Ageing influences haloperidol-induced changes in the permeability of the blood-brain barrier in the rat.

The effect of the dopaminergic antagonist haloperidol on the permeability of the blood-brain barrier (BBB) to [14C]alpha-aminoisobutyric acid was studied in 10-12- and 28-30-week old rats. Following the intraperitoneal injection of haloperidol (1 mg kg-1), an increase in the permeability of the BBB, with respect to younger animals, was observed within the occipital cortex, striatum, hippocampus and hypothalamus in the older rats. No correlation was found between haloperidol-induced changes and age-related differences in the permeability of the BBB. Such age-associated increase in the vulnerability of the BBB when challenged with haloperidol might be related to a deterioration of the dopaminergic control of cerebrovascular permeability.     

Olanzapine, but not haloperidol, enhances PSA-NCAM immunoreactivity in rat prefrontal cortex

Repeated antipsychotic treatment may produce adaptive changes ranging from cytoarchitectural rearrangements to synaptic modifications that might contribute to clinical improvement. We performed a prolonged treatment (2 wk) with the first-generation antipsychotic (FGA) haloperidol (1 mg/kg) and the second-generation antipsychotic (SGA) olanzapine (2 mg/kg twice daily) and analysed the expression of the polysialylated form of neural cell adhesion molecule (PSA-NCAM) in rat hippocampus and prefrontal cortex via immunohistochemistry. We found a regional- and drug-selective increase of PSA-NCAM expression in prefrontal cortex of olanzapine-treated rats with no effects in hippocampus; conversely, haloperidol did not produce a change in either brain region. Our findings reveal a possible role for PSA-NCAM in the mechanism of action of the SGA olanzapine adding complexity as well as specificity to the molecular changes set in motion by this drug.     

An irreversible anticholinesterase probe for studying increased permeability of the rat blood-brain barrier

Phospholine iodide, a potent anticholinesterase quarternary salt, was found to be a useful probe in studying changes in blood-brain barrier permeability in rats exposed to various insults. Based on brain acetylcholinesterase (AChE) activity measurements, it was concluded that phospholine iodide, injected i.m. at a dose of 65 μg/kg, inhibited brain AChE activity in three different regions, provided that the blood-brain barrier integrity was damaged by exposing rats to osmotic shock (glycerol), convulsions (metrazole), or γ-irradiation. Enzyme activity was not inhibited in sham-handled controls treated with phospholine iodide. Possible complication from blood contamination during brain processing was ruled out. It was suggested that phospholine iodide can be used as a semi-quantitative probe to detect an increase in blood-brain barrier permeability by the establishment of a unidirectional flow of the marker from brain capillaries into extravascular spaces and the phosphorylation of brain AChE. Based on the stability of the inhibited AChE and its 100 per cent reactivability in the presence of specific nucleophiles, this probe may be useful for the study of blood-brain barrier resistance in conscious, freely moving rats exposed to various stresses.     

Clozapine, but not haloperidol, increases neuropeptide Y neuronal expression in the rat hypothalamus

Many atypical antipsychotic drugs, such as clozapine, can induce significant weight gain which can have serious implications for drug compliance and morbidity. Food intake and weight gain are regulated primarily by the hypothalamus; the arcuate nucleus (ARC) of the hypothalamus is the region initially mediating the effects of circulating hormones on food intake. Neuropeptide Y (NPY) is an important hypothalamic peptide involved in body weight regulation. Immunohistochemical staining of NPY in the ARC was carried out in male Sprague-Dawley rats treated with haloperidol (1.5 mg/kg, i.p.) or clozapine (25 mg/kg, i.p.) for 3 weeks. Clozapine, but not haloperidol, produced an increase in NPY immunoreactivity in the ARC, suggesting that effects on NPY may be involved in increases in body weight following clozapine treatment.     

动脉内输注高渗性甘露醇改变大鼠血脑屏障对甲氨喋呤的通透性(英文)

目的:研究高渗性溶液开放血脑屏障能否提高甲氨喋呤在皮层内的含量及这一开放过程的时程变化。方法:1)大鼠颈内动脉注射甘露醇,10分钟后分别从股静脉及颈内动脉给予甲氨喋呤,1小时后测定脑皮层内浓度。2)大鼠颈内动脉注射甘露醇,分别在不同时间间隔给予甲氨喋呤,给药1小时后测定脑皮层内药物浓度及脑皮层密度。结果:给予甘露醇后,静注甲氨喋呤和颈内动脉注射甲氨喋呤可以使相应侧脑皮层内浓度分别提高2.54倍和3.41倍。此作用在给予甘露醇10分钟后达到最大,6小时后完全消失;同时并不伴随明显的皮层密度改变。结论:甘露醇可逆性地开放血脑屏障,提高甲氨喋呤在脑皮层内的浓度,同时不会造成明显的脑损伤。     

Seizure-induced changes in the permeability of the blood-brain barrier following administration of anticholinesterase drugs to rats

