; n, ~ <O)~~~1::lvt~;/);, 4-13 f,.::lUOO ; ;/)'1<:' *n -CP t,.:p. z r.. -e1:tmE!tll$!;j1;~~m;/);W551l?Jf!, S.il!!l?J~ ~ C ? ~5JU It-C~';:';/J' ~m~1:::rn~I'BI<:.itfIl«, z O)~~M* c vt*OO ; ;/)'1<:' *n -C*t.:nJQI<:.tJ;-:5P-C, iff{t 1Jl€1J!f{t!llbl]:ltiiJil<:..J; -C1:t;t;:, ~~'~5JHtIWjO) 'C 7' Jl-Ij;>~~ It, "~~'~5JU:1Jl'i1~" t,,;:, t.0) ~'? <'? tc.IntroductionOne of the most striking features of olfactorysystem is its power to discriminate among a largenumber of odors. Consequently, the manner bywhich odor quality is analyzed and encoded byolfactory system has long been a question offundamental importance. However, it is painfullyapparent that our understanding of this branchof physiology is little more advanced today thanit was at its inception. This has been due in largepart to a lamentable lack of understanding ofthe basic neurophysiological principles underlyingthis subject. This communication present atheoretical basis for olfactory discrimination basedon the neurophysiological observation.We had assumed at first that there might bea specific receptor or group of receptors for eachsubjectively distinguishable odor quality. Odorquality was thus coded in terms of activity orinactivity in .particular receptors, and intensityin terms of the degree of that activity.We become heartened in this notion of specificreceptors by the existence of those congenitalanosmias being collected by Amoore (1964). Thereare some people who cannot smell cyanides, otherswho cannot smell butyric acid or butyrates, otherswho cannot smell whatever the compound is thatissues in the urine of one who has eaten asparagus.But these people seem to be able to distinguishother smells perfectly well. Their blindness isvery similar to a notch defect in audition. It isthis analogy with sound that underlies the questfor chemically specific receptors just as onesearches for frequency specific elements in theear·>. Besides, in the electrophysiological studyof the olfactory receptors of insects it was foundthat there does exist many odor-specific receptors(which we call "odor specialists") for the detectionof food, or pheromonesv", On the other hand,except for these "odor specialists" the bulk of theolfactory receptors in the antennae are not odor-specific. They respond differentially to the odorouscompounds; that is, they respond more to somecompounds than to others. Moreover, Gestelandet al, (1965) hypothesized, on the basis of theirrecordings from single olfactory receptors of thefrog, that ..·.. ·.. in the very limit we have utterchaos; that every fiber is sensitive, more or less,to every odor from being greatly inhibited tobeing highly excited, and the receptors are notlike each other in their response to any groupof odors." In such a situation it is evident thatodor quality could not be coded in terms of activityor inactivity in particular receptors as we expectedat first. Accordingly, the work to be reportedhere is an attempt to detect the behavior ofsingle olfactory receptors of insects to their foodattractant and repellent with a view towardunderstanding the mechanism of quality discrimi-nation.Materials and MethodsThe antennal olfactory hair of the fruit-piercing69~fj !It n ~j~ m 35 &- 11 1moth A dris tyrannus anturcnsts Sta udi nge r , wasused. The recor ding tech nique and the s t im ula t ingmeth od we re a lm os t th e sa me as that desc r ibedby Ya mada (1967) . Sing le rece ptor recordin g isdo ne ex t racell u la r ly with a glass ca pilla ry e lec t ro dethr us t in to an a nte nna I ha ir se ns illum , whi le theindif ferent el ect rod e is placed in th e hem olymphs pace of th e a n te nna. This method permitss im ulta neous r eco rd ings of receptor poten