Effects of metabotropic glutamate receptor stimulation on blood-brain barrier permeability during focal cerebral ischemia.

This investigation was performed to evaluate whether ACPD [(1S, 3R)-1-aminocyclopentane-1, 3-dicarboxylic acid], a metabotropic glutamate receptor agonist, would enhance the degree of increase in blood-brain barrier (BBB) permeability caused by focal cerebral ischemia. In this study, male Wistar rats were placed in control (n = 7) and ACPD (n = 7) groups under isoflurane anesthesia. Twenty minutes after middle cerebral artery (MCA) occlusion, patches of 10(-5) M ACPD or normal saline were placed on the ischemic cortex (IC) for a period of 40 min. Patches were changed every 10 min. One hour after MCA occlusion, BBB permeability was determined by measuring the transfer coefficient (Ki) of [alpha-14C] aminoisobutyric acid. There were no statistical differences in systemic blood pressures and heart rates between these groups. Blood gases were within normal limits. In the control group, the Ki of ischemic cortex (IC) was 2.1 times that of the contralateral cortex (CC) (3.7+/-0.9 vs. 1.8+/-0.3 microl/g/min). In the ACPD group, the Ki of the IC was 3.3 times that of the CC (5.0+/-0.7 vs. 1.5+/-0.4 microl/g/min). The increase in Ki of the ACPD group in the ischemic cortex was significantly greater than that in the control group. There was no significant difference in the Ki of the CC between these groups. Our data suggest that activation metabotropic glutamate receptors in the cortex can further augment the increase in BBB permeability caused by focal ischemia.