Effect of a single ethanol administration on the permeability of the hemato-encephalic barrier for 14C-tyrosine, 14C-DOPA and horseradish peroxidase

Single injection of ethanol at a dose of 2 and 4 g/kg has been shown to increase blood-brain barrier penetration for peripherally administered 14C-tyrosine and 14C-DOPA. No changes in blood-brain barrier penetration for horseradish peroxidase has been found. Acute effect of ethanol on blood-brain barrier systems of specific and nonspecific transport is discussed.     

Effect of chronic administration of ethanol on the blood-brain barrier permeability of 14C-tyrosine and horseradish peroxidase in rats

Chronic 10-days oral ethanol administration in doses 8-11 g/kg per day has been shown to increase blood-brain barrier penetration for peripherally administered 14C-tyrosine in Wistar heavy- and light-drinker rats. No changes in BBB permeability for horseradish peroxidase has been found. Chronic effect of ethanol on BBB systems of specific and unspecific transport in rats heavy- and light-drinkers is discussed.     

Blood–Brain Barrier Permeability to Sodium. Modification by Glucose or Insulin?

In order to explore the pathogenetic mechanism underlying the changes in blood-brain barrier sodium transport in experimental diabetes, the effects of hyperglycemia and of hypoinsulinemia were studied in nondiabetic rats. In untreated diabetes, the neocortical blood-brain barrier permeability for sodium decreased by 20% (5.6 +/- 0.7 versus 7.0 +/- 0.8 X 10(5) ml/g/s) as compared to controls. Intravenous infusion of 50% glucose for 2 h was associated with a decrease in the blood-brain barrier permeability to sodium (5.4 +/- 1.2 X 10(5) ml/g/s), whereas rats treated with an inhibitor of insulin-secretion (SMS 201-995, a somatostatin-analogue) had normal sodium permeability (7.3 +/- 2.0 X 10(5) ml/g/s). Acute insulin treatment of diabetic rats normalized the sodium permeability within a few hours as compared to a separate control group (7.7 +/- 1.1 versus 6.9 +/- 1.4 X 10(5) ml/g/s). To elucidate whether the abnormal blood-brain barrier passage is caused by a metabolic effect of glucose or by the concomitant hyperosmolality, rats were made hyperosmolar by intravenous injection of 50% mannitol. Although not statistically significant, blood-brain barrier sodium permeability increased in hyperosmolar rats as compared to the control rats (8.3 +/- 1.0 and 7.0 +/- 1.9 X 10(5) ml/g/s, respectively). It is concluded that either hyperglycemia per se or a glucose metabolite is responsible for the blood-brain barrier abnormality which occurs in diabetes. Further, we suggest that the specific decrease of sodium permeability could be the result of glucose-mediated inhibition of the Na+K+-ATPase localized at the blood-brain barrier.     

Abdominal vagal mediation of the satiety effects of CCK in rats

CCK type 1 (CCK1) receptor antagonists differing in blood-brain barrier permeability were used to test the hypothesis that satiety is mediated in part by CCK action at CCK1 receptors on vagal sensory nerves innervating the small intestine. Devazepide penetrates the blood-brain barrier; A-70104, the dicyclohexylammonium salt of N alpha-3-quinolinoyl-D-Glu-N,N-dipentylamide, does not. At dark onset, non-food-deprived control rats and rats with subdiaphragmatic vagotomies received a bolus injection of devazepide (2.5 micromol/kg i.v.) or a 3-h infusion of A-70104 (3 micromol.kg(-1).h(-1) i.v.) either alone or coadministered with a 2-h intragastric infusion of peptone (0.75 or 1 g/h). Food intake was determined from continuous computer recordings of changes in food bowl weight. In control rats both antagonists stimulated food intake and attenuated the anorexic response to intragastric infusion of peptone. In contrast, only devazepide was effective in stimulating food intake in vagotomized rats. Thus endogenous CCK appears to act both at CCK1 receptors beyond the blood-brain barrier and by a CCK1 receptor-mediated mechanism involving abdominal vagal nerves to inhibit food intake.     

