Microvascular changes during the early phase of experimental bacterial meningitis

We investigated the temporal profile of the changes in regional CBF (rCBF) and intracranial pressure (ICP) during the early phase of pneumococcal meningitis in the rat. rCBF, as measured by laser-Doppler flowmetry, and ICP were continuously monitored during 6 h post infection (p.i.). Brain edema formation was assessed by brain water content determinations. Meningitis was induced by intracisternal injection of 75 microliters of 10(7) colony-forming units/ml pneumococci (n = 7). In control animals (n = 6), saline was injected. There was no change in the rCBF or ICP of controls throughout the experiment. However, there was a dramatic increase in rCBF and ICP associated with brain edema formation in untreated meningitis animals. rCBF increased to 135.3 +/- 33.8% (mean +/- SD) in the untreated animals at 1 h p.i. and reached 211.1 +/- 40.5% at 6 h p.i. (p less than 0.05 compared with controls). ICP increased from 2.9 +/- 1.4 to 10.4 +/- 4.7 mm Hg at 6 h p.i. (p less than 0.05 compared with controls). Brain water content was significantly elevated (79.69 +/- 0.24 compared with 78.94 +/- 0.16% in the control group, p less than 0.05). We investigated the effect of dexamethasone (3 mg/kg i.p.), which was given prior to the induction of meningitis (n = 3) or at 2 h after pneumococcal injection (n = 5), indomethacin (10 mg/kg i.v., n = 5), and superoxide dismutase (SOD; 132,000 U/kg i.v. per 6 h, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibody neutralization of vascular endothelial growth factor (VEGF) fails to attenuate vascular permeability and brain edema in experimental pneumococcal meningitis

To determine the contribution of vascular endothelial growth factor (VEGF) to cerebral edema formation in bacterial meningitis, we used a VEGF neutralizing antibody to block VEGF in rabbits, following induction of meningitis by intracisternal inoculation with 10⁹ heat-killed pneumococci. At 8 h, cerebrospinal fluid (CSF) VEGF was significantly elevated in infected untreated animals, and correlated with CSF white blood cell (WBC) count (r=0.56, P=0.004), and brain water content (r=0.42, P=0.04). Blocking of VEGF did not attenuate brain edema, blood–brain barrier disruption, or CSF pleocytosis. The functional role of VEGF in the pathophysiology of BM remains elusive.     

Diagnostic capability of CSF ferritin in children with meningitis

The current study was performed to determine the normal cerebrospinal fluid (CSF) ferritin level according to age and cut-off value for early diagnosis of bacterial menignitis. The subjects (N = 203) consisted of children who received the CSF examination at Department of Pediatrics in Chonnam National University Hospital between May 1996 and July 2001. The subjects were classified into four groups; non-meningitis, viral meningitis, bacterial meningitis, and bacterial meningitis suspected group. CSF ferritin of the meningitis group was significantly higher than that of the non-meningitis or viral meningitis groups. CSF ferritin had positive correlation with white blood cell (WBC) count and protein in CSF but negative correlation with CSF glucose (P < 0.01). CSF ferritin decreased progressively up to 1 year but such a tendency was not evident in patients over 1 year in age in the non-meningitis group. For early diagnosis of bacterial meningitis, 15.6 ng/mL was considered as the appropriate cut-off value of CSF ferritin (a sensitivity of 96.2% and a specificity of 96.6%).     

Cerebral infarction in bacterial meningitis: predictive factors and outcome

In this study, we analysed the frequency, morphological patterns and clinical characteristics of cerebral ischaemia in bacterial meningitis. We sought to determine predictors for the development of vasculopathy and ischaemic infarction in patients with bacterial meningitis. Consecutive adult patients admitted between March 1998 and February 2009 to a neurological intensive care unit at a university hospital in Germany with the diagnosis of bacterial meningitis were included in the study. Standard criteria were used to define bacterial meningitis. From 68 patients with bacterial meningitis, six patients suffered from cerebral ischaemia (8.8%). In our cohort, reduced level of consciousness on admission (p = 0.01) and lower white blood cell (WBC) count in cerebrospinal fluid (CSF) (p = 0.012) were associated with development of ischaemic cerebrovascular complications. The short-term outcome of all patients was poor (median modified Rankin scale 4.5). In patients presenting with reduced level of consciousness on admission and/or low WBC count in CSF early cerebral imaging including MR angiography or CT angiography are warranted to detect impending cerebrovascular complications.     

