Fig. 12.

Dose–effect relations for morphine in rats with unilateral Ce lesions or unilateral Ce sham lesions (n = 5–8 per group). For these curves, the dose of morphine was varied, whereas the concentration of formalin injected into either the ipsilateral (A) orcontralateral (B) hindpaw was held constant at 1.0%. Rating scale nociceptive scores were averaged across the second phase of the formalin test for all rats. The mean second phase nociceptive score for systemic saline-treated control rats (either lesion or sham lesion) was used asE_min for calculation of percentage of maximum possible antinociceptive effect (%MPE; see Experiment 4, Materials and methods).