bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Acetylcholine-Induced Relaxation of Rabbit Isolated Middle Cerebral Artery: Effects of Inhibitors of Nitric Oxide Synthesis, Na,K-ATPase, and ATP-Sensitive K Channels
Authors: Parsons Andrew A. , Schilling Lothar , Wahl Michael
Published: April 2011

The functional importance of membrane hyperpolarization through activation of ATP-sensitive K channels, or activation of the Na,K–ATPase, was investigated for acetylcholine (ACh)-induced relaxation of the rabbit isolated middle cerebral artery (MCA) precontracted with uridine triphosphate. Incubation with glibenclamide (1 μ M), a known blocker of ATP-sensitive K channels, or precontraction with a high concentration of KCl (50 m M) had no effect on ACh-induced relaxation. Similarly, inhibition of the Na,K–ATPase with ouabain (10 μ M) or incubation with a potassium-free solution had either no or only a small effect on ACh-induced relaxation. In contrast, NG-nitro-L-arginine (NOLAG) (1 to 10 μ M), a structural analogue of L-arginine and an inhibitor of nitric oxide synthesis, produced concentration-dependent although apparently noncompetitive inhibition of ACh-induced relaxation. This inhibition was partially reversed by application of L-arginine (100 μ M), a putative precursor for nitric oxide synthesis. It is concluded that membrane hyperpolarization induced by activation of ATP-sensitive K channels or Na,K–ATPase does not play a major functional role in ACh-induced relaxation of rabbit MCA. The potent inhibitory actions of NOLAG would suggest that the major mechanism of ACh-induced relaxation is by release of nitric oxide as in other cerebral and peripheral arteries.
In vivo Binding of Nimodipine in the Brain: I. The Effect of Focal Cerebral Ischemia
Authors: Hakim Antoine M. , Hogan Matthew J.
Published: April 2011

We report the regional variation in [3H]nimodipine binding in vivo during focal cerebral ischemia. After intravenous injection, 30 min of circulation of [3H]nimodipine was sufficient to establish a secular equilibrium of distribution in the brain. Rats sustained left middle cerebral and common carotid artery occlusions for 5 min, and 4, 24, and 48 h (n ≥ 6 per group). They were decapitated 30 min after injection of 250 μCi of [3H]nimodipine and their brains were submitted to autoradiography. The concentrations of [3H]nimodipine in plasma and brain structures, corrected for metabolism of nimodipine, were used to calculate the regional volumes of distribution ( V) in the ischemic left (L) and control right (R) hemispheres. Log (VL/VR) was then defined as the group mean of the logarithms of the left-to-right ratio of V of [3H]nimodipine. In the lateral caudate, binding of [3H]nimodipine on the ischemic side was highest within 5 min of occlusion. Log ( VL/ VR) in this region for the combined sham-operated and normal control rats and those after 5 min and 4 and 24 h of ischemia were −0.014 ± 0.025, 0.137 ± 0.056*, −0.201 ± 0.367, and −0.049 ± 0.370 (mean ± SD, *represents p < 0.01 compared with controls). By contrast, in the superior frontal cortex, values for log ( VL/ VR) in the same sequence were −0.016 ± 0.025, 0.028 ± 0.056, 0.284 ± 0.228*, and 0.224 ± 0.069*, thus showing a significant rise in [3H]nimodipine binding only at 4 h. Structures such as the cingulate and striate cortex, sufficiently removed from the ischemic core, showed only small changes in log ( VL/ VR) at all times. Correlating these data with CBF and histologic determinations performed in separate groups of rats, we conclude that [3H]nimodipine binding increases earlier in the more severely ischemic structures than in those with more moderate reductions in perfusion. Furthermore, when binding declines in a region where it was previously increased, infarction is likely. These studies afford new insight into the concept of ischemic penumbra and suggest that this model may allow testing for therapeutic effectiveness.
The Effects of a Competitive NMDA Receptor Antagonist (CGS-19755) on Cerebral Blood Flow and pH in Focal Ischemia
Authors: Takizawa Shunya , Hogan Matthew , Hakim Antoine M.
Published: April 2011

We report the effects of intravenous infusion of CGS-19755, a potent competitive N-methyl-D-aspartate (NMDA) antagonist, on local cerebral pH (LCpH) and local CBF (LCBF) in rats with occluded left middle cerebral and common carotid arteries. LCpH and LCBF were determined simultaneously by a double-label autoradiographic technique 4 h after vascular occlusion in three groups: No treatment, carrier infused, and a group receiving CGS-19755 at 10 mg/kg bolus immediately after occlusion followed by infusion at 5 mg kg−1 h−1 for 4 h. Compared with rats receiving carrier, several cortical structures on the side of occlusions showed significantly higher CBF in rats receiving CGS-19755. This drug also corrected the pH in several left cortical structures to values significantly higher than in the rats receiving carrier. The correction in LCpH was not limited to those regions showing significant elevations in LCBF. In the nonoccluded hemisphere, CGS-19755 significantly increased the hemispheric mean blood flow from 122 ± 17 to 221 ± 64 ml 100 g−1 min−1 (mean ± SD of all structures, p < 0.01) without any changes in LCpH. Cortical but not basal ganglia infarct volume was significantly smaller in rats receiving CGS-19755 than in the carrier-treated group. These results suggest that, at least partially, the neuroprotective effect of CGS-19755 in ischemia may be related to changes in CBF and pH in addition to its antagonist effect on the NMDA receptor.
Electrical Stimulation of Cerebellar Fastigial Nucleus Reduces Ischemic Infarction Elicited by Middle Cerebral Artery Occlusion in Rat
Authors: Reis Donald J. , Berger Scott B. , Underwood Mark D. , Khayata Mazen
Published: April 2011

