Catechol-O-methyltransferase polymorphism alters hypothalamic-pituitary-adrenal axis responses to naloxone: a preliminary report

Background A common polymorphism in the catechol-O-methyltransferase gene involves a valine to methionine mutation that results in a threefold to fourfold decrease in enzyme activity. This polymorphism has been associated with altered μ-opioid receptor binding potential and prefrontal cognitive performance, as well as risk for several neuropsychiatric conditions. We hypothesized that subjects homozygous for the low-activity allele would have greater hypothalamic-pituitary-adrenal axis responses to opioid blockade than subjects with the high-activity allele. Methods Forty-six healthy adults were genotyped and underwent a procedure in which adrenocorticotropin hormone and cortisol responses to the opioid antagonist naloxone were examined. Results Findings showed that adrenocorticotropin hormone and cortisol responses were greater in subjects with the methionine/methionine genotype compared to subjects homozygous or heterozygous for the valine allele. Conclusions These findings suggest that individual differences in catecholamine metabolism may impact hypothalamic-pituitary-adrenal axis function and may play a pharmacogenetic role in responses to naloxone.