Fig. 5.

The effects of naltrindole (3 mg/kg) on SNC80 (200 μg)-mediated antinociception and block of substance P release after formalin. (A) Tactile threshold in grams plotted as a function of time after intraplantar λ-carrageenan. Naltrindole (i.p.) or saline (i.p.) was administered at 40 minutes after carrageenan and SNC80 (i.t.) was injected 20 minutes after naltrindole. (B) Cumulative flinches after intraplantar formalin in phase 1 (1–9 minutes) and phase 2 (10–60 minutes). Rats were treated with naltrindole (i.p.) or saline followed by intrathecal SNC80 (20 minutes after naltridole) and intraplantar formalin (10 minutes after SNC80). (C) Percentage of NK1R (+) neurons showing internalization in lamina I of the lumbar spinal cord 10 minutes after paw formalin. Rats were treated the same way as in B. Data are presented as mean ± S.E.M. n = 5–7 (A and B), n = 3 (C), *P < 0.05.