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