Taurine activates strychnine-sensitive glycine receptors in neurons freshly isolated from nucleus accumbens of young rats

Although functional glycine receptors (GlyRs) are present in the mature nucleus accumbens (NAcc), an important area of the mesolimbic dopamine system involved in drug addiction, their role has been unclear because the NAcc contains little glycine. However, taurine, an agonist of GlyRs, is abundant throughout the brain, especially during early development. In the present study on freshly dissociated NAcc neurons from young Sprague-Dawley rats (12- to 21-day old), we found that both glycine and taurine can strongly depolarize NAcc neurons and modulate their excitability. In voltage-clamped NAcc neurons, glycine and taurine elicited chloride currents (I-Gly and I-Tau) with an EC50 of 0.12 and 1.25 mM, respectively. The reversal potential of IGly or I-Tau was 0 mV in conventional whole cell mode and -30 mV in gramicidin-perforated mode. At concentrations <1 mM, both glycine and taurine were very effectively antagonized by strychnine and by picrotoxin (with an IC50 of 60 nM and 36.5 mu M for I-Gly, and 40 nM and 42.2 mu M for I-Tau) but were insensitive to 10 mu M bicuculline. The currents elicited by taurine (<= 1 mM) showed complete cross-desensitization with I-Gly, but none with gamma-aminobutyric acid (GABA)-induced currents (I-GABA). However, I Tau elicited by very concentrated taurine (10 mM) showed partial cross-desensitization with I-GABA, and it was substantially antagonized by 10 mu M bicuculline. These results indicate that taurine binds mainly to GlyRs in NAcc, but it could be a partial agonist of GABA(A) receptors. By activating GlyRs, taurine may play an important physiological role in the control of NAcc function, especially during development.