Serotonin 5-HT(3) receptors in rat CA1 hippocampal interneurons: functional and molecular characterization.
The molecular makeup of the serotonin 5-HT(3) receptor (5-HT(3)R) channel was investigated in rat hippocampal CA1 interneurons in slices using single-cell RT-PCR and patch-clamp recording techniques. We tested for the expression of the 5-HT(3A) (both short and long splice variants) and 5-HT(3B) subunits, as well as the expression of the alpha4 subunit of the neuronal nicotinic ACh receptors (nAChRs), the latter of which has been shown to co-assemble with the 5-HT(3A) subunit in heterologous expression systems. Both the 5-HT(3A)-short and alpha4-nAChR subunits were expressed in these interneurons, but we could not detect any expression of either the 5-HT(3B) or the 5-HT(3A)-long subunits. Furthermore, there was a strong tendency for the 5-HT(3A)-short and alpha4-nAChR subunits to be co-expressed in individual interneurons. To assess whether there was any functional evidence for co-assembly between the 5-HT(3A)-short and alpha4-nAChR subunits, we used the sulphydryl agent 2-aminoethyl methanethiosulphonate (MTSEA), which has previously been shown to modulate expressed 5-HT(3)Rs that contain the alpha4-nAChR subunit. In half of the interneurons examined, MTSEA significantly enhanced the amplitude of the 5-HT(3)R-mediated responses, which is consistent with the notion that the alpha4-nAChR subunit co-assembles with the 5-HT(3A) subunit to form a native heteromeric 5-HT(3)R channel in rat CA1 hippocampal interneurons in vivo. In addition, the single-channel properties of the 5-HT(3)R were investigated in outside-out patches. No resolvable single-channel currents were observed. Using non-stationary fluctuation analysis, we obtained an estimate of the single-channel conductance of 4 pS, which is well below that expected for channels containing both the 5-HT(3A) and 5-HT(3B) subunits.
Sudweeks
Sterling N
SN
Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, PO Box 12233, Research Triangle Park, NC 27709, USA.
Hooft
Johannes A van
JA
Yakel
Jerrel L
JL
D000200:Action Potentials; D000818:Animals; D016477:Artifacts; D004553:Electric Conductivity; D005020:Ethyl Methanesulfonate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3
D007473:Ion Channels; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; C093171:methanethiosulfonate ethylammonium; D005020:Ethyl Methanesulfonate