PT - JOURNAL ARTICLE AU - Erika I. Puente, Sr. AU - Lizbeth De la Cruz, Sr. AU - Isabel Arenas, Sr. AU - David Elias-Vinas V AU - David E. Garcia V TI - Voltage-independent inhibition of the TTX-sensitive Na+ currents by oxotremorine and angiotensin II in rat sympathetic neurons AID - 10.1124/mol.115.101931 DP - 2016 Jan 01 TA - Molecular Pharmacology PG - mol.115.101931 4099 - http://molpharm.aspetjournals.org/content/early/2016/02/11/mol.115.101931.short 4100 - http://molpharm.aspetjournals.org/content/early/2016/02/11/mol.115.101931.full AB - TTX-sensitive Na+ currents have been extensively studied as they play a major role in neuronal firing and bursting. Here, we show that voltage-dependent Na+ currents are regulated in a slow manner by oxotremorine (Oxo-M) and angiotensin II (Angio II) in rat sympathetic neurons. We found that these currents can be readily inhibited through a signaling pathway mediated by G proteins and PLCĪ²1. This inhibition is slowly established, PTX-insensitive, is partially reversed within tens of seconds after Oxo-M washout and is not relieved by a strong depolarization, suggesting a voltage-insensitive mechanism of inhibition. Specificity of the M1 receptor was tested by the MT-7 toxin. Activation and inactivation curves show no shift on the voltage-dependency under the inhibition by Oxo-M. This inhibition is blocked by a PLC inhibitor (U73122), and the recovery from inhibition is prevented by wortmannin (WMN), a PI3/4 kinase inhibitor. Hence, the pathway involves Gq/11 and is mediated by a diffusible second messenger. Oxo-M inhibition is occluded by screening PIP2 negative charges with poly-L-lysine (PLL) and prevented by intracellular dialysis with a PIP2 analog. In addition bisindolylmaleimide I (BIS-I), a specific ATP-competitive PKC inhibitor, rules out that this inhibition may be mediated by this protein kinase. Furthermore, Oxo-M-induced suppression of Na+ currents remains unchanged when neurons are treated with calphostin C (Cal-C), a PKC inhibitor that targets the diacylglycerol-binding site of the kinase. These results support a general mechanism of Na+ current inhibition that is widely present in excitable cells through modulation of ion channels by specific G protein-coupled receptors (GPCR).