ti a lsa nd nerve impul ses .Resu lt s a nd Dtscuss in nMa ny recepto rs show a low rate of dischargea t rest. T h is r a te is a lmos t rhythm ic in somecases, a n d seems a lmost co m ple te ly ir r egu la r inot he r s . Olfacto r y s t im uli eit he r ind uce a n im pulsefreq uen cy inc rea se , depress s ponta neous d is-cha rges , o r produ ce no resp onse a t a ll. F igu re Ishows respon ses of a receptor whi c h has nosp ont an eou s d is .ha rge to th eir food attract ant(g r a pe odor ) and re pellent (.I- me thyl- I- phenyl-hexen - x- one) _ W hen th e recep tor is s t im ula te d ,tw o com po ne nts ca n be di stingui sh ed in th eelec t ri ca l response , a s low pot entia l and s pikepote n t ial s , as seen from Fig . 1 a a nd b. Sin ce t hemai n pu rpose o f th is pa per is to xpla in t he qua litycod ing of odors, it is suffi ci ent here to not e thatthe s low pot entia l (t he generat or pot entia l) arisesup on s t im ula t ion, acco mp an ying the tra in ofim pulses and its polar ity is negative a t t hereco rd ing poi n t with ref er ence to the hemo lym phAaspace of th e bod y' .12) •At first we expec te d that food att rac ta n t a ndre pellent wou ld be very different in s t imula t iveeffec ts on each recept or , fo r behav ior a lly th einsects resp ond in quite oppos ite manne rs to t hesetw o co m pounds'" . Therefore it was rathe r as-toni shing that both food attractant and rep ellentinduced a negative s low potentia l (depola r iza t ionof receptor m e rn br une) ac co m panied by a n inc reasein impu lse f req uency.However , wh en we ca re fully compa re th e sha pesof slow potent ia ls and tem pora l pa tt er ns of im pu lsef ir ing , t he re seems to exis t so me diffe rence int he responses to food a tt ract a n t and re pellent .For exa m pi , food att rac ta nt indu ced th e sus ta inednega t ive monophas ic poten t ia l acc om pan ied byt ra ins of impu lses, wh ile repellent evo ke d theirreg ula r negative pot en t ia l accom pa nied by theim pulse fr eq uen cy inc reased o r dec reased witha fall or a ri se of th e slow potent ia l, res pec tive ly.T heref ore . we mi g ht sa y that the temporalpa tt e rn s of ex c ita t ion provide th e basis for odordi scrimination . So fa r we hav e recorded theactiv iti es of more th an 20 receptors in va r iousregions of t he a ntenna. So me of th em resp ond edto food a tt rac ta n t with a irregula r negativepoten tial , but wi th the susta ined negat ive mono-ph asic poten tia l to repellent. Howev- r , in manyreceptors test ed it is ve ry ha rd to co m pa re thed iffe rences of tempora l pattern of exc ita t ion. for( I) t he d if fe renc es in response patt rn s are ve ryBbFi g . J. 1\ , Method of recordi i g ac t ion pot enti a ls wit h g la ss ca pilla ry e lec t rodes fr om asing le olfac to ry sensill um . B. Resp onses of a I' c pt or to food a tt rac ta n t (a) . a ndre p II nt (b) . pper ( D- C) t ra c ings show r eceptor pot n t ia l with ne r ve im pulses ;lower (I{- ' ) traci ngs show only nerve impulses. T he down wa r d deflec t ionre presents n gative pote ntia l at t he recor di ng e lec t rod e . T he black bars beloweac h tracin g indicat e th e dura t ion of th e s t im ulat ion.70small; (2) the receptors do not always elicit aunique and stable response pattern to the repetitivestimulations of the same odor; (3) the stimuli tobe tested are not quantitatively wel1 control1ed.In the light of these observations it seemspossible to assume that the receptors possess somedegree of odor specificity. It is apparent. however,that the absolute amount of activity in any thesereceptors cannot by itself encode odor quality.because. as can be seen