Transient receptor potential channels - emerging novel drug targets for the treatment of pain.

In mammals several members of the Transient Receptor Potential channel family (TRPs), expressed mainly in the sensory neurons and skin keratinocytes, are implicated in relevant physiological functions, including thermosensation,nociception and vision. Since the TRPV1-4, TRPA1 and TRPM8 channels from this family play a pivotal role in both the detection and possibly modulation of painful stimuli, they are regarded as a very promising target of novel analgesic drugs. A few agents acting at TRPs, such as capsaicin or menthol, have a long history of their application as analgesics,whereas others (e.g. SB705498, JTS653, JNJ17203212, AP18, A967079, Chembridge-5861528 or PBMC) are currently being evaluated both in animals and in humans. In this review we discuss pain physiology, as well as the pharmacological properties of the TRPs involved in pain detection as potential critical peripheral analgesic targets. We present one of the most relevant strategies in the search for novel analgesic drugs, namely the TRP channels and their ligands, both agonists and antagonists as potential novel therapeutics for inflammatory and neuropathic pain syndromes. The safety profile of these agents, in particular their impact on thermosensation, is also discussed below.