WordNet sense 1 (any stimulating information or event; acts to arouse action):

input, stimulation, stimulus

WordNet sense 2 (a drug that temporarily quickens some vital process):

excitant, stimulant drug

WordNet sense 3 (that stimulates):

stimulating

WordNet sense 4 (capable of arousing or accelerating physiological or psychological activity or response by a chemical agent):

stimulative