Decreased neurotransmitter receptor binding in striatum and cortex from adult hypothyroid rats

The consequences of propylthiouracil-induced thyroid deficiency on pre- and postsynaptic biochemical markers in the corpus striatum and the visual cortex were investigated in adult rats. Hypothyroidism in adult rats significantly impaired (by 30%) striatal [3H]spiroperidol binding capacity. In the visual cortex, small but significant reductions in [3H]WB.4101 and in [3H]muscimol binding were evident, whereas glutamate decarboxylase activity was increased by 18% in the thyroid-deficient rats. Compatible with previous morphological evidence (Ruiz-Marcos et al.), the present observations may imply alterations in dendritic morphology of neurones in the striatum and cortex during long-term hypothyroidism in adult rats. However, the molecular changes observed suggest a differential sensitivity of transmitter-specific neurones in the central nervous system to thyroid hormone.