Abstract
Thyroid hormone (TH) is essential for normal brain development. TH insufficiency during early stages of development may increase the risk for attention deficit/hyperactivity disorder, in which malfunction of brain monoaminergic systems is likely involved. However, little is known about the effects of perinatal hypothyroidism on behaviors and brain monoaminergic systems in offspring mice. The present study examined in mice (1) whether perinatal hypothyroidism causes hyperactive behavioral phenotypes, (2) how perinatal hypothyroidism influences brain monoaminergic systems, and (3) whether hyperactive behavioral phenotypes are associated with the state of brain monoaminergic systems. When dams were exposed to propylthiouracil, offspring mice developed hypothyroidism during the perinatal period. Offspring mice with perinatal hypothyroidism exhibited hyperactive behavioral phenotypes such as hyper-ambulatory activity and an increased response rate in the two-way active avoidance test in a male-specific manner. Significant decreases in dopamine (DA) and serotonin turnover were observed in the striatum (ST), nucleus accumbens, hypothalamus, and hippocampus in male mice with perinatal hypothyroidism. A significant correlation between ambulatory activity and DA turnover in the ST and an augmented ambulatory response to the DA reuptake inhibitor bupropion suggested that DA in the ST was involved in the hyper-ambulatory activity in mice with perinatal hypothyroidism.
Highlights
Exposure to artificial chemicals may increase the risk of neurodevelopmental disorders [9]
In mice, we focused on (1) whether perinatal hypothyroidism causes hyperactive behavioral phenotypes, (2) how perinatal hypothyroidism influences brain monoaminergic systems, and (3) whether behavioral phenotypes are associated with the state of brain monoaminergic systems
These results indicate that offspring mice experienced hypothyroidism following exposure of their dams to 125–500 ppm PTU
Summary
Exposure to artificial chemicals may increase the risk of neurodevelopmental disorders [9]. A high rate of attention deficit/hyperactivity disorder (ADHD), of which the major symptoms are hyperactivity, inattention, and impulsiveness, is observed in children with iodine deficiency, which causes TH insufficiency [24,39] and in children with resistance to TH [15] that is caused by mutation of a TH receptor beta isoform (TRβ) [32]. These observations suggest that TH disruption during early life stages impacts brain development and increases the risk of ADHD. Behavioral effects of hypothyroidism during development in mice have not been elucidated well
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