%0 Journal Article
%T Activation of Glycine and Extrasynaptic GABAA Receptors by Taurine on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis
%A Thi Thanh Hoang Nguyen
%A Janardhan Prasad Bhattarai
%A Soo Joung Park
%A Seong Kyu Han
%J Neural Plasticity
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/740581
%X 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£¿¦ÌM to 3£¿mM) showed a concentration dependent depolarizations and inward currents with the EC50 of 84.3£¿¦ÌM and 723£¿¦ÌM, respectively. Taurine-mediated responses were partially blocked by picrotoxin (50£¿¦ÌM) and almost completely blocked by strychnine (2£¿¦ÌM), suggesting that taurine-mediated responses are via glycine receptor (GlyR) activation. In addition, taurine (1£¿mM) activated extrasynaptic GABAA receptor (GABAAR)-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 GABAARs on the SG neurons. 1. Introduction Taurine (2-amino-ethane sulfonic acid) is one of the most plentiful free amino-acids in humans [1, 2]. In the human body, taurine is distributed with high concentration in various tissues that are excitable and/or prone to generate free radicals in retina, white blood cells, platelets, central nervous system (CNS), heart, skeletal muscles, spleen, and liver [3]. In physiological condition, taurine is accumulated in brain cells at concentration of 5¨C70£¿mM [4, 5] and is released in high amounts under various pathological conditions such as anoxaemia or ischemia and seizure [6¨C8]. Since its first discovery in 1827, a number of studies have been done to find out the various physiological functions and the significance of taurine. It has been reported that taurine has various functions including bile acid production [9¨C12], antiarrhythmic effects [13¨C15], and oxidant scavenging effects [16]. In central nervous system, taurine has also been reported to modulate calcium homeostasis [17, 18], neuronal excitabilities [19, 20], and excitotoxic cell death [21, 22]. The pain transmission from the orofacial region to the trigeminal subnucleus caudalis (Vc) is
%U http://www.hindawi.com/journals/np/2013/740581/