excitant
Concise Oxford English Dictionary © 2008 Oxford University Press:
excitant /ˈɛksɪt(ə)nt, ɪkˈsʌɪt(ə)nt, ɛk-/
▶noun Biology a substance which elicits an active physiological or behavioural response.
'excitant' also found in these Oxford entries:

