REGULATION OF HIPPOCAMPAL 5-HT1A RECEPTOR GENE-EXPRESSION BY DEXAMETHASONE

The effect of dexamethasone, a selective GR agonist, on hippocampal, 5-HT1A receptor mRNA expression and 5-HT1A binding was examined using in situ hybridization histochemistry and in vitro receptor autoradiography. One week after adrenalectomy, both 5-HT1A receptor mRNA expression and 5-HT1A binding were increased throughout the hippocampus. Administration of dexamethasone at the time of adrenalectomy significantly attenuated the increases in 5-HT1A mRNA expression in all hippocampal subfields (p<.05, Fisher Test), although 5-HT1A mRNA levels remained significantly higher than sham levels in all subfields with the exception of CA(1). However, 5-HT1A binding levels were responsive to dexamethasone administration only within particular hippocampal subfields, CAI, and dentate gyrus. We conclude that GX occupation negatively regulates 5-HT1A receptor mRNA expression within the hippocampus and that 5-HT1A receptor sites are most sensitive to modulation in those hippocampal subfields expressing higher levels of GR receptors.