In Vivo Association Between Alcohol Intoxication, Aggression, and Serotonin Transporter Availability in Nonhuman Primates

OBJECTIVE: Studies on brain serotonin metabolism in human and nonhuman primates have indicated that dysfunction of serotonin transmission may play a role in the biological vulnerability to dependence on alcohol. Among young men, low sensitivity to alcohol intoxication predicts subsequent alcohol abuse and dependence. METHOD: The authors used single photon emission computed tomography and the radioligand [^I123]β-CIT ([^I123]methyl 3β-(4-iodophenyl) tropane-2-carboxylate) to measure the availability of serotonin transporters in 11 male rhesus monkeys, and the monkeys were genotyped for a functional polymorphism of the serotonin transporter gene. The 11 monkeys had experienced parental separation after birth; their behavior and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in CSF had been assessed regularly. RESULTS: In the 5-year-old monkeys, there was a significant negative correlation between β-CIT binding to serotonin transporters in the brainstem and 5-HIAA concentrations in CSF. Animals with greater β-CIT binding and low CSF 5-HIAA concentrations displayed greater aggressiveness and were less sensitive to alcohol-induced intoxication. The genetic constitution of the serotonin transporter promoter gene did not significantly contribute to the availability of brainstem serotonin transporters as measured by β-CIT binding. CONCLUSIONS: In adult nonhuman primates who underwent early developmental stress, variables indicating a low serotonin turnover rate were associated with behavior patterns similar to those predisposing to early-onset alcoholism among humans. (Am J Psychiatry 1998; 155:1023–1028)