Chronic buspirone treatment differentially regulates 5-HT_1A and 5-HT_2A receptor mRNA and binding sites in various regions of the rat hippocampus

Groups of rats were treated with buspirone (1 mg/kg/day) for 21 days using osmotic minipumps implanted subcutaneously. After buspirone treatment, the 5-HT_1A receptor mRNA levels were significantly decreased in the CAl and CA2 of the hippocampus, but were markedly increased in the dentate gyrus (DG), CA3 and CA4. The level of the 5-HT_1A receptor binding sites was not significantly changed in these subhippocampal areas. Buspirone treatment markedly increased 5-HT_2A receptor mRNA levels in the DG, CA2, CA3 and CA4. This was accompanied by a significant increase in the level of 5-HT_2A receptor binding sites in all subhippocampal regions. These results demonstrate that chronic buspirone treatment differentially regulates 5-HT_1A and 5-HT_2A receptor mRNA as well as their expressed binding sites in various regions of the hippocampus.