O'Brien Julie A, Lemaire Wei, Wittmann Marion, Jacobson Marlene A, Ha Sookhee N, Wisnoski David D, Lindsley Craig W, Schaffhauser Hervé J, Rowe Blake, Sur Cyrille, Duggan Mark E, Pettibone Douglas J, Conn P Jeffrey, Williams David L
Neuroscience-WP, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
J Pharmacol Exp Ther. 2004 May;309(2):568-77. doi: 10.1124/jpet.103.061747. Epub 2004 Jan 27.
We found that N-[4-chloro-2-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]phenyl]-2-hydroxybenzamide (CPPHA), is a potent and selective positive allosteric modulator of the metabotropic glutamate receptor subtype 5 (mGluR5). CPPHA alone had no agonist activity and acted as a selective positive allosteric modulator of human and rat mGluR5. CPPHA potentiated threshold responses to glutamate in fluorometric Ca(2+) assays 7- to 8-fold with EC(50) values in the 400 to 800 nM range, and at 10 microM shifted mGluR5 agonist concentration-response curves to glutamate, quisqualate, and (R,S)-3,5-dihydroxyphenylglycine (DHPG) 4- to 7-fold to the left. The only effect of CPPHA on other mGluRs was weak inhibition of mGluR4 and 8. Neither CPPHA nor the previously described 3,3'-difluorobenzaldazine (DFB) affected [(3)H]quisqualate binding to mGluR5, but although DFB partially competed for [(3)H]3-methoxy-5-(2-pyridinylethynyl)pyridine binding, CPPHA had no effect on the binding of this 2-methyl-6-(phenylethynyl)-pyridine analog to mGluR5. Although the binding sites for the two classes of allosteric modulators seem to be different, these different allosteric sites can modulate functionally and mechanistically similar allosteric effects. In electrophysiological studies of brain slice preparations, it had been previously shown that activation of mGluR5 receptors by agonists increased N-methyl-D-aspartate (NMDA) receptor currents in the CA1 region of hippocampal slices. We found that CPPHA (10 microM) potentiated NMDA receptor currents in hippocampal slices induced by threshold levels of DHPG, whereas having no effect on these currents by itself. Similarly, 10 microM CPPHA also potentiated mGluR5-mediated DHPG-induced depolarization of rat subthalamic nucleus neurons. These results demonstrate that allosteric potentiation of mGluR5 increases the effect of threshold agonist concentrations in native systems.
我们发现N-[4-氯-2-[(1,3-二氧代-1,3-二氢-2H-异吲哚-2-基)甲基]苯基]-2-羟基苯甲酰胺（CPPHA）是代谢型谷氨酸受体5（mGluR5）的一种强效且选择性的正变构调节剂。单独使用CPPHA没有激动剂活性，并且作为人和大鼠mGluR5的选择性正变构调节剂发挥作用。在荧光钙（Ca²⁺）检测中，CPPHA使对谷氨酸的阈值反应增强7至8倍，其半数有效浓度（EC₅₀）值在400至800 nM范围内，并且在10 μM时将mGluR5激动剂对谷氨酸、喹啉酸和（R,S）-3,5-二羟基苯甘氨酸（DHPG）的浓度-反应曲线向左移动4至7倍。CPPHA对其他mGluR的唯一作用是对mGluR4和8的微弱抑制。CPPHA和先前描述的3,3'-二氟苯醛嗪（DFB）均不影响[³H]喹啉酸与mGluR5的结合，但是尽管DFB部分竞争[³H]3-甲氧基-5-（2-吡啶乙炔基）吡啶的结合，CPPHA对这种2-甲基-6-（苯乙炔基）-吡啶类似物与mGluR5的结合没有影响。尽管这两类变构调节剂的结合位点似乎不同，但这些不同的变构位点可以调节功能和机制上相似的变构效应。在脑片制备的电生理研究中，先前已经表明激动剂激活mGluR5受体会增加海马切片CA1区的N-甲基-D-天冬氨酸（NMDA）受体电流。我们发现CPPHA（10 μM）增强了由阈值水平的DHPG诱导的海马切片中的NMDA受体电流，而其本身对这些电流没有影响。同样，10 μM CPPHA也增强了mGluR5介导的DHPG诱导的大鼠丘脑底核神经元的去极化。这些结果表明mGluR5的变构增强增加了天然系统中阈值激动剂浓度的作用。
