Suppression of food intake and food-reinforced behavior produced by the novel CB1 receptor antagonist/inverse agonist AM 1387

The Novel Cannabinoid CB1 Receptor Neutral Antagonist AM4113 Suppresses Food Intake and Food-Reinforced Behavior but Does not Induce Signs of Nausea in Rats

“…AM4113, AM251, and SR141716A were tested for binding to the CB1 receptor using a rat brain membrane preparation, and for CB2 receptor binding using HEK293 cell membranes expressing hCB2 membranes, as previously described using [ 3 H]CP-55,940 (Morse et al, 1995;Lan et al, 1999;Makriyannis et al, 2005;McLaughlin et al, 2006). The concentrated stocks (10 mM) were diluted into TME buffer (50 mM Tris-HCl, 3 mM MgCl 2 , 100 mM NaCl, 0.2 mM EDTA, pH 7.4) with 0.1% BSA, and transferred to 96-well plates containing [ 3 H]CP-55,940 (specific activity 128 Ci/mmol; NIDA) at a final concentration of 0.76 nM.…”

“…Intracellular cyclic AMP levels were measured with a competitive protein-binding assay using intact HEK293 cells expressing hCB1 or hCB2 as previously described (McLaughlin et al, 2006). These cells were resuspended in 20 mM HEPES buffer, pH 7.3, containing 0.1 mM RO-20-1724 (4-[(3-butoxy-4-methoxyphenyl)-methyl]-2-imidazolidinone) and 1 mM IBMX (isobutylmethylxanthine) in DME media with 0.1% BSA to a final concentration of 1 Â 10 6 cells/ml.…”

“…Although it is clear that drugs that interfere with CB1 transmission can suppress food intake, the mechanisms by which they accomplish this are less well understood. Biochemical studies indicate that many of these drugs, including SR141716, AM251, and AM1387, act as inverse agonists and exert actions on signal transduction mechanisms when administered in the absence of CB1 receptor stimulation (ie they inhibit GTPgS and increase cAMP production; Landsman et al, 1997;Mato et al, 2002;McLaughlin et al, 2006). In one recent study, CB1-knockout and wild-type mice responded comparably on a progressive ratio schedule reinforced with corn oil, while wild-type mice treated with SR141716 decreased responding, suggesting that SR141716 may exert inverse agonist effects in addition to simply blocking CB1 receptors (Ward and Dykstra, 2005).…”

“…Experiment 2 characterized the CB1 antagonist activity of AM4113 by assessing the ability of this drug to reverse the behavioral effects of the CB1 agonist AM411 (McLaughlin et al, 2005a) using tests that are associated with cannabinoid receptor activation (eg Martin et al, 1991). Experiments 3-5 assessed the behavioral effects of AM4113, employing the same food-related tasks previously used to characterize the actions of AM251, AM1387, and SR141716 (McLaughlin et al, 2003(McLaughlin et al, , 2005b(McLaughlin et al, , 2006. Experiment 3 examined the effects of AM4113 on food-reinforced lever pressing using two different fixed-ratio (FR) schedules.…”

“…Experiment 3 examined the effects of AM4113 on food-reinforced lever pressing using two different fixed-ratio (FR) schedules. Experiment 4 studied the effects of AM4113 on the consumption of diets with different macronutrient compositions (eg high fat, high carbohydrate, and lab chow; McLaughlin et al, 2003McLaughlin et al, , 2005bMcLaughlin et al, , 2006. Finally, experiment 5 employed the taste reactivity test developed by Grill and Norgren (1978) to determine if AM4113 can produce conditioned gaping in a manner similar to that previously shown to occur after administration of AM251 (McLaughlin et al, 2005b).…”