Comparison of the effects of adaptation on olfaction and taste in fish.

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To understand the function of chemical sense organ under natural conditions, responsibility of olfactory and gustatory organs to amino acids in some marine and freshwater fish were studied electrophysiologically at various background levels of the amino acids.1. Effects of self-adaptation on olfaction and taste in fish : Rainbow trout and Japanese char as fresh water fish and greenling as marine fish were used.Olfactory responses to amino acids reduced according to the increse of backgroud level. Olfactory organ adapted comparatively slowly and were considered to detect small increase as 10% of the back-ground level. Stimulas-to-background ratio-response relationship of the olfactory response to L-serine in the Japanese char shifted upper left according to the increase of the background level of the amino acids, indicating the acceleration of ditecting ability. On the other hand, gustatory responses to L-proline reduced progressively according to the increse of backgroud level, and no response was observed to ten times increase of the background level. But gustatory responses to quinne-HCI and taurolithocholic acid adapted comparatrively slowly. So, effects of self-adaptation on gustatoin differed depending the kind of taste stimulants.2. Frequency spectral analysis of olfactory bulbar resposes in rainbow trout : Peak frequency of the olfactory bulbar responses induced by chemical stimulation with amino acid before adaptation shifted due to the stimulus intensity. During self-adaptation the shift of the peak frequency were affected by the background level of the amino acid.During crossadaptation the peak frequency shifted in some cases and power density at the peak frequency changed or unchanged. These indicate that the olfactory organ of rainbow trout discriminate the kind and intensity of the stimulus. The frequency spectral analysis of olfactory bulbar responses may provide further significant clues for undestanding olfactory reception.