Characterization of metabotropic glutamate receptors negatively linked to adenylyl cyclase in brain slices

• Published in: Brain research Vol. 622; no. 1; pp. 132 - 138
• Main Authors: Genazzani, A.A., Casabona, G., L'Episcopo, M.R., Condorelli, D.F., Dell'Albani, P., Shinozaki, H., Nicoletti, F.
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 17.09.1993; Amsterdam Elsevier; New York, NY
• Subjects: Adenylyl Cyclases - metabolism; Animals; Biological and medical sciences; Brain - drug effects; Brain - enzymology; Brain - metabolism; Brain slice; cAMP; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Colforsin - pharmacology; Cyclic AMP - biosynthesis; Forskolin; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Male; Membranes - metabolism; Metabotropic glutamate receptor; mGluR2 mRNA; Nucleic Acid Hybridization; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate - drug effects; Receptors, Metabotropic Glutamate - genetics; Receptors, Metabotropic Glutamate - metabolism; RNA, Messenger - analysis; Vertebrates: nervous system and sense organs; mGluR2 mRNA; Brain slice; cAMP; Metabotropic glutamate receptor; Forskolin; Northern blotting; Adenylate cyclase; Vertebrata; Mammalia; Rat; Metabotropic receptor; Enzyme; Rodentia; Central nervous system; Cyclic AMP; Glutamate receptor; Brain (vertebrata)
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/0006-8993(93)90811-Z

We have characterized the pharmacological profile of activation of metabotropic glutamate receptors negatively linked to adenylyl cyclase ( mGluR ↓cAMP ) in brain slices. Among the putative mGluR agonists, (2 S,1′ R,2′ R,3′ R)-2-(2,3-dicar☐ycyclopropyl)glycine (DCG-IV) and (1 S,3 R)-1-aminocyclopentane-1,3-dicar☐ylic 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 β-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 ↓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 ↓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 ↓cAMPs , as estimated by using 1 S,3 R-ACPD as an agonist, did not correlated with the steady-state levels of mGluR2 mRNA. Thus, 1 S,3 R-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. 1 S,3 R-ACPD also inhibited forskolin-stimulated cAMP formation in cortical membranes, excluding the involvement of trans-synaptic mechanisms in the activity of mGluR ↓cAMPs . Finally, 1 S,3 R-ACPD not only failed to reduce, but rather enhanced, norepinephrine or N-ethylcar☐amidoadenosine (NECA)-stimulated cAMP formation in hippocampal slices, indicating the existence of multiple levels of interaction between mGluRs and adenylyl cyclase activity.