Effects of Early-Life Stress on Serotonin1A Receptors in Juvenile Rhesus Monkeys Measured by Positron Emission Tomography

BackgroundTraumatic experiences in early childhood are associated with increased risk for developing mood and anxiety disorders later in life. Low serotonin1A receptor (5-HT1AR) density during development has been proposed as a trait-like characteristic leading to increased vulnerability of stress-related neuropsychiatric disorders.MethodsTo assess the relationship between early-life stress and alterations in the serotonin system during development, we used positron emission tomography to measure in vivo 5-HT1AR density and apparent dissociation constant (KDapp) in the brain of juvenile Rhesus monkeys exposed to the early-life stress of peer-rearing.ResultsIn general, 5-HT1AR density and KDapp were decreased in peer-reared compared with control mother-reared animals. However, increase in receptor density was found in the dorsomedial prefrontal cortex of peer-reared females.ConclusionsThese findings suggest that exposure to an adverse early-life environment during infancy is associated with long-term alterations in the serotonin system and support previous studies suggesting that reduced 5-HT1AR density during development might be a factor increasing vulnerability to stress-related neuropsychiatric disorders. Furthermore, alterations in the serotonin system seemed to be gender- and region-specific, providing a biological basis for the higher prevalence of affective disorders in women.