Electrical stimulation of the cerebellar fastigial nucleus (FN) globally and profoundly increases cerebral blood flow via a cholinergic mechanism. In cerebral cortex, the vasodilation is unassociated with alterations in cerebral glucose utilization, a condition favoring protection against cerebral ischemia. We sought to determine whether FN stimulation would modify the size of the focal ischemic infarction resulting from occlusion of the middle cerebral artery (MCA). The MCA was occluded in anesthetized rats of the spontaneously hypertensive (SHR) or Sprague-Dawley (SD) strains with or without 1 h of electrical stimulation of the FN. Twenty-four hours later, rats were killed and the volume of the infarction established in thionin-stained sections. In SHRs, FN stimulation reduced by 40% the well-established cortical and partially subcortical infarctions elicited by occlusion of the MCA (from 186 ± 35.2 to 113 ± 47.1 mm3, mean ± SD, n = 15; p < 0.001). The zone of retrieval was anatomically constant, consisting of a rim of cortex dorsal and ventral to the infarction and medially within the thalamus and striatum corresponding to the penumbral zone described by others. The effect was comparable in rats of the SD strain having smaller infarctions. The effect of FN stimulation appears to be selective for the FN system in that it is not evoked by stimulation of the dentate nucleus and is blocked by systemic administration of atropine (1.0 mg/kg). We conclude that excitation of an intrinsic system in brain represented in the rostral FN has the capacity to reduce substantially an ischemic infarction. Whether the result is a consequence of an action of the FN upon cerebral blood flow and/or results from protective actions of released transmitter is yet unknown.
Simultaneous and Continuous Measurement of Choroid Plexus Blood Flow and Cerebrospinal Fluid Production: Effects of Vasoactive Intestinal Polypeptide
Authors: Nilsson Christer , Lindvall-Axelsson Maria , Owman Christer
Published: April 2011

Using laser-Doppler flowmetry during ventriculocisternal perfusion with inulin-[14C]carboxylic acid, choroid plexus blood flow (CPBF) and CSF production were measured simultaneously in rats during periods of 3 h. Blood flow and CSF production decreased only slightly during control experiments. The effect of vasoactive intestinal polypeptide (VIP) was studied at different concentrations of the peptide given either intraventricularly or intravenously. Intraventricular administration of VIP (10−9 or 10−7 M) resulted in a decrease in CSF production of up to 30%, while CPBF increased by 20%, also demonstrating that CSF production and blood flow are not directly coupled in the choroid plexus. When infused intravenously, VIP (10 or 100 pmol/kg/min) increased CPBF, an effect partly antagonized at higher concentrations owing to a VIP-induced systemic hypotension. No effect of VIP on CSF production could be seen with intravenous administration.
GAB Aergic Innervation in Cerebral Blood Vessels: An Immunohistochemical Demonstration of L-Glutamic Acid Decarboxylase and GABA Transaminase
Authors: Imai H. , Okuno T. , Wu J. Y. , Lee T. J-F.
Published: April 2011

The presence of GAB Aergic innervation in cerebral arteries of several species was investigated by an immunohistochemical method using antibodies against glutamic acid decarboxylase (GAD) and GABA transaminase (GABA-T). Both GAD and GABA-T immunoreactivities were found to be associated with large bundles and single fibers in the adventitial layer of arteries examined. The density and distribution pattern of both GAD-and GABA-T-immunoreactive fibers were found to be comparable at most regions examined. Both fibers were found to be most dense in the anterior cerebral artery and its adjacent part of the circle of Willis. Several peripheral arteries were found to receive very sparse or no GAD-and GABA-T-immunoreactive fibers. Superior cervical ganglionectomy did not appreciably affect the distribution of both fibers. Cold-storage denervation, however, resulted in a drastic decrease in both fibers. At ultrastructural levels, both GAD- and GABA-T-immunoreactive nerve profiles were found to be very close to the smooth muscle cells. These results demonstrate the presence of a potentially functional GAB Aergic innervation in cerebral circulation. On few occasions, GAD immunoreactivities were also found in some endothelial cells, suggesting that a nonneuronal GABA system may also be present in cerebral arteries.
L-6-[18F]Fluoro-DOPA Metabolism in Monkeys and Humans: Biochemical Parameters for the Formulation of Tracer Kinetic Models with Positron Emission Tomography
Authors: Melega William P. , Grafton Scott T. , Huang Sung-Cheng , Satyamurthy Nagichettiar , Phelps Michael E. , Barrio Jorge R.
Published: April 2011

Characterization of peripheral and cerebral l-3,4-dihydroxy-6-[18F]fluorophenylalanine (FDOPA) metabolism in humans and monkeys has shown FDOPA to be an analogue of l-DOPA for the study of the dopaminergic system with positron emission tomography (PET). In human studies with carbidopa pretreatment, l-3,4-dihydroxy-6-[18F]fluoro-3- O-methylphenylalanine (3-OMFD) was the only FDOPA metabolite detected in plasma. FDOPA administration in monkeys resulted in selective accumulation of FDOPA metabolites in central dopaminergic regions, whereas 3-OMFD of peripheral origin was uniformly distributed among putamen, caudate, frontal cortex, and cerebellum. At 60 min, 3-OMFD and 6-[18F]fluorodopamine (FDA) each represented ∼35% of the total activity, the remainder being FDOPA and FDA metabolites. These data on monkey and human FDOPA metabolism provide the basis for the configuration of an FDOPA tracer kinetic model with PET.
Adenosine Release and Changes in Pial Arteriolar Diameter during Transient Cerebral Ischemia and Reperfusion
Authors: Meno Joseph R. , Ngai Al C. , Ibayashi Setsuro , Winn H. Richard
Published: April 2011

