Electrophysiological studies of the olfactory system of the goldfish, Carassius auratus L.—III. Effects of sex hormones on olfactory activity

1. The effects of estradiol or testosterone administration on evoked olfactory activity were studied. Specifically, observations and measurements were made of evoked potentials in the olfactory bulb after chemical stimulation of the olfactory epithelium, or after electrical stimuli applied at various loci. The principal results may be summarized as follows. 2. Intraperitoneal administration of estradiol and testosterone produced no recognizable change in the resting or spontaneous electrical activity (EEG) of the olfactory bulb. 3. Administration of estradinol [(25 μg/animal)/dau] to goldfish of both sexes markedly increased the olfactory bulb response evoked by salt infusion into the nasal cavity. The effect of the hormone was much greater in male fish than in females. 4. The daily administration of testosterone (25 μ/animal) was slightly excitatory in male fish, but the effect was opposite in females. 5. Evoked single pulse potentials were also largely affected by administration of the sex steroids. Positive after-potential was markedly increased by estradiol injection and decreased by testosterone. Consequently, the excitability cycle was accelerated by testosterone and delayed by estradiol. 6. The evidence suggests that there may be a hormone-sensitive “centre” in the diencephalin or telencephalon. Further discussion treats the function of olfactory centrifugal fibre systems in relation to site(s) of action of the sex steroids.