Nitric oxide enhances homomeric ρ1 GABAc receptor function

San Diego

Congreso; 40th Annual Meeting Neuroscience 2010; 2010

Society for Neuroscience

Nitric oxide (NO) is a diffusible gas produced in the central nervous system by the neural nitric oxide synthase (nNOS). Several neurotransmitter receptors and voltage-gated channels can be modulated by NO by s-nitrosylation of one or more cysteines. Nitrogen reactive specieshave been involved in the regulation of inhibitory gabaergic neurotransmission. NO was shown to increase the frecuency of spontaneous and miniature inhibitory postsynaptic currents mediated by GABAA receptors in hippocampal, thalamic and hypothalamic neurons (Zanelli, Brain Res, 2009; Yang, J Neurophysiol, 2007; Li, J Neurophysiol, 2002). Past work demonstrated that homomeric ρ1 GABAC receptors (GABAρ1R) can be modulated by reducing and oxidizing agents acting on extracellular cysteines forming the cys-loop (Calero, J Neurochem, 2008). Based on these data, we examined if NO could also modulate GABAρ1R activity. Human GABAρ1R were expressed in Xenopus laevis oocytes and GABA-evoked responses (chloride currents) recorded by two-electrode voltage clamp in the presence or absence of the NO donor 1,1-diethyl-2-hydroxy-2-nitroso-hydrazine sodium (DEA/NO). DEA/NO applications (100μM) significantly enhanced GABAρ1R-mediated responses. DEA/NO-induced potentiation of the ionic currents elicited by low concentrations of GABA (0.3μM) was +60.4±18.6% (n=14) and effects were fast and reversible. Meanwhile, DEA/NO also increased current maximal values in a +9.8±2.9 % (n=8) and this effects were only partially washed out. The co-application of the specific NO scavenger 2-(4-carboxyphenyl)-4,4,5,5 tetramethylimidazoline-1-oxyl-3-oxide potassium salt (CPTIO) (100 mM) and DEA/NO completely prevented potentiation of currents evoked by 0.3μM GABA, indicating that this modulation is due to a genuine action of NO. Our results demonstrate that GABAC receptors can be modulated by nitrogen reactive species, particularly by NO. The fast and reversible character of NO potentiation at low GABA concentrations suggests that at least part of NO effects could be produced directly on the ρ1 receptor subunits, possibly by s-nitrosylation of cysteines.