Characterization and distribution of binding sites for [3H]-SR 141716A, a selective brain (CB1) cannabinoid receptor antagonist, in rodent brain.
SR 141716A belongs to a new class of compounds (diarylpyrazole) that inhibits brain cannabinoid receptors (CB1) in vitro and in vivo. The present study showed that [3H]-SR 141716A binds with high affinity (Kd=0.61 +/- 0.06 nM) to a homogenous population of binding sites (Bmax=0.72 +/- 0.05 pmol/mg of protein) in rate whole brain (minus cerebellum) synaptosomes. This specific binding was displaced by known cannabinoid receptor ligands with the following rank order of potency SR 141716A > CP 55,940 > WIN 55212-2 = delta9-THC > anandamide. Apart from anandamide, all these compounds were found to interact competitively with the binding sites labeled by [3H]-SR 141716A. On the other hand, agents lacking affinity for cannabinoid receptors were unable to displace [3H]-SR 141716A from its binding sites (IC50 > 10 microM). In addition, the binding of [3H]-SR 141716A was insensitive to guanyl nucleotides. Regional rat brain distribution of CB1 cannabinoid receptors detected by [3H]-SR 141716A saturation binding and autoradiographic studies, showed that this distribution was very similar to that found for [3H]-CP 55,940. In vivo, the [3H]-SR 141716A binding was displaced by SR 141716A with ED50 values of 0.39 +/- 0.07 and 1.43 +/- 0.29 mg/kg following intraperitoneal and oral administration, respectively. Finally, the [3H]-SR 141716A binding sites remained significantly occupied for at least 12 hr following oral administration of 3 mg/kg SR 141716A. Taken together, these results suggest that SR 141716A in its tritiated form is a useful research tool for labeling brain cannabinoid receptors (CB1) in vitro and in vivo.
Rinaldi-Carmona
M
M
Sanofi Recherche, Montpellier, France.
Pialot
F
F
Congy
C
C
Redon
E
E
Barth
F
F
Bachy
A
A
Brelière
J C
JC
Soubrié
P
P
Le Fur
G
G
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D010880:Piperidines / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D011720:Pyrazoles / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors*; D000077285:Rimonabant; D012680:Sensitivity and Specificity; D013574:Synaptosomes / Q000378:metabolism; D014018:Tissue Distribution; D014316:Tritium
D010880:Piperidines; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D014316:Tritium; D000077285:Rimonabant