▁gl ut am ate ▁re ceptor ▁ 8 ▁is ▁a ▁protein ▁that ▁in ▁humans ▁is ▁encoded ▁by ▁the ▁GR M 8 ▁gene . ▁ ▁Function ▁▁ ▁L - gl ut am ate ▁is ▁the ▁major ▁exc itat ory ▁ne uro trans mit ter ▁in ▁the ▁central ▁nerv ous ▁system ▁and ▁activ ates ▁both ▁ion otrop ic ▁and ▁met ab otrop ic ▁gl ut am ate ▁re cept ors . ▁ ▁Gl ut am ater g ic ▁ne uro trans mission ▁is ▁involved ▁in ▁most ▁aspects ▁of ▁normal ▁brain ▁function ▁and ▁can ▁be ▁pert urbed ▁in ▁many ▁ne urop ath olog ic ▁conditions . ▁The ▁met ab otrop ic ▁gl ut am ate ▁re cept ors ▁are ▁a ▁family ▁of ▁G ▁protein - cou ple d ▁re cept ors , ▁that ▁have ▁been ▁divided ▁into ▁ 3 ▁groups ▁on ▁the ▁basis ▁of ▁sequence ▁hom ology , ▁put ative ▁signal ▁trans du ction ▁mechan isms , ▁and ▁ph arm ac olog ic ▁properties . ▁ ▁Group ▁I ▁includes ▁GR M 1 ▁and ▁GR M 5 ▁and ▁these ▁re cept ors ▁have ▁been ▁shown ▁to ▁activ ate ▁ph osph ol ip ase ▁C . ▁ ▁Group ▁II ▁includes ▁GR M 2 ▁and ▁GR M 3 ▁while ▁Group ▁III ▁includes ▁GR M 4 , ▁GR M 6 , ▁GR M 7 ▁and ▁GR M 8 . ▁ ▁Group ▁II ▁and ▁III ▁re cept ors ▁are ▁linked ▁to ▁the ▁in hib ition ▁of ▁the ▁cy clic ▁A MP ▁cas cade ▁but ▁differ ▁in ▁their ▁ag on ist ▁select