The effect of adrenaline on peripheral vascular resistance at different temperatures in a hind part preparation of rainbow trout ( Salmo Gairdnerii R.)

1. Preparations of rainbow trout were perfused with oxygenated Hepes buffered dextran solution, and the mean perfusion pressures were monitored. 2. Adrenaline caused a maximal constriction in the range of 64–92 mm Hg. 3. Adrenaline effect of PRU 100 was greater at 5°C than at 0.5 or 10°C. 4. The adrenaline affinity (pD 2) was highest at 0.5°C, but not significantly different at 5, 10 or 18°C. 5. Our results indicate that the potential regulatory efficiency of adrenaline on the peripheral circulation is highest at the normal habitat temperature of the fish (5–8°C).