In vivo model of pruritus

AG1529 (0.1 and 1% w/v) dissolved in acetone was applied topically (100 µL) with a syringe 30 min before histamine injection in a 1 cm² area in the back of the neck. Control animals were treated with 100 µL acetone. AG1529 ointment formulation (0.1 and 1% w/w) or placebo cream (8% glyceryl behenate, 8% glyceryl stearate, 4% hydrogenated castor oil 5% diethylene glycol monoethyl ether, 0.1% alpha-tocopherol, 75% caprylic/capric triglyceride) was applied topically twice/day for 3 days with a spatula in a 1 cm² shaved area in the back of the neck. Control animals were treated with placebo cream. Histamine solution (1 mg/ml in saline) was injected subcutaneously in a volume of 100 µL into the shaved area, 30 min after application of AG1529 dissolved in acetone or on day 4 after first AG1529 cream administration. Scratching behavior was observed during 60 min after histamine injection. The number of scratching bouts (counts of scratching/60 min), defined as the action of scratching the affected area, was measured from the start of the first scratching movement.