Bacterial hydrogen peroxide contributes to cerebral hyperemia during early stages of experimental pneumococcal meningitis.

Alterations of blood flow contribute to major clinical complications in invasive infections such as sepsis and bacterial meningitis. As a unique feature streptococci -- in particular, Streptococcus pneumoniae, the most frequent pathogen in bacterial meningitis -- release hydrogen peroxide (H(2)O(2)) because of the absence of functional catalase. In a 6 h rat model of experimental meningitis, we studied the impact of bacterial H(2)O(2) production on regional cerebral blood flow (rCBF) and intracranial pressure (ICP). Compared to wild-type D39 pneumococci, the increase of rCBF was diminished in meningitis induced by the H(2)O(2) defective SpxB(-) mutant (maximum increase, 135% +/- 17% versus 217% +/- 23% of the individual baseline; P<0.01) or after treatment of D39-induced meningitis with H(2)O(2)-degrading catalase or with tetraethylammonium (TEA), a blocker of calcium-sensitive potassium channels, which mediate H(2)O(2)-induced vasodilation. Catalase did not significantly reduce the remaining rCBF increase caused by SpxB(-), supporting the predominant role of bacterial H(2)O(2). We conclude that in addition to host-sided mediators, bacterial-derived H(2)O(2) acts as a potent vasodilator, which accounts for a certain proportion of the early cerebral hyperperfusion in pneumococcal meningitis.     

Increased intracranial pressure is associated with elevated cerebrospinal fluid ADH levels in closed-head injury

Abstract

Objectives: Head injury frequently results in increased intracranial pressure and brain edema. Investigators have demonstrated that ischemic injury causes an increase in cerebrospinal fluid (CSF) levels of antidiuretic hormone (ADH); increased CSF ADH levels exacerbate cerebral edema, and inhibition of the ADH system with specific ADH antagonists reduces cerebral edema. The current study was designed to test the hypothesis that elevated levels of ADH are present in the CSF of subjects with head injury.

Methods: Ventricular CSF and blood samples were taken from 11 subjects with head injury and 12 subjects with no known head trauma or injury. ADH levels were analyzed using radioimmunoassay. Severity of increased intracranial pressure (ICP) was rated in head-injured subjects using a four-point ordinal scale, based on which treatments were necessary to reduce ICP.

Results: Subjects with head injury had higher CSF (3.2 versus 1.2 pg/ml; P<0.02) and plasma (4.1 versus 1.4 pg/ml; P<0.02) levels of ADH than did control subjects. In head-injured subjects, CSF ADH levels positively correlated with severity of ICP.

Discussion: The results of this study suggest that ADH plays a role in brain edema associated with closed head injury.     

Inflammatory response during bacterial meningitis is unchanged in Fas- and Fas ligand-deficient mice

Fas (CD95) and Fas ligand (FasL, CD95L) have been implicated to be involved in the acute inflammatory response by attracting neutrophils and regulating their survival. Increased levels of soluble Fas and FasL are found in cerebrospinal fluid (CSF) samples of patients with bacterial meningitis but not in controls. Functional FasL (gld)- or Fas (lpr)-deficient mice were used to assess their role in the pathophysiology of pneumococcal meningitis. Induction of meningitis in wild-type (WT) mice caused an increase in CSF white blood cell (WBC) count, intracranial pressure (ICP), and vessel permeability, paralleled by a worse clinical status at 24 h. The inflammatory response was accompanied by elevated levels of IL-1beta, MMP-2, and MMP-9 in the brain. Neither gld- nor lpr-mice showed significant differences in the above-mentioned pneumococci-induced pathophysiological alterations. These results indicate that Fas and FasL are not essential in the regulation of the acute inflammatory response during pneumococcal meningitis.     