We utilized the closed cranial window technique in the anesthetized rat to determine changes in CSF concentrations of adenosine, inosine, and hypoxanthine and pial arteriolar diameter during transient (20 min) forebrain ischemia and reperfusion. After mock CSF under the cranial window was allowed to equilibrate with cerebral interstitial fluid, endogenous adenosine concentration was found to be 0.16 ± 0.05 μ M, while inosine and hypoxanthine were 0.35 ± 0.17 and 1.23 ± 0.47 μ M, respectively. The concentration of adenosine in CSF increased 4.2-fold during ischemia and 13.8-fold during the first 5 min of reperfusion. Inosine and hypoxanthine concentrations were also significantly increased during ischemia and reperfusion. After 1 h of reperfusion, CSF adenosine and inosine levels had decreased from peak values but remained significantly above preischemic values. In contrast, hypoxanthine remained at peak concentrations even after 60 min of reperfusion. Preischemic arteriolar diameter was 42.6 ± 11.3 μm and was not significantly changed after 20 min of ischemia. However, during the first 5 min of reperfusion, arteriolar diameter increased significantly (p < 0.05), coincident with peak adenosine concentrations. By 60 min of reperfusion, arteriolar diameter had returned to baseline. These results indicate that during the postischemic period, adenine nucleosides and hypoxanthine in CSF are elevated and could affect reperfusion.
The Contribution of Reoxygenation to Ischemic Brain Damage
Authors: Halsey James H. , Conger Karl A. , Garcia Julio H. , Sarvary Eniko
Published: April 2011

This study examined the hypothesis that the level of postischemic reperfusion affects the severity of the resulting neuronal necrosis. In rats, tissue Po2% was monitored as an index of flow (reoxygenation) at four cortical sites by chronically implanted platinum electrodes. Twenty minutes of total global cerebral ischemia was followed by 30 min of reoxygenation. The level of reoxygenation was controlled to maintain the Po2 nearly constant at one or more of the cortical electrodes. Tissue from within 400 μm of each of 19 electrode sites among seven rats was evaluated histologically. There was a positive correlation between reoxygenation level and severity of neuronal damage. Perineuronal lucent halo formation, probably representing astrocyte foot process swelling, was negatively correlated with reoxygenation level. This study demonstrates that ischemic neuronal damage was aggravated by increased reoxygenation but that perineuronal swelling, as evidenced by halo formation, was somewhat ameliorated.
Insulin Attenuates Ischemic Brain Damage Independent of its Hypoglycemic Effect
Authors: Voll C. L. , Auer R. N.
Published: April 2011

Insulin, an endogenously produced circulating peptide that enters the brain, has been shown to reduce ischemic brain and spinal cord damage in several animal models. Because of its potential clinical use in humans, the present study was undertaken to test the hypotheses that (a) survival and regional ischemic brain necrosis are improved by insulin; (b) insulin requires concomitant hypoglycemia to exert its neuroprotective effect; (c) insulin is still neuroprotective with delayed administration after an episode of postischemic hypotension; and (d) insulin is beneficial after normoglycemic, as well as hyperglycemic ischemia. Rats were subjected to 10.5 min two-vessel occlusion forebrain ischemia followed by 30 min of hypotension to increase the infarction rate. Insulin administered concomitantly with glucose significantly reduced the seizure rate, as well as cortical and striatal neuronal necrosis below that seen in untreated animals. Neuroprotection was seen whether insulin was given before or after a 30-min episode of postischemic hypotension. Insulin reduced pan-necrosis in addition to selective neuronal necrosis: The infarction rate was reduced in the cerebral cortex, thalamus, and substantia nigra pars reticulata. Normoglycemic ischemia produced only selective neuronal necrosis, but a beneficial effect on structural damage was also seen. The results indicate that insulin acts directly on the brain, independent of hypoglycemia, to reduce ischemic brain necrosis. Possible direct CNS mechanisms of action include an effect on central insulin receptors mediating inhibitory neuromodulation, an effect on central neurotransmitters, or a growth factor effect of insulin.
Ischemia of Rat Brain Decreases Pertussis Toxin-Catalyzed [32P]ADP Ribosylation of GTP-Binding Proteins (Gi1 and G0) in Membranes
Authors: Takenaka Katsunobu , Kanaho Yasunori , Nagata Koh-Ichi , Sakai Noboru , Yamada Hiromu , Nozawa Yoshinori
Published: April 2011

As an approach to understanding the molecular basis of the pathophysiology of cerebral ischemia, we examined qualitative and quantitative changes in pertussis toxin substrates, Gi1 and G0, in the membrane of rat cerebral cortex after decapitation. Within 1 min after decapitation, the extent of pertussis toxin-catalyzed [32P]ADP ribosylation of the G proteins in the cerebral cortex membrane was significantly decreased and the magnitude of the decrease became slightly larger upon further incubation of the decapitated brain. Addition of guanine nucleotides, GTP and GDP, or the purified βγ subunits of transducin to the membranes of control and ischemic cerebral cortex stimulated [32P]ADP ribosylation of the G proteins. The stimulation of [32P]ADP ribosylation in the control situation by guanine nucleotides was almost to the same extent as that in ischemia. However, the stimulation by transducin βγ subunits was different; the control stimulation was greater than that in ischemia. In immunoblots probed with antibodies against Gi1α G0α and Tβ, the immunoreactivity of the corresponding proteins in ischemia was similar to that in control, suggesting that the amounts of G proteins were not changed in ischemia. These results suggest that ischemia accelerates the dissociation of α–GDP–βγ to α–GDP and free βγ and causes the denaturation of the dissociated α–GDP, thereby decreasing [32P]ADP ribosylation.
Contractile and Endothelium-Dependent Dilatory Responses of Cerebral Arteries at Various Extracellular Magnesium Concentrations
Authors: Faragó Mária , Szabó Csaba , Dóra Eörs , Horváth Ildikó , Kovách Arisztid G. B.
Published: April 2011