Powerful inhibitors of acetylcholinesterase (phospholine iodide, paraoxon, and Soman) were used either separately or in combination with an anesthetizing drug (nembutal), an acetylcholine antagonist (atropine sulfate), or a convulsive drug (metrazole) to study the resistance of the blood-brain barrier to their effects. On the basis of measurements of acetylcholinesterase inhibition in rat brain stem and corpus striatum, it was concluded that these anticholinesterase drugs increased the permeability of the blood-brain barrier, provided that seizures were manifested shortly after administration of these drugs. Rats that were treated prophylactically with either nembutal or atropine sulfate did not convulse and, consequently, damage to the blood-brain barrier integrity was reduced significantly, despite a high degree of acetylcholinesterase and butyrylcholinesterase inhibition. It is suggested that anticholinesterase drugs enhance brain AChE inhibition by inducing strong convulsions and, thereby, increase their own penetration through the blood-brain barrier. It does not appear likely that acetyl- or butyrylcholinesterase located in the walls of the brain capillaries is involved in maintenance of the blood-brain barrier.     

Sex-dependent changes in blood-brain barrier permeability in epileptic rats following acute hyperosmotic exposure.

Osmotic and ionic balance in the central nervous system is especially regulated by solutes and water transport across the blood-brain barrier. The aim of this study was to investigate the effect of systemic hyperosmolarity on the blood-brain barrier permeability in both sexes after experimentally induced seizures. Eight groups of rats were studied: Group I: female control; Group II: male control; Group III: hyperosmotic female; Group IV: hyperosmotic male; Group V: non-hyperosmotic female + seizure; Group VI: non-hyperosmotic male + seizure; Group VII: hyperosmotic female + seizure; Group VIII: hyperosmotic male + seizure. In female rats with pentylenetetrazol-induced seizures, the extravasation of Evans-blue was greater in the brains of hyperosmotic animals than that in normal rats (P < 0.02). However, in male rats, the extravasation of Evans-blue was similar in the brains of hyperosmotic male rats and normal rats after seizure. Our results concluded that hyperosmotic female rats were shown to have a large increase in blood-brain barrier permeability in comparison to hyperosmotic male rats after pentylenetetrazol-induced seizures.     

Clozapine, but not haloperidol, increases brain concentrations of neuroactive steroids in the rat.

The extrapyramidal side effects of typical antipsychotics, which are induced to a markedly reduced extent by clozapine, have been linked to a dysfunction of central gamma-aminobutyric acid (GABA)-mediated neurotransmission. The effects of clozapine on the brain concentrations of 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone, AP) and 3alpha,21-dihydroxy-5alpha-pregnan-20-one (allotetrahydrodeoxycorticosterone, THDOC), two potent and endogenous positive allosteric modulators of GABA-mediated chloride current intensities at GABA(A) receptors, were compared with those of the typical antipsychotic haloperidol. A single administration of clozapine (1.25-20 mg/kg, IP), but not of haloperidol (0.1 or 0.5 mg/kg, IP), induced dose- and time-dependent increases in the concentrations of progesterone, AP, and THDOC in the cerebral cortex and striatum of rats. Clozapine (at 10 mg/kg, but not at lower doses) also increased the concentrations of these steroids as well as that of corticosterone in plasma in intact rats, but failed to increase the cortical concentrations of AP and THDOC in adrenalectomized-orchidectomized rats. An acute challenge with clozapine (10 mg/kg), administered 48 h after the termination of daily treatment with the same dose for 19 days, still increased the cortical concentrations of progesterone, AP, and THDOC. These results suggest that the clozapine-induced increases in neuroactive steroid concentrations in the brain may contribute to the atypical pharmacological profile of this antipsychotic drug.     

Debilitating stresses do not increase blood-brain barrier permeability: Lack of the involvement of corticosteroids

The involvement of corticosteroids in stress-induced change in blood–brain barrier (BBB) permeability was investigated. Mice were adrenalectomized and administered with pyridostigmine bromide (PB) or Evan's blue, markers of BBB penetration, followed by 18-h cold-restraint stress (CRS). Rats were administered with mifepristone, a corticosteroid receptor blocker, and the markers, followed by 4-h water immersion-restraint stress (WIRS). Separately, soman was administered to induce seizures-mediated BBB opening. CRS did not induce PB and Evan's blue penetration, which were not affected by adrenalectomy. Also, the markers were not detected in the brain of rats subjected to WIRS, regardless of the treatment of mifepristone. In comparison, 1-h epileptic seizures increased the penetration of Evan's blue by 875%. The results suggest that in contrast to seizure-related BBB opening, profound stresses do not practically increase the BBB permeability, and that corticosteroids are not involved in the stress-induced BBB penetration of charged chemicals and albumin–dye complex.     

Effect of alcohols on the permeability of blood-brain barrier

Effect of alcohols on the permeability of blood-brain barrier was studied in anaesthetised dogs using sodium fluorescein as circulant. Entry of sodium fluorescein in the cerebrospinal fluid (CSF) was measured spectrophotofluorometrically. Methyl, ethyl, propyl and butyl alcohols were used in the study. Methyl alcohol did not increase the entry of sodium fluorescein in CSF compared to control. However, ethyl, propyl and butyl alcohols significantly increased the entry of sodium fluorescein. The increase was dependent upon the length of alkyl chain of alcohols. Longer was the aliphatic chain more marked was the effect. The increase in permeability was also dependent upon the concentration of the alcohol. Thus 90% ethyl alcohol was more effective than 30% and this effect was concentration-dependent. The increase in permeability of blood-brain barrier could be correlated to the lipid solubility of alcohols.     