Noninvasive early detection of brain edema in mice by near-infrared light scattering

Brain edema accounts for significant morbidity and mortality in many neurologic conditions such as head trauma, stroke, meningitis, and brain tumor. The water channel aquaporin-4 (AQP4) has been found to be an important determinant of brain water accumulation and clearance of excess brain water. We report the development of a noninvasive near-infrared (NIR) light-scattering method to compare the early kinetics of brain swelling in normal and AQP4-deficient mice. Brain tissue was illuminated through the intact skull with NIR light at 850 nm, and steady-state scattered light intensity was monitored at an angle of 90 degrees at a position on the skull approximately 10 mm from the illuminated site. NIR light scattering reversibly increased with brain swelling (DeltaI/Io approximately 25% per 1% increase in brain water content), but was insensitive to changes in cerebral blood flow, blood oxygenation, or blood flow-related changes in intracranial pressure (ICP). DeltaI/Io increased approximately linearly with brain water content as measured by wet-to-dry weight ratios. Acute water intoxication (intraperitoneal water, 20% body weight) produced a gradual increase in DeltaI/Io of 12 +/- 4% in wild-type mice at 5 min, much greater than that of 2 +/- 1% in AQP4-null mice. Correlation of the NIR signal with ICP showed that increased DeltaI/Io preceded measurable increases in ICP, indicating the ability of the NIR method to detect early brain edema before ICP elevation. NIR light scattering provides a simple noninvasive method to monitor brain edema in mice, with potential clinical applications.     

Effects of microbial invasion on cerebral hemodynamics and oxygenation monitored by near infrared spectroscopy in experimental Escherichia coli meningitis in the newborn piglet.

This study was carried out to elucidate the pathophysiologic mechanism of cerebral hyperemia observed during the early phase of bacterial meningitis. We tested the hypothesis that microbial invasion through the blood-brain barrier is responsible for cerebral vasodilation and hyperemia in meningitis. Escherichia coli was given either intravenously (i.v.) or intracisternally (i.c.) to closely mimic the primary or secondary bacterial invasion occurring in meningitis and newborn piglets were grouped according to their invasion results (+ or -); 12 in the i.v. (+) group, 14 in the i.v. (-) group, 13 in the i.c. (+) group, 15 in the i.c. (-) group. The results were compared with eight animals in the control group. Near infrared spectroscopy (NIRS) was employed to monitor changes in total hemoglobin (HbT), oxygenated hemoglobin (HbO), deoxygenated hemoglobin (Hb), deduced hemoglobin (HbD), and oxidized cytochrome aa3 (Cyt aa3). HbT, as an index of cerebral blood volume, increased progressively in both i.v. (+) and i.v. (-) groups and became significantly different from control and baseline values at 2 h. Hb significantly increased only in i.v. (+) group. HbD, as an index of cerebral blood flow, decreased significantly in i.v. (+), i.v.(-) and i.c. (-) groups and this change was mitigated in i.c. (+) group, HbO was reduced in i.c. (-) group and this decrease was attenuated in i.c. (+) group. Increased Cyt aa3 was observed in all experimental groups after bacterial inoculation. Changes in ICP, blood pressure, cerebral perfusion pressure, blood or CSF glucose or lactate, CSF TNF-alpha level, or CSF leukocytes number were not associated with changes in NIRS findings. These findings suggest that primary or secondary bacterial invasion across the blood-brain barrier is primarily responsible for cerebral vasodilation and hyperemia observed during the early phase of bacterial meningitis.     

