GSK189254 is a highly potent histamine 3 (H3) receptor antagonist which has demonstrated efficacy in the reduction of mechanical hyperalgesia and allodynia in the chronic constriction injury pre-clinical model of neuropathic pain (NP). The mechanism of action of GSK 189254 in the pain model is hypothesised to be via enhanced release of monoamines in the central nervous system (CNS). A similar mechanism of action has also been shown for duloxetine. In this phase I study, the safety and efficacy of GSK189254 will be investigated in the electrical hyperalgesia (EH) model in healthy volunteers to build confidence that the preclinical efficacy demonstrated by this compound will translate into patients.