Figure 1. Nociceptive scores (+/-SEM) in response to a 50-micro liter hind paw injection of formalin in rats given intrathecal cerebrospinal fluid or lidocaine (30 micro liter, 2.0%) 5 min before (CSF-pre, n = 8,8,7 or lido-pre, n = 9,12,10 for 2.5, 3.75 and 5.0% formalin, respectively) or 5 min after (CSF, n = 6,6,6 or lido-post, n = 10,8,6 for 2.5, 3.75 and 5.0% formalin, respectively) the formalin injection. Analysis of variance reveals a significant effect of treatment (F(3,77) = 22.6, P < 0.001) and formalin concentration (F(2,77) = 47.1, P < 0.001), as well as a significant treatment X formalin concentration interaction (F(6,77) = 27.9, P < 0.001). Significant differences from the cerebrospinal fluid pre and post group for each concentration are indicated by an asterisk (*P < 0.05, Newman Keuls).