Primary Outcome Measures:
- The effects of JNJ-39439335 on the relief of paradoxical pain (the illusion of pain) [ Time Frame: at predose and at 4 hours postdose ]
Secondary Outcome Measures:
- The effects of JNJ-39439335 on the non-painful cold and warm sensations corresponding respectively to the cold and warm temperatures used to induce paradoxical pain [ Time Frame: at predose and at 4 hours postdose in each of the 2 treatment periods ]
- The effects of JNJ-39439335 on the normal cold- and heat-pain induced by supra-threshold cold and heat stimuli. [ Time Frame: at predose and at 4 hours postdose in each of the 2 treatment periods ]
This exploratory study will use a thermal-grill experimental model to assess the effects of JNJ-39439335 (50 mg, single oral dose) on the relief of pain. The study drug will be tested in healthy adult males to find out if a single 50 mg oral dose of JNJ-39439335 will be better than placebo (an inactive substance, like a sugar pill) in relieving pain. Study volunteers will experience the pain sensation (the illusion of pain) as a result of placing the palm of the hand on a small device that consists of harmless warm and cool flat metal bars known as a thermal grill. Volunteers will receive JNJ-39439335 or its matching placebo in the study unit on Day 1 of each of the 2 treatment periods. The treatment sequence for each volunteer will be assigned randomly (like flipping a coin). On the dosing day, the pain sensation will be induced and the following outcome measures will be assessed before dosing and at 4 hours after dosing: (1) volunteer's heat pain threshold [HPT] and cold pain threshold [CPT], i.e., the hot or the cold temperature at which it begins to elicit pain, (2) the intensity and the unpleasantness of the pain sensation resulting from simultaneous application of a warm temperature [4 C below HPT] and a cold temperature [4 C above CPT], (3) the intensity of non-painful warm and cold sensations following application of temperatures 4 C below HPT or 4 C above CPT, respectively, and (4) the intensity of pain following application of temperatures 2 C above HPT and 2 C below CPT. All of these assessments will be performed at a constant room temperature of approximately 21 C. During the trial volunteers will be closely monitored for safety, including the evaluation of adverse events, vital signs, 12-lead ECG, clinical laboratory testing (hematology and serum chemistry), and full neurological examination. Two blood samples for the measurement of JNJ-39439335 plasma concentrations will be collected immediately before and immediately after the thermal-grill assessments. At approximately 6 hours post-dose, volunteers will be discharged from the study unit. The study duration for each volunteer is approximately 9 weeks, including a screening phase that starts within 3 weeks before the first study drug administration, a washout of at least 3 weeks between the 2 treatment periods, and a final follow-up visit that will take place at approximately 3 weeks after the last study drug administration. Each volunteer will receive a single oral dose of JNJ-39439335 (50 mg) or placebo tablet on Day 1 of each of the 2 treatment periods. The study duration for each subject is ~9 weeks.