Meeting Abstract
Individuals able to persist without changes in physiology and behavior in the face of external disruptions can be said to be stress resilient. The neural mechanisms for this resilience are poorly understood, but vitally important, given that stressors such as climate change, habitat destruction and species invasions now affect all animals. Although the neurotransmitter dopamine is best known for its role in reward-motivated behavior, the mesocorticolimbic dopamine system of the brain also responds strongly to stressors. We hypothesized that stress resilience may involve limiting the effects of powerful neuromodulators like dopamine on the brain. To test this hypothesis, we examined whether striatal D2 receptor binding potential (BP, assessed using positron emission tomography imaging with the D2 antagonist 11C-raclopride) was correlated with behavior in response to chronic captivity stress in wild-caught house sparrows (Passer domesticus, n=15). D2 BP is an in vivo integrated measure of dopamine physiology, reflecting both synaptic dopamine concentrations and numbers of inhibitory dopamine D2 receptors in striatum. We found that striatal D2 BP 24 h after capture was not correlated with initial behavior, but did predict the frequency of multiple behaviors several weeks later. Specifically, individuals with higher D2 BP (=a less reactive dopamine phenotype, with less synaptic dopamine and/or more D2 receptors) spent less time engaged in anxiety-related behavior and more time feeding compared to individuals with lower BP. These data support our hypothesis that a reduced dopamine response may be associated with stress resilience, and demonstrate the usefulness of in vivo imaging for revealing relationships between individual variation in neuroendocrine phenotypes and behavior.
