PR 2 , ▁and ▁N MD A ▁re cept ors ▁have ▁been ▁proposed ▁to ▁be ▁the ▁re cept ors ▁through ▁which ▁SP M s ▁may ▁operate ▁to ▁down - reg ulate ▁TR P s ▁and ▁thereby ▁pain ▁per ception . ▁ ▁Lig and ▁examples ▁ ▁Ag on ists ▁▁ 4 - O x o - 2 - non en al ▁ ▁Al lic in ▁ ▁Al ly l ▁is oth i oc yan ate ▁ ▁C ann ab idi ol ▁ ▁G inger ol ▁ ▁I cil in ▁ ▁Pol yg od ial ▁ ▁He po x il ins ▁A 3 ▁and ▁B 3 ▁▁ 1 2 S - H ydro per ox y - 5 Z , 8 Z , 1 0 E , 1 4 Z - e icos at etra eno ic ▁acid ▁▁ 4 , 5 - E po xy e icos atri eno ic ▁acid ▁C BC ▁C inn am al de hy de ▁ ▁An tagon ists ▁ ▁H C 0 3 0 0 3 1 ▁ ▁G RC 1 7 5 3 6 ▁ ▁A - 9 6 7 0 7 9 ▁ ▁AL G X - 2 5 1 3 ▁ ▁AL G X - 2 5 4 1 ▁ ▁AL G X - 2 5 6 3 ▁ ▁AL G X - 2 5 6 1 ▁ ▁AL G X - 2 5 4 2 ▁ ▁References ▁ ▁External ▁links ▁▁▁▁ ▁Category : M emb rane ▁prote ins ▁Category : I on ▁channels <0x0A>