Fig. 2. Sensitivity of topical mu opioid analgesia to naloxone.
Groups (n=10) of animals received systemic naloxone (1 mg/kg, s.c.) given in the midscapular region 20 min or saline before topical drug administration of the indicated opiate (10 mM). Analgesia was assessed using the tail-flick assay, as described under Methods.
