Influence of temperature upon tricaine methane sulphonate uptake and induction of anesthesia in rainbow trout ( Salmo Gairdneri)

Abstract

1. The influence of temperature upon the uptake of tricaine methane sulphonate and induction of anesthesia has been evaluated in rainbow trout exposed to eight combinations of test conditions (5° and 15°C, Stage I and 15 min exposures, 60 and 100 mg/1 anesthetic solutions). 2. While all factors considered tended to prompt increases in anesthetic levels and to decrease the time required for induction of the Stage I level of anesthesia several combinations of conditions were without significant effect. 3. Several combinations of conditions lead to attainment of the brain anesthetic levels required for deep anesthesia and two combinations (15°C, 60 mg/l; 5°C, 100 mg/l) lead to particularly high levels, and presumably to more prolonged anesthesia, than did the combination of higher dosage and temperature (15°C, 100 mg/l). However, surgical planes of anesthesia were achieved at 5°C with lower brain anesthetic concentrations than are usually regarded as essential. 4. Cold-acclimated animals consistently displayed higher muscle anesthetic levels than were encountered in 15°C trout. In contrast to the situation observed in the latter group “volumes of anesthetic distribution” consistently exceeded extracellular phase volumes, suggesting a major distinction in anesthetic handling by the muscle tissue of warm- and cold-adapted specimens. 5. Onset of anesthesia can be correlated with attainment of a critical blood level of tricaine methane sulphonate which is apparently weight- and temperature-independent.