Level of transforming growth factor beta 1 is elevated in cerebrospinal fluid of children with acute bacterial meningitis

We investigated the levels of transforming growth factor beta 1 (TGF-β1) in cerebrospinal fluid (CSF) in children with meningitis, with a view to prognostic relevance. CSF TGF-β1 levels on admission were measured by a sandwich enzyme immunoassay in children with bacterial meningitis (n = 16), aseptic meningitis (n = 12), and control subjects without evidence of central nervous system (CNS) infection (n = 16). Patients were followed up for a mean duration of 13 months, and neurodevelopmental sequelae was determined for those with bacterial meningitis. On admission, CSF TGF-β1 levels were significantly higher in children with bacterial meningitis (mean, standard error, 32.92, 2.36 pg/ml) as opposed to those with aseptic meningitis (25.26, 1.72 pg/ml) (P = 0.0155), or control subjects (20.53, 1.05 pg/ml) (P < 0.0001). The CSF TGF-β1 levels in children with aseptic meningitis were higher than those in the control group, but without significance (P = 0.02). No apparent correlation existed between CSF TGF-β1 levels and CSF protein or cell counts in patients with bacterial meningitis. No significant difference in CSF TGF-β1 levels was found between patients with or without major sequelae following bacterial meningitis. Received: 19 March 1997 Received in revised form: 24 June 1997 Accepted: 20 August 1997     

Effects of microbial invasion on cerebral hemodynamics and oxygenation monitored by near infrared spectroscopy in experimental Escherichia coli meningitis in the newborn piglet

Abstract

This study was carried out to elucidate the pathophysiologic mechanism of cerebral hyperemia observed during the early phase of bacterial meningitis. We tested the hypothesis that microbial invasion through the blood-brain barrier is responsible for cerebral vasodilation and hyperemia in meningitis. Escherichia coli was given either intravenously (i.v.) or intracisternally (i.e.) to closely mimic the primary or secondary bacterial invasion occurring in meningitis and newborn piglets were grouped according to their invasion results (+ or -); 7 2 in the i. v. (+) group, 14 in the i. v.{-) group, 73 in the i. c.( + ) group, 7 5 in the i. c. (-) group. The results were compared with eight animals in the control group. Near infrared spectroscopy (NIRS) was employed to monitor changes in total hemoglobin (HbT), oxygenated hemoglobin (HbO), deoxygenated hemoglobin (Hb), deduced hemoglobin (HbD), and oxidized cytochrome aa3 (Cyt aa3). HbT, as an index of cerebral blood volume, increased progressively in both i.v. (+) and i.v. (-) groups and became significantly different from control and baseline values at 2 h. Hb significantly increased only in i.v. ( + ) group. HbD, as an index of cerebral blood flow, decreased significantly in i.v. ( + ), i.v.(-) and i.e. (-) groups and this change was mitigated in i.e. ( + ) group. HbO was reduced in i.e. (-) group and this decrease was attenuated in i.e. ( + ) group. Increased Cyt aa3 was observed in all experimental groups after bacterial inoculation. Changes in ICP, blood pressure, cerebral perfusion pressure, blood or CSF glucose or lactate, CSF TNF-a level, or CSF leukocytes number were not associated with changes in NIRS findings. These findings suggest that primary or secondary bacterial invasion across the blood-brain barrier is primarily responsible for cerebral vasodilation and hyperemia observed during the early phase of bacterial meningitis. [Neurol Res 1999; 21: 391-398]     

Cerebrovascular changes elicited by electrical stimulation of the centromedian-parafascicular complex in rat

Electrical stimulation of the centromedian-parafascicular complex (CM-Pf) in anesthetized (chloralose) and paralyzed (tubocurarine) rats elicites a widespread cerebrovascular dilatation. Regional cerebral blood flow (rCBF) was measured in dissected tissue samples of 10 brain regions (medulla, pons, cerebellum, inferior colliculus, superior colliculus, frontal parietal and occipital cortices, caudate-putamen and corpus callosum) by [¹⁴C]iodoantipyrine method. In unstimulated and sham-operated rats rCBF ranged from 40±3 (ml/100g/min) in corpus callosum to 86±6 (ml/100g/min) in inferior colliculus. During CM-Pf stimulation, rCBF increased significantly P < 0.05, analysis of variance and Scheffe's test) in all cerebral regions bilaterally ranging from +118% in parietal cortex to +38% in cerebellum. Although cerebral vasodilation elicited by CM-Pf stimulation persisted after unilateral transection of the cervical sympathetic trunk, the cortical CBF was significantly reduced (P < 0.05) on the denervated side. Acute adrenalectomy significantly (P < 0.05) decreased elevated rCBF during CM-Pf stimulation in all cortical regions (frontal −36%, parietal −34%, and occipital −27%) and in caudate nucleus (−37%). Thus, excitation of neurons originating in, or fibers passing through the CM-Pf can elicit a powerful cerebral vasodilation. The cerebral vasodilation is modulated by cervical sympathectomy and circulating adrenal hormones. We conclude that CM-Pf elicited vasodilation is at least partly mediated by intrinsic neural pathways.     

