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NEUROPHARMACOLOGY
Neuroscienze S.c.a r.l., Cagliari, Italy (S.R., G.M., S.T., P.C.); Department of Pharmacology, Chemistry, and Toxicology, University of Sassari, Sassari, Italy (G.A.P., J.-M.M.); "B.B. Brodie" Department of Neuroscience, University of Cagliari, Cagliari, Italy (P.S.); Section of Human Physiology and Nutrition, Department of Applied Sciences to Biosystems, University of Cagliari, Cagliari, Italy (R.V.); and C.N.R. Institute of Neurogenetics and Neuropharmacology and Neuroscienze S.c.a r.l, Selargius, Italy (L.P.)
The compound
N-piperidinyl-[8-chloro-1-(2,4-dichlorophenyl)-1,4,5,6-tetrahydrobenzo
[6,7]cyclohepta[1,2-c]pyrazole-3-carboxamide] (NESS 0327) was
synthesized and evaluated for binding affinity toward cannabinoid
CB1 and CB2 receptor. NESS 0327 exhibited a stronger
selectivity for CB1 receptor compared with
N-piperidinyl-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide
(SR 141716A), showing a much higher affinity for CB1 receptor
(Ki = 350 ± 5 fM and 1.8 ± 0.075 nM,
respectively) and a higher affinity for the CB2 receptor
(Ki = 21 ± 0.5 nM and 514 ± 30 nM,
respectively). Affinity ratios demonstrated that NESS 0327 was more than
60,000-fold selective for the CB1 receptor, whereas SR 141716A only
285-fold. NESS 0327 alone did not produce concentration-dependent stimulation
of guanosine 5'-O-(3-[35S]thio)-triphosphate
([35S]GTP
S) binding in rat cerebella membranes. Conversely,
NESS 0327 antagonized
[R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrolol
[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl)methanone mesylate] (WIN
55,212-2)-stimulated [35S]GTP
S binding. In functional assay,
NESS 0327 antagonized the inhibitory effects of WIN 55,212-2 on electrically
evoked contractions in mouse isolated vas deferens preparations with
pA2 value of 12.46 ± 0.23. In vivo studies
indicated that NESS 0327 antagonized the antinociceptive effect produced by
WIN 55,212-2 (2 mg/kg s.c.) in both tail-flick (ID50 = 0.042
± 0.01 mg/kg i.p.) and hot-plate test (ID50 = 0.018 ±
0.006 mg/kg i.p.). These results indicated that NESS 0327 is a novel
cannabinoid antagonist with high selectivity for the cannabinoid
CB1 receptor.
Address correspondence to: Dr. Luca Pani, Institute of Neurogenetic and Neuropharmacology, Via Boccaccio 8, 09047 Selargius, Italy. E-mail: l.pani{at}inn.cnr.it
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