To clarify the effect of extracellular magnesium (Mg2+) on the vascular reactivity of feline isolated middle cerebral arteries, the effects of slight alterations in the Mg2+ concentration on the contractile and endothelium-dependent dilatory responses were investigated in vitro. The contractions, induced by 10−8-10−5 M norepinephrine, were significantly potentiated at low Mg2+ (0.8 m M v. the normal, 1.2 m M). High (1.6 and 2.0 m M) Mg2+ exhibited an inhibitory effect on the contractile responses. No significant changes, however, in the EC50 values for norepinephrine were found. The endothelium-dependent relaxations induced by 108–10−5 M acetylcholine were inhibited by high (1.6 and 2.0 m M) Mg2+. Lowering of the Mg2+ concentration to 0.8 m M or total withdrawal of this ion from the medium failed to alter the dilatory potency of acetylcholine. The changes in the dilatory responses also shifted the EC50 values for acetylcholine to the right. The present results show that the contractile responses of the cerebral arteries are extremely susceptible to the changes of Mg2+ concentrations. In response to contractile and endothelium-dependent dilatory agonists, Mg2+ probably affects both the calcium influx into the endothelial and smooth muscle cells as well as the binding of acetylcholine to its endothelial receptor. Since Mg2+ deficiency might facilitate the contractile but not the endothelium-dependent relaxant responses, the present study supports a role for Mg2+ deficiency in the development of the cerebral vasospasm.
Factors Affecting Accuracy and Precision in PET Volume Imaging
Authors: Karp Joel S. , Daube-Witherspoon Margaret E. , Muehllehner Gerd
Published: April 2011

Volume imaging positron emission tomographic (PET) scanners with no septa and a large axial acceptance angle offer several advantages over multiring PET scanners. A volume imaging scanner combines high sensitivity with fine axial sampling and spatial resolution. The fine axial sampling minimizes the partial volume effect, which affects the measured concentration of an object. Even if the size of an object is large compared to the slice spacing in a multiring scanner, significant variation in the concentration is measured as a function of the axial position of the object. With a volume imaging scanner, it is necessary to use a three-dimensional reconstruction algorithm in order to avoid variations in the axial resolution as a function of the distance from the center of the scanner. In addition, good energy resolution is needed in order to use a high energy threshold to reduce the coincident scattered radiation.
PET Measured Evoked Cerebral Blood Flow Responses in an Awake Monkey
Authors: Perlmutter J. S. , Lich L. L. , Margenau W. , Buchholz S.
Published: April 2011

We have developed a method to measure task-related regional cerebral blood flow (BF) responses in an awake, trained monkey using positron emission tomography (PET) and H215O. We trained an animal with operant conditioning using only positive reinforcement to climb unassisted into a modified primate chair that was then positioned in the PET scanner. A special headholder and acrylic skull cap permitted precise placement and accurate repositioning. We measured BF qualitatively with bolus injection of H215O and a 40-s scan. Each session included scans at rest interposed with scans during vibration of a forepaw. Regional responses were identified using subtraction image analysis. After global normalization, a resting image was subtracted on a pixel-by-pixel basis from a comparable image collected during vibration. The region of peak response occurred in contralateral sensorimotor cortex with a mean magnitude of 11.6% (±3.2%) of the global mean value for 10 separate experiments, significantly greater than the mean qualitative BF change (0.4 ± 3.6%; p < 0.00001) in the same region for seven rest-rest pairs. This newly developed technique forms the basis for a wide variety of experiments.
Simultaneous Measurement of Cerebral Blood Flow and Energy Metabolites in Piglets Using Deuterium and Phosphorus Nuclear Magnetic Resonance
Authors: Corbett Ronald J. T. , Laptook Abbot R. , Olivares Edward
Published: April 2011

This report demonstrates the feasibility of using deuterium (2H) and phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy to make multiple simultaneous determinations of changes in cerebral blood flow, brain intracellular pH, and phosphorylated metabolites for individual animals. In vivo spectra were obtained from the brains of newborn piglets immediately following an intracarotid bolus injection of deuterium oxide. Experiments were performed at magnetic field strengths of 1.9 T (2H NMR only) or 4.7 T (interleaved 2H and 31P NMR). The rate of clearance of deuterium signal was used to calculate cerebral perfusion rates (CBFdeuterium) during a stable control physiologic state and conditions known to alter blood flow. CBFdeuterium values measured at 1.9 T under conditions of control (normocarbia, normotension), hypercarbia, hypocarbia, and varying degrees of ischemia induced by hypotension showed a significant positive correlation with values measured simultaneously using radiolabeled microspheres (CBFdeuterium = 0.4 × CBFmicrospheres + 8; r = 0.8). Simultaneous interleaved 2H and 31P NMR measurements under control conditions indicate that brain energy metabolites and intracellular pH remained at constant levels during the time course of the administration and clearance of deuterium oxide. Also, brain phosphorylated metabolites and intracellular pH did not differ significantly from their preinjection levels. Under control physiologic conditions, CBFdeuterium varied by ±6% and phosphorylated metabolite levels did not show a significant change with time, as measured from 15 blood flow determinations collected over 4 h. The results indicate that CBFdeuterium determinations have excellent reproducibility and do not affect brain energy metabolite levels. The procedures described here have the potential to bring a novel methodology to bear on investigating the relationship between cerebral perfusion and energy status during conditions such as ischemia or asphyxia.
Induced Tolerance to Ischemia in Gerbil Hippocampal Neurons
Authors: Kirino Takaaki , Tsujita Yoshihiko , Tamura Akira
Published: April 2011

