The effects of (RS)-alpha-cyclopropyl-4-phosphonophenylglycine ((RS)-CPPG), a potent and selective metabotropic glutamate receptor antagonist.
1. In this study we describe the potent antagonist activity of a novel metabotropic glutamate (mGlu) receptor antagonist (RS)-alpha-cyclopropyl-4-phosphonophenylglycine ((RS)-CPPG) which exhibits selectivity for mGlu receptors (group II and III) negatively coupled to adenylyl cyclase in the adult rat cortex. 2. Both the L-2-amino-4-phosphonobutyrate (L-AP4) and (2S, 1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-1) inhibition of forskolin-stimulated cyclic AMP accumulation were potently reversed by (RS)-CPPG (IC50 values: 2.2 +/- 0.6 nM and 46.2 +/- 18.2 nM, respectively). 3. In contrast, (RS)-CPPG acted as a weak antagonist against group I mGlu receptors. In neonatal rat cortical slices, (RS)-CPPG antagonized (KB = 0.65 +/- 0.07 mM) (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD)-stimulated phosphoinositide hydrolysis. (RS)-CPPG (100 microM) failed to influence L-quisqualate-stimulated phosphoinositide hydrolysis in cultured cerebellar granule cells. 4. In the rat cerebral cortex, (RS)-CPPG is the most potent antagonist of group II/III mGlu receptors yet described (with 20 fold selectivity for group III mGlu receptors), having negligible activity at group I mGlu receptors.
Toms
N J
NJ
Department of Pharmacology, School of Medical Sciences, University of Bristol.
Jane
D E
DE
Kemp
M C
MC
Bedingfield
J S
JS
Roberts
P J
PJ
D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors*
D018691:Excitatory Amino Acid Antagonists; D018094:Receptors, Metabotropic Glutamate; C104331:cyclopropyl-4-phosphonophenylglycine; D005998:Glycine