I(KACh) inward rectifier potassium channel complex
i(kach) inward rectifier potassium channel complex
"An inward rectifier potassium channel complex expressed in cardiac muscle, specifically the sinoatrial node and atria, where it controls the heart rate, via regulation by G protein-coupled receptor signaling. In mammals it is composed of GIRK1 (or Kir3.1) and GIRK4 (or Kir3.4) subunits."