Brief ischemia induced tolerance to subsequent ischemia in the hippocampal neurons. Male Mongolian gerbils were subjected to 2 min of ischemia in an awake condition. This ischemic insult only rarely produced neuronal damage in the gerbil brain. One day ( n = 9), 2 days ( n = 9), or 4 days ( n = 10) following the first brief ischemia, the animals (double-ischemia group) were subjected to the second ischemia for 5 min. The single-ischemia group received a sham procedure instead of the first ischemia and was identically subjected to the second ischemia 1 day ( n = 9), 2 days ( n = 10), and 4 days ( n = 13) following the sham procedure. One week following the second ischemia, all gerbils were perfusion fixed and the neuronal density in the hippocampal CA1 sector was measured. In double-ischemia groups, the neuronal density per 1-mm length of the pyramidal cell layer was 103.4 ± 93.1 (SD) in the 1-day subgroup, 125.6 ± 64.2 in the 2-day subgroup, and 176.2 ± 93.7 in the 4-day subgroup, while the density in normal gerbils was 254.7 ± 18.6. The average neuronal density in the single-ischemia group was much lower than that in the double-ischemia group (whole control group: 10.9 ± 27.4). Immunostaining using monoclonal antibody raised against 70-kDa heat-shock protein revealed an increase in 70-kDa heat-shock protein in the CA1 area following 2 min of ischemia. Very brief ischemia induces heat-shock proteins and, presumably, thereby renders neurons more tolerant to subsequent metabolic stress.
Effects of Lesioning of the Substantia Innominata on Autoregulation of Local Cerebral Blood Flow in Rats
Authors: Gomi Shintaro , Gotoh Fumio , Ishihara Naoki , Tanaka Kortaro , Ishikawa Yoshiki , Takashima Shutaro , Mihara Ban
Published: April 2011

Recently, accumulated data have suggested that the nucleus basalis magnocellularis, i.e., the substantia innominata (SI), may represent the primary source of central cholinergic innervation in the rat cortical vasculature. We therefore examined the effects of unilateral lesion of the SI on the autoregulation of local CBF (1CBF) during induced hypotension in rats. Male Wistar rats were divided into three groups. The animals of groups 1 and 2 received an injection of 5 μg of ibotenate into the right SI stereotaxically. At 7 days after the injection, the 1CBF was measured by the [14C]iodoantipyrine technique in the awake state. Group 1 was used as the normotensive group (MABP = 113.1 ± 12.2 mm Hg). Group 2 formed the hypotensive group, and the 1CBF was measured during hypotension (MABP = 80.0 ± 5.5 mm Hg) induced by hemorrhage. Group 3, the sham-operated normotensive group, received vehicle injection into the right SI at 7 days prior to the 1CBF measurement. In group 1, 1CBF was significantly lower in the frontal, parietal, temporal, and striate cortices on the lesioned side compared to that on the contralateral side. In group 2, 1CBF was significantly decreased in the cortices on the lesioned side, but there was no significant difference in magnitude of the 1CBF reduction between groups 1 and 2. Group 3 exhibited no hemispheric asymmetries in 1CBF. These findings suggest that the SI exerts an influence on cortical 1CBF, but does not play a role in the autoregulation of 1CBF during hypotension.
Mechanism of the Enhanced Vasoconstrictor Responses to Endothelin-1 in Canine Cerebral Arteries
Authors: Tanoi Chiharu , Suzuki Yoshio , Shibuya Masato , Sugita Kenichiro , Masuzawa Kaoru , Asano Masahisa
Published: April 2011

Vasoconstrictor effects of endothelin-1 (ET) were investigated in endothelium-denuded strips of cerebral (basilar and posterior cerebral) and mesenteric arteries of the dog. ET produced a concentration-dependent contraction in these arteries. Contractile responses to lower concentrations (below 3 × 10−10 M) of ET were significantly greater in the cerebral arteries than in the mesenteric artery. Inhibition by nifedipine of the contractile responses to ET was greater in the basilar artery than in the mesenteric artery. After the inhibition by 10−7 M nifedipine, the remaining responses to ET were similar in the two arteries. Cerebral arteries, but not the mesenteric artery, relaxed significantly from the resting level when placed in a Ca2+ -free solution containing 0.1 m M EGTA (0-Ca solution). Readdition of Ca2+ to the cerebral arteries placed in the 0-Ca solution caused a biphasic contraction that was sensitive to nifedipine. When 10−9 M ET was introduced before the Ca2+-induced contraction, this peptide produced only a very small contraction, but enhanced the Ca2+-induced contraction. The extent of the enhancement induced by ET was much greater in the cerebral arteries than in the mesenteric artery. These results indicate that the enhanced responses to ET in the cerebral arteries were dependent to a large extent on Ca2+ influx through voltage-dependent Ca2+ channels (VDCs). It is likely that the VDCs in these arteries are more activated in the resting state than those in the mesenteric artery.
Opioids and the Prostanoid System in the Control of Cerebral Blood Flow in Hypotensive Piglets
Authors: Armstead William M. , Mirro Robert , Busija David W. , Leffler Charles W.
Published: April 2011

The interaction between opioid and prostanoid mechanisms in the control of cerebral hemodynamics was investigated in the conscious hypotensive piglet. Radiomicrospheres were used to determine regional cerebral blood flow (rCBF) in piglets pretreated with the opioid receptor antagonist, naloxone, or its vehicle, saline, during normotension, hypotension, and after the administration of indomethacin, a cyclooxygenase inhibitor, during hypotension. Hemorrhage (30 ml/kg) decreased systemic arterial pressure from 68 ± 12 to 40 ± 10 mm Hg but did not decrease blood flow to any brain region. Indomethacin treatment (5 mg/kg) of hypotensive piglets decreased blood flow to all brain regions within 20 min; this decrease in CBF resulted from increases in cerebral vascular resistance of 65 and 281% at 20 and 40 min after treatment, respectively. In hypotensive piglets, cerebral oxygen consumption was reduced from 2.62 ± 0.71 to 0.53 ± 0.27 ml 100g−1 min−1 and to 0.11 ± 0.04 ml 100 g−1 min−1 at 20 and 40 min following indomethacin, respectively. Treatment with naloxone (1 mg/kg) had no effect on rCBF, calculated cerebral vascular resistance, or cerebral oxygen consumption of normotensive or hypotensive piglets. However, decreases in CBF and oxygen consumption and increases in cerebral vascular resistance upon treatment of hypotensive piglets with indomethacin were attenuated in animals pretreated with naloxone. These data indicate that the removal of prostanoid modulation of an opioid-mediated constrictor influence on the cerebral circulation is a potential mechanism for the increase in cerebral vascular resistance that follows indomethacin treatment of hypotensive piglets.
Hyperthermia-Induced Neuronal Protection against Ischemic Injury in Gerbils
Authors: Kitagawa Kazuo , Matsumoto Masayasu , Tagaya Masafumi , Kuwabara Keisuke , Hata Ryuji , Handa Nobuo , Fukunaga Ryuzo , Kimura Kazufumi , Kamada Takenobu
Published: April 2011

