Extinction of a conditioned response in rainbow trout selected for high or low responsiveness to stress

摘要: Two lines of rainbow trout (Oncorhynchus mykiss) that exhibit divergent endocrine responsiveness to stressors also display disparate behavioral traits. To investigate whether the high-responding (HR) and low-responding (LR) fish differ in cognitive function, rate extinction a conditioned response was compared between two lines. Groups HR LR were exposed paired stimulus (CS; water off) unconditioned (US; confinement stressor). After exposure 18 CS–US pairings, at least 70% individuals both acquired (CR) manifested as an elevation blood cortisol levels on presentation CS only. Post-conditioning, tested by weekly intervals, for 4 weeks, with no further reinforcement, CR compared. The decline mean plasma after over successive tests suggested retained shorter period among (<14 days) than (<21 days). frequency within each line whose indicated stress when significantly greater 14 21 days falling into this category days. At 28 post-conditioning, there only three categorized “stressed”. These results suggest are differences function Possible mechanisms underlying these discussed.