title: Characterization of metabotropic glutamate receptors negatively linked to adenylyl cyclase in brain slices.
abstract: 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)
authors.affiliation: Institute of Pharmacology, University of Catania School of Medicine, Italy.
authors.forename: A A
authors.initials: AA
authors.lastname: Genazzani
authors.forename: G
authors.initials: G
authors.lastname: Casabona
authors.forename: M R
authors.initials: MR
authors.lastname: L'Episcopo
authors.forename: D F
authors.initials: DF
authors.lastname: Condorelli
authors.forename: P
authors.initials: P
authors.lastname: Dell'Albani
authors.forename: H
authors.initials: H
authors.lastname: Shinozaki
authors.forename: F
authors.initials: F
authors.lastname: Nicoletti
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D018094:Receptors, Metabotropic Glutamate; D005576:Colforsin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases