Gtropcatt Jotcrnal of Pharwtacolr~gy,220 (1992) 275-277 @ 1992 Elsevier Science Publishers B.V. All rights resewed ~14-2999~92/$~5.W
EJP 0372R
Rapid communication
Chaim G. Pick ‘, Bernard Roques ‘, Gilles Gacel ” and Gavril W. Pasternak i1-c
Received 25 August 1992, accepted 26 AugustI992
TRIMCJ-S (Tyr-D-Ala-Gly-NHC,H,CH(CH,),) is a patent p2-opioid agonist/h,-opioid antagonist. A supraspinal dose (0.5 pg i.c.v.) of TRIMU-S which is not analgesic when given alone antagonizes the analgesia produced by intracerchrc~ventricular (i.c.v.) morphine, a p, action. In contrast, in a synergy model consisting of the simultaneous administration of intrathccal morphine (0.1 Fg) with multiple doses of i.c.v. morphine, the same supraspinal TRIMU-5 dose (0.5 fig i.c.v.1enhances analgesia. Supraspinal TRIMU-5 also potentiatcs spinal morphine directly, shifting its dose-rcsponsc to the left. These results imply that within the hrainstcm p, receptors mcdiatc supraspinal analgesia while gZ rcccptors mcdiatc the synergy with spinat p systems. Morphine; Annlgcsia; p-Opioid rcccptors
Supraspinal morphine elicits analgesia aIonc or synergistically with the concurrent administration of spinal momhine (Yeung and Rudy, 1980). Although in mice EL,-opioid receptors mediate the analgesic actions of supraspina~ morphine alone fPatlf et al., 1989; Pick et al., in press), the brainstem p receptors involved in spinal/ supraspinal synergy differ. Studies using genetic models along with the selective mu antagonists ~-funaltrexamine and Raloxonazine suggest that brainstem y,-opioid receptors are responsible far the synergy with spinal systems (Pick et al., in press). TRIMU-5 ~Tyr-D-Ada-GIy-NffC~ff ~CH~CH~)~) is a potent and highly selcctivc I_Cligand in receptor binding assays. Selective CL, and pZ functional assays reveal that TRIMU-5 is a pZ-opioid agonist while potently antagonizing morphine actions at CL,receptors (Tive et al., in press). ‘Thus, TRIMU-5 is a mixed pz-opioid agonist/ p,-opioid antagonist. We have exploited this unique property to cxaminc the brainstem p receptor subtype mediating spinal/supraspinaI synergy. lntra~rebroventricular (i.c.v.1 and intrathecal (i.t.1 irijections in male CD-1 mice (25-35 g; Charles River Breeding Laboratories, Wilmington, MA) were made as previously described (Paul et al., 1989; Pick et al., in
Correspondence IO: GW. Pasternak, ~ern~ri~l Si~an-Kettering Cancer Center, 1275 York kvcnue. New York, NY 10021, USA. Tel. I (212) 039-7046, fi~x I (212) 717-3296.
press). TRIMUJ was synthesized as described previously (Gacel et al., 19%). Analgesia was assessed quantally as a douhlit?g or greater of baseline latencies in the radiant heat tail-flick assay (Pa& et al., 1989; Pick et al., in press). Dose-rcsponsc curves were anafyzed using a modification of the BLISS-20 computer program. Single-dose comparisons utilized the Fisher cxact test. At a dose which is inactive aIone, TRIMU-5 (0.5 r_tg i.c.v.1 shifts the dose-response curve for i.c.v. morphine almost 4-fold to the right (fig. IA), confirming its antagonism of p, receptors (Eve et al., in press). However, the same supraspinal TRIMU-5 dose produces a very different response in the morphine synergy model, The addition of a fixed spinal dose of morphine (0.1 pg i.t.1 potentiates the actions of i.c.v, morphine, confirming the interactions of spinal and supraspinal morphine (Yeung and Rudy, 1981~. In contrast to its effects upon supraspinat morphine alone, the addition of supraspina~ TRIMU-5 (0.5 pg i&v.) in the synergy mode1 enhances morphine analgesia, shifting the dose-response curve for supraspinal morphine analgesia almost 4-fold further to the left (fig. IB). Finally, supraspinal TRIMU-5 without any i.c.v. morphine also potentiates intrathecal morphine (fig. 10. TRIMUJ has very different actions upon supraspinal morphine depending upon whether the morphine is given i.c.v. alone or in the synergy model. Against supraspinal morphine alone, TRiMW-S at a
0.1
Morphtne
dose tll-fold
lower
Morphine
(pg, i.c.v.)
than its own ED5,, value (Tive ct al..
in press) antagonizes morphine analpcsia. a I* ,-opioid action. while in the synergy model TRiMU-S enhances rn~~rp~i~~ analgesia. These diffcrcnccs arc most easily
utility
(pg, i.c.v.)
in cxaming the role of ,u rcccptor suhtypcs in
opioid actions.
