Identification of an Endogenous 5-Hydroxytryptamine2A Receptor in NIH-3T3 Cells: Agonist-Induced Down-Regulation Involves Decreases in Receptor RNA and Number

摘要: NIH-3T3 cells, a nontransformed murine fibroblast cell line previously found to be unresponsive 5-hydroxytryptamine (5-HT) when cultured in 5-HT-free medium, became responsive 5-HT, which induced an increase intracellular calcium concentration. Pharmacological and ligand binding studies showed that cells endogenously express 5-HT 2A receptor that, activated, mobilizes from ionomycin-sensi-tive stores via coupling pertussis toxin-insensitive pathway. Using reverse transcriptase-PCR cloning northern blot analysis, the presence of 2 RNA with similar nucleotide sequence (99% identity) molecular size brain was detected cells. Responsiveness endogenous A nontransfected completely desensitized after chronic treatment (half-time = h) 1 μM resensitized on removal 5-HT. In contrast transfected cDNA under control viral promoter, long-term agonist-induced functional desensitization paralleled by decrease both density level. These results show is agonist down-regulation number mRNA. The provide novel system for understanding (NR> regulation.