Pharmacological characterization of GABAA receptors in taurine-fed mice
Taurine is one of the most abundant free amino acids, especially in excitable tissues, with wide physiological actions. Chronic supplementation of taurine in drinking water to mice increases brain excitability, mainly through alterations in the inhibitory GABAergic system. These changes include elevated expression level of glutamic acid decarboxylase (GAD) and increased levels of GABA. Additionally, we reported that GABAA receptors were down regulated with chronic administration of taurine. Here, we investigated pharmacologically the functional significance of decreased / or change in subunit composition of the GABAA receptors by determining the threshold for picrotoxin-induced seizures. Picrotoxin, an antagonist of GABAA receptors that blocks the channels while in the open state, binds within the pore of the channel between the b2 and b3 subunits. These are the same subunits to which GABA and presumably taurine binds.