Gastric ulcers reduce A-type potassium currents in rat gastric sensory ganglion neurons

Voltage-dependent potassium currents are important contributors to neuron excitability and thus also to hypersensitivity after tissue insult. We hypothesized that gastric ulcers would alter K+ current properties in primary sensory neurons. The rat stomach was surgically exposed, and a retrograde tracer (1,1'-dioctadecyl-3,3,3,3'-tetramethylindocarbocyanine methanesulfonate) was injected into multiple sites in the stomach wall. Inflammation and ulcers were produced by 10 injections of 20% acetic acid (HAc) in the gastric wall. Saline (Sal) injections served as control. Nodose or T9-10 dorsal root ganglia (DRG) cells were harvested and cultured 7 days later to record whole cell K+ currents. Gastric sensory neurons expressed transient and sustained outward currents. Gastric inflammation significantly decreased the A-type K+ current density in DRG and nodose neurons (Sal vs. HAc-DRG: 82.9+/-7.9 vs. 46.5+/-6.1 pA/pF; nodose: 149.2+/-10.9 vs. 71.4+/-11.8 pA/pF), whereas the sustained current was not altered. In addition, there was a significant shift in the steady-state inactivation to more hyperpolarized potentials in nodose neurons (Sal vs. HAc: -76.3+/-1.0 vs. -83.6+/-2.2 mV) associated with an acceleration of inactivation kinetics. These data suggest that a reduction in K+ currents contributes, in part, to increased neuron excitability that may lead to development of dyspeptic symptoms.