Memory performance after flurothyl treatment in rainbow trout.

Fingerling rainbow trout (N = 436) were trained in one trial with brief electric shock (2.0 V/cm) to suppress their spontaneous upstream swimming into a quiet well. Memory retention one day later was not influenced by the temperature at which they had been acclimated, trained and tested (10 degrees C, 15 degrees C or 20 degrees C). When exposed 4 min after training for 2 min, to a flurothyl solution (10, 25, 50, 100 or 200 mul/l) trout convulsed and overturned. The onset of overturn was concentration- and temperature-dependent. Flurothyl altered the one-day retention of avoidance behavior; low concentrations enhanced, whereas high concentrations impaired. Memory-enhancing low concentrations of flurothyl, applied after post-training amnesic treatment with carbon dioxide, reversed the carbon dioxide amnesia.