Nociceptive response of PrP+/+ and PrP-/- mice under acute stimulation. Nociceptive response of wild type or PrPc null mice in the first (panel A) and second (panel B) phases of formalin-induced (0.7% or 1.25%) nociception. C, D Effect of pretreatment of animals with MK-801 (3 nmol/i.t.) for the first (panel C) and second (panel D) phases of the formalin response. E. Nociceptive responses of WT and null mice following intraplantar injection of glutamate. Each column represents the mean ± S.E.M. (n = 6-9). *P < 0.05, ***P < 0.001.