Utility of cerebrospinal fluid cortisol level in acute bacterial meningitis

Background:

Meningitis remains a serious clinical problem in developing as well as developed countries. Delay in diagnosis and treatment results in significant morbidity and mortality. The role and levels of intrathecal endogenous cortisol is not known.

Objective:

To study the cerebrospinal fluid (CSF) cortisol levels and to evaluate its role as a diagnostic and therapeutic marker in acute bacterial meningitis.

Materials and Methods:

Thirty patients with acute bacterial meningitis with no prior treatment were evaluated. Cortisol levels were compared with 20 patients with aseptic (viral) meningitis and 25 control subjects.

Results:

Mean CSF cortisol level was 13.85, 3.47, and 1.05 in bacterial meningitis, aseptic meningitis, and controls, respectively. Mean CSF cortisol level in bacterial meningitis was significantly higher as compared to controls (P < 0.001). There was significant difference in CSFcortisol levels in bacterial and aseptic meningitis (P < 0.001).

Conclusions:

Cortisol levels in CSF are highly elevated in patients with acute bacterial meningitis. This suggests that intrathecalcortisol may serve as a valuable, rapid, relatively inexpensive diagnostic marker in discriminatingbetween bacterial and aseptic meningitis. This helps in earlier institution of appropriate treatment and thereby decreasing morbidity and mortality.     

Effect of induced hyperglycemia on brain cell membrane function and energy metabolism during the early phase of experimental meningitis in newborn piglets

This study was done to elucidate the mechanism of hypoglycorrhachia and elevated lactate concentrations leading to neuronal dysfunction in neonatal meningitis, and to determine the effects of induced hyperglycemia on these disturbances. Thirty-eight newborn piglets were divided into three groups: 12 in the control group (CG), 12 in the normoglycemic meningitis group (NG), and 14 in the hyperglycemic meningitis group (HG). Meningitis was induced by intracisternal injection of 108 cfu of Escherichia coli. Hyperglycemia (blood glucose 300–400 mg dl⁻¹) was induced and maintained for 60 min before induction of meningitis and throughout the experiment using modified glucose clamp technique. CSF-to-blood glucose ratio decreased significantly in NG. In HG, baseline CSF-to-blood glucose ratio was lower than two other groups, but increased at 1 h after induction of meningitis. CSF lactate concentration was increased progressively in both meningitis groups, and positively correlated with CSF leukocyte numbers (r=0.41, p<0.001) and TNF-α level (r=0.43, p<0.001). Brain glucose concentration was significantly increased in HG and showed inverse correlation with CSF leukocyte numbers (r=−0.59, p<0.01). Brain lactate concentration was not significantly different among three groups and positively correlated with the CSF TNF-α level (r=0.51, p<0.05). Lipid peroxidation products were increased in NG. Na⁺,K⁺-ATPase activity, ATP/PCr concentrations were not different among three groups. Increased intracranial pressure, CSF pleocytosis (214±59 vs. 437±214/mm³, p<0.02) and increased lipid peroxidation products observed in NG were reduced in HG. These results suggest that hypoglycorrhachia and elevated lactate concentration in the CSF during meningitis originates primarily from the increased anaerobic glycolysis in the subarachnoid space, induced by TNF-α and leukocytes. Induced hyperglycemia attenuates the inflammatory responses of meningitis and might be beneficial by providing an increased glucose delivery to meet its increased demand in meningitis.     

