Mechanical and thermal withdrawal threshold of PrP+/+ and PrP-/- mice. Time course of basal mechanical (panel A) and thermal (panel B) nociceptive threshold of wild type or PrPc null mice as a function of the age of the animal. (C) Effect of pretreatment of 3 months old mice with MK-801 (3 nmol/i.t.) on mechanical withdrawal threshold. Each point or column represents the mean ± S.E.M. (n = 5-6). *P < 0.05, **P < 0.01.