The present study was carried out to investigate the effects of dopaminergic drugs and the role of specific dopamine(DA) receptors on the release of TSH, T₄ and T₃. Serum TSH levels (cold-induced, 4℃) were determined using RIA (radioimmunoassay) at 30 min after administration of dopamine agonists and antagonists. Serum T₄ and T₃ levels were detected after these dopaminergic drugs were administered subcutaneously twice a day for a week. The results of the study are summarized as follows :
Apomorphine, a nonspecific DA receptor agonist, produced a dose-depedent decrease in serum TSH, T₄ and T₃ levels. However, only low doses (0.3, 1.0㎎/㎏) of SKF38393, a specific D₁-receptor agonist, produced a decrease in serum lelvels of TSH. I,Y171555, a specific D₂-receptor agonist, produced a dose dependent decrease in serum TSH, T₄ and T₃levels. However, SCH23390, a specific D₁-receptor antagonist, produced a decrease except in serum T levels which were increased dose dependently. High doses (1.0, 3.0㎎/㎏) of sulpiride, a specific D₂-receptor antagonist, made a increase in the serum levels of TSH and T₃. The effects of dopaminergic drugs in serum TSH and T₄levels was potentiated by the pretreatment of apomorphine.
The overall results of this study suggest that the regulation of TSH, T₄ and T₃ secretion were mediated via specific D₁ and D₂receptor.
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