Musk, Inability To Smell

Whissell-Buechy and Amoore (1973) suggested that inability to smell musk is an autosomal recessive trait. Musk pentadecalactone could not be smelled by about 7% of Caucasians, but this deficiency was not found in any Blacks. The authors stated that there were 27 discrete anosmias. Kalmus and Seedburgh (1975) confirmed the work of Whissell-Buechy and Amoore (1973). They also found a highly correlated bimodality (presumed to be caused by the absence or inactivity of certain receptor sites) for another structurally different substance, musk ambrette. The thresholds for musk ketone showed no bimodality and a low correlation with the thresholds for the other two musks. The olfactory system has to discriminate between a large number of low molecular weight compounds in the air. The elucidation of how this is done is a challenge comparable to discovering how the immune system works. Odorant receptors appear to activate a cyclic nucleotide enzyme cascade, including a GTP-binding protein, analogous with the processes of hormone, neurotransmitter and visual reception (Lancet and Pace, 1987). Odorants may excite olfactory receptor cells by activating ion channels. This, in turn, may generate patterns of different neuronal activity which are relayed to the CNS and decoded as distinct odors (Anholt, et al. 1987). The guanine nucleotide-binding proteins (G or N proteins) are ubiquitous features of signal transduction mechanisms involving control of intracellular calcium and second messengers, regulation of cell growth, gating of ion channels, olfaction, vision, and possibly other sensory systems. Possibly because of their key role in signal transduction, G proteins have been singled out as targets by toxins from several types of bacteria, e.g., those causing diphtheria, cholera, and pertussis. These toxins have proved valuable in identifying the function of the different G proteins (Dolphin, 1987).

It is possible that specific anosmia or 'smell blindness' in the olfactory system is analogous to colorblindness in vision, where unequal crossing over between the highly homologous receptors within a cluster during gametogenesis results in the formation of new hybrid receptors and/or the deletion of receptor genes (Reed, 1996). The inheritance of specific anosmia to pentadecalactone as a recessive is consistent with mutation or loss of the receptor gene for this particular odorant.