Fan Jing, Wu Xiaoyin, Cao Zhijun, Chen Shengliang, Owyang Chung, Li Ying
Gastroenterology Research Unit, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan.
Gastroenterology Research Unit, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan.
Gastroenterology. 2009 May;136(5):1732-1740.e3. doi: 10.1053/j.gastro.2009.01.069. Epub 2009 Feb 6.
BACKGROUND & AIMS: Electrophysiologic and behavioral studies have shown that increased N-methyl-D-aspartate (NMDA)-receptor activation of anterior cingulate cortex (ACC) neurons has a critical role in modulating visceral pain responses in viscerally hypersensitive (VH) rats. This study aimed to identify the NMDA receptor subtypes in perigenual ACC (pACC) neurons involved in the facilitation of visceral nociception.
We performed in vivo electrophysiologic recordings of pACC neurons and examined the visceromotor response (VMR) to colorectal distention (CRD) in normal and VH rats induced by colonic anaphylaxis. The NR2A-subtype-receptor antagonist [(R)-[(S)-1-(4-bromo-phenyl)-ethylamino]-(2,3-dioxo-1,2,3,4-tetrahydroquinoxalin-5-yl)-methyl]-phosphonic acid (NVP-AAM077) and the NR2B-receptor-antagonist Ro25-6981 were microinjected into the pACC. To down-regulate NR2B-receptor gene expression, an NR2B-specific small interfering RNA (siRNA) and a plasmid (pEGFP-N1) that expressed the green fluorescent protein were administered into ACC neurons by electroporation.
Reverse microdialysis of NVP-AAM077 had no effect on basal and CRD-induced ACC neuronal firing in VH and control groups. In VH rats, Ro25-6981 (500 micromol/L) inhibited ACC neuronal firing, evoked by 30 and 50 mm Hg CRD, by 98% and 52%, respectively. NVP-AAM077 did not affect the VMR in either group. Ro25-6981 significantly suppressed the VMR in VH but not normal rats. Immunoblot analysis showed increased NR2B-receptor expression in the pACC of VH rats. NR2B siRNA-treated VH rats showed a significant reduction in the VMR, compared with controls.
The NR2B subunit of the NMDA receptor has a critical role in the modulation of ACC sensitization and visceral pain responses in VH rats.
电生理和行为学研究表明，前扣带回皮质（ACC）神经元的N-甲基-D-天冬氨酸（NMDA）受体激活增加在调节内脏高敏感（VH）大鼠的内脏痛反应中起关键作用。本研究旨在确定参与促进内脏伤害感受的膝周ACC（pACC）神经元中的NMDA受体亚型。
我们对pACC神经元进行了体内电生理记录，并检测了正常大鼠和由结肠过敏反应诱导的VH大鼠对结肠扩张（CRD）的内脏运动反应（VMR）。将NR2A亚型受体拮抗剂[(R)-[(S)-1-(4-溴苯基)-乙氨基]-(2,3-二氧代-1,2,3,4-四氢喹喔啉-5-基)-甲基]-膦酸（NVP-AAM077）和NR2B受体拮抗剂Ro25-6981微量注射到pACC中。为了下调NR2B受体基因表达，通过电穿孔将NR2B特异性小干扰RNA（siRNA）和表达绿色荧光蛋白的质粒（pEGFP-N1）导入ACC神经元。
NVP-AAM077的反向微透析对VH组和对照组的基础及CRD诱导的ACC神经元放电均无影响。在VH大鼠中，Ro25-6981（500 μmol/L）分别抑制了由30和50 mmHg CRD诱发的ACC神经元放电的98%和52%。NVP-AAM077对两组的VMR均无影响。Ro25-6981显著抑制了VH大鼠而非正常大鼠的VMR。免疫印迹分析显示VH大鼠pACC中NR2B受体表达增加。与对照组相比，经NR2B siRNA处理的VH大鼠的VMR显著降低。
NMDA受体的NR2B亚基在调节VH大鼠的ACC敏化和内脏痛反应中起关键作用。
