Expression patterns of 5-HT receptor subtypes 1A and 2A on GABAergic neurons within the spinal dorsal horn of GAD67-GFP knock-in mice

5-HT plays an important role in GABA transmission at the spinal cord level. The main purpose of the present article is to find out, which 5-HT receptor subtypes may be involved in the regulation of GABAergic transmission in the spinal dorsal horn, by using the combination of tissue RT-PCR, single-cell RT-PCR and double immunofluorescent staining on the GAD67-GFP knock-in mice. The present result showed that 5-HT1A receptor subtype mRNA was present on about half of GFP-positive GABAergic interneurons in the spinal dorsal horn, which suggests a role of 5-HT1A receptor in GABA-mediated modulation of nociception at the spinal cord level. However, it is unexpected that just a very limited sub-population of the total GABAergic interneurons express 5-HT2A receptor mRNA or proteins in the spinal dorsal horn, which suggests that the 5-HT2A receptor subtype may not be important for spinal GABAergic effects in nociceptive modulation.