Genazzani, AA; Casabona, G; L'Episcopo, MR; Condorelli, DF; Dell'Albani, P; Shinozaki, H; Nicoletti, F; ,
We have characterized the pharmacological profile of activation of metabotropic glutamate receptors negatively linked to adenylyl cyclase (mGluR decreases cAMP) in brain slices. Among the putative mGluR agonists, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) and (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), were the most potent inhibitors of forskolin-stimulated cAMP formation in hippocampal slices, followed by ibotenate, L-2-amino-3-phosphonopropionate (AP3), quisqualate, L-glutamate and beta-N-methylamino-L-alanine (BMAA). Inhibition of forskolin-stimulated cAMP formation by DL-2-amino-4-phosphonobutanoate (AP4) was biphasic, suggesting that the drug interacts with more than one mGluR decreases cAMP subtype. Both L-AP4 and L-serine-O-phosphate (a restricted analogue of AP4) were much more effective in inhibiting forskolin-stimulated cAMP formation than their D-isomers, indicating that interaction of these drugs with the mGluR decreases cAMP is stereoselective. Despite the fact that DCG-IV and ibotenate behave as NMDA receptor agonists, their effect was insensitive to MK-801. The regional pattern of expression of mGluR decreases cAMPS, as estimated by using 1S,3R-ACPD as an agonist, did not correlate with the steady-state levels of mGluR2 mRNA. Thus, 1S,3R-ACPD inhibited forskolin-stimulated cAMP in slices from hippocampus, cerebral cortex, corpus striatum, olfactory tubercle or hypothalamus, but not in slices from olfactory bulb or cerebellum; in contrast, mGluR2 mRNA levels were high in the olfactory bulb and very low in the corpus striatum. 1S,3R-ACPD also inhibited forskolin-stimulated cAMP formation in cortical membranes, excluding the involvement of trans-synaptic mechanisms in the activity of mGluR decreases cAMPS.(ABSTRACT TRUNCATED AT 250 WORDS)
Brain slice; cAMP; Forskolin; Metabotropic glutamate receptor; mGluR2 mRNA; 1 amino 1,3 cyclopentanedicarboxylic acid; 2 (2,3 dicarboxycyclopropyl)glycine; 2 amino 3 methylaminopropionic acid; 2 amino 3 phosphonopropionic acid; 2 amino 4 phosphonobutyric acid; cyclic amp; excitatory amino acid receptor; forskolin; glutamic acid; glycine derivative; ibotenic acid; metabotropic receptor; phosphoserine; quisqualic acid; animal tissue; article; brain slice; controlled study; enantiomer; hippocampus; male; nonhuman; priority journal; rat; Adenylate Cyclase; Animal; Brain; Cyclic AMP; Forskolin; In Vitro; Male; Membranes; Nucleic Acid Hybridization; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; RNA, Messenger