Implications of power law exponent in synergy and inhibition of olfactory mixtures

Abstract

An index of olfactory quantitative interaction has been defined by Laffort and Dravnieks (1982). This index is obtained by combining the experimental effectiveness of mixtures with the power law exponent of the components. When its value equals 1, this means that the ‘apparent’ inhibitions and synergies can be expressed only through the power law exponents of the components. This, of course, holds true when a substance is added to itself. Values less than or greater than 1 are interpreted as ‘true’ inhibition and synergy respectively. In a slightly modified definition, this index [called Γ (Gamma)] has been applied to two sets of data, (i) By using an appropriate computer program, theoretical iso-intensity curves for binary mixtures were generated by given values of this index, the variables being the concentrations. The diversity of curves is comparable to that observed in certain psychophysical studies (Köster, 1969). (ii) EAG responses of honey bees to 18 binary mixtures of three reciprocal concentrations each, have been recorded. Absence of true interaction was observed in two-thirds of cases and the results concerning the last third are discussed. These two sets of results illustrate the integrative strength of the Γ index. The present work was also presented in a condensed form in French by Laffort et al. (1984).