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Enhancement of GABA-activated currents by arginine vasopressin in rat dorsal root ganglion neurons

QIU Fang, HU Wang-Ping, YANG Zhi-Fan

Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Sciences, Hubei University, Wuhan 430062, China； Department of Pharmacology, Hubei University of Science and Technology, Xianning 437100, China

Abstract

A growing number of studies have shown that arginine vasopressin (AVP) plays an analgesia role in the modulation of nociception. Previous studies have focused on the central mechanisms of AVP analgesia. The aim of the present study was to find out whether peripheral mechanisms are also involved. The effect of AVP on GABA-activated currents (IGABA) and GABAA receptor function in freshly isolated dorsal root ganglion (DRG) neurons of rats were studied using whole cell patch clamp technique. The result showed that, IGABA were potentiated by pre-treatment with AVP (1 × 10−10–1 × 10−5 mol/L) in a concentration-dependent manner. Meanwhile, the GABA concentration-response curve was shifted upwards, with an increase of (49.1 ± 4.0)% in the maximal current response but with no significant change in the EC50 values. These results indicate that the enhancing effect is non-competitive. In addition, the effects of AVP on IGABA might be voltage-independent. This potentiation of IGABA induced by AVP was almost completely blocked by the V1a receptor antagonist SR49059 (3 × 10−6 mol/L). Also it could be removed by intracellular dialysis of either GDP-β-S (5 × 10−4 mol/L), a non-hydrolyzable GDP analog, or GF109203X (2 × 10−6 mol/L), a selective protein kinase C (PKC) inhibitor, with the re-patch clamp. These results suggest that AVP up-regulates the function of the GABAA receptor via G protein-coupled receptors and PKC-dependent signal pathways in rat DRG neurons, and this potentiation may underlie the analgesia induced by AVP.

Key words: Arginine vasopressin; GABA-activated current; dorsal root ganglion neurons; patch clamp technique; intracellular dialysis

Received: 2014-03-24　　Accepted: 2014-08-22

Corresponding author: 杨之帆　　E-mail: sailyangzhf@gmail.com

Citing This Article：

QIU Fang, HU Wang-Ping, YANG Zhi-Fan. Enhancement of GABA-activated currents by arginine vasopressin in rat dorsal root ganglion neurons. Acta Physiol Sin 2014; 66 (6): 647-657 (in Chinese with English abstract).