Hyperthyroidism decreases thyrotropin-releasing hormone gene expression in the caudal raphe nuclei and the parapyramidal regions in rats

[摘要] Altered thyroid statuses are associated with autonomic disorders. Medullary thyrotropin-releasing hormone (TRH) and substance P (SP) regulate autonomic nervous activity. The influences of thyroid statuses on TRH and SP gene expressions in the caudal raphe nuclei and the parapyramidal regions were studied using quantitative in situ hybridization histochemistry. In male rats thyroidectomized (Tx) for 30 days, the serum T-4 levels decreased by 64% and the medullary pro-TRH mRNA signals (silver grains per neuron) significantly increased by 32-45%. These changes were prevented by daily i.p. T-4 (2 mu g/100 g) injection in Tx rats. In sham operated/T-4 (20 mu g/100 g, daily) injected rats, T-4 levels significantly increased by 88% and the silver g rains decreased by 38-40%. Medullary SP mRNA signals were not significantly:changed by altering thyroid status. These results support the concept that thyroid hormone regulates medullary TRH gene expression by negative feedback. (C) 1999 Elsevier Science Ireland Ltd. Ail rights reserved.

[发布日期] 1999-12-10

[关键词] autonomic disorders;hypothyroid;substance P;in situ hybridization;thyroid hormones;feedback regulation