In vitro intercellular adhesion molecule-1 expression on brain endothelial cells in multiple sclerosis

To investigate the origin of intercellular adhesion molecule-1 (ICAM-1) and its expression on brain endothelial cells, we studied the expression in vitro of ICAM-1 on human brain endothelial cells after incubation of T cells from patients with multiple sclerosis (MS) using a histochemical technique and flow cytometry. We determined soluble forms of ICAM-1 (sICAM-1) in the supernatants after mixtures of brain endothelial cells and T cells from patients with MS using an enzyme-liked immunosorbent assay. Flow cytometric analysis showed that a number of ICAM-1-positive cells were significantly increased after incubation of brain endothelial cells with T cells from patients with acute relapsing MS during an exacerbation as compared with those of controls (P<0.01). Patients with acute relapsing MS during an exacerbation and chronic progressive MS exhibited higher levels of ICAM-1 in the supernatants of mixtures with brain endothelial cells and lymphocytes than those of controls (P<0.001 and P<0.01, respectively). These results suggest that lymphocytes from patients with acute relapsing MS during an exacerbation lead to an increased expression of ICAM-1 on the brain endothelial cells and add to evidence involving this adhesion molecule in the pathogenesis of MS.     

颅脑损伤病人血浆和脑脊液中EAA含量与颅内压力变化关系的探讨

目的 探讨颅脑损伤后和脑脊液（CSF）中兴奋性氨基酸（EAA）变化的相关因素。方法 应用LYJ－1型颅内压监护仪动态观察了30例重型颅脑 损伤病人不同ICP对血浆和CSF中谷氨酸（GLU）和天门冬氨酸（ASP）含量变化。结果 创伤早期重型病人血浆和CSF中EAA含量即高于对照组（P＜0.05),随着ICP的升高EAA与之平行上升,二呈正相关。结论 颅脑损伤病人持续的ICP升高是引起EAA过度释放的重要因素之一。     

Management of intracranial pressure in tuberculous meningitis

Tuberculous meningitis (TBM) remains a common serious neurological emergency—especially in the developing world. Elevated intracranial pressure (ICP) is often a feature of severe TBM and is associated with high morbidity and mortality. The pathology associated with TBM, such as cerebral edema, hydrocephalus, tuberculoma(s), and infarcts related to arthritis, contribute to increase in intracranial volume and, therefore, elevated ICP. The three types of edema (vasogenic, cytotoxic, and interstitial) may contribute to cerebral edema. The molecular mechanisms underlying the events that ultimately lead to brain damage and cerebral edema during infection are complex. Similarly to bacterial meningitis, cerebral blood flow autoregulation is probably impaired in TBM, and the mechanisms are unclear. Although no universal guidelines are available to institute ICP monitoring in patients with severe TBM, it is be prudent to monitor patients at risk for increases in ICP. Such an approach helps to detect the secondary brain insults, allowing for a more informed approach to treatment. Treatment of elevated ICP involves a multipronged approach. The first step should be to identify focal brain lesions and hydrocephalus (which require surgical intervention) by brain imaging. Cerebral edema is treated with hyperosmolar agents. Mannitol is currently the most commonly used agent. It appears that use of hypertonic saline as an osmotic agent in infection-related cerebral edema has certain advantages. However, this needs to be established by well-designed trials. Use of steroids reduces not only cerebral edema but also the production of cytokines and other chemicals involved in the immunopathogenesis of TBM. Fever associated with TBM should be aggressively treated, because fever can worsen the impact of elevated ICP. Hyponatremia may complicate TBM and requires appropriate correction because it can aggravate cerebral edema.     

Widespread reductions in cerebral blood flow and metabolism elicited by electrical stimulation of the parabrachial nucleus in rat

