x ins ▁present ▁in ▁the ▁ven oms ▁of ▁sn akes ▁and ▁shell fish es , ▁like ▁α - b ung ar ot ox in . ▁Dru gs ▁such ▁as ▁the ▁neur om us cular ▁blocking ▁agents ▁bind ▁revers ibly ▁to ▁the ▁nic ot in ic ▁re cept ors ▁in ▁the ▁neur om us cular ▁j unction ▁and ▁are ▁used ▁rout in ely ▁in ▁an a est hes ia . ▁ ▁Nic ot in ic ▁re cept ors ▁are ▁the ▁primary ▁medi ator ▁of ▁the ▁effects ▁of ▁nic ot ine . ▁In ▁my as then ia ▁gra vis , ▁the ▁re ceptor ▁at ▁the ▁neur om us cular ▁j unction ▁is ▁target ed ▁by ▁ant ib od ies , ▁leading ▁to ▁mus cle ▁weak ness . ▁ ▁Mus car in ic ▁ac et yl ch oline ▁re cept ors ▁can ▁be ▁blocked ▁by ▁the ▁dru gs ▁at rop ine ▁and ▁sc opol am ine . ▁ ▁Cong en ital ▁my as then ic ▁synd rome ▁( C MS ) ▁is ▁an ▁inherited ▁neur om us cular ▁dis order ▁caused ▁by ▁defect s ▁of ▁several ▁types ▁at ▁the ▁neur om us cular ▁j unction . ▁Post syn apt ic ▁defect s ▁are ▁the ▁most ▁frequent ▁cause ▁of ▁C MS ▁and ▁often ▁result ▁in ▁ab normal ities ▁in ▁nic ot in ic ▁ac et yl ch oline ▁re cept ors . ▁The ▁majority ▁of ▁mut ations ▁causing ▁C MS ▁are ▁found ▁in ▁the ▁A Ch R ▁sub un its ▁gen es . ▁ ▁Out ▁of ▁all