Changes of 5-HT receptor subtype mRNAs in rat dorsal root ganglion by bee venom-induced inflammatory pain

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-HT1A, 5-HT1B, 5-HT2A and 5-HT3 receptor subtypes were observed at 1 and 4 h after the BV injection, while increase of 5-HT2C, 5-HT4, 5-HT6 and 5-HT7 receptor subtype mRNAs was detected at 4 h only. No such changes were observed in the expressions of 5-HT1D, 5-HT1F and 5-HT5A receptor subtype mRNAs. Upregulation of 5-HT1A, 5-HT1B and 5-HT2A receptor subtype mRNAs was also observed in the contralateral DRG at 4 h. The presence of 5-HT1E, 5-HT2B and 5-HT5B 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.