The Effects of Glutamate NMDA Receptor Antagonist MK-801 on Gastrointestinal Motility after Middle Cerebral Artery Occlusion in Rats

This study was performed to investigate the role of glutamate neurotransmitter system on gastrointestinal motility in a middle cerebral artery occlusion (MCAO) model of rats. The right middle cerebral artery was occluded by surgical operation, and intestinal transit and geometric center as a parameter of gastrointestinal motility and expression of c-Fos protein in the insular cortex and cingulate cortex were measured at 2 and 12 h after MCAO. Intestinal transit was $66.3{\pm}7.5%$ and $62.3{\pm}5.7%$ 2 and 12 h after sham operation, respectively, and MCAO significantly decreased intestinal transit to $39.0{\pm}3.5%$ and $47.0{\pm}5.1%$ at 2 and 12 h after the occlusion, respectively (p<0.01). The geometric center was $5.6{\pm}0.4$ and $5.2{\pm}0.9$ at 2 and 12 h after sham operation, respectively, and MCAO significantly decreased geometric center to $2.9{\pm}0.8$ and $3.0{\pm}0.3$ at 2 and 12 h after the occlusion, respectively (p<0.01). In control animals, injection of atropine decreased intestinal transit to $35.9{\pm}5.2%$, and injection of glutamate NMDA receptor antagonist, MK-801, decreased intestinal transit to $28.8{\pm}9.5%$. Pretreatment with MK-801, a glutamate NMDA receptor antagonist, in the MCAO group decreased intestinal transit to $11.8{\pm}3.2%$, which was significantly decreased compared to MCAO group (p<0.01). MCAO markedly increased the expression of c-Fos protein in the insular cortex and cingulate cortex ipsilateral to the occlusion 2 h after MCAO, and pretreatment with MK-801 produced marked reduction of c-Fos protein expression compared to MCAO group (p<0.01). These results suggest that modulation of gastrointestinal motility after MCAO might be partially mediated through a glutamate NMDA receptor system.