We have studied the effect of electrical stimulation of the parabrachial nucleus (PBN) and adjacent areas of dorsal pons on regional cerebral blood flow (rCBF) and glucose utilization (rCGU) in anesthetized (chloralose), paralyzed (tubocurarine) rats. rCBF and rCGU were measured in dissected tissue samples of 9 brain regions by the [¹⁴C]iodoantipyrine and [¹⁴C]2-deoxyglucose method, respectively. Electrical stimulation restricted to the medial parabrachial nucleus (PBNm, n=5) elicited significant (P < 0.05) reductions in rCBF in 7 out of 9 brain regions. Reductions were greatest in cerebral cortex (up to 35% in occipital cortex) and least in the white matter of the corpus callosum (23%). The effect on rCBF persisted after transection of the cervical sympathetic trunk (n=5). In contrast, stimulation of the lateral portion of PBN (n=5), periventricular gray (n=5) and interestingly, the nucleus locus coeruleus (n=5) failed to elicit similar changes in rCBF. PBNm stimulation also elicited decreases in rCGU (n=4) in 5 out of 9 brain areas, most notably regions of cerebral cortex. The decreases in rCGU (ΔrCGU) were linearly related to the decreases in rCBF (ΔrCBF) according to the equationΔrCBF=2.37 ΔrCGU+2.1 (r=0.72; P<0.001). We conclude that excitation of neural pathways originating in, or passing through, PBNm elicits a widespread reduction in cerebral metabolism and secondarily in blood flow (secondary vasoconstriction). Since projections of the PBNm do not involve the entire cortex, it seems likely that the effect is mediated via inhibition of diffuse cortical projections through a subcortical site.     

Electrical stimulation of cerebellar fastigial nucleus increases cerebral cortical blood flow without change in local metabolism: Evidence for an intrinsic system in brain for primary vasodilation

We sought to determine whether the increase in regional cerebral blood flow (rCBF) elicited by electrical stimulation of the fastigial nucleus of the cerebellum (FN) is secondary to, or independent of, increased local cerebral metabolism (rGMR) in anesthetized (chloralose) paralyzed rats. rCBF and rGMR were determined autoradiographically in separate groups of animals with comparable blood gases and systemmic pressure, by the [¹⁴C]iodoantipyrine and [¹⁴C]2-deoxyglucose methods respectively. In sham-operated controls, rCBF (n = 5) and rGMR (n = 5) were closely related in the 28 brain areas studied (r = 0.733; P < 0.005). During FN stimulation, rCBF (n = 6) increased significantly in 24 of the 28 areas, the greatest increase being in the cerebral cortex (up to 215%). rGMR (n = 9) increased in only 15 areas, so that the correlation between rCBF and rGMR throughout the brain became weaker (r = 0.568; P < 0.005). Where the rCBF increases were the greatest (particularly in the cerebral cortex), rGMR was unchanged. This suggests that the rCBF increase was not a consequence of the increased rGMR. We conclude that neurons originating in or passing through FN may influence local cerebral circulation through a primary cerebral vasodilatation not coupled to metabolism.     

3-Aminobenzamide, a poly (ADP-ribose) synthetase inhibitor, attenuates the acute inflammatory responses and brain injury in experimental Escherichia coli meningitis in the newborn piglet.

The aim of the present study was to evaluate the anti-inflammatory and neuroprotective effects of a poly (ADP-ribose) synthetase inhibitor 3-aminobenzamide during the early phase of experimental bacterial meningitis in the newborn piglet. Meningitis was induced by intracisternal injection of 10(8) colony forming units of Escherichia coli in 100 microl of saline. 3-Aminobenzamide, given 30 mg kg(-1) as a bolus i.v. injection 30 min before induction of meningitis, significantly attenuated the meningitis-induced acute inflammatory responses such as increased cerebrospinal fluid (CSF) lactate concentration, CSF leukocytosis and increased CSF tumor necrosis factor-alpha level. However, meningitis-induced increase in intracranial pressure and decrease in CSF glucose level were not significantly improved. Increased cerebral cortical cell membrane lipid peroxidation products (conjugated dienes) and decreased brain ATP/phosphocreatine levels observed in the meningitis group were also significantly improved with 3-aminobenzamide treatment. However, the improvement of reduced Na+, K+-ATPase activity did not reach a statistical significance (p = 0.06). In summary, 3-aminobenzamide significantly attenuated the acute inflammatory responses and the ensuing brain injury during the early phase of neonatal bacterial meningitis. These findings suggest that poly (ADP-ribose) synthetase inhibitors such as 3-aminobenzamide might be a promising novel anti-inflammatory and neuroprotective adjuvant therapy in neonatal bacterial meningitis.