Temperature and pH-dependent potassium currents of muscles of the stomatogastric nervous system of the crab, Cancer borealis.

Marine crustaceans such as the crab, Cancer borealis , experience fluctuations in temperature and pH, yet their stomatogastric neuromuscular system must remain functional for feeding. We examined 16 of ∼40 stomach muscle pairs and found that warming consistently hyperpolarized muscle fibers (∼10 mV per 10°C) and reduced excitatory junctional potentials and currents. Muscle responses were also strongly influenced by extracellular pH, with an optimal range between pH 6.7 and 8.8; outside this window, abnormal activity emerged. Voltage-clamp analysis of gastric muscle gm5b revealed a temperature- and pH-sensitive conductance with a reversal potential near the potassium equilibrium potential and insensitivity to tetraethylammonium and barium, providing evidence against classical voltage-gated potassium channels. Quantitative RT-PCR detected the expression of two putative two-pore domain potassium (K2P) channels in these muscles. Together, these results suggest that muscle excitability in C. borealis is shaped by temperature- and pH-sensitive potassium currents consistent with contributions from K2P channels.