We investigated the effect of hyperthermic pretreatment before induction of ischemia using a gerbil model of 5-min forebrain ischemia. A single hyperthermic treatment 18 h before ischemia exhibited a partial protective effect, and repetitive hyperthermic pretreatments at 18-h intervals before ischemia showed clear protection against neuronal death in the CA1 area of the hippocampus, whereas single hyperthermic treatment 3, 6, 24, or 50 h before ischemia exhibited little protective effect. This transient and cumulative neuroprotective effect of hyperthermic pretreatment strongly suggested the involvement of stress reactions after hyperthermia in the protective mechanism against ischemic neuronal death.
Viability of Neocortical Function Shown in Behavioral Activation State PET Studies in Alzheimer Disease
Authors: Duara Ranjan , Barker Warren W. , Chang Jen , Yoshii Fumihito , Loewenstein David A. , Pascal Shlomo
Published: April 2011

Twenty subjects with mildly to moderately severe Alzheimer disease (AD) and 14 normal elderly control subjects were studied using [18F]fluorodeoxyglucose and positron emission tomography (PET) to investigate regional cerebral glucose metabolism during both a resting state and a behavioral activation state, utilizing a reading memory task (RMT). The RMT produced significant global metabolic activation of 15 ± 15% in normal subjects and 11 ± 13% in AD subjects. The occipital regions were preferentially activated, but all regions in both groups were also significantly activated. The RMT did not allow a better discrimination of AD patients from normal controls on the basis of regional metabolic deficits. Regions in the AD group that were individually classified as hypometabolic during rest also exhibited metabolic activation. The apparent viability of hypometabolic regions in AD patients challenges current hypotheses regarding the cause of abnormal metabolism in AD.
Changes in Brain Monoaminergic Neurotransmitter Concentrations in Rat after Intracerebroventricular Injection of Streptozotocin
Authors: Ding Andreas , Nitsch Roger , Hoyer Siegfried
Published: April 2011

The tissue concentrations of the monoaminergic neurotransmitters noradrenaline (NA), dopamine, and serotonin (5-HT) and of their major metabolites were measured by HPLC and electrochemical detection in several rat brain areas after intracerebroventricular injection of streptozotocin (STZ). NA levels were found to be decreased in the frontal cortex by 14%, in the entorhinal cortex by 18%, and in the striatum by 38%. In the entorhinal cortex, 5-HT levels were decreased by 19% and the 5-HT turnover rate, measured as the 5-hydroxyindoleacetic acid/5-HT ratio, was found to be increased by 48%. These results may be indicative of a distinct susceptibility of some neurotransmitters in certain brain areas after a more general impairment of brain metabolism by means of intracerebroventricular application of the diabetogenic compound STZ.
Functional Changes in Thalamic Relay Neurons after Focal Cerebral Infarct: A Study of Unit Recordings from VPL Neurons after MCA Occlusion in Rats
Authors: Tokuno Tatsuya , Kataoka Kazuo , Asai Toshiharu , Chichibu Shiko , Kuroda Ryotaro , Ioku Masahiko , Yamada Kazuo , Hayakawa Toru
Published: April 2011

We evaluated neuronal and histological changes of thalamic neurons 1, 4, 7, and 14 days after middle cerebral artery (MCA) occlusion in rats. After the somatosensory evoked potentials (SEPs) were measured from the cerebral cortex, the thalamic relay neuronal activities were recorded with a glass microelectrode following repetitive electrical stimulation of the contralateral forepaw at frequencies ranging from 1 to 50 Hz. In ∼95% of the occluded rats, the ipsilateral somatosensory cortex and/or the subcortical somatosensory pathway developed infarct, resulting in SEP loss. We evaluated unit data from rats with abolished SEPs. The average firing rate of the nucleus ventralis posterolateralis (VPL) neurons in response to 25 stimulations at 30 Hz was significantly reduced to 0.1 spike/stimulus 1 day after MCA occlusion. In sham-operated rats, the same stimulation produced 0.7 spike/stimulus. The firing rate recovered to 0.4 spike/stimulus at 30-Hz stimulation 4 and 7 days after occlusion. This was followed by resuppression (0.1 spike/stimulus) 14 days after occlusion. Histological study revealed some abnormal neurons in the ipsilateral thalamus 7 days after occlusion. We were unable to find normal-shaped neurons in the VPL 14 days after occlusion. The present study demonstrates that cortical infarct produces functional and morphologic changes that gradually and progressively affect the ipsilateral thalamus, although incomplete transient recovery of somatosensory transmission may occur.
Stimulation of the Fastigial Nucleus Enhances EEG Recovery and Reduces Tissue Damage after Focal Cerebral Ischemia
Authors: Zhang Fangyi , Iadecola Costantino
Published: April 2011

