5-hydroxytryptamine (5-HT) is a potent proinflammatory and noxious agent, which can causes pain and hyperaigesia both in human and rodents. The determination of which subtypes of 5-HT receptors are involved in 5-HT-induced pain and hyperalgesia will allow the development of more selective drugs for inflammatory pain and hyperalgesia. In the present study, reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization histochemistry and behavioral test were used to investigate the distribution of 5-HT1 receptor 5-hydroxytryptamine (5-HT) is a potent proinflammatory and noxious agent, which can causes pain and hyperaigesia both in human and rodents. The determination of which subtypes of 5-HT receptors are involved in 5-HT-induced pain and hyperalgesia will allow the development of more selective drugs for inflammatory pain and hyperalgesia. In the present study, reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization histochemistry and behavioral test were used to investigate the distribution of 5-HT1 receptor