rhesus macaque has an orthologous polymorphism (rh-5HTTLPR) in the promoter region of serotonin transporter gene. In these animals, early life stress exposure led to dyscontrolled behavior and enhanced stress response later in life (for review see Ref.96). Consistent with findings in humans, rh-5HTTLPR influenced alcohol consumption and stress response, depending on rearing conditions. Carriers of the low-expression serotonin transporter genotype that were separated from their moth ers at an early age displayed higher stress reactivity and ethanol preference.97 Similarly to humans,95 the combined effect of rh-HTTLPR and environment on stress reactivity appeared to be mediated by the hypothalamic-pituitary-adrenal (HPA) axis.
