administration of the alpha 1-adrenoceptor selective antagonist prazosin produced a dose-dependent blockade of nm contractions without altering phenylephrine-induced mydriasis when given as pretreatment ( 1.0 mg/kg i.v . ) or post-treatment ( 0.01-1.0 mg/kg i.v . ) .
C0031469
phenylephrine
C0026961
mydriasis