to examine the development of tolerance the fish were pre-exposed to 0.1 m tris buffer solutions containing 0.0 , 0.010 , 0.015 and 0.025 mg/ml of sodium pentobarbital for 6 , 24 or 48 hr at which time the overturn times and the pentobarbital brain concentrations at overturn in the challenge solution were determined .
C0006104
brain
C0086045
concentrations