(A) In the absence of mGlu3 activation, mGlu5 interacts with Homer
protein to engage the PI3K/Akt/GSK3β pathway, resulting in the
internalization of AMPA receptors and generation of LTD. (B) In the PCP model of
schizophrenia, NMDA receptor hypofunction has been linked to increased
inhibitory tone onto the hippocampal pyramidal cells, resulting in impaired LTP
(10). (C) Activation of mGlu3
switches mGlu5-mediated plasticity towards the generation of LTP by promoting
endocannabinoid-mediated inhibition of GABAergic interneurons (disinhibition) to
drive hippocampal pyramidal cells, resulting in increased NMDA receptor
function. mGlu3 and mGlu5, metabotropic glutamate receptor subtypes 3 and 5;
PI3K, phosphoinositide 3-kinase; Akt, known as protein kinase B (PKB);
GSK3β, glycogen synthase kinase 3β; AMPA,
α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor; LTD,
long-term depression; NMDA, N-methyl-D-aspartate receptor; LTP, long-term
potentiation; 2-AG, 2-arachidonoylglycerol; CB1, cannabinoid receptor type 1.
Grey indicates hypofunction.