Magnesium sulfate attenuates increased blood-brain barrier permeability during insulin-induced hypoglycemia in rats

Magnesium probably protects brain tissue against the effects of cerebral ischemia, brain injury and stroke through its actions as a calcium antagonist and inhibitor of excitatory amino acids. The effects of magnesium sulfate on cerebrovascular permeability to a dye, Evans blue, were studied during insulin-induced hypoglycemia with hypothermia in rats. Hypoglycemia was induced by an intramuscular injection of insulin. After giving insulin, each animal received MgSO4 (270 mg/kg) ip, followed by a 27 mg/kg dose every 20 min for 2.5 h. Plasma glucose and Mg2+ levels of animals were measured. Magnesium concentrations increased in the serum following MgSO4 administration (6.05+/-0.57 vs. 2.58+/-0.14 mg/dL in the Mg2+ group, and 7.14+/-0.42 vs. 2.78+/-0.06 mg/dL in the insulin + Mg2+ group, P < 0.01). Plasma glucose levels decreased following hypoglycemia (4+/-0.66 vs. 118+/-2.23 mg/dL in the insulin group, and 7+/-1.59 vs. 118+/-4.84 mg/dL in the insulin + Mg2+ group, P < 0.01). Blood-brain barrier permeability to Evans blue considerably increased in hypoglycemic rats (P < 0.01). In contrast, blood-brain barrier permeability to Evans blue was significantly reduced in treatment of hypoglycemic rats with MgSO4 (P < 0.01). These results indicate that Mg2+ greatly reduced the passage of exogenous vascular tracer bound to albumin into the brain during hypoglycemia with hypothermia. Mg2+ could have protective effects on blood-brain barrier permeability against insulin-induced hypoglycemia.     

Damage to the hemato-encephalic barrier during one-time immobilization stress

Intravenous injection of trypan blue followed by treatment of the brain according to the Falc-Hillarp was used for morphological study of the blood-brain barrier in control rats and in animals exposed to the 6.5-hour stress. The density of the blood-brain barrier as regards the macromolecules in control animals was found to be liable to noticeable areal variations. The zones of primary increased barrier permeability were found near the basal surface of the brain. Prolonged single immobilization stress gave rise to destructive changes in the blood-brain barrier in the reticular formations of the midbrain and medulla oblongata. Besides, in control animals, there was a slight increase in permeability of the brain areas marked by the reduced barrier density.     

Effects of peripheral CCK receptor blockade on food intake in rats

Type A cholecystokinin receptor (CCKAR) antagonists differing in blood-brain barrier permeability were used to test the hypothesis that satiety is mediated, in part, by CCK action at CCKARs located peripheral to the blood-brain barrier. At dark onset, non-food-deprived rats received a bolus injection of devazepide (2.5 micromol/kg iv), a 3-h infusion of A-70104 (1 or 3 micromol x kg-1 x h-1 iv), or vehicle either alone or coadministered with a 3-h infusion of CCK-8 (10 nmol x kg-1 x h-1 iv) or a 2-h intragastric infusion of peptone (1 g/h). Food intake was determined from continuous computer recordings of changes in food bowl weight. Devazepide penetrates the blood-brain barrier; A-70104, the dicyclohexylammonium salt of Nalpha-3-quinolinoyl-d-Glu-N,N-dipentylamide (A-65186), does not. CCK-8 inhibited 3-h food intake by more than 50% and both A-70104 and devazepide abolished this response. A-70104 and devazepide stimulated food intake and similarly attenuated the anorexic response to intragastric infusion of peptone. Thus endogenous CCK appears to act, in part, at CCKARs peripheral to the blood-brain barrier to inhibit food intake.     

