Inhibition of Nitric Oxide Synthase Activity Attenuates Striatal Malonate Lesions in Rats

Mitochondrial inhibitors such as malonate are potent neurotoxins in vivo. Intrastriatal injections of malonate result in neuronal damage reminiscent of “excitotoxic” lesions produced by compounds that activate NMDA receptors. Although the mechanism of cell death produced by malonate is uncertain, overactivation of NMDA receptors may be involved; pretreatment of animals with NMDA antagonists provides neuroprotection against malonate lesions. NMDA receptor activation stimulates the enzyme nitric oxide (NO) synthase (NOS). Elevated tissue levels of NO may generate highly reactive intermediates that impair mitochondrial function. We hypothesized that NO may be a mediator of malonate toxicity. We investigated whether in vivo inhibition of NO production by the NOS inhibitor N Ω -nitro-l-arginine (NLA) would attenuate lesions produced by intrastriatal injections of malonate. We found that systemic injections of 3 mg/kg of NLA significantly reduced the extent of histologic damage elicited by intrastriatal injections of 1.5 µmol of malonate in adult rats.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66435/1/j.1471-4159.1995.64052362.x.pd

N -Methyl-D-Aspartate-Mediated Injury Enhances Quisqualic Acid-Stimulated Phosphoinositide Turnover in Perinatal Rats

Previous work in our laboratory demonstrated that ischemic-hypoxic brain injury in postnatal day 7 rats causes a substantial increase in phosphoinositide (PPI) turnover stimulated by the glutamate analogue quisqualic acid (QUIS) in the hippocampus and striatum. To examine this phenomenon in more detail, we performed similar experiments after producing injury by unilateral intracerebral injections of the glutamate analogue N -methyl-D-aspartate (NMDA). The 7-day-old rodent brain is hypersensitive to NMDA neurotoxicity and NMDA injection causes histopathology that closely resembles that produced by ischemia-hypoxia. NMDA, 17 nmol in 0.5 Μl, was injected into the right posterior striatum of 7-day-old rat pups and they were killed 3 days later. Hippocampal or striatal tissue slices were prepared from ipsilateral and contralateral hemispheres from vehicle-injected control and from noninjected control rat pups. Slices were then incubated with myo -[ 3 H]inositol plus glutamate agonists or antagonists in the presence of lithium ions and [ 3 H]inositol monophosphate ([ 3 H]IP 1 ) accumulation was measured. The glutamate agonists, QUIS, L-glutamic acid, and ( RS )-Α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, stimulated greater [ 3 H]IP 1 release in tissue ipsilateral to the NMDA injection compared with that in the contralateral side and in control pups. The glutamate antagonists, D,L-2-amino-7-phosphonoheptanoic acid, 3-[(+)-2-carboxypiperazin-4-yl]-propyl-l-phosphoric acid, kynurenic acid, and 6,7-dinitroquinoxaline-2,3-dione did not inhibit QUIS-stimulated [ 3 H]IP 1 release. The enhanced PPI turnover in the lesioned tissue was specific to glutamate receptors because carbachol (CARB) failed to elicit preferential enhanced stimulation. To investigate the possibility that alterations in the release of endogenous neurotransmitters had a role in potentiating QUIS-stimulated PPI turnover after NMDA injection, we examined the effect of tetrodotoxin. Tetrodotoxin (0.5 Μ M ) did not alter QUIS-or CARB-stimulated PPI hydrolysis in the lesioned or unlesioned tissue. The influence of extracellular calcium concentration on QUIS-stimulated [ 3 H]IP 1 formation was also examined after the NMDA lesion. Moderate reduction of calcium in the buffer (1 Μ M ) enhanced the lesion effect. Low calcium buffer enhanced QUIS-stimulated PPI turnover in the lesioned hippocampal slices, but reduced QUIS stimulation in contralateral slices and controls. In contrast, CARB-stimulated PPI turnover was not enhanced in low Ca 2+ buffer. A similar pattern of Ca 2+ dependency was observed in striatal slices. Calcium-free (<10 n M ) buffer suppressed PPI turnover in all groups. These studies demonstrate that NMDA-induced excitotoxic injury in neonatal rats causes a selective enhancement of QUIS-stimulated PPI turnover that resembles the effects of ischemia-hypoxia. In addition, we found that agonist-stimulated PPI turnover is sensitive to the in vitro Ca 2+ concentration. These changes could reflect altered coupling of non-NMDA receptors to phospholipase C activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65991/1/j.1471-4159.1992.tb08337.x.pd

