QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: jpet.107.124701v1 323/1/147    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Suzuki, G. Articles by Ohta, H. Search for Related Content PubMed PubMed Citation Articles by Suzuki, G. Articles by Ohta, H. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB CALCIUM COMPOUNDS CALCIUM, ELEMENTAL

NEUROPHARMACOLOGY

In Vitro Pharmacological Characterization of Novel Isoxazolopyridone Derivatives as Allosteric Metabotropic Glutamate Receptor 7 Antagonists

Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., Tsukuba, Japan

Novel isoxazolopyridone derivatives that are metabotropic glutamate receptor (mGluR) 7 antagonists were discovered and pharmacologically characterized. 5-Methyl-3,6-diphenylisoxazolo[4,5-c]pyridin-4(5H)-one (MDIP) was identified by random screening, and 6-(4-methoxyphenyl)-5-methyl-3-pyridin-4-ylisoxazolo[4,5-c]pyridin-4(5H)-one (MMPIP) was produced by chemical modification of MDIP. MDIP and MMPIP inhibited L-(+)-2-amino-4-phosphonobutyric acid (L-AP4)-induced intracellular Ca²⁺ mobilization in Chinese hamster ovary (CHO) cells coexpressing rat mGluR7 with G₁₅ (IC₅₀ = 20 and 26 nM). The maximal response in agonist concentration-response curves was reduced in the presence of MMPIP, and its antagonism is reversible. MMPIP did not displace [³H](2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495) bound to mGluR7. These results suggested that these isoxazolopyridone derivatives are allosteric antagonists. In CHO cells expressing rat mGluR7, MDIP and MMPIP inhibited L-AP4-induced inhibition of forskolin-stimulated cAMP accumulation (IC₅₀ = 99 and 220 nM). In CHO cells coexpressing human mGluR7 with G₁₅, MDIP and MMPIP also inhibited the L-AP4-induced cAMP response. The maximal degree of inhibition by MMPIP was higher than that by MDIP in a cAMP assay. MMPIP was able to antagonize an allosteric agonist, the N,N'-dibenzhydryl-ethane-1,2-diamine dihydrochloride (AMN082)-induced inhibition of cAMP accumulation. In the absence of these agonists, MMPIP caused a further increase in forskolin-stimulated cAMP levels in CHO cells expressing mGluR7, whereas a competitive antagonist, LY341495, did not. This result indicates that MMPIP has an inverse agonistic activity. The intrinsic activity of MMPIP was pertussis toxin-sensitive and mGluR7-dependent. MMPIP at concentrations of at least 1 µM had no significant effect on mGluR1, mGluR2, mGluR3, mGluR4, mGluR5, and mGluR8. MMPIP is the first allosteric mGluR7-selective antagonist that could potentially be useful as a pharmacological tool for elucidating the roles of mGluR7 on central nervous system functions.

Address correspondence to: Gentaroh Suzuki, Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., 3 Okubo, Tsukuba, Ibaraki 300-2611, Japan. E-mail: gentaroh_suzuki{at}merck.com