Different mechanisms mediate development and expression of tolerance and dependence for peripheral mu-opioid antinociception in rat

Abstract

The mu-opioid [D-Ala2,N-Me-Phe4,Gly-ol5]-enkephalin (DAMGO) exerts a peripheral antinociceptive effect against prostaglandin E2 (PGE2)-induced mechanical hyperalgesia in the hindpaw of the rat. Tolerance and dependence develop to this effect. We have shown previously that tolerance and dependence can be dissociated and are mediated by different second messenger systems. In the present study, we evaluated whether the same or different second messenger systems mediate the development of this peripheral opioid tolerance or dependence compared with the expression of the loss of antinociceptive effect or rebound opioid antagonist hyperalgesia (i. e., expression of tolerance and dependence). DAMGO-induced tolerance was prevented by pretreatment with the nitric oxide synthase inhibitor NG-methyl-L-arginine (NMLA) but not by the protein kinase C (PKC) inhibitor chelerythrine, the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine (ddA), or the calcium chelators 3,4,5-trimethoxybenzoic acid 8-(diethylamino)-octyl ester (TMB-8) and 2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)-methyl]-6-methoxy-8-bis [carboxymethyl]aminoquinoline (Quin-2). Once established, however, expression of DAMGO tolerance was acutely reversed by TMB-8 or Quin-2 but not by chelerythrine or NMLA. In contrast, naloxone-precipitated hyperalgesia in DAMGO-tolerant paws, a measure of dependence, was blocked by pretreatment with chelerythrine but not by NMLA, ddA, TMB-8, or Quin-2. Naloxone-precipitated hyperalgesia in DAMGO-tolerant paws was acutely reversed by chelerythrine, ddA, TMB-8, or Quin-2 but not by NMLA. Taken together, these results provide the first evidence that different mechanisms mediate the development and expression of both tolerance and dependence to the peripheral antinociceptive effect of DAMGO. However, although the development of tolerance and dependence are entirely separable, the expression of tolerance and dependence shares common calcium-dependent mechanisms.

Fig. 1.

A, Role of NO in development of peripheral opioid tolerance. Effects of PGE₂ (100 ng;PGE₂; n = 16), DAMGO (1 μg) plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by DAMGO plus PGE₂ at the fourth hour (DAMGO×3,DAMGO+PGE₂;n = 12), saline (n = 6), NMLA (1 μg) plus PGE₂(NMLA+PGE₂; n = 8), NMLA alone (NMLA; n = 6), three hourly injections of NMLA followed by PGE₂ at the fourth hour (NMLA×3,PGE₂;n = 6), and three hourly injections of NMLA plus DAMGO followed by DAMGO plus PGE₂[(NMLA+DAMGO)×3,DAMGO+PGE₂;n = 12] on mechanical paw withdrawal threshold in rats. In this and all subsequent figures, an asteriskindicates p < 0.05, and NSindicates not significant statistically. B, Lack of role of PKC in development of peripheral opioid tolerance. Effects of PGE₂ (100 ng; PGE₂;n = 16), DAMGO (1 μg) plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by DAMGO plus PGE₂(DAMGO×3,DAMGO+PGE₂;n = 12), chelerythrine (1 μg) alone (Ch; n = 6), chelerythrine plus PGE₂ (Ch+PGE₂;n = 6), chelerythrine plus DAMGO plus PGE₂ (Ch+DAMGO+PGE₂;n = 6), and three hourly injections of chelerythrine plus DAMGO followed by DAMGO plus PGE₂[(Ch+DAMGO)×3,DAMGO+PGE₂;n = 6] on mechanical paw withdrawal threshold in rats. C, Lack of role of cAMP in development of peripheral opioid tolerance. Effects of PGE₂ (100 ng;PGE₂; n = 16), DAMGO (1 μg) plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by DAMGO plus PGE₂(DAMGO×3,DAMGO+PGE₂;n = 12), ddA (1 μg) plus PGE₂(ddA+PGE₂; n = 6), ddA alone (ddA; n = 6), three hourly injections of ddA followed by PGE₂ at the fourth hour (ddA×3,PGE₂;n = 6), and three hourly injections of ddA (1 μg) plus DAMGO followed by DAMGO plus PGE₂ at the fourth hour [(ddA+DAMGO)×3,DAMGO+PGE₂;n = 12] on mechanical paw withdrawal threshold in rats. D, Lack of role of calcium in development of peripheral opioid tolerance. Effect of PGE₂ (100 ng;PGE₂; n = 16), DAMGO (1 μg) plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by DAMGO plus PGE₂(DAMGO×3,DAMGO+PGE₂;n = 12), TMB-8 (1 μg) alone (TMB;n = 6), TMB-8 plus PGE₂, (TMB+PGE₂; n = 6), TMB-8 plus DAMGO plus PGE₂(TMB+DAMGO+PGE₂;n = 6), and three hourly injections of TMB-8 plus DAMGO followed by DAMGO plus PGE₂ at the fourth hour [(TMB+DAMGO)×3,DAMGO+PGE₂;n = 6] on mechanical paw withdrawal threshold in rats. E, Lack of role of calcium in development of peripheral opioid tolerance. Effects of PGE₂ (100 ng;PGE₂; n = 16), DAMGO (1 μg) plus PGE₂(DAMGO+PGE₂; n = 16), three hourly injections of DAMGO followed by DAMGO plus PGE₂(DAMGO×3,DAMGO+PGE₂;n = 12), Quin-2 (1 μg) alone (Quin; n = 6), Quin-2 plus PGE₂ (Quin+PGE₂;n = 6), Quin-2 plus DAMGO plus PGE₂(Quin+DAMGO+PGE₂;n = 6), and three hourly injections of Quin-2 plus DAMGO followed by DAMGO plus PGE₂ at the fourth hour [(Quin+DAMGO)×3,DAMGO+PGE₂;n = 6] on mechanical paw withdrawal threshold in rats.

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.

Fig. 3.

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

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.