Hematological monitoring during therapy with carbamazepine in children

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50302/1/410130622_ftp.pd

Effect of depolarization on striatal amino acid efflux in perinatal rats: An in vivo microdialysis study

We used in vivo microdialysis to determine if infusion of depolarizing concentrations of potassium stimulated striatal excitatory amino acid (EAA) efflux in post-natal day (PND) 7 rats. Dialysis probes were perfused with 100 mM KCl for 60 min (n = 6); EAA efflux was unaffected until 40-60 min after onset of the infusion, when a trend towards increased EAA efflux was observed (glutamate 284 +/- 56% of baseline). In animals exposed to 8% oxygen (n = 7) before a more prolonged (100 min) KCl infusion, again over the first 40 min of KCl there were no changes in EAA efflux; subsequently, glutamate, aspartate and taurine efflux increased (peak values 682 +/- 187%, 228 +/- 32%, and 1208 +/- 437% of baseline). These data suggest that in PND 7 rats a substantial contribution to basal striatal EAA efflux may be derived from non-neurotransmitter pools.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29230/1/0000285.pd

Developmental changes in the expression of chemokine receptor CCR1 in the rat cerebellum

Chemokines are small, soluble proteins that regulate leukocyte migration, adhesion, and proliferation. Recent evidence suggests that chemokine receptors are expressed in the central nervous system and that their functions extend beyond their roles in inflammation. Specific chemokines and their receptors are implicated in cerebellar development. In this study, we evaluated the expression of Β-chemokine receptor CCR1 in the immature and adult rat cerebellum and report striking developmental changes in CCR1 expression. Reverse transcriptase polymerase chain reaction assays of cerebellum revealed moderate increases in CCR1 mRNA expression from postnatal day (P) 3 to adulthood. Light and confocal microscopy were used to evaluate developmental changes in the neuroanatomical and cell-specific distribution of CCR1 immunoreactivity. CCR1 immunoreactivity was detected as early as P3 and peaked between P7 and P21. The predominant CCR1-immunoreactive neuronal cell types included granule cells of the internal granular layer, Purkinje cells, Golgi cells, and molecular layer interneurons; Bergmann glia, astrocytes, and resting microglia also expressed CCR1. In contrast, granule cells in the external germinal layer, descending granule cells, and activated microglia rarely expressed CCR1. We also evaluated the expression of the CCR1 ligand macrophage inflammatory protein-1Α (MIP-1Α/CCL3). Two cell populations expressed MIP-1Α: physiologically activated microglia in white matter (P7–P14) and Purkinje cells (P7–adult). MIP-1Α-positive cells were frequently located near the processes and cell bodies of CCR1-immunoreactive cells, during times of neuronal and glial maturation (second and third postnatal weeks). These findings provide support for the hypothesis that CCR1 plays a role in postnatal cerebellar development. J. Comp. Neurol. 457:7–23, 2003. © 2003 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34466/1/10554_ftp.pd

Perinatal Hypoxic-Ischemic Brain Injury Enhances Quisqualic Acid-Stimulated Phosphoinositide Turnover