~~~la~~~d hy its g,-opioid agonist/p ,-opioid antagcjnist ~~c~~~r~tcs. The ability of su~rasp~nal T~I~iU-S also to ~~~t~~t~at~ the actions of spinaf mrtrphinc directly further impiicatcs supraspinal p+pioid rcccptars in the synergy model. These results are consistent with other studies utilizing the JL ,-opioid rcceptor-dcficicnt CXBK strain and the w antagonists p-
This work was supported. Inslitutc
in p;lrt. by ;I grant from the National
on Drug A.huse tl>AO732t
a Re>c;lrch
Scientist
Development
to GWP. Award
CiWP is a recipient
from the Natinnal
elf
Insli-
tutr on Drug Ahusc (lIAtltI13X).
~unalt~~xarn~~c and naloxonazine. In conclusion, our results c~~rrciatc brainstem g, and pZ receptors in
References
s~~~aspi~a? analgesia and spinal/ supraspinal synergy, respectively. I(n additive, they illustrate the unique ~~arrnac~i~~~ica~ characteristics of TRIMU-S and its
Gael.
G., J.M. Z:tjac. I’. l~~l~iy-~(iy~t,
1%-S. In~~sii~~ItiIln of the slrucrurai and 6 opioid rcccptor discrimination peptides. J. Med. Chem.
31, 374.
V. Diiuge and 1f.P. Rttyues, paritmt!Wrs
invcllvod in the g
of linear cnkcphalin-related
Paul. D.. R.J. Bodnar, MA. Gistrak and G.W. P~sternitk. IYXY, Different mu rwcptor subtypes modiatc spinal and supraspinal ;malgcsia in mice. Eur. J. Pharmacol. 168. 307. Pick, C.G., R. Nejat and G.W. Pasternak. Independent genetic control of IWO ph~~rrn;~c~~i~~~i~ily distinct supraspinal mu analgesic systems, J. Ph:trmacol. Exp. Thu. iin prcssf. Tive. LA., C.G. Pick, D. Paul. B.P. Roques. GA. Gad and C.W. P:etcrnak. Analgesic potency of TRIMU-S: a mixed pz opioid
receptor agonist,/.g, opioid receptor anlqonist. Eur. J. phtirmacol. (in press). Y~uII~, J-c‘. and T.A. Rudy, IYtiO. Multiplicatitc itwraction hctween narcotic agonisms exprcssrd al spinal and supraspinal sites nf antinociccplivc :Iction us rcveaied by concurrent intrathecal and inlr;iccrchroventricul;tr injectionc 01 morphine. J. Pharmacol. Exp. Ther. 215. h33.
EJP 0372R
Rapid communication
Chaim G. Pick ‘, Bernard Roques ‘, Gilles Gacel ” and Gavril W. Pasternak i1-c
Received 25 August 1992, accepted 26 AugustI992
TRIMCJ-S (Tyr-D-Ala-Gly-NHC,H,CH(CH,),) is a patent p2-opioid agonist/h,-opioid antagonist. A supraspinal dose (0.5 pg i.c.v.) of TRIMU-S which is not analgesic when given alone antagonizes the analgesia produced by intracerchrc~ventricular (i.c.v.) morphine, a p, action. In contrast, in a synergy model consisting of the simultaneous administration of intrathccal morphine (0.1 Fg) with multiple doses of i.c.v. morphine, the same supraspinal TRIMU-5 dose (0.5 fig i.c.v.1enhances analgesia. Supraspinal TRIMU-5 also potentiatcs spinal morphine directly, shifting its dose-rcsponsc to the left. These results imply that within the hrainstcm p, receptors mcdiatc supraspinal analgesia while gZ rcccptors mcdiatc the synergy with spinat p systems. Morphine; Annlgcsia; p-Opioid rcccptors
Supraspinal morphine elicits analgesia aIonc or synergistically with the concurrent administration of spinal momhine (Yeung and Rudy, 1980). Although in mice EL,-opioid receptors mediate the analgesic actions of supraspina~ morphine alone fPatlf et al., 1989; Pick et al., in press), the brainstem p receptors involved in spinal/ supraspinal synergy differ. Studies using genetic models along with the selective mu antagonists ~-funaltrexamine and Raloxonazine suggest that brainstem y,-opioid receptors are responsible far the synergy with spinal systems (Pick et al., in press). TRIMU-5 ~Tyr-D-Ada-GIy-NffC~ff ~CH~CH~)~) is a potent and highly selcctivc I_Cligand in receptor binding assays. Selective CL, and pZ functional assays reveal that TRIMU-5 is a pZ-opioid agonist while potently antagonizing morphine actions at CL,receptors (Tive et al., in press). ‘Thus, TRIMU-5 is a mixed pz-opioid agonist/ p,-opioid antagonist. We have exploited this unique property to cxaminc the brainstem p receptor subtype mediating spinal/supraspinaI synergy. lntra~rebroventricular (i.c.v.1 and intrathecal (i.t.1 irijections in male CD-1 mice (25-35 g; Charles River Breeding Laboratories, Wilmington, MA) were made as previously described (Paul et al., 1989; Pick et al., in
Correspondence IO: GW. Pasternak, ~ern~ri~l Si~an-Kettering Cancer Center, 1275 York kvcnue. New York, NY 10021, USA. Tel. I (212) 039-7046, fi~x I (212) 717-3296.
