Abstract

[³H]5-HT revealed the presence of serotonin receptors in cultured rat sensory neurons. [³H]5-CT binding was inhibited by cyanopindolol with an IC₅₀ of 0.87 ± 0.30 nM, suggesting the expression of the 5-HT_1B receptor in these neurons. The presence of 5-HT_1B receptors was confirmed by the displacement of [¹²⁵I]Iodocyanopindolol binding by cyanopindolol with an IC₅₀ of 2.43 ± 0.81 nM. 5-HT_1B receptors are the predominant type of serotonin receptors labeled by [³H]5-HT in cultured DRG neurons, representing ∼60% of the specific [³H]5-HT binding sites. In addition, 5-HT_1D and 5-HT_2A receptor binding was also found in these neurons. RT-PCR analysis of RNA isolated from embryonic sensory neurons in culture confirmed the expression of 5-HT_1B, 5-HT_1D and 5-HT_2A receptor mRNA. It also demonstrated the presence of 5-HT_1F, 5-HT_2C, 5-HT₃, 5-HT₄, 5-HT_5A and 5-HT_5B receptor mRNA and the absence of 5-HT_1A, 5-HT_1E, 5-HT_2B, 5-HT₆ and 5-HT₇ mRNA. The identification of multiple subtypes of serotonin receptors expressed in cultured embryonic sensory neurons suggests that DRG neuronal cultures may be an excellent model to examine the direct effects of serotonin on the activity of these sensory neurons.