In an experimental model of perinatal hypoxic-ischemic brain injury, we examined quisqualic acid (Quis)-stimulated phosphoinositide (PPI) turnover in hippocampus and striatum. To produce a unilateral forebrain lesion in 7-day-old rat pups, the right carotid artery was ligated and animals were then exposed to moderate hypoxia (8% oxygen) for 2.5 h. Pups were killed 24 h later and Quis-stimulated PPI turnover was assayed in tissue slices obtained from hippocampus and striatum, target regions for hypoxic-ischemic injury. The glutamate agonist Quis (10 -4 M ) preferentially stimulated PPI hydrolysis in injured brain. In hippocampal slices of tissue derived from the right cerebral hemisphere, the addition of Quis stimulated accumulation of inositol phosphates by more than ninefold (1,053 ± 237% of basal, mean ± SEM, n = 9). In contrast, the addition of Quis stimulated accumulation of inositol phosphates by about fivefold in the contralateral hemisphere (588 ± 134%) and by about sixfold in controls (631 ± 177%, p < 0.005, comparison of ischemic tissue with control). In striatal tissue, the corresponding values were 801 ± 157%, 474 ± 89%, and 506 ± 115% (p < 0.05). In contrast, stimulation of PPI turnover elicited by the cho-linergic agonist carbamoylcholine, (10 -4 or 10 -2 M ) was unaffected by hypoxia-ischemia. The results suggest that prior exposure to hypoxia-ischemia enhances coupling of excitatory amino acid receptors to phospholipase C activity. This activation may contribute to the pathogenesis of irreversible brain injury and/or to mechanisms of recovery.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66017/1/j.1471-4159.1988.tb01046.x.pd

Pathogenesis of hypoxic-ischemic brain injury in a perinatal rodent model

Exposure of immature rats to 8% oxygen after unilateral carotid artery ligation (UCL) causes metabolic, neurochemical and histopathological changes in the ipsilateral forebrain that resemble those in human perinatal hypoxic-ischemic encephalopathy. Regional cerebral perfusion in this model was examined by visual analysis of India ink trapped in cerebral vessels and measurement of [14C]iodoantipyrine ([14C]IAP) and [3H]flunitrazepam extraction into the brain. UCL alone reduced [14C]IAP accumulation in the ipsilateral hemisphere by 20% and hypoxia superimposed on UCL progressively reduced ipsilateral hemisphere perfusion by 71% at 2 h. Hypoxia probably injures neurons in this model by causing a critical reduction in cerebral perfusion, an effect which also appears to be important in the human disorder.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24718/1/0000140.pd

The glutamate analogue quisqualic acid is neurotoxic in striatum and hippocampus of immature rat brain

To assess the neurotoxic properties of the glutamate agonist quisqualic acid (QA) in immature brain, we injected this compound (100 nmol QA/l [mu]l) directly into the striatum of 7-day-old rats. QA produced neuronal necrosis and glial infiltration in 14 pups and reduced the size of the striatum and hippocampus on the side of injection. Intracerebral injection of QA provides a new method for producing neuronal lesions in the developing brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26009/1/0000076.pd

Transient Hypoxia Alters Striatal Catecholamine Metabolism in Immature Brain: An In Vivo Microdialysis Study

Microdialysis probes were inserted bilaterally into the striatum of 7-day-old rat pups (n = 30) to examine extracellular fluid levels of dopamine, its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). The dialysis samples were assayed by HPLC with electrochemical detection. Baseline levels, measured after a 2-h stabilization period, were as follows: dopamine, not detected; DOPAC, 617 ± 33 fmol/min; HVA, 974 ± 42 fmol/min; and 5-HIAA, 276 ± 15 fmol/min. After a 40-min baseline sampling period, 12 animals were exposed to 8% oxygen for 120 min. Hypoxia produced marked reductions in the striatal extracellular fluid levels of both dopamine metabolites ( p < 0.001 by analysis of variance) and a more gradual and less prominent reduction in 5-HIAA levels ( p < 0.02 by analysis of variance), compared with controls (n = 12) sampled in room air. In the first hour after hypoxia, DOPAC and HVA levels rose quickly, whereas 5-HIAA levels remained suppressed. The magnitude of depolarization-evoked release of dopamine (elicited by infusion of potassium or veratrine through the microdialysis probes for 20 min) was evaluated in control and hypoxic animals. Depolarization-evoked dopamine efflux was considerably higher in hypoxic pups than in controls: hypoxic (n = 7), 257 ± 32 fmol/min; control (n = 12), 75 ± 14 fmol/min ( p < 0.001 by analysis of variance). These data demonstrate that a brief exposure to moderate hypoxia markedly disrupts striatal catecholamine metabolism in the immature rodent brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66218/1/j.1471-4159.1990.tb01914.x.pd

MK-801 protects the neonatal brain from hypoxic-ischemic damage

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26610/1/0000151.pd