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Prenatal and childhood mercury (Hg) exposures have been associated with negative impacts on child neurodevelopment. It is unclear if associations persist at the low Hg exposures typical in Western countries. To examine associations between prenatal/childhood blood Hg concentrations and child IQ in Canadian male and female children while considering the potential modifying role of prenatal fish consumption. We analyzed data from the Maternal-Infant Research on Environmental Chemicals study. Hg was measured in first trimester (n = 527), cord (n = 430), and child (at 3–4 years of age, n = 355) blood and examined sex-stratified associations between blood Hg and children's Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ), and General Language Composite (GLC) scores (assessed with WPPSI-III). Prenatal Hg analyses were further stratified by prenatal fish consumption (low: 0–2, moderate: 3–7, or high: ≥8 times/month). Higher cord blood Hg concentrations were associated with lower PIQ (ß = −3.27; 95%CI: 6.44, −0.09) in male children with the lowest prenatal fish consumption. Progressively stronger positive associations were observed with PIQ in male children for moderate (ß = 1.08; 95%CI: 0.10, 2.26) and high (ß = 3.07; 95%CI: 1.95, 4.19) prenatal fish consumption. Cord blood Hg concentrations were positively associated with female children's FSIQ (ß = 1.29; 95% CI: 0.77, 1.81) and PIQ (ß = 2.01; 95% CI: 1.19, 2.83); however, when stratified only in the highest fish consumption subgroup. Among female children, higher child blood Hg concentrations were associated with an approximately 1-point increase in FSIQ, VIQ, and GLC. Prenatal exposure to low levels of Hg was associated with lower PIQ scores in male children with low prenatal fish intake. Positive associations between cord and child blood Hg concentrations and IQ were primarily observed in female children and may be due to beneficial effects of prenatal fish intake. • Examined associations between prenatal and child blood mercury (Hg) with child IQ. • Cord blood Hg with low fish intake was associated with lower performance IQ in males. • Cord blood Hg with high fish intake was associated with higher IQ in females. • Each doubling of child blood Hg associated with 1-point increase in IQ in females. • Results highlight the beneficial effects of fish intake during pregnancy. [ABSTRACT FROM AUTHOR]

Abstract: Rodent studies suggest that prefrontal dopamine neurotransmission plays an important role in the neural processing of psychosocial stress. Human studies investigating stress-induced changes in dopamine levels, however, have focused solely on striatal dopamine transmission. The aim of this study was to investigate in vivo dopamine release in the human prefrontal cortex in response to a psychosocial stress challenge, using the highly selective dopamine D2/3 PET radioligand [18F]fallypride in healthy subjects. Twelve healthy subjects (age (y): 39.8; SD=15.8) underwent a single dynamic Positron Emission Tomography (PET) scanning session after intravenous administration of 185.2 (SD=10.2) MBq [18F]fallypride. Psychosocial stress was initiated at 100min postinjection. PET data were analyzed using the linearized simplified reference region model (LSRRM), which accounts for time-dependent changes in [18F]fallypride displacement. Voxel-based statistical maps, representing specific D2/3 binding changes, were computed to localize areas with increased ligand displacement after task initiation, reflecting dopamine release. The psychosocial stress challenge induced detectable amounts of dopamine release throughout the prefrontal cortex, with dopaminergic activity in bilateral ventromedial prefrontal cortex being associated with subjectively rated experiences of psychosocial stress. The novel finding that a mild psychosocial stress in humans induces increased levels of endogenous dopamine in the PFC indicates that the dynamics of the dopamine-related stress response cannot be interpreted by focusing on mesolimbic brain regions alone. [Copyright &y& Elsevier]