DEVELOPMENT AND LOSS OF TOLERANCE TO ETHANOL IN GOLDFISH

¹ Research Institute on Alcoholism, New York State Department of Mental Hygiene and Department of Pharmacology, State University of New York at Buffalo, Buffalo, New York

The brain concentration of ethanol at the time when goldfish lose their righting reflex (overturn) upon immersion iim 3.1% (w/v) ethanol and the time for onset of overturn were used as measures of ethanol action. In studies of tolerance to ethanol the fish were exposed continuously to 0.8% ethanol in time aquarium water and then tested for overturn in time 3.1% ethanol. After the exposure to the 0.8% solution for periods of time ranging from 3 to 48 hours. significant increases in brain ethanol content at overturn (7-10 µg/mg of wet brain) relative to control levels (3.59 ± 0.4 µg/mg of wet brain) were observed. The increase is interpreted as representing acquired tolerance to ethanol by goldfish. Sustained exposure to 0.8% ethanol for periods up to 48 hours produced no greater tolerance than did exposure for three hours. This tolerance disappeared within two to six hours, as measured by the decline in brain ethanol content at overturn, after return of the fish to water subsequent to a 24-hour exposure to O.8% ethanol. Thus goldfish reproducibly exhibit acquired tolerance which has a rapid time course for both onset and disappearance.