in Fig. 1 two chemicalscan elicit impulse discharges in the same receptor.Furthermore. temporal patterns of excitation ofa single receptor during stimulation seemsimpossible to provide the basis for qualitydiscrimination. for the receptors could not havea unique and reproducible temporal patterns ofexcitation for each odorant under our experimentalconditions.How may olfactory receptors. with the propertiesoutlined above. encode odor quality? It seemslogical to assume that one mechanism basic toquality coding by this insect may involve thesort of combination of the activity of all individualolfactory receptors on the antenna.From these reasonings we present the fol1owingequation as the model of quality coding (or "odorquality coding equation")( 1 )where the direction of the vector YJ representsthe odor quality j: the length of the vector YJrepresents the intensity of odor quality j: theunit vector XI denotes the unit activity of neuronei: and the coefficients CJI is the sensitivity ofneurone i to the compound [,Implicit in this theory of coding is the assumptionthat (1) the relative amounts of activity elicitedby different chemicals in each neurone will notbe altered significantly by changes in stimulus-"concentration; (2) n vectors XI <I•••2... • .. ·.n) aremutual1y orthogonal. for we would treat thecharacteristic of every neurone as independent:(3) temporal pattern of impulse firing in a singlereceptor during stimulation are ignored to simplifythe coding problem.According to the model. it would be possible.by simply having very many receptors possessingdifferential sensitivity. to distinguish very manycompounds. for each odor quality could beexpressed as a point in n coordinates system inspace whose axes are mutual1y perpendicularstraight lines. It could also be applicable to thecoding of insect's sex attractants of the moths?For example. insect sex attractants are veryeffective stimulant only to the sex- attractantreceptors. but not to the other olfactory receptors.Therefore, the equation (1) could be written inthe form of Kronecker's delta function:-" ->.YR=~ AloslX\,i0<1={I (i e sex attractant receptors) (2)o (i vsex attractant receptors)where AIOsl corresponds to Cli of the equation(1). This equation implies that the absoluteamount of activity in anyone "odor specialist"could by itself encode quality.The important features of these equation (1)and (2) are that 1) the transformation fromchemical compound space to physiological smellspace partakes the linear combinations of theactivities in every olfactory receptor: 2) odorquality could be represented as the set of {C ll}·1.1.2,•••••n; 3) because the direction of the vectorYl represents the odor quality j. the folIowingequation could be used as the criteria of odorsimilarity.->. -" ,SlJ'=cosO=-YL:....XL. -1<Sl3'<1 (3)I~HY1'1We define S as the function to represent thedegree of odor similarity, therefore. the largevalue means the high degree of odor similarity.It should be noted here that this equation makesit possble to measure quantitatively the degreeof similarity between odorants in the numericalscales. Using the equation (3). we are going toclassify the odor similarities of many compoundsby the help of electric computer.In conjunction with the above discussion. it isperhaps worth describing the classification ofsmel1s by man. Given sufficient training, someof us can become expert in picking out the partsof a complex odor. or small differences of thesmell. But there is no way of telling theseperceptions to others except by simile. Even whenprofessional perfumers address each other. it isin a cant that evokes intuition rather than71understanding. In short there is no coherentaccount