Multiple subtypes of serotonin receptors are expressed in rat sensory neurons in culture

[H-3]5-HT revealed the presence of serotonin receptors in cultured rat sens ory neurons. [H-3]5-CT binding was inhibited by cyanopindolot with an IC50 of 0.87 +/- 0.30 nM, suggesting the expression of the 5-HT1B receptor in th ese neurons. The presence of 5-HT1B. receptors was confirmed by the displac ement of [I-125]Iodocyanopindolol binding by cyanopindolol with an IC50 of 2.43 +/- 0.81 nM. 5-HT1B receptors are the predominant type of serotonin re ceptors labeled by [H-3]5-HT in cultured DRG neurons, representing similar to 60% of the specific [H-3]5-HT binding sites. In addition, 5-HT1D and 5-H T2A receptor binding was also found in these neurons. RT-PCR analysis of RN A isolated from embryonic sensory neurons in culture confirmed the expressi on of 5-HT1B, 5-HT1D and 5-HT2A receptor mRNA. It also demonstrated the pre sence of 5-HT1F, 5-HT2C, 5-HT3, 5-HT4, 5-HT5A, and 5-HT5B, receptor mRNA an d the absence of 5-HT1A, 5-HT1E, 5-HT2B, 5-HT6 and 5-HT7 mRNA. The identifi cation of multiple subtypes of serotonin receptors expressed in Cultured em bryonic sensory neurons suggests that DRG neuronal cultures may be an excel lent model to examine the direct effects of serotonin on the activity of th ese sensory neurons.