Fish in hot water: Hypoxaemia does not trigger catecholamine mobilization during heat shock in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) exposed to an acute heat shock (1 h at 25 degrees C after raising water temperature from 13 degrees C to 25 degrees C over 4 h) mount a significant catecholamine response. The present study investigated the proximate mechanisms underlying catecholamine mobilization. Trout exposed to heat shock in vivo exhibited a significant reduction in arterial O-2 tension, but arterial O-2 concentration was not affected by heat shock, nor was catecholamine release during heat shock prevented by prior and concomitant exposure to hyperoxia (to prevent the fall in arterial O-2 tension). Thus, catecholamine mobilization probably was not triggered by impaired blood O-2 transport. Heat-shocked trout also exhibited an elevation of arterial CO2 tension coupled with a fall in arterial pH, but these factors are not expected to trigger catecholamine release. The changes in blood O-2 and CO2 tension occurred despite a significant hyperventilatory response to heat shock. Future studies should investigate whether catecholamine mobilization during heat shock in rainbow trout is triggered by a specific effect of high temperature activating the sympathetic nervous system via a thermosensitive transient receptor potential channel. (C) 2013 Elsevier Inc. All rights reserved.