Role of TRPV1 receptors in descending modulation of pain.

Transient receptor potential vanilloid type 1 (TRPV1) receptor is a ligand-gated non-selective cation channel activated by heat (>43 degrees C), low pH and endogenous lipid molecules such as anandamide, N-arachidonoyl-dopamine, N-acyl-dopamines and products of lipoxygenases (12- and 15-(S)-HPETE) termed endovanilloids. Apart from peripheral primary afferent neurons and dorsal root ganglia, TRPV1 receptor is expressed throughout the brain. Recent evidence shows that TRPV1 receptor stimulation by endocannabinoids or by capsaicin within the periaqueductal grey (PAG) leads to analgesia and this effect is associated with glutamate increase and the activation of OFF cell population in the rostral ventromedial medulla (RVM). Activation of the antinociceptive descending pathway via TPRV1 receptor stimulation in the PAG may be a novel strategy for producing analgesia. This review will summarize the more recent insights into the role of TRPV1 receptor within the antinociceptive descending pathway and its possible exploitation as a target for novel pain-killer agents.