title: Activation of glycine and extrasynaptic GABA(A) receptors by taurine on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis.
abstract: The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been known for the processing and transmission of orofacial nociceptive information. Taurine, one of the most plentiful free amino-acids in humans, has proved to be involved in pain modulation. In this study, using whole-cell patch clamp technique, we investigated the direct membrane effects of taurine and the action mechanism behind taurine-mediated responses on the SG neurons of the Vc. Taurine showed non-desensitizing and repeatable membrane depolarizations and inward currents which remained in the presence of amino-acid receptors blocking cocktail (AARBC) with tetrodotoxin, indicating that taurine acts directly on the postsynaptic SG neurons. Further, application of taurine at different doses (10  μM to 3 mM) showed a concentration dependent depolarizations and inward currents with the EC50 of 84.3  μM and 723  μM, respectively. Taurine-mediated responses were partially blocked by picrotoxin (50  μM) and almost completely blocked by strychnine (2  μM), suggesting that taurine-mediated responses are via glycine receptor (GlyR) activation. In addition, taurine (1 mM) activated extrasynaptic GABA(A) receptor (GABA(A)R)-mediated currents. Taken together, our results indicate that taurine can be a target molecule for orofacial pain modulation through the activation of GlyRs and/or extrasynaptic GABA(A)Rs on the SG neurons.
authors.affiliation: Department of Oral Physiology & Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Thi Thanh Hoang
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Department of Oral Physiology & Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Janardhan Prasad
authors.initials: JP
authors.lastname: Bhattarai
authors.affiliation: Department of Oral Physiology & Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Soo Joung
authors.initials: SJ
authors.lastname: Park
authors.affiliation: Department of Oral Physiology & Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Seong Kyu
authors.initials: SK
authors.lastname: Han
mesh_terms: D000818:Animals; D003627:Data Interpretation, Statistical; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D018755:GABA Agonists; D018756:GABA Antagonists / Q000494:pharmacology; D018684:Glycine Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010852:Picrotoxin / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000187:drug effects*; D018009:Receptors, Glycine / Q000819:agonists*; D013331:Strychnine / Q000494:pharmacology; D013376:Substantia Gelatinosa / Q000166:cytology* / Q000187:drug effects*; D013654:Taurine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014278:Trigeminal Nuclei / Q000187:drug effects*
chemical_list: D018755:GABA Agonists; D018756:GABA Antagonists; D018684:Glycine Agents; D010852:Picrotoxin; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D013331:Strychnine; D013654:Taurine