Effects of peripheral CCK receptor blockade on gastric emptying in rats

Type A CCK receptor (CCKAR) antagonists differing in blood-brain barrier permeability [devazepide penetrates; the dicyclohexylammonium salt of Nalpha-3-quinolinoyl-d-Glu-N,N-dipentylamide (A-70104) does not] were used to test the hypothesis that duodenal nutrient-induced inhibition of gastric emptying is mediated by CCKARs located peripheral to the blood-brain barrier. Rats received A-70104 (700 or 3,000 nmol. kg(-1). h(-1) iv) or devazepide (2.5 micromol/kg iv) and either a 15-min intravenous infusion of CCK-8 (3 nmol. kg(-1). h(-1)) or duodenal infusion of casein, peptone, Intralipid, or maltose. Gastric emptying of saline was measured during the last 5 min of each infusion. A-70104 and devazepide abolished the gastric emptying response to a maximal inhibitory dose of CCK-8. Each of the macronutrients inhibited gastric emptying. A-70104 and devazepide attenuated inhibitory responses to each macronutrient. Intravenous injection of a CCK antibody to immunoneutralize circulating CCK had no effect on peptone or Intralipid-induced responses. Thus endogenous CCK appears to act in part by a paracrine or neurocrine mechanism at CCKARs peripheral to the blood-brain barrier to inhibit gastric emptying.     

Production and effects of platelet-activating factor in the rat brain

The synthesis of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in rat brain was evaluated. Extracted PAF was characterized using standard HPLC and TLC techniques, and by correlation of its bioactivity with the acetylation state of the 2-position of the molecule. PAF was quantified by bioassay, its ability to cause [3H]serotonin release from washed rabbit platelets. The low basal level of PAF (0.25 +/- 0.15 pmol/g wet wt., mean +/- S.E.) in the brain of the intact rat was greatly increased by intraperitoneal injection of the chemoconvulsant drugs picrotoxin or bicuculline, to levels of 10.68 +/- 2.18 and 4.97 +/- 0.75 pmol/g wet wt., respectively. Electroconvulsion also increased brain PAF, to 1.76 +/- 0.30 pmol/g wet wt. Equivalent experiments using bicuculline in the isolated perfused rat brain yielded qualitatively similar results, indicating that the production of PAF in the brain is independent of systemic metabolism. When a 32P-labeled nerve-ending (synaptosome) preparation from rat brain was challenged with synthetic PAF (denoted AGEPC) at 0.1 nM concentration, responses were observed consistent with accelerated turnover of polyphosphoinositides. AGEPC also caused an increase in the Na+-Ca2+ exchange of synaptic membrane vesicles. Furthermore, AGEPC infused into the vasculature of the isolated perfused rat brain caused changes consistent with an increase in blood-brain barrier permeability, although AGEPC did not itself significantly penetrate the blood-brain barrier. It is concluded from these studies that PAF is synthesized within the rat brain in response to convulsant stimuli and that one of its effects is to accelerate synaptic polyphosphoinositide turnover. In addition, circulating PAF can influence blood-brain barrier permeability without itself penetrating the blood-brain barrier.     

Estrogen attenuates VEGF-initiated blood-retina barrier breakdown in male rats

17β-Estradiol has been demonstrated to protect blood-brain barrier from disruption and attenuate brain injury in various conditions. The aim of this study was to investigate the effect of 17β-estradiol on the blood-retina barrier (BRB) breakdown induced by intravitreous injection of vascular endothelial growth factor (VEGF), a significant mediator of vascular permeability. Intravitreous injection of VEGF was performed to initiate BRB breakdown in male rats with PBS in the contralateral eye as control. 2 doses of 17β-estradiol and vehicle control were given to 3 groups of rats. The integrity of the BRB was quantified by Evans blue technique and assessed by fluorescent dyes in retinal sections and wholemounts. BRB breakdown was achieved by VEGF as retinal vascular permeability was increased compared with control eyes (14.66±4.09 vs. 4.94±1.20 μl/g/h, p<0.01). Vascular permeability in the 2 groups treated with 17β-estradiol was reduced compared with control (14.66±4.09 vs. 10.26±3.67 vs. 7.37±2.22 μl/g/h, p<0.01). Rhodamine isothiocyanate (RhIC) extravasation in retinal sections and Evans blue-albumin complex leakage in retinal wholemounts were also decreased in the 2 treatment groups. These results suggest that 17β-estradiol attenuates BRB breakdown induced by VEGF in male rats, which may provide a new role of 17β-estradiol in ocular diseases.     

Interaction of ethanol and microwaves on the blood-brain barrier of rats

The combined effects of ethanol and microwaves on the permeation of Evans blue dye through the mammalian blood-brain barrier was studied in male Wistar rats. Anesthetized rats were infused through a cannula in the left femoral vein with 0.1, 0.3, 0.5 or 0.7 grams of absolute ethanol per kilogram of body mass. A control group was given 0.7 g/kg of isotonic saline. The left hemisphere of the brain was irradiated by 3.15-GHz microwave energy at 3.0 W/cm2 rms for 15 min. The rat's rectal temperature was maintained at 37.0 degrees C. Immediately after irradiation, 2% Evans blue dye in saline (2.0 ml/kg body mass) was injected through the cannula. The results show that as the quantity of alcohol was increased, the degree of staining was decreased or eliminated. The temperature of the irradiated area of the brain increased for the first 4 to 5 minutes of irradiation and then stabilized for the remainder of the irradiation period. The steady-state temperature was highest in animals receiving saline or the smallest dose of alcohol. As the quantity of alcohol was increased, the steady-state temperature was reduced. These results indicate that ethanol inhibits microwave-induced permeation of the blood-brain barrier through reduced heating of the brain.     

Ineffectiveness of dimethyl sulfoxide in altering the permeability of the blood-brain barrier

The failure of DMSO to alter the permeability of the blood-brain barrier has been studied using several polar, nonpolar, hydrophilic, and hydrophobic compounds labeled with selected radioactive isotopes. The metabolites were Na¹³¹I, ¹³¹I-iodinated human serum albumin, l-[³⁵S]methionine, dl-[ring-2-¹⁴C]tryptophan, [U-¹⁴C]sucrose, d-[6-¹⁴C]glucose, and [4-¹⁴C]cholesterol. DMSO was injected intraperitoneally at a dose of 1 g/kg followed after 1 hr by the intracarotid injection of the labeled metabolite. An appropriate volume of saline was substituted for the DMSO in control animals. The brain and one gastrocnemius muscle were removed at selected intervals up to 30 min and the uptake into these tissues was measured.It was found that the permeability of neither the blood-brain barrier nor skeletal muscle was altered by this concentration of DMSO. This dose of DMSO, administered intravenously, frequently caused death and, intraperitoneally, caused muscular twitching, lethargy, and hematuria.     

Effects of ethanol infusion on foetal EEG and breathing movements

Ethanol (0.3 g/kg and 0.5 g/kg administered over 2 hours) was infused intravenously into 15 chronically instrumented pregnant ewes between 128 to 135 days of gestation (0.85 to 0.92 gestation time, term 147 days). Brainstem dissection above the pons was made in 7 foetuses. Foetal breathing movements were suppressed for 7 hours following a 30 ml ethanol infusion. Low voltage foetal electrocortical activity was suppressed or replaced by an intermediate voltage electrocortical activity for 5 and 3 hours following the 60 ml and 30 ml ethanol infusions, respectively. In brainstem dissected foetuses the effects of ethanol infusion on the foetal EEG were similar. Foetal blood gases and pH were not altered. These data suggest that ethanol moves across the foetal blood-brain barrier and suppresses foetal breathing movements by a direct central mechanism.     

