Fig. 4.

PKC, calcium, and cAMP, but not NO, play a role in expression of peripheral opioid dependence. Effects of PGE₂(PGE₂; n = 16), DAMGO plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by naloxone at the fourth hour (DAMGO×3,NAL; n = 12), three hourly injections of DAMGO followed by chelerythrine plus naloxone at the fourth hour (DAMGO×3,Ch+NAL;n = 10), three hourly injections of DAMGO followed by ddA plus naloxone at the fourth hour (DAMGO×3,ddA+NAL; n = 6), three hourly injections of DAMGO followed by TMB-8 plus naloxone at the fourth hour (DAMGO×3,TMB+NAL; n = 12), three hourly injections of DAMGO followed by Quin-2 plus naloxone at the fourth hour (DAMGO×3, Quin+NAL; n= 12), and three hourly injections of DAMGO followed by NMLA plus naloxone at the fourth hour (DAMGO×3,NMLA+NAL;n = 8) on mechanical paw withdrawal threshold in rats.