Evidence that Functional Glutamate Receptors are not Expressed on Rat or Human Cerebromicrovascular Endothelial Cells

Morley, Paul; Small, Daniel L.; Murray, Christine L.; Mealing, Geoff; Poulter, Michael O.; Durkin, Jon P.; Stanimirovic, Danica

doi:10.1097/00004647-199804000-00008

Cited by 79 publications

(58 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…48 This discrepancy is probably due to the di erences in the drug dose and application procedure, and the injury model (Table 3). Interestingly, these authors also found that MK801 reduced the size of hemorrhage in grey matters and protected the spinal cord white matter, though NMDA receptors probably do not present on the vessels of neural tissue 77,78 and CNS white matter. 79,80 However, our results are consistent with some investigations on the role of ionotropic glutamate receptor antagonists.…”

Section: Discussionmentioning

confidence: 93%

Effects of MK801 on evoked potentials, spinal cord blood flow and cord edema in acute spinal cord injury in rats

Tator

1999

Spinal Cord

View full text Add to dashboard Cite

Objectives: To determine whether MK801, an NMDA receptor antagonist, blocks glutamate excitotoxicity directly or via other mechanisms such as improving blood supply at the injury site in a rat model of spinal cord injury (SCI). In the present study, the e ects of pre-and posttreatment with MK801 on axonal function, spinal cord blood¯ow (SCBF) and cord water content were studied after acute SCI in rats. Methods: Somatosensory evoked potentials (SSEPs) and cerebellar evoked potentials (CEPs) were used to quantify electrophysiological function, and the hydrogen clearance technique and wet-dry weight measurements were used to measure SCBF and cord water content, respectively. Twenty rats received a 21 g clip compression injury of the cord at T1, and were then randomly and blindly allocated to either MK801 or saline groups. Each rat received an intravenous infusion of drug or saline four times during the experiment (16 min/infusion) with the ®rst infusion (MK801 3 mg/kg) beginning 8 min pre-injury, and the other infusions (MK801 1.5 mg/kg) at 1 h intervals after injury. Control experiments on uninjured rats were performed in 10 rats using the same procedure as above except the clip compression injury of the cord was omitted. Results: In the MK801 groups with or without SCI, the amplitude of the evoked potential peaks, especially the SSEPs, was signi®cantly lower than in the saline group. There were no di erences in SCBF or cord water content between the MK801 and saline groups. Conclusion: Pre-and posttreatment with MK801 inhibits evoked potentials, but does not improve SCBF or cord edema after acute compression SCI in rats. For the ®rst time it has been shown that MK801 produced a blockade of glutamate excitatory transmission in a erent pathways after SCI. Further work is required to determine whether this inhibition is reversible and related to neuroprotection and functional recovery after SCI.

show abstract

Section: Discussionmentioning

confidence: 93%

Effects of MK801 on evoked potentials, spinal cord blood flow and cord edema in acute spinal cord injury in rats

Tator

1999

Spinal Cord

View full text Add to dashboard Cite

show abstract

“…In contrast, a very detailed study by Morley et al (31) was unable to find any NMDA or AMPA receptor expression in rat or human CMVEC cultures assessed at both mRNA and protein levels. Some mRNA expression of kainate receptor subunits was shown in rat CMVECs only, but the CMVECs were unresponsive to kainate stimulation.…”

Section: Discussionmentioning

confidence: 75%

“…First, many studies have failed to find any functional glutamate receptors in ovine, bovine, rat, and human cerebral microvessels or cerebral arteries (2,31,44). Second, very high doses of L-glut can be ingested without any neurotoxic effects in humans (41,43) or in experimental animals (42).…”

