Fig. 5. Dose-response curves for nociceptive responses to von Frey stimuli (cumulative scores) and heat stimuli at days 3 and day 7 after either saline or morphine systemic injection in animals treated previously with either vehicle (v) injection or dibutyltin dichloride (DBTC) injection. *P < 0.05 versus that group's own baseline (Student paired t test). +P < 0.05 comparing saline and morphine groups (Student unpaired t test). **,++P < 0.01. (A ) Day 3 responses to von Frey stimuli. (B ) Day 3 responses to heat stimuli. (C ) Day 7 responses to von Frey stimuli. (D ) Day 7 responses to heat stimuli. AWE = average withdrawal event (the summation of responses to three von Frey filaments; see Methods). Error bars denote SEM.