| A substantial part of the biological propensity for sociality is shaped by experiences of the care-giver in early life. Parents psychobiologically attune the behavior and physiology of their young, in coordination with existing ecological and social demands. This is particularly true of primates, which, by nature of their altriciality, are extremely dependent on parents for nourishment, thermoregulation, and protection from predators for periods that are longer, on average, than most mammals.; Research on the neonatal environment has demonstrated links between the behavioral consequences of maternal deprivation and the abnormal physiology of serotonin, norepinephrine, and cortisol. However, many correlates of early insult are also reminiscent of human psychopathologies and dementias involving defects in dopamine neurotransmission. The brain dopamine system is critically important for primate survival and reproduction because it functions to assimilate and integrate environmental stimuli that inform the behavioral adjustments necessary for survival, reproduction and thus, adaptation.; The dopaminergic modulation of behavioral and physiological development was addressed through four comparative studies of six nursery-reared and six mother-reared, captive juvenile rhesus monkeys. Basic neuroendocrine functioning was assessed by a single sampling of cerebrospinal fluid chemicals, which was analyzed by High Performance Liquid Chromatography. As a test of dopaminergic tone, serum testosterone, cortisol, and prolactin were sampled, before and after treatment with the dopamine receptor-2 antagonist Raclopride, and analyzed by Radioimmunoassay. These neuroendocrine results were statistically related to social behavioral data collected during 720 minutes of observation. Over 216 hours of observation, agonists and antagonists for dopamine receptor-1 and dopamine receptor-2, including SKF81297, SCH23390, Quinpirole, and Raclopride, were used to discriminate the behavior-pharmacology of rearing. Using receptor autoradiography, the relative densities of dopamine receptor-1 and dopamine receptor-2 in the prefrontal cortex and basal ganglia were determined in postmortem specimens harvested from a complementary group of nursery-reared and mother-reared monkeys.; The behavioral correlates of nursery-rearing were associated with lower dopaminergic tone, the levels of cerebrospinal fluid dopamine metabolites, reduced prefrontal dopamine receptor densities, and altered sensitivities to the pharmacological manipulation of dopamine systems. Consequently, dopamine systems are as vulnerable to early insult as the serotonergic, noradrenergic and glucocorticoid systems. |
