The expression of thyrotropin receptor in the brain

The regulation of the thyroid gland by TSH is mediated by a heterotrimeric G protein-coupled receptor. Nonthyroid effects of TSH have been reported, a nd expression of its receptor has been described in adipocytes and lymphocy tes. We have previously reported the existence of specific and saturable bi nding sites of TSH and specific TSH effects in primary cultured rat brain a stroglial cells. We now report expression of the TSH receptor gene in these cells; the coding sequence of the corresponding complementary DNA is ident ical to that previously established in thyroid. Using specific antisense RN A probe, expression of this gene was detected in some isolated or clustered glial fibrillary acidic protein-positive primary cultured cells by in situ hybridization. With this technique, we further detected TSH receptor messe nger RNA (mRNA) expression in rat brain cryoslices in both neuronal cells a nd astrocytes. Its presence predominated in neuron-rich areas (pyriform and postcingulate cortex, hippocampus, and hypothalamic nuclei) and was mostly colocalized with neuron-specific enolase. In astrocytes, this mRNA was det ected in the ependymal cell layer and the subependymal zone, and several is olated cells were also found in the brain parenchyma. We also detected TSH receptor mRNA and protein in primary cultured human astrocytes. The protein was detected as well in both rat and human brain cryoslices. Together, the se findings clearly demonstrate the expression of the TSH receptor gene in the brain in both neuronal cells and astrocytes.