374 JOURNAL OF COSMETIC SCIENCE Exposure to the Methyl Esters of 3M2H -a- M-3M2H ' +' 3M2H 125 100 75 5O 25 Exposure to 3M2H -'•- 3M2H ' +' M-3M2H !1• Recove!I•1'+II' , !, • II ' • ,,-.I .t. I ..+"• I ' +fi t4)]• I.' Adaptation "" •'"" "- • l•,, • •'•' 'l-If •11 • b , , , i . . , I . . . i , . . i . . • I • , , i , , , i , . . i . , . I . I i I 1 2 3 4 5 6 7 8 9 lO Time (min) Figure 2. Mean magnitude estimates (with standard errors) as a percentage of the initial estimates for 3M2H and ME3M2H following adaptation to each compound. olfactory receptor cells and found that sensitivity depended upon both carbon chain length and the terminal functional group (carboxyl, hydroxyl, or amino), with some cells responding specifically to an acid and its esters. Overall, these results further demonstrate that structurally similar, yet perceptually

CROSS-ADAPTATION BY STRUCTURAL ANALOGS 375 Table I Mean Magnitude Estimates as a Percentage of Initial Estimates and Associated F-Values for Comparisons of Mean Magnitude Estimates for 3M2H and ME3M2H During and Following Adaptation to Each of the Adapting Odorants Adaptation Recovery Odorant X (S.E.) _F X (S.E.) _F Exposure to 3M2H 3M2H 48.1% (7.07) 53.95*** 79.9% (9.12) 4.87* ME3M2H 79.5% (8.59) 5.69* 86.0% (9.08) 2.37 Exposure to ME3M2H 3M2H 65.7% (12.26) 7.80** 86.3% (13.04) 1.10 ME3M2H 32.2% (6.75) 100.95'** 83.0% (6.15) 7.66** *p .05 **p .02 ***p .001. Note: The values in the table represent the mean magnitude estimate for an odorant expressed as a percentage of the initial estimate. Each F-test compares these mean magmtude estimate with the initial magnitude estimates for that odorant. Degrees of freedom for all F-tests = (1,11). distinct, odorants may cross-adapt, and support the idea that the extent of cross- adaptation may be affected by the degree of structural similarity among odorants. Practically, the easy-to-prepare methyl and ethyl esters of 3M2H may be incorporated into a variety of consumer products used to reduce the perception of malodors that contain organic acids. REFERENCES (lO) (11) (12) (1) T. Engen, The Perception of Odors (Academic Press, New York, 1982). (2) R. W. Moncrieff, Olfactory adaptation and odour likeness, J. Physiol., 133, 301-316 (1956). (3) J. D. Pierce, Jr., C.J. Wysocki, and E. V. Aronov, Mutual cross-adaptation of the volatile steroid androstenone and a non-steroid perceptual analog, Chem. Senses, 18, 245-256 (1993). (4) J. Todran, C. J. Wysocki, and G. K. Beauchamp, The effects of adaptation on the perception of similar and dissimilar odors, Chem. Senses, 16, 467-482 (1991). (5) W. S. Cain and E. H. Polak, Olfactory adaptation as an aspect of odor similarity, Chem. Senses, 17, 481-491 (1992). (6) W. S. Cain, Odor intensity after self-adaptation and cross-adaptation, Percept. Psychophys., 7, 271-275 (1970). (7) W. S. Cain and T. Engen, Olfactory adaptation and the scaling of odor intensity, in Oilaction and Taste, C. Pfaffmann, Ed. (Rockefeller University Press, New York, 1969), pp. 127-141. (8) T. Engen and C. O. Lindstrom, Cross-adaptation to the aliphatic alcohols, Amer. J. Psych., 76, 96-102 (1963). (9) J. D. Pierce, Jr., D.H. Blank, X.-N. Zeng, G. Preti, and C.J. Wysocki, Cross adaptation of a sweaty-smelling 3-methyl-2-hexenoic acid by its ethyl esters is determined by structural similarity,J. Soc. Cosmet. Chem. 47, 363-375 (1996). J. D. Pierce, Jr., X.-N. Zeng, E. V. Aronov, G. Preti, and C.J. Wysocki, Cross-adaptation of sweaty smelling 3-me•hyl-2-hexenoic acid by a structurally-similar, pleasant-smelling odorant, Chem. Senses, 20, 401-411 (1995). X.-N., Zeng, J. J. Leyden, H. J. Lawley, K. Sawano, I. Nohara, and G. Preti, Analysis of characteristic odors from human male axillae, J. Chem. Ecol., 17, 1469-1492 (1991). X.-N. Zeng, J. J. Leyden, A. I. Spielman, and G. Preti, Analysis of characteristic human female axillary odors: Qualitative comparison to males,J. Chem. Ecol., 22, 237-257 (1996).