“…The chemical activators group is divided in turn into two subgroups depending on the origin of the activator/modulator: exogenous and endogenous. Exogenous stimuli are capsaicin [ 38 ] and its antagonist capsazepine [ 39 ], resiniferatoxin (RTX) [ 37 , 40 ], bradykinin [ 41 ], yohimbine [ 42 ], ethanol [ 43 ], evodiamine [ 44 ], 17-β-estradiol [ 45 ], quinazoline [ 46 ], progesterone [ 47 ], numerous opioids [ 48 ], nicotine [ 49 ], hyaluronan [ 50 ], insulin [ 51 ], tinyatoxin [ 52 ], olvanil [ 53 ], acetylsalicylic acid [ 54 ], eugenol [ 55 ], sesquiterpenes [ 56 , 57 , 58 ], cannabidiol [ 59 ], prenylphenols [ 60 ], zingerone [ 61 ], shogaol [ 61 ], PPAHV [ 62 ], gingerol [ 63 ], numerous pharmacological antagonists [ 64 , 65 , 66 , 67 ], and peptide toxins from different species [ 4 , 68 ]. Endogenous activators comprise numerous compounds [ 1 ], such as the wide family derived from polyunsaturated fatty acids (PUFAs).…”