KCNA3 and congenital myasthenic syndrome: It is, however, ineffective or dangerous in CMS due to mutations in COLQ, DOK7 and CHRNA1. 3,4-Diaminopyridine, a potassium channel blocker that enables the release of ACh from the presynaptic terminal, is used as an adjunctive treatment with pyridostigmine and ChAT CMS could theoretically worsen in response.