Oscillatory electric potential changes on the olfactory epithelium of the Japanese toad, Bufo japonicus

During the breeding season, characteristic oscillatory potential changes (OSC) with a high frequency were detected on the surface of the olfactory mucosa in the Japanese toad, Bufo japonicus, when the olfactory epithelium was stimulated by an air puff. The OSC was superimposed on the commonly observed slow electric change known as the electro-olfactogram in various vertebrates. We measured plasma gonadotropin levels and OSC amplitude in individual toads caught during the breeding migration. There was a significant correlation (r = 0.81, p = 0.01, n = 8) between OSC amplitudes and plasma gonadotropin levels in males. OSC could not be induced by i.p. injections of hCG, PMSG, testosterone or estradiol in the non-breeding season. Just before the breeding season (January), 50% of male toads of both estradiol-treated and control groups showed OSC when stimulated with isoamyl acetate odor. There was a significant correlation between the testes/body weight ratio and the OSC amplitude. These results indicate an intimate relationship between OSC appearance and breeding in the Japanese toad.