4-Aminopyridine (4-AP) is a non-selective blocker of voltage-dependent K+-channels (Kv proteins in the KCN gene family). It has greatest potency at Kv1 (KCNA) and Kv3 (KCNC) family members (IC50s = 290, 590, 195, 13, 29, and 100 μM for subunits 1.1, 1.2, 1.3, 1.4, 3.1, and 3.2, respectively). 4-AP also blocks Kv2 and Kv4 subunits at millimolar concentrations. When administered orally, 4-AP has benefits against multiple sclerosis, while injection into the brain produces epileptiform activity and can be used to study seizures.
