The canary in the coalmine: the sensitivity of mesolimbic dopamine to environmental adversity during development

The hypothalamic-pituitary-adrenal axis has been the focus of extensive research with regard to the phenotypic plasticity this system shows in response to environmental influences on mammalian development. This review proposes that the mesolimbic dopamine system is similarly reactive to indicators of environmental adversity during development. Physical, physiological, and toxicological stressors encountered during perinatal development have been routinely demonstrated to affect dopamine neurophysiology, most likely through consequent exposure to maternal glucocorticoids or a reduction in oxygen supply. However, findings remain inconsistent with regard to the nature of impact these events have on the dopamine system. Both hyper- and hypo-dopaminergic changes have been noted. This review argues that the directionality of change is a function of chronicity and severity of the insult, and that both resultant phenotypes are adaptive developmental responses, despite their potential for conferring vulnerability for psychopathology in humans.