Similar serotonin-2A receptor binding in rats with different coping styles or levels of aggression.

Individual differences in coping style emerge as a function of underlying variability in the activation of a mesocorticolimbic brain circuitry. Particularly serotonin seems to play an important role. For this reason, we assessed serotonin-2A receptor (5-HT2A R) binding in the brain of rats with different coping styles. We compared proactive and reactive males of two rat strains, Wild-type Groningen (WTG) and Roman high- and low avoidance (RHA, RLA). 5-HT2A R binding in (pre)frontal cortex (FC) and hippocampus was investigated using a radiolabeled antagonist ([(3) H]MDL-100907) and agonist ([(3) H]Cimbi-36) in binding assays. No differences in 5-HT2A R binding were observed in male animals with different coping styles. [(3) H]MDL-100907 displayed a higher specific-to-nonspecific binding ratio than [(3) H]Cimbi-36. Our findings suggest that in these particular rat strains, 5-HT2A R binding is not an important molecular marker for coping style. Because neither an antagonist nor an agonist tracer showed any binding differences, it is unlikely that the affinity state of the 5-HT2A R is co-varying with levels of aggression or active avoidance in WTG, RHA and RLA.