Alterations in brain dopaminergic receptors in developing hypo- and hyperthyroid rats

The administration of an iodide-rich diet to pregnant and lactating rats, and to their weaned litters, or the anti-thyroid drug methimazole injected into high-iodide pups induced a mild and a severe hypothyroidism, respectively. Treatment of newborn rats with triiodothyronine provoked neonatal hyperthyroidism. The binding of [(3)H]spiroperidol to dopaminergic receptors in striatal membranes from 31 day-old, hypo- and hyperthyroid rats was significantly decreased, compared to euthyroids. These alterations appeared to involve the density of dopaminergic receptors, and not their affinity for the radioligand, the only exception being a hyperthyroidism-caused decrease in the dissociation constant.