双氟沙星对异育银鲫血脑屏障渗透性及消除规律

以异育银鲫（Carassais auratus gibebio）为研究对象,采用组织匀浆法和高效液相色谱法,研究了双氟沙星（Difloxacin,DIF）通过异育银鲫血脑屏障情况,并比较分析了大脑和外周组织中DIF消除差异。结果显示,根据DIF 96h 半数致死剂量（2840 mg/kg b.W）给药后,第96h时异育银鲫大脑组织匀浆中DIF的含量为（10.490.35） g/g;同时在临床推荐用药剂量（20 mg/kg）给药后的15个时间点（0960h）上均能从大脑组织匀浆中检测出DIF。上述结果表明DIF能渗透通过血脑屏障而进入异育银鲫大脑组织。另外,在大脑和外周组织消除过程上,以大脑组织中的DIF消除过程最为平缓（按照20 mg/kg给药）。到试验第960h,大脑组织中DIF含量最高,为（0.3920.007） g/g,且大脑中的消除半衰期最长,为1157.713h。因此,异育银鲫大脑组织可作为DIF药物残留分析的靶组织。另根据欧盟关于食品中DIF最大残留限量（MRL）之规定,实验条件下DIF休药期至少为25d。结果为研究鱼类血脑屏障作用,DIF神经毒性及其在水产养殖上的临床应用提供了参考。       

Modulation of cerebral microvascular permeability by endothelial nicotinic acetylcholine receptors

Nicotine increases the permeability of the blood-brain barrier in vivo. This implies a possible role for nicotinic acetylcholine receptors in the regulation of cerebral microvascular permeability. Expression of nicotinic acetylcholine receptor subunits in cerebral microvessels was investigated with immunofluorescence microscopy. Positive immunoreactivity was found for receptor subunits alpha3, alpha5, alpha7, and beta2, but not subunits alpha4, beta3, or beta4. Blood-brain barrier permeability was assessed via in situ brain perfusion with [14C]sucrose. Nicotine increased the rate of sucrose entry into the brain from 0.3 +/- 0.1 to 1.1 +/- 0.2 microl.g(-1).min(-1), as previously described. This nicotine-induced increase in blood-brain barrier permeability was significantly attenuated by both the blood-brain barrier-permeant nicotinic antagonist mecamylamine and the blood-brain barrier-impermeant nicotinic antagonist hexamethonium to 0.5 +/- 0.2 and 0.3 +/- 0.2 microl.g(-1).min(-1), respectively. These data suggest that nicotinic acetylcholine receptors expressed on the cerebral microvascular endothelium mediate nicotine-induced changes in blood-brain barrier permeability.     

Altered blood-brain barrier permeability and its effect on the distribution of Evans blue and sodium fluorescein in the rat brain applied by intracarotid injection

The aim was to study the blood-brain permeability according to the distribution in the rat brain of Evans blue (EB) and sodium fluorescein (NaFl) administered by an intracarotid injection. Eighteen animals were divided into six groups according to the state of the blood-brain barrier (BBB) at the moment when the dyes were being applied. In the first two groups, the BBB was intact, in groups 3 and 4 the barrier had been opened osmotically prior to the application of the dyes, and in groups 5 and 6 a cellular edema was induced by hyperhydration before administration of the dyes. The intracellular and extracellular distribution of the dyes was studied by fluorescence microscopy. The histological picture thus represented the morphological correlate of the way BBB permeability had been changed before the application of the dyes.     

TNFalpha-induced cyclooxygenase 2 not only increases the vasopermeability of blood-brain barrier but also enhances the neutrophil survival in Escherichia coli-induced brain inflammation.

In Escherichia coli-induced brain inflammation, cyclooxygenase-2 was induced not only on brain arterioles at 3 h, but also on infiltrating neutrophils at 9 h post-intracerebral injection. Intravenous injection of E. coli or recombinant TNFalpha also induced cyclooxygenase-2 expression on arterioles. Cyclooxygenase-2 and TNFalpha were co-localized on the arterioles as well as the infiltrating neutrophils by serial-section staining, indicating that cyclooxygenase-2 was induced by TNFalpha. NS398 (a cyclooxygenase-2 selective inhibitor) not only inhibited the increase of blood-brain barrier permeability, but also enhanced the apoptosis of the infiltrating neutrophils after E. coli stimulation. This suggests that TNFalpha-stimulated cyclooxygenase-2 induction play an important role on E. coli-induced brain inflammation. Its inhibition would help the resolution of neutrophil-mediated brain inflammation.     

