DESENSITIZATION OF THE CARDIAC MUSCARINIC POTASSIUM CURRENT TO ACETYLCHOLINE - A BRIEF REVIEW

During an exposure to acetylcholine (ACh), the cardiac muscarinic K+ c urrent (I-K,I-ACh) declines in a biphasic manner as a result of desens itization to ACh. The fast phase may be the result of dephosphorylatio n of the K+ channel (or the G-protein, G(K)) and a decrease in the mea n open time of the channel, whereas the slow phase may be the result o f the phosphorylation of the muscarinic ACh receptor (mAChR) and a dec rease in high-affinity agonist binding.