Behavioural Brain Research 175 (2006) 90–95 Research report Influence of parenting style on the offspring’s behaviour and CSF monoamine metabolite levels in crossfostered and noncrossfostered female rhesus macaques Dario Maestripieri a,b,∗ , Kai McCormack b,c , Stephen G. Lindell d , J. Dee Higley d , Mar M. Sanchez b,e a Department of Comparative Human Development, The University of Chicago, Chicago, USA b Yerkes National Primate Research Center, Emory University, Atlanta, USA c Department of Psychology, Spelman College, Atlanta, USA d Section for the Study of Primate Models of Psychopathology, National Institute on Alcohol Abuse and Alcoholism, Poolesville, USA e Department of Psychiatry, Emory University, Atlanta, USA Received 15 June 2006; received in revised form 27 July 2006; accepted 2 August 2006 Available online 12 September 2006 Abstract We investigated the association between variation in parenting style and the offspring’s behaviour and CSF monoamine metabolite (5-HIAA, HVA, and MHPG) levels in rhesus monkeys. Study subjects were 25 two-year-old females reared by their biological mothers and 15 same-aged females that were crossfostered at birth and reared by unrelated mothers. Subjects that were rejected more by their mothers in the first 6 months of life engaged in more solitary play and had lower CSF concentrations of 5-HIAA than subjects that were rejected less. The relation between these variables was generally similar in crossfostered and noncrossfostered females. CSF levels of 5-HIAA were negatively correlated with rates of scratching, a behavioural indicator of anxiety. These results suggest that that early exposure to high rates of maternal rejection can result in higher anxiety later in life, and that this effect may be mediated by serotonergic mechanisms. Variation in maternal protectiveness did not affect offspring behaviour and neither protectiveness nor rejection affected CSF levels of HVA and MHPG. CSF levels of MHPG, however, were negatively correlated with solitary play behaviour and avoidance of other individuals, suggesting that individuals with lower CSF MHPG were more fearful and socially phobic than those with higher CSF MHPG. Taken together, these findings suggest that individual differences in anxiety and fearfulness in young rhesus monkeys are accounted for, at least in part, by variation in CSF levels of monoamine metabolites, and that the development of brain monoamine systems, particularly serotonin, can be affected by early exposure to variable maternal behaviour. © 2006 Elsevier B.V. All rights reserved. Keywords: Parenting style; Early experience; Behavioural development; Brain monoamines; Primates 1. Introduction Nonhuman primates (hereafter primates) are excellent ani- mal models for investigating the effects of early experience on the development of brain and behaviour [19,21]. Similar to humans, primates have an extended period of post-natal growth and maturation, in which the developing neural systems have ample opportunity to be influenced by experience [18]. Most ∗ Corresponding author at: Department of Comparative Human Development, The University of Chicago, 5730 S. Woodlawn Avenue, Chicago, IL 60637, USA. Tel.: +1 773 834 4104; fax: +1 773 834 0320. E-mail address: dario@uchicago.edu (D. Maestripieri). of a primate infant’s early experience occurs in interaction with its mother and this experience can be highly variable. In cerco- pithecine monkeys such as macaques (Macaca spp.), baboons (Papio spp.) and vervet monkeys (Chlorocebus aethiops), there is a great deal of interindividual variation in parenting style along the two orthogonal dimensions of maternal protectiveness and rejection [13,22]. The protectiveness dimension includes variation in the extent to which the mother physically restrains infant exploration, initiates proximity and contact, and cradles and grooms her infant. The rejection dimension includes vari- ation in the extent to which the mother limits the timing and duration of contact, suckling, and carrying. Although studies of rodents have demonstrated that offspring reared by mothers 0166-4328/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2006.08.002