WordNet sense 1 (easily impressed or influenced):

impressible

WordNet sense 2 (susceptible to criticism or persuasion or temptation):

vulnerable

WordNet sense 3 (readily reacting to suggestions and influences):

responsive

WordNet sense 4 (made susceptible):

predisposed

WordNet sense 5 ((often followed by `to') likely to be affected with):

liable

WordNet sense 6 (possibly accepting or permitting):

capable, open, subject, subject