Effect of the NT receptor antagonist SR 142948A on the acquisition of LI. Data are expressed as suppression ratio (mean ± SEM). a, Dose–response curve for the effects SR 142948A on the acquisition of LI after 25 pre-exposures to the conditioned stimulus. *p < 0.05 compared with the 25 pre-exposure control group. +p < 0.05 compared with the 0 pre-exposure group at the same dose of NT receptor antagonist (n = 5 or 6). b, Effect of the NT receptor antagonist SR 142948A on haloperidol-induced enhancement of latent inhibition in pre-exposed (10 pre-exposures) rats. *p < 0.05 compared with all other treatment groups (n = 5 or 6 mixed male and female).