5-HT_1A receptor expression is modulated by corticosteroid receptor agonists in primary rat hippocampal culture

The effects of corticosteroid receptor agonists on the expression of 5-HT_1A receptor mRNA were measured in rat hippocampal cultures using in situ hybridization histochemistry. In our normal culture system, grown in serum and steroid-free media, moderate to heavy signal for 5-HT_1A mRNA transcripts were detected in hippocampal neurons and glial cells. Aldosterone, a type I corticosteroid receptor agonist (10^-9 M), significantly reduced the expression of 5-HT_1A mRNA both in neurons and glial fibrillary acidic protein (GFAP)-immuno-reactive (IR) cells. The type II corticosteroid receptor agonist, Ru28362 (10^-8 M), also significantly decreased neuronal 5-HT_1A mRNA expression. However, it was not as effective as aldosterone in reducing the label over GFAP-IR cells. These data indicate that corticosteroids may directly regulate the expression of hippocampal 5-HT_1A receptors at the mRNA level in cultured hippocampal cells.