Variable neuroendocrine responses to ecologically-relevant challenges in sticklebacks (original) (raw)

2007, Physiology & Behavior

BELL, A.M., BACKSTRÖM, T.B., HUNTINGFORD, F.A., POTTINGER, T.P., WINBERG, S. 25 Variable neuroendocrine responses to ecologically-relevant challenges in sticklebacks. 26 PHYSIOL BEHAV 00(0) 000-000, 2006. Here, we compare the behavioral, endocrine and 27 neuroendocrine responses of individual sticklebacks exposed to either an unfamiliar conspecific 28 or to a predator. We found that the two stressors elicited a similar hypothalamic-pituitary-29 interrenal response as assessed by whole-body concentrations of immunoreactive corticosteroids, 30 but produced quite different patterns of change in brain monoamine and monoamine metabolite 31 content as assessed by concentrations of serotonin (5-HT), dopamine (DA), norepinephrine (NE) 32 and the monoamine metabolites 5-hydroxyindole acetic acid (5-HIAA), homovanillic acid 33 (HVA) and 3-4-dihydroxyphenylacetic acid (DOPAC). For example, relative to baseline levels, 34 NE levels were elevated in individuals exposed to a predator but were lower in individuals 35 confronted by a challenging conspecific. Levels of monoamine neurotransmitters in specific 36 regions of the brain showed extremely close links with behavioral characteristics. Frequency of 37 attacking a conspecific and inspecting a predator were both positively correlated with 38 concentrations of NE. However, whereas serotonin was negatively correlated with frequency of 39 attacking a conspecific, it was positively associated with predator inspection. The data indicate 40 that the qualitative and quantitative nature of the neuroendocrine stress response of sticklebacks 41 varies according to the nature of the stressor, and that interindividual variation in behavioural 42 responses to challenge are reflected by neuroendocrine differences. 43 Running head: Individual differences in sticklebacks 46 3 INTRODUCTION 47 48 Both attacking a conspecific and confronting a potential predator are dangerous. In 49 addition to energetic costs [1], aggression can result in injury [2] and exposure to predation risk 50 while fighting [3]. Similarly, an encounter with a potential predator can impose energetic costs of 51 escape [4], injury [5] or even death. Not surprisingly, both confrontation by a challenging 52 conspecific [6-11] and exposure to a predator [12-15] elicit a neuroendocrine stress response. 53