Fig. 11.

Average nociceptive and horizontal locomotor activity scores of unilateral Ce-treated rats in Experiment 3. Error bars indicate SEM. Rating scale nociceptive scores are shown inA, flinch nociceptive scores are shown inB, and horizontal locomotor activity scores are shown inC. In this experiment, Ce-treated rats (sham lesion and lesion) received systemic morphine and intraplantar formalin on two separate occasions. On one occasion, formalin was delivered to the hindpaw ipsilateral to theCe treatment (lesion or sham lesion), and on the other occasion formalin was delivered to the contralateralhindpaw. Note the similar pattern of results obtained with the rating scale and flinch-frequency methods of nociceptive scoring. Under morphine, there were no significant differences in nociceptive scores between either group of unilateral Ce sham lesion rats and unilateral Ce lesion rats treated with contralateral formalin. In unilateral Ce lesion rats treated with ipsilateralformalin, however, morphine sulfate (6 mg/kg, s.c.) produced significantly less antinociception compared with all other groups. As was the case in Experiment 1 (Fig. 3), this effect was dissociable from the effects of morphine on horizontal locomotor activity, because morphine-induced increases in locomotor activity were unaffected by unilateral Ce lesions (C). B, *p < 0.05, Mann–Whitney U test, compared with all other groups.