DEVELOPMENT OF FUNCTIONAL TOLERANCE TO PENTOBARBITAL IN GOLDFISH

  • 1 January 1979
    • journal article
    • research article
    • Vol. 208  (1) , 123-127
Abstract
The acute effects of pentobarbital in Carassius auratus were measured by the times required for the loss of righting reflex (overturn point) and the pentobarbital brain concentration associated with the overturn. The test consisted of immersing the fish in a 0.3 mg/ml Na pentobarbital in 0.1 M Tris buffer challenge solution until the overturn point was reached. 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 Na pentobarbital for 6, 24 or 48 h at which time the overturn times and the pentobarbital brain concentrations at overturn in the challenge solution were determined. The mean pentobarbital content in the brain at overturn of fish pre-exposed to 0.015 or 0.025 mg/ml solution was significantly higher (P < 0.01) than in control fish. The loss of tolerance was determined at 3 h after termination of the pre-exposure of the fish to the various pentobarbital solutions; tolerance was measured only in the group of animals pre-exposed to the 0.025 solution by the significant increase (P < 0.01) in the pentobarbital brain levels over control fish. The equilibration curve for fish swimming in 0.025 mg/ml of Na pentobarbital was determined for 48 h. A steady state was attained within 6 h with brain levels that reached approximately 80% of the concentration of the external solution.

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