of how to tell one smell from another.In that sense, the equation (3) could be regardedas a new step to approach the mechanism ofclassification of odors.Finally, in view of the fundamental likenessfound in the response behavior of single olfactoryreceptors in insect antennaev", and in the verte-brate olfactory mucosasv, the equation (1) wouldappear to be the "quality coding equation" basicfor the odor quality coding in the invertebrateas well as the vertebrate.Acknowledgement We thank Drs. T. Tamura,K. Iyatomi and T. Saito of Nagoya University fortheir encouragement and valuable advices, MissK. Kamiya and Mr. H. Honda for their assistance.References1) Amoore, J. E.: Ann. N. Y. Acad. Sci. 116,457(1964).2) Boeckh, J., K. E. Kaissling, and D. Schneider:Cold. Spring Harbor Symp. Qunt. Bioi.30, 263 (1965).3) Gesteland, R. C., B. Howland, J. Y. Lettvin,and W. H. Pitts: ]. Physiol. 181, 525 (1965).4) Helmholtz, H.: Gesellsch.Deutsch. Naturf.Aerzte. Amtl. Ber. 34, 157 (1859).5) O'Connell, R. J. and M. M. Mozell:]. Neurophysiol, 32, 51 (1969).6) Saito, T., K. Munakata, and K. Iyatomi:In symp. on "Protections from the' fruit-piercing moths" (Ed. by Asami Y.), 91-99(1962), Japan Plant Protection Association,Tokyo.7) Schneider, D., B. Lacher, and K. E. Kaissling:Z. vergl. Physiol. 48. 632 (1964).8) Yamada, M.: Appl. Ent. Zool. 2,22 (1967).9) Yamada, M.: Nature 217, 778 (1968).10) Yamada, M., S. Ishii, and Y. Kuwahara:Botyu-Kagaku 33, 37 (1968).11) Yamada, M., S. Ishii, and Y. Kuwahara:Nature in press.12) Yamada, M.: ]. Insect Physiol. in press.Method for the Determination of Residues of Meobal&i (3, 4-Dimethylphenyl N-MethylCarbamate) in Rice Grains. Seizo SUMIDA, Masahiro TAKAKI, and Junshi MIYAMOTO (ResearchDepartment, Pesticides Division, Sumitomo Chemical Co., Ltd., Konohana-ku, Osaka, Japan)Received July 14, 1970, Boiyu-Kagaku 35, 72, 1970.9. ~*rf:l0)C ;;f"'\-J!-® (3,4-dimethylphenyl N-methyl carbamate) O)~il~tfimlUWi1i· 7.'6*lEl:I9 • '&.f2I>:~1iz (a::tt1~~Imtli~~ttm~m!,;'HmjjJf,'G*1l, *1~!jtmJ!t:lE[&1f:B WillI) 45.7. 14 ~J.!I!=«*Jt:t0) ;t ::t I"{ - )vO) 7!:7. 7 t:I "'< I- 7' ") 7 -1 -IC J: Q ~fi1:5ttJT~ ~¥IH!f"9Q. f5}i1' ut::r:*~ ~7 t:I )v;t 11 :;-7 -e 1-:;-7l<O)l[lftllX"t'MUl V. illHfH?J~ "JJ ") J,. &(f/f!jJrj} 7 t:I "'< I- If") 7 -1 - -r: 7 ~-:; 7 -:J 7'"9 Q. lXlC, HE,;!.t:1ttfl~pO);t ::t I"{ - )vO)1J!l*:5tm&(f ~:=. I- t:I 7 s: :=.)v{I:J~ fillD!j((1ICfib-lt DNP-;t 7)v7 ~:; (2,4-dinitrophenyl methylamine) ~mQ. DNP-;t 7)v7 ~ :; ~;I'.V71-t:l:;4'-.y7'7-\,- tJ:7.7t:1"'< 1-7·")7-1-ICJ:9JE:I.i1"9Q, [illJ!lt~l;l: 0.5ppm v-.()v-z:>87f6 "t'ih.,t:. *mll:J:nli, O.Olppm 3Z,1:l"Cnl'-t"F;:f-z:>O);t ::t/"{-)vO)£JGfi1L1~:5ttJT-z:>~ Q.Meobalte (3,4-dimethylphenyl N-methyl car-bamate) is an insecticidal compound developedby Sumitomo Chemical Co., Ltd. for pest controlmainly of rice plant. From the standpoint ofpublic hygiene, it is quite important to haveinformation on the residues of this compoundleft in the rice grains. Methods had been reportedfor the determination of N-methyl carbamatesin a number of plants,I,2> but they failed to giveconsistent results with rice grains, as tested in72our laborotory. Under these circumstances, anattempt was made to develop a new method toserve our purposes.We have reported elsewhere" that micro-quantities of N-methyl carbamates can be de-termined by converting them to 2,4-dinitrophenylmethylamine (DNP-MA) in a novel fashion, i. e.,N-methyl carba~ate is heated at 100'C and atpH 9 in the presence of 2,4-dinitro-l-fluorobenzene(DNFB). The carbamate breaks down under these

8.嗅覚受容器における匂い識別機構のモデル

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8.嗅覚受容器における匂い識別機構のモデル

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