| Abstract: | The effects of the thiol-specific reagent N-ethylmaleimide (NEM)used in the vapour phase have been tested on the olfactory epitheliumof the frog when recording the electro-olfactogram (EOG) andspike activity from single receptor cells. The reagent was deliveredalone or mixed with the odorant isoamyl acetate. At low concentrationthe reagent induced slow potentials resembling simple EOGs.At higher concentrations (20% of the saturated vapour) threenegative and one positive slow components were observed in theresponse. A complex relationship was found between the amplitudeof the slow potential and the concentration of the reagent.Repeated stimulations at high concentration caused the suppressionof the negative voltage transients and the development of thepositive component. NEM vapour elicited spike discharges insome of the recorded units, with the responses resembling thoseevoked by usual odorants. After long-lasting stimulations (30 sec) with NEM, the receptorsfailed to respond to both reagent and odorant. This suppressionof response could be partly prevented by exposing the olfactoryepithelium to the odorant vapour before and during the exposureto the reagent (protection). The results indicate that NEM acts on the olfactory epitheliumin several ways, including an odorant-like action on olfactoryreceptor sites. An effect on the supporting cells is also suggested.Hypotheses for explaining the protection mechanism are considered. |
