title: 5-HT(3A) receptor subunit is expressed in a subpopulation of GABAergic and enkephalinergic neurons in the mouse dorsal spinal cord.
abstract: 5-Hydroxytryptamine (5-HT)(3) receptors have been proposed to modulate nociception and pain responses at the spinal level. To gain insight into the cellular mechanism of 5-HT(3) receptors, we examined their expression in GABAergic and enkephalinergic (ENKergic) neurons in the spinal dorsal horn (SDH) using single-cell reverse transcription-polymerase chain reaction (RT-PCR). The glutamic acid decarboxylase (GAD)(67)-green fluorescent protein (GFP) knock-in mouse was used in which all GABAergic neurons were fluorescent. The general tissue RT-PCR results showed that 5-HT(3A) receptor subunit mRNA was present in the mouse SDH, while 5-HT(3B) receptor subunit was absent. Single-cell RT-PCR results showed that 76.2% (16/21) and 33.3% (7/21) of the total 5-HT(3A)-expressing neurons were positive for GAD(67) and preproenkephalin (PPE, a precursor of ENK), respectively. 5-HT(3A) receptor subunit was detected in 28.1% (16/57) of GABAergic neurons and 22.6% (7/31) of ENKergic neurons. About 40.4% (23/57) of GABAergic neurons expressed PPE mRNA. Of the neurons that co-express GAD(67) mRNA and PPE mRNA, about 22% expressed 5-HT(3A) mRNA. These observations indicate that 5-HT(3A) receptor co-localizes with GABA and ENK in the SDH, suggesting that serotonin may activate GABAergic and ENKergic neurons via 5-HT(3A) receptor subunit and therefore affect the release of GABA and ENK. The different cellular localization of 5-HT(3A) receptor subunit suggest the complex participation of this receptor in the inhibitory neuronal circuits of the SDH neurons.
authors.affiliation: Department of Anatomy and KK Leung Brain Research Centre, Faculty of Basic Medicine, Fourth Military Medical University, Xi'an, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Ya-Yun
authors.initials: YY
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Yun-Qing
authors.initials: YQ
authors.lastname: Li
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Tamamaki
authors.forename: Sheng-Xi
authors.initials: SX
authors.lastname: Wu
mesh_terms: D000818:Animals; D004745:Enkephalins / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics*; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D020671:Posterior Horn Cells / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D044406:Receptors, Serotonin, 5-HT3 / Q000235:genetics / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D004745:Enkephalins; D012333:RNA, Messenger; D044406:Receptors, Serotonin, 5-HT3; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1