press). TRIMUJ was synthesized as described previously (Gacel et al., 19%). Analgesia was assessed quantally as a douhlit?g or greater of baseline latencies in the radiant heat tail-flick assay (Pa& et al., 1989; Pick et al., in press). Dose-rcsponsc curves were anafyzed using a modification of the BLISS-20 computer program. Single-dose comparisons utilized the Fisher cxact test. At a dose which is inactive aIone, TRIMU-5 (0.5 r_tg i.c.v.1 shifts the dose-response curve for i.c.v. morphine almost 4-fold to the right (fig. IA), confirming its antagonism of p, receptors (Eve et al., in press). However, the same supraspinal TRIMU-5 dose produces a very different response in the morphine synergy model, The addition of a fixed spinal dose of morphine (0.1 pg i.t.1 potentiates the actions of i.c.v, morphine, confirming the interactions of spinal and supraspinal morphine (Yeung and Rudy, 1981~. In contrast to its effects upon supraspinat morphine alone, the addition of supraspina~ TRIMU-5 (0.5 pg i&v.) in the synergy mode1 enhances morphine analgesia, shifting the dose-response curve for supraspinal morphine analgesia almost 4-fold further to the left (fig. IB). Finally, supraspinal TRIMU-5 without any i.c.v. morphine also potentiates intrathecal morphine (fig. 10. TRIMUJ has very different actions upon supraspinal morphine depending upon whether the morphine is given i.c.v. alone or in the synergy model. Against supraspinal morphine alone, TRiMW-S at a
0.1
Morphtne
dose tll-fold
lower
Morphine
(pg, i.c.v.)
than its own ED5,, value (Tive ct al..
in press) antagonizes morphine analpcsia. a I* ,-opioid action. while in the synergy model TRiMU-S enhances rn~~rp~i~~ analgesia. These diffcrcnccs arc most easily
utility
(pg, i.c.v.)
in cxaming the role of ,u rcccptor suhtypcs in
opioid actions.
~~~la~~~d hy its g,-opioid agonist/p ,-opioid antagcjnist ~~c~~~r~tcs. The ability of su~rasp~nal T~I~iU-S also to ~~~t~~t~at~ the actions of spinaf mrtrphinc directly further impiicatcs supraspinal p+pioid rcccptars in the synergy model. These results are consistent with other studies utilizing the JL ,-opioid rcceptor-dcficicnt CXBK strain and the w antagonists p-
This work was supported. Inslitutc
in p;lrt. by ;I grant from the National
on Drug A.huse tl>AO732t
a Re>c;lrch
Scientist
Development
to GWP. Award
CiWP is a recipient
from the Natinnal
elf
Insli-
tutr on Drug Ahusc (lIAtltI13X).
~unalt~~xarn~~c and naloxonazine. In conclusion, our results c~~rrciatc brainstem g, and pZ receptors in
References
s~~~aspi~a? analgesia and spinal/ supraspinal synergy, respectively. I(n additive, they illustrate the unique ~~arrnac~i~~~ica~ characteristics of TRIMU-S and its
Gael.
G., J.M. Z:tjac. I’. l~~l~iy-~(iy~t,
1%-S. In~~sii~~ItiIln of the slrucrurai and 6 opioid rcccptor discrimination peptides. J. Med. Chem.
31, 374.
V. Diiuge and 1f.P. Rttyues, paritmt!Wrs
invcllvod in the g
of linear cnkcphalin-related
Paul. D.. R.J. Bodnar, MA. Gistrak and G.W. P~sternitk. IYXY, Different mu rwcptor subtypes modiatc spinal and supraspinal ;malgcsia in mice. Eur. J. Pharmacol. 168. 307. Pick, C.G., R. Nejat and G.W. Pasternak. Independent genetic control of IWO ph~~rrn;~c~~i~~~i~ily distinct supraspinal mu analgesic systems, J. Ph:trmacol. Exp. Thu. iin prcssf. Tive. LA., C.G. Pick, D. Paul. B.P. Roques. GA. Gad and C.W. P:etcrnak. Analgesic potency of TRIMU-S: a mixed pz opioid
receptor agonist,/.g, opioid receptor anlqonist. Eur. J. phtirmacol. (in press). Y~uII~, J-c‘. and T.A. Rudy, IYtiO. Multiplicatitc itwraction hctween narcotic agonisms exprcssrd al spinal and supraspinal sites nf antinociccplivc :Iction us rcveaied by concurrent intrathecal and inlr;iccrchroventricul;tr injectionc 01 morphine. J. Pharmacol. Exp. Ther. 215. h33.