Permeation of blood-borne IL15 across the blood-brain barrier and the effect of LPS

Interleukin15 (IL 15) is a proinflammatory cytokine with elevated concentrations in autoimmune diseases involving the periphery (e.g. rheumatoid arthritis) and CNS (e.g. multiple sclerosis). Its interactions with the blood-brain barrier (BBB) were studied in normal and lipopolysaccharide (LPS)-treated mice. ¹²⁵I-IL15 remained intact for at least 10 min after i.v. injection and reached CNS parenchyma with regional differences between brain and spinal cord. Both in vivo and in situ brain perfusion of ¹²⁵I-IL15 showed that its permeation of the BBB was non-saturable. LPS induced a significant increase of IL15 uptake by the brain and spinal cord, partly related to a higher general permeability of the BBB. The results suggest that the BBB is an interface for blood-borne IL15 to interact with the CNS in the basal state and during inflammation.     

Methyl ester of prostaglandin D2 as a delivery system of prostaglandin D2 into brain

We examined the permeability of the blood-brain barrier to a methyl ester of prostaglandin D2 and the brain uptake was assessed by radioactivity measurements and radioimmunoassay. When the methyl ester (1 mg/kg) was administered intravenously into mice, it was rapidly taken up by the brain (189 ng/g brain at 30 s) and disappeared from the brain with a half-life of 9 s, whereas it was hardly detectable in the blood. The methyl ester transported into the brain was hydrolyzed to prostaglandin D2 and the time course of prostaglandin D2 levels showed an accumulation phase with a peak at 30 s. The total amount of prostaglandin D2 and its methyl ester was 279 ng/g brain at 30 s after injection, corresponding to 0.5% of the administered dose and being 6-times higher than that after prostaglandin D2 injection. The advantage of the methyl ester over prostaglandin D2 for brain uptake was observed at doses higher than 0.2 mg/kg where the methyl ester which escaped from hydrolysis in the blood was taken up more effectively than prostaglandin D2. In in vitro experiments, the esterase activity on the methyl ester was shown to be 20-times greater in the plasma than in the brain homogenate. These results indicate that the esterification of prostaglandin D2 may serve as a good system for the delivery of prostaglandin D2 into the brain.     

Effects of postnatal dexamethasone on blood-brain barrier permeability and brain water content in newborn lambs

We showed that antenatal corticosteroids reduced blood-brain barrier permeability in fetuses at 60 and 80%, but not 90% of gestation, and decreased brain water content in fetuses. Our objective was to examine the effects of postnatal corticosteroids on regional blood-brain barrier permeability and brain water content in newborn lambs. Three dexamethasone treatment groups were studied in 3- to 5-day-old lambs. A 0.01 mg/kg dose was selected to estimate the amount of dexamethasone that might have reached fetuses via antenatal treatment of ewes in our previous studies. The other doses (0.25 and 0.5 mg/kg) were chosen to approximate those used clinically to treat infants with bronchopulmonary dysplasia. Lambs were randomly assigned to receive four intramuscular injections of dexamethasone or placebo given 12 h apart on days 3 and 4 of age. Blood-brain barrier function was measured with the blood-to-brain transfer constant (K(i)) to alpha-aminoisobutyric acid, brain plasma volume was measured with polyethylene glycol for the calculation of K(i,) and brain water was measured by wet-to-dry tissue weights. Postnatal treatment with corticosteroids did not reduce barrier permeability in newborn lambs. Brain blood volume was higher in the 0.25 and 0.5 mg/kg dose dexamethasone groups than in the placebo group. Brain water content did not differ among the groups. We conclude that postnatal treatment with corticosteroids did not reduce regional blood-brain barrier permeability or brain water content but increased the brain plasma volume in newborn lambs. These findings are consistent with our previous work indicating that barrier permeability is responsive to corticosteroids at 60 and 80% of gestation and brain water regulation at 60% of gestation, but not in near-term fetuses or newborn lambs.