mentioning

confidence: 99%

Cerebromicrovascular endothelial cells are resistant to l-glutamate

Domoki

Kis

Gáspár

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

Cerebral microvascular endothelial cells (CMVECs) have recently been implicated as targets of excitotoxic injury by L-glutamate (L-glut) or N-methyl-Daspartate (NMDA) in vitro. However, high levels of L-glut do not compromise the function of the blood-brain barrier in vivo. We sought to determine whether primary cultures of rat and piglet CMVECs or cerebral microvascular pericytes (CMVPCs) are indeed sensitive to L-glut or NMDA. Viability was unaffected by 8-h exposure to 1-10 mM L-glut or NMDA in CMVECs or CMVPCs isolated from both species. Furthermore, neither 1 mM L-glut nor NMDA augmented cell death induced by 12-h oxygen-glucose deprivation in rat CMVECs or by 8-h medium withdrawal in CMVPCs. Additionally, transendothelial electrical resistance of rat CMVEC-astrocyte cocultures or piglet CMVEC cultures were not compromised by up to 24-h exposure to 1 mM L-glut or NMDA. The Ca 2ϩ ionophore calcimycin (5 M), but not L-glut (1 mM), increased intracellular Ca 2ϩ levels in rat CMVECs and CMVPCs assessed with fluo-4 AM fluorescence and confocal microscopy. CMVEC-dependent pial arteriolar vasodilation to hypercapnia and bradykinin was unaffected by intracarotid infusion of L-glut in anesthetized piglets by closed cranial window/intravital microscopy. We conclude that cerebral microvascular cells are insensitive and resistant to glutamatergic stimuli in accordance with their in vivo role as regulators of potentially neurotoxic amino acids across the blood-brain barrier.N-methyl-D-aspartate; blood-brain barrier; cerebrovascular reactivity; glutamate excitotoxicity; intracellular calcium L-GLUTAMATE (L-glut) is one of the most important excitatory amino acids in the central nervous system. Apart from its well-known neurotransmitter role, L-glut plays a critical role in ammonia removal from the brain. L-Glut transported from the blood plasma takes up ammonia and leaves as L-glutamine (12). This balanced L-glutamate/L-glutamine countertransport is regulated by cerebral microvascular endothelial cells (CMVECs) forming the blood-brain barrier (BBB). Furthermore, CMVECs can pump L-glut from the brain to the blood, and thus they provide a functional interface for the regulated bidirectional transport of L-glut (18, 39). Human blood plasma L-glut levels range between 20 and 200 M, and they may exceed 700 M after ingestion of high amounts of L-glut under experimental conditions (4, 41). These plasma L-glut concentrations are not neurotoxic in vivo, although these levels are excitotoxic to neurons in vitro, suggesting that CMVECs are resistant to high L-glut levels and prevent the passive transport of L-glut into the brain.Surprisingly, several recent reports have proposed that the L-glut levels that occur during cerebral ischemia can injure or kill CMVECs via excitotoxic mechanisms in vitro. CMVECs have been reported to possess various L-glut receptor subunits or L-glut binding sites in rat, piglet, or human CMVECs (1,5,27,34,36,45). High concentrations of L-glut (1-3 mM), at least in vitro, are claimed to result in N-met...

show abstract

“…54 Five days following infection, neurons were loaded with fura-2 by incubating them for 30 min at 37°C in a normal buffer solution (NBS; 140 mm NaCl, 5 mm KCl, 1 mm CaCl 2 , 3 mm glucose, 30 mm glycine and 10 mm Hepes), containing 2.5 mm fura-2/AM. Experiments were conducted at room temperature on small groups of cells on glass coverslips in a custommade coverslip holder on the stage of a Zeiss IM inverted microscope (Carl Zeiss Canada, Don Mills, ON, Canada) coupled to a CM3 cation measurement spectrofluorimeter (Spex, Newark, NJ, USA).…”

Section: Cell Stainingmentioning

confidence: 99%

Helper-dependent adenovirus vectors: their use as a gene delivery system to neurons

et al. 2000

View full text Add to dashboard Cite

Recombinant adenovirus vectors have provided a major advance in gene delivery systems for post-mitotic neurons. However, the use of these first generation vectors has been limited due to the onset of virally mediated effects on cellular function and viability. In the present study we have used primary cultures of cerebellar granule neurons to examine the efficacy and cytotoxic effects of a helper-dependent adenovirus vector (hdAd) in comparison with a first generation vector. Our results demonstrate that the hdAd system provides equally efficient infectivity with significantly reduced toxicity in comparison to first generation vectors. Neurons transduced with a high titre of a first generation vector exhibited a time-dependent shut down in global protein synthesis and impaired physiological function as demonstrated by a

show abstract

Evidence that Functional Glutamate Receptors are not Expressed on Rat or Human Cerebromicrovascular Endothelial Cells

Cited by 79 publications

References 41 publications

Effects of MK801 on evoked potentials, spinal cord blood flow and cord edema in acute spinal cord injury in rats

Effects of MK801 on evoked potentials, spinal cord blood flow and cord edema in acute spinal cord injury in rats

Cerebromicrovascular endothelial cells are resistant to l-glutamate

Helper-dependent adenovirus vectors: their use as a gene delivery system to neurons

Contact Info

Product

Resources

About