Isolation-rearing of weanling rats produces a syndrome of behavioral and neurochemical effects that are indicative of enhanced ventrostriatal dopamine function observed in adulthood. By contrast, maternal deprivation of neonatal rats decreases behavioral responses to dopamine agonists when tested in adults, which may indicate the opposite situation. However, in the present study it is reported that in vivo microdialysis of the nucleus accumbens (NAC) revealed enhanced release of dopamine (DA) in response to both d-amphetamine and high K+ perfusate in maternally deprived subjects. Thus, behavioral responses to d-amphetamine are diminished in maternally deprived rats despite apparent increases in presynaptic dopaminergic function in the NAC.