The reverse transcriptase polymerase chain reaction (RT-PCR) technique was used to examine the changes of the expression of 5-hydroxytryptamine (5-HT) receptors in the rat lumbar dorsal root ganglion (DRG) following subcutaneous bee venom (BV) injection into the plantar surface of the unilateral hindpaw. In the DRG ipsilateral to the BV injection, significant increase of mRNA levels of 5-HT(1A), 5-HT(1B), 5-HT(2A) and 5-HT(3) receptor subtypes were observed at 1 and 4h after the BV injection, while increase of 5-HT(2C), 5-HT(4), 5-HT(6) and 5-HT(7) receptor subtype mRNAs was detected at 4h only. No such changes were observed in the expressions of 5-HT(1D), 5-HT(1F) and 5-HT(5A) receptor subtype mRNAs. Upregulation of 5-HT(1A), 5-HT(1B) and 5-HT(2A) receptor subtype mRNAs was also observed in the contralateral DRG at 4 h. The presence of 5-HT(1E), 5-HT(2B) and 5-HT(5B) receptor subtype mRNAs was not detected in the rat DRG. The present results suggest that different sets of 5-HT receptor subtypes work at different stages of the inflammatory pain induced by subcutaneous BV injection.