Stimulation of the cerebellar fastigial nucleus (FN) increases CBF but not metabolism and reduces the tissue damage resulting from focal cerebral ischemia. This effect may result from enhancing CBF in the ischemic tissue without increasing local metabolic demands. To test this hypothesis, we studied whether the reduction in tissue damage is restricted to the neocortex, a region in which the CBF increase is independent of metabolism, and whether stimulation of the dorsal medullary reticular formation (DMRF), a treatment that increases both cerebral metabolism and CBF, also protects the brain from ischemia. In halothane-anesthetized Sprague–Dawley rats, the middle cerebral artery (MCA) was occluded either proximally or distally to the lenticulostriate branches. The FN or DMRF were then stimulated for 1 h (50–100 μA; 50 Hz; 1 s on/1 s off). Twenty-four hours later, the infarct volume was determined. FN stimulation substantially reduced the size of the infarct, an effect that was greater with distal (− 69 ± 8%; n = 6; p < 0.001; mean ± SD) than with proximal (−38 ± 8%; n = 8; p < 0.001) MCA occlusion. The reduction occurred only in neocortex (−43 ± 9%; p < 0.001) and not in striatum (− 16 ± 21%; p > 0.05). Stimulation of the FN also enhanced recovery of EEG amplitude in the ischemic cortex (+ 48%; p < 0.003). DMRF stimulation (n = 7) did not affect the stroke size or EEG recovery ( p > 0.05). Thus, stimulation of the FN, but not the DMRF, attenuates the damage resulting from focal ischemia. The finding that the protection is limited to the neocortex and that the amount of tissue salvaged is greater after distal occlusions suggests that the FN, unlike the DMRF, may rescue tissue from infarction by enhancing collateral flow without increasing local energy requirements. Activation of selected neural networks may modulate the expression of the damage resulting from focal cerebral ischemia.
Focal Cerebral Ischemia in Rats: Effect of Hemodilution with α-α Cross-Linked Hemoglobin on CBF
Authors: Cole Daniel J. , Schell Randall M. , Przybelski Robert J. , Drummond John C. , Bradley Kenneth
Published: April 2011

Hemodilution has had limited success as a treatment of cerebral ischemia. When using a nonoxygen binding fluid, the therapeutic efficacy of hemodilution-induced increases in CBF are offset by concomitant decreases in oxygen content. The effect of hemodilution, with diaspirin α-α cross-linked hemoglobin (DCLHb), on CBF during middle cerebral artery occlusion was assessed. Rats were hemodiluted to one of the following hematocrits (Hct): (a) 44/Hct, (b) 37/Hct, (c) 30/Hct, (d) 23/Hct, (e) 16/Hct, or (f) 9/Hct. After 10 min of ischemia, CBF was determined with 14C-iodoantipyrine. Coronal brain sections were evaluated for areas with a CBF of 0–10 and 11–20 ml 100 g−1 min−1. In addition, oxygen delivery was calculated. In the center of the ischemic zone, both areas of low CBF were less in the 30/Hct, 23/Hct, and 16/Hct groups compared with the 44/Hct and 37/Hct groups; and both areas were less in the 9/Hct group compared with the other five groups ( p < 0.05). For the hemisphere contralateral to occlusion, there was a direct correlation between hematocrit and oxygen delivery. However, for the hemisphere ipsilateral to occlusion, oxygen delivery increased as hematocrit decreased (44/Hct, 8.6 ± 0.3 vs. 9/Hct, 13.6 ± 0.4 [mean ± SD, ml 100 g−1 min−1]). The results of this study support a hypothesis that hemodilution with DCLHb decreases the extent of focal cerebral ischemia.
Plasticity in the Rat Hippocampal Formation following Ibotenic Acid Lesion of the Septal Region: A Quantitative [14C]Deoxyglucose and Acetylcholinesterase Study
Authors: Schulz Jörg-Bernhard , Wree Andreas , Schleicher Axel , Zilles Karl
Published: April 2011

The local cerebral glucose utilization was measured in the hippocampal formation 3, 21, and 90 days after bilateral lesions of the medial septal nucleus and the nucleus of the diagonal band of Broca by multiple ibotenic acid injections. The CMRglc was determined in hippocampal areas and layers and various limbic and visual regions by quantitative [14C]2-deoxyglucose autoradiography using a computerized image-processing system. Three days after lesion, CMRglc was significantly decreased in 26 of the 38 structures examined. The most pronounced reductions were found in CA2 and CA3, the subiculum, and the parasubiculum. The CMRglc values of the 21- and 90-day postlesion groups did not differ significantly from control data when univariate statistics were used. However, by means of a factor analysis and subsequently a discriminant analysis as a multivariate test for group differences, significant lesion-induced CMRglc changes could be detected between the control group, the 3-day group, and the 90-day group. The 21-day group did not differ significantly from the controls. The data indicate that 90 days after lesion of the medial septum/diagonal band complex (MSDB), a considerable recovery of the mean CMRglc was found in the hippocampal region, although a normal level was not reached. In a parallel series, processing of sections for acetylcholinesterase (AChE) histochemistry revealed a severe destruction of AChE-positive fibers in the hippocampus at 3 days after lesion and a conspicuous recovery in the amount of stain-able fibers and their staining intensity at 21 days postlesion. In the 90-day group, the AChE fibers recovered even further but did not reach the values of unlesioned sham-operated controls. The present study indicates that sprouting of surviving cholinergic afferents might be an important morphological substrate for CMRglc recovery in the hippocampus after MSDB lesion.
Maturation of Cerebral Oxidative Metabolism in the Cat: A Cytochrome Oxidase Histochemistry Study
Authors: Hovda David A. , Chugani Harry T. , Villablanca Jaime R. , Badie Bahman , Sutton Richard L.
Published: April 2011

