Substituent effects of N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamides on positive allosteric modulation of the metabotropic glutamate-5 receptor in rat cortical astrocytes.
CDPPB [3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide] was recently described as the first centrally active, positive allosteric modulator of rat and human metabotropic glutamate receptor (mGluR) mGluR5 subtype. We explored the structural requirements for potentiation of glutamate-induced calcium release in naturally expressed mGluR5 in cultured rat astrocytes and increasing affinity for the allosteric antagonist binding site by evaluating 50 analogues of CDPPB. In the fluorometric calcium assay, CDPPB exhibited an EC50 value of 77 +/- 15 nM in potentiating mGluR5-mediated responses in cortical astrocytes and a Ki value of 3760 +/- 430 nM in displacing [3H]methoxyPEPy binding in membranes of cultured HEK-293 cells expressing rat mGluR5. The structure-activity relationships showed that electronegative aromatic substituents in the para-position of the benzamide moiety of CDPPB increase potency. Both binding and functional activities were further increased with a halogen atom in the ortho-position of the 1-phenyl ring. These effects of substitution do not match those of either aromatic ring of MPEP [2-methyl-6-(phenylethynyl)pyridine] for the antagonist allosteric binding site. Combination of the optimal substituents and aromatic positions resulted in 4-nitro-N-(1-(2-fluorophenyl)-3-phenyl-1H-pyrazol-5-yl)benzamide (VU-1545) showing Ki = 156 +/- 29 nM and EC50 = 9.6 +/- 1.9 nM in the binding and functional assays, respectively.
de Paulis
Tomas
T
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA. tomas.depaulis@vanderbilt.edu
Hemstapat
Kamondanai
K
Chen
Yelin
Y
Zhang
Yongqin
Y
Saleh
Samir
S
Alagille
David
D
Baldwin
Ronald M
RM
Tamagnan
Gilles D
GD
Conn
P Jeffrey
PJ
D000494:Allosteric Regulation; D000495:Allosteric Site; D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001549:Benzamides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D006801:Humans; D010069:Oxadiazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D021281:Quantitative Structure-Activity Relationship; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects*
C511636:4-nitro-N-(1-(2-fluorophenyl)-3-phenyl-1H-pyrazol-5-yl)benzamide; D001549:Benzamides; C578935:GRM5 protein, human; C578937:Grm5 protein, rat; D010069:Oxadiazoles; D010880:Piperidines; D011720:Pyrazoles; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C533862:S-(4-fluorophenyl)-(3-(3-(4-fluorophenyl)-(1,2,4)-oxadiazol-5-yl)piperidin-1-yl)methanone; D002118:Calcium