A study of olfactory mechanisms

A structure-activity relationship study examining the change in odour quality with systematic variation of alkyl and alkanoate groups of esters (up to C10) has shown that an exposed ester group is necessary for giving esters a fruity smell. Steric hindrance of the ester group results in a minty odour quality becoming predominant. Alkyl haloacetates have been shown to be capable of specifically inhibiting EOG responses in a manner most easily explained by an affinity labelling mechanism. Such compounds may be useful as a means of labelling olfactory receptors so that they may be identified during isolation. Experiments to clarify the role of cyclic AMP in the olfactory transduction mechanism showed that odorant in solution (pentyl acetate) was antagonistic to the effects of SQ 20,009, a potent phosphodiesterase inhibitor. Positive after-potentials to ethanol were stimulated by SQ 20,009, suggesting an alternative mechanism for the effects of cyclic AMP on the EOG response involving increased permeability of the supporting cell membrane to chloride ions. Biochemical studies in olfaction are hampered by the lack of a method for isolating the chemoreceptive membrane. Here experiments have been carried out at the level of the whole tissue using the EOG response to monitor events in the receptor cells. EOG responses, stable over a period of several hours, were obtained from mammalian olfactory epithelium maintained in vitro. Animals such as the sheep and the cow can provide large quantities of tissue that may be necessary for biochemical studies. The preparation described here provides a convenient method of obtaining electro- physiological responses from the olfactory epithelium of such animals