Role of cations in olfactory reception.

The effects of changed ionic environments on the olfactory responses in the carp, the rainbow trout, and the bullfrog were examined by recording the stimulant-induced waves from the olfactory bulb. (a) Application of stimulants (various species of amino acids and beta-ionone) dissolved in deionized water to the EDTA-treated olfactory epithelium of the carp did not induce any response. The addition of various species of salts to the stimulating solution reversibly restored the response. (b) The responses of the carp to L-alanine in the presence of MgCl2 and MgSO4 and those in the presence of KCl and K4Fe(CN)6 are described by single curves, respectively, as a function of concentration of the cations, suggesting that the cations support olfactory reception. (c) All the inorganic cations examined (Li+, NH3+, K+, Ca2+, Mg2+, Co2+, Mn2+, Cd2+) and organic cations (Tris+, choline+, bis-Tris propane2+) were effective to support the response of the carp, whereas TEA+, TBA+, triethanolamine+, and bis-Tris+ were ineffective. (d) The olfactory responses of the rainbow trout and the bullfrog were also reduced by removal of ions from the surface of the epithelia and recovered by addition of ions. (e) It is suggested that the cations do not act as current carriers across the apical olfactory cell membrane for the generation of the receptor potential.