Capsaicin, the primary constituent of pepper sprays and its pharmacological effects on mammalian ocular tissues
Capsaicin is the principal constituent of oleoresin capsicum, or pepper spray, as it is commonly known. Pepper sprays are frequently used in riot control situations by defence organizations all over the world to deal with uncontrolled civil or criminal disturbances. Although capsaicin is noted for its irritant and inflammatory properties, the ocular profile of capsaicin has not been specifically studied and interpreted. The present review analyses the mammalian opthalmological profile of capsaicin and its pharmacological and toxicological manifestations including capsaicin induced corneal changes, neurogenic inflammation, neuroprotective influences on retinal ganglion cells (RGCs), depletion of neuropeptide content in sensory nerve terminals etc. Substantial views on the capsaicin receptor Transient Receptor Potential Vanilloid V1 (TRPV1), its presence, significance and capsaicin induced mediations have been presented. Studies conducted previously on the reversal of capsaicin evoked ocular responses have been briefly demonstrated. In this regard, TRPV1 antagonists (especially the competitive antagonist Capsazepine) have been indicated as potential candidates in mitigating or alleviating capsaicin elicited ocular responses. The review overall is a comprehensive perspective of the ocular inflammatory and pharmacological responses generated on exposure to capsaicin and concludes suggesting a possible regulatory framework for relief from the same presumably by the employment of specialized and target specific TRPV1 antagonists.