Background: To study genetic and environmental contributions to cerebrospinal fluid (CSF) monoamine concentrations, 55 young rhesus monkeys (Macaca mulatta) were reared apart from their 10 fathers to perform a paternal half-sibling analysis.
Methods: To study maternal genetic contributions, 23 infants were reared with their mothers, 23 infants were removed from their mothers at birth and fostered to unrelated lactating female monkeys, and 24 infants were removed from their mothers at birth and reared with age-matched peers. When the monkeys reached age 6 months, CSF samples were obtained via cisternal puncture prior to and during a series of social separations.
Results: When the results were statistically pooled according to the biological father, comparisons using analysis of variance indicated that both CSF 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) concentrations showed significant heritable (h2) effects (h2 > 0.5) for both sons and daughters, whereas 3-methoxy-4-hydroxyphenylglycol (MHPG) showed a nearly significant paternal genetic effect only for sons (h2 > 0.5). In addition, there were substantial maternal genetic influences on the young monkeys' CSF MHPG and 5-HIAA (h2 > 0.5) levels. Structural equation analyses indicated a maternal genetic contribution without a maternal environmental contribution to CSF 5-HIAA concentration; on the other hand, there was both a maternal genetic and environmental contribution to MHPG.
Conclusions: These findings suggest that a significant portion of the variance in the turnover of the monoamine neurotransmitters is determined by genetic mechanisms.