CB1 antagonist 4 is an antagonist of cannabinoid receptor type 1 (CB1), with potential for the treatment of obesity and type 2 diabetes.

CB1 antagonist 4, a novel, largely peripherally restricted CB1 antagonist, in terms of fear-promoting consequences of systemic vs. intracerebral injections.Different groups of male C57BL/6 N mice underwent auditory fear conditioning, followed by re-exposure to the tone.Mice were treated per os (p.o.) with CB1 antagonist 4 (10, 30, or 100 mg/kg), rimonabant (10 mg/kg;a brain penetrating CB1 antagonist/inverse agonist which served as a positive control), or vehicle, 2 h prior the tone presentation.Only the high dose of CB1 antagonist 4 (100 mg/kg) induced a significant increase in freezing behavior, similar to that induced by rimonabant (10 mg/kg) (p <0.001).?If injected into the brain both CB1 antagonist 4 (10 or 30 μg/mouse) and rimonabant (1 or 10 μg/mouse) caused a sustained fear response to the tone, which was more pronounced after rimonabant treatment.Taken together, CB1 antagonist 4 was at least one order of magnitude less effective in promoting fear responses than rimonabant.Given the equipotency of the two CB1 antagonists with regard to weight loss and metabolic syndrome-like symptoms in rodent obesity models, our results point to a critical dose range in which CB1 antagonist 4 might be beneficial for indications such as obesity and metabolic disorders with limited risk of fear-promoting effects[1].