the affinity of both the ( + ) - and the ( - ) -stereoisomer of biperiden for different muscarinic receptor subtypes was investigated in vitro in functional studies with field-stimulated rabbit vas deferens ( m1-receptor ) , guinea-pig ileum ( smooth muscle m2 beta-receptor ) and rat left atrium ( cardiac m2 alpha-receptor ) .
C0034826
muscarinic receptor
C0531859
m1-receptor