Drug interactions in goldfish tolerant to ethanol and pentobarbital

The interactions between short- and long-term exposure to ethanol and pentobarbital were characterized in goldfish tolerant to one of these drugs. The effects of ethanol and pentobarbital were measured by the overturn test as the time of onset of the loss of the righting reflex and the corresponding drug concentration in brain of fish immersed in 674 mumol/ml ethanol or 1.21 mumol/ml sodium pentobarbital (challenge solutions). The chronic treatment consisted of 6- or 24-h preexposure to 130 mumol/ml ethanol or 0.06 mumol/ml sodium pentobarbital in Tris buffer solution. Fish preexposed to ethanol for 6 or 24 h or to pentobarbital for 24 h were rendered more tolerant to pentobarbital or ethanol, respectively. Preexposure to pentobarbital for 6 h, however, produced in goldfish the same degree of tolerance to ethanol and to pentobarbital.