ANTAGONISM OF THE PRESUMED PRESYNAPTIC ACTION OF L-AP4 ON GABAERGIC TRANSMISSION IN THE VENTROBASAL THALAMUS BY THE NOVEL MGLUR ANTAGONIST MPPG

The metabotropic glutamate receptor (mGluR) agonists CCG-I and r-AP4, acting at Group II and Group III mGluRs respectively, can reduce GABAe rgic synaptic inhibition on single neurones in the rat thalamus in viv o via a presumed presynaptic mechanism. The actions of L-AP4 were anta gonized by (+/-)-alpha-methyl-4-phosphonophenylglycine (MPPG), whereas CCG-I was significantly less affected. Thus MPPG may be a useful tool for detecting physiological roles for Group III mGluRs.