The maturation of brain oxidative capacity was studied in kittens, using cytochrome oxidase histochemistry, at different ages throughout development. Optical densitometry values of reacted tissue were obtained for 50 different structures of the brain. In general, most structures reached adult levels of oxidative capacity by 30 days of age with some motor areas (e.g., cerebellum, red nucleus) exhibiting adult values as early as 7 days of age. Thereafter, some structures (e.g., basal ganglia, thalamus) exhibited levels of cytochrome oxidase activity that exceeded adult values for varying periods of time. These findings indicate regional heterogeneity in the maturation of cerebral oxidative capacity. Furthermore, these maturational patterns appear to correlate well with previous observations from anatomical, physiological and neuro-behavioral studies.
Effects of l-NMMA and l-NNA on the Selective ATP-Induced Enhancement of Intratumoral Blood Flow
Authors: Natori Y. , Moriguchi M. , Fujiwara S. , Takeshita I. , Fukui M. , Iwaki T. , Kanaide H.
Published: April 2011

We studied the effects of NG-monomethyl-l-arginine (l-NMMA) and Nω-nitro-l-arginine (l-NNA) on the selective ATP and adenosine-induced enhancement of intratumoral blood flow in rats measured by the hydrogen clearance method. Both adenosine and ATP produced a selective enhancement of the intratumoral blood flow. Neither l-NMMA nor l-NNA had a significant effect on either the CBF or the intratumoral blood flow. Adenosine-induced enhancement was not inhibited by l-NMMA or l-NNA. On the other hand, the ATP-induced enhancement was totally inhibited by both l-NMMA and l-NNA. The inhibitory action of l-NMMA against ATP was blocked by l-arginine, but not by d-arginine. It is suggested that the ATP-induced increase of intratumoral blood flow is evoked by nitric oxide synthesized from the endothelium of the intratumoral blood vessels.
Failure of the Lipid Peroxidation Inhibitor, U74006F, to Prevent Postischemic Selective Neuronal Injury
Authors: Buchan Alastair M. , Bruederlin Barbara , Heinicke Elizabeth , Li Hui
Published: April 2011

The lipid peroxidation inhibitor, U74006F, was tested for neuroprotective properties using the rat four-vessel occlusion model. Adult Wistar rats (136) were randomized to receive pretreatment with either vehicle or U74006F, and exposed to either 15 min ( n = 103) or 5 min ( n = 33) of transient but severe forebrain ischemia. Surviving criterial animals were reperfused for 72 h, and in the multidose experiments, animals were injected with repeated doses of U74006F or vehicle during the reperfusion period. Vehicle-treated animals exposed to 15 min of ischemia sustained 60 ± 35% ( n = 16) CA1 pyramidal cell necrosis whereas U74006F-treated animals lost 61 ± 30% (3 mg/kg, n = 9), 42 ± 35% (10 mg/kg, n = 15), 62 ± 28% (5 × 10 mg/kg, n = 10), and 74 ± 30% (8 × 10 mg/kg, n = 10) of CA1 pyramidal cells. No improvement was seen in the injury to cortex or striatum with either pre- or pre- and posttreatment with U74006F. For animals suffering 5 min of transient forebrain ischemia, vehicle-treated rats lost 19 ± 26% ( n = 14), whereas U74006F-treated (8 × 10 mg/kg) animals lost 36 ± 39% ( n = 15) of CA1 neurons. In addition, no protection was discerned in the mildly injured striatum or cortex of these animals. Given the potent effect of U74006F in inhibiting iron-dependent lipid peroxidation in vitro, we question the importance of oxy radicals in the mechanism of postischemic selective neuronal injury in vivo.
Focal and Perifocal Changes in Tissue Energy State during Middle Cerebral Artery Occlusion in Normo- and Hyperglycemic Rats
Authors: Folbergrová Jaroslava , Memezawa Hajime , Smith Maj-Lis , Siesjö Bo K.
Published: April 2011

The objective of the present study was to assess changes in cellular energy metabolism in focal and perifocal areas of a stroke lesion and to explore how these changes are modulated by preischemic hyperglycemia. A model for reversible occlusion of the middle cerebral artery (MCA) in rats was used to study changes in energy metabolism. Following MCA occlusion for 5, 15, or 30 min in normoglycemic rats, the tissue was frozen in situ, and samples from the lateral caudoputamen and from two neocortical areas were collected for metabolite analyses, together with a control sample from the contralateral, nonischemic hemisphere. Two other groups, subjected to 30 min of MCA occlusion, were made hyperglycemic by acute glucose infusion or by prior injection of streptozotocin. Enzymatic techniques were used for measurements of phosphocreatine, creatine, ATP, ADP, AMP, glycogen, glucose, pyruvate, and lactate. The neocortex of the contralateral, nonischemic hemisphere had labile metabolites that were similar to those measured in control animals. Ipsilateral neocortex bordering the focus, and thus constituting the “penumbra,” showed mild to moderate ischemic changes. In the “focus” (lateral caudoputamen plus the overlying neocortex), deterioration of energy state was rapid and relatively extensive (ATP content 20–40% of control). After 5 min of occlusion, no further deterioration of metabolic parameters was observed. Substrate levels were markedly reduced, and lactate content rose to ∼10 mM kg−1. In the animals with the most severe energy depletion, no additional accumulation of lactate occurred, suggesting substrate depletion. This was confirmed by the results obtained in the hyperglycemic subjects whose tissue lactate contents rose to ∼20 m M kg−1. However, the energy state of the focus was better preserved in both hyperglycemic groups as compared with the normoglycemic group. It has been shown, in this model, that relatively brief occlusion periods are required to induce infarction. The present results demonstrate that this can occur in spite of the absence of pronounced depletion of energy reserves. After 30 min of MCA occlusion, infarction developed in the lateral caudoputamen, but not in the neocortex. Since a similar perturbation in metabolic state was demonstrated here, other factors must contribute to the degree of tissue damage. The present results suggest that damage is exaggerated by hyperglycemia because it allows additional lactate to accumulate in the partially substrate-depleted tissue.