Species-specific in vitro pharmacological effects of the cannabinoid receptor 2 (CB2) selective ligand AM1241 and its resolved enantiomers.
OBJECTIVE
Racemic (R,S) AM1241 is a cannabinoid receptor 2 (CB(2))-selective aminoalkylindole with antinociceptive efficacy in animal pain models. The purpose of our studies was to provide a characterization of R,S-AM1241 and its resolved enantiomers in vitro and in vivo.


METHODS
Competition binding assays were performed using membranes from cell lines expressing recombinant human, rat, and mouse CB(2) receptors. Inhibition of cAMP was assayed using intact CB(2)-expressing cells. A mouse model of visceral pain (para-phenylquinone, PPQ) and a rat model of acute inflammatory pain (carrageenan) were employed to characterize the compounds in vivo.


RESULTS
In cAMP inhibition assays, R,S-AM1241 was found to be an agonist at human CB(2), but an inverse agonist at rat and mouse CB(2) receptors. R-AM1241 bound with more than 40-fold higher affinity than S-AM1241, to all three CB(2) receptors and displayed a functional profile similar to that of the racemate. In contrast, S-AM1241 was an agonist at all three CB(2) receptors. In pain models, S-AM1241 was more efficacious than either R-AM1241 or the racemate. Antagonist blockade demonstrated that the in vivo effects of S-AM1241 were mediated by CB(2) receptors.


CONCLUSIONS
These findings constitute the first in vitro functional assessment of R,S-AM1241 at rodent CB(2) receptors and the first characterization of the AM1241 enantiomers in recombinant cell systems and in vivo. The greater antinociceptive efficacy of S-AM1241, the functional CB(2) agonist enantiomer of AM1241, is consistent with previous observations that CB(2) agonists are effective in relief of pain.
Bingham
B
B
Neuroscience Discovery Research, Wyeth Research, Princeton, NJ 08543, USA. binghab@wyeth.com
Jones
P G
PG
Uveges
A J
AJ
Kotnis
S
S
Lu
P
P
Smith
V A
VA
Sun
S-C
SC
Resnick
L
L
Chlenov
M
M
He
Y
Y
Strassle
B W
BW
Cummons
T A
TA
Piesla
M J
MJ
Harrison
J E
JE
Whiteside
G T
GT
Kennedy
J D
JD
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology; D016466:CHO Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology; D001892:Camphanes / Q000494:pharmacology; D002186:Cannabinoids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002351:Carrageenan / Q000633:toxicity; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism; D003511:Cyclohexanols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology / Q000517:prevention & control; D007211:Indoles / Q000494:pharmacology; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013237:Stereoisomerism; D014316:Tritium
C439263:AM 1241; D000700:Analgesics; D048588:Benzoxazines; D002121:Calcium Channel Blockers; D001892:Camphanes; D002186:Cannabinoids; D003511:Cyclohexanols; D007211:Indoles; D009025:Morpholines; D009281:Naphthalenes; D011720:Pyrazoles; D043885:Receptor, Cannabinoid, CB2; C110630:SR 144528; D014316:Tritium; D005576:Colforsin; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D002351:Carrageenan; D000242:Cyclic AMP; C094023:iodopravadoline