This study will be conducted as a double-blind, double-dummy, placebo-controlled, incomplete block, two period crossover study. Up to 40 healthy male or female volunteers, aged 18-45 years old, will be randomised into the study in order to achieve 32 evaluable subjects. Subjects will undergo two 3-week treatment periods and will be randomised to receive placebo and either GSK189254 (up to 100µg once daily) or duloxetine (up to 60mg daily). There will be a one week washout between treatment periods. The effects of repeated oral dosing of GSK189254 and duloxetine on secondary hyperalgesia in the EH model will be determined. Subject: GSK189254, Neuropathic pain (NP), H3 antagonist, duloxetine, Electrical hyperalgesia, Phase I, Healthy volunteers, Double blind, Safety, tolerability.