Calcium antagonists: effects on cerebral blood flow and blood-brain barrier permeability in the rat

1 Because they affect isolated cerebral arteries, some calcium antagonists have been studied on the intact cerebral circulation of the rat.

2 Global cerebral blood flow (¹³³Xe clearance technique) was measured in anaesthetized rats. Neither perhexiline (0.1 μg/kg to 1.0 mg/kg, i.v.) nor diltiazem (0.06-0.6 mg/kg, i.v.) had any significant effect on resting cerebral blood flow when measured 5 min after each dose. A high dose of nifedipine (1.0 mg/kg, i.v.) was administered during induced hypocapnia. Nifedipine failed to modify the hypocapnic vasoconstriction of the cerebral vasculature when compared to vehicle-treated rats.

3 The possibility of discrete changes in regional cerebral blood flow was investigated. Local cerebral blood flow was measured in a number of brain regions by the [¹⁴C]-ethanol technique 15 min after the administration of nifedipine (20 or 100 μg/kg, i.v.). Nifedipine had no apparent effect on regional blood flow in the rat brain.

4 Acute arterial hypertension increases protein leakage into the brain, a phenomenon susceptible to drugs that act on endothelial pinocytosis which is known to be calcium-dependent. The increase in protein extravasation, induced by the intravenous administration of either angiotensin II or adrenaline, was unchanged in rats previously treated with either nimodipine (20 μg/kg, i.v.) or nifedipine (50 μg/kg, i.v.) when dissolved in ethanol alone. However, nifedipine (20 μg/kg, i.v.) when dissolved in a solution of polyethylene glycol and ethanol further enhanced the hypertension-induced increase in brain albumin permeability.

5 In conclusion, we have been unable to demonstrate any apparent effects of various calcium antagonists on the intact cerebral circulation of the rat, despite the number of different experimental models used.

     

Histamine- and acetylcholine-induced changes in the permeability of the blood-brain barrier of normotensive and spontaneously hypertensive rats

Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats were given saline, histamine (1.25, 2.5 or 5.0 micrograms/kg) or acetylcholine (1.0 or 2.0 micrograms/kg). Both agents caused a dose-dependent decrease in blood pressure which was greater in the spontaneously hypertensive animals. The permeability of the blood brain-barrier was measured with 131I-labelled serum albumin (RISA) or with 99mTc-sodium pertechnetate (TcO4-). The lowest dose of histamine caused a decrease in permeability of the blood-brain barrier to serum albumin in normotensive rats and acetylcholine caused an increase. Only the largest dose of histamine increased the permeability of the blood-brain barrier to serum albumin in spontaneously hypertensive rats. All doses of histamine and acetylcholine increased the permeability of the blood-brain barrier to sodium per technetate in nomotensive rats and the two lower doses of histamine increased the permeability in spontaneously hypertensive animals. This provides another example of the dissociation of change in the systemic blood pressure and change in the permeability of the blood-brain barrier.     

Methods to assess drug permeability across the blood-brain barrier

Much research has focussed on the development of novel therapeutic agents to target various central nervous system disorders, however less attention has been given to determining the potential of such agents to permeate the blood-brain barrier (BBB), a factor that will ultimately govern the effectiveness of these agents in man. In order to assess the potential for novel compounds to permeate the BBB, various in-vitro, in-vivo and in-silico methods may be employed. Although in-vitro models (such as primary cell culture and immortalized cell lines) are useful as a screening method and can appropriately rank compounds in order of BBB permeability, they often correlate poorly to in-vivo brain uptake due to down-regulation of some BBB-specific transporters. In-vivo models (such as the internal carotid artery single injection or perfusion, intravenous bolus injection, brain efflux index and intracerebral microdialysis) provide more accurate information regarding brain uptake, and these can be complemented with novel imaging techniques (such as magnetic resonance imaging and positron emission tomography), although such methods are not suited to high-throughput permeability assessment. This paper reviews current methods used for assessing BBB permeability and highlights the particular advantages and disadvantages associated with each method, with a particular focus on methods suitable for moderate- to high-throughput screening.     

纳米氧化铝对血脑屏障通透性影响的体外研究

目的建立体外血脑屏障模型,评价纳米氧化铝对血脑屏障通透性的影响。方法粒度仪测定纳米氧化铝粒径及电位,透射电子显微镜观察纳米氧化铝形态与尺寸。从新生1～3 d Wistar鼠取大脑皮质分别原代培养脑微血管内皮细胞和星形胶质细胞,并进行免疫组化鉴定。应用Transwell进行两种细胞共培养建立体外血脑屏障模型,并对模型的有效性进行鉴定。以125、250和500μmol/L的50 nm氧化铝对血脑屏障模型进行染毒,比较染毒前后血脑屏障模型对芦丁通透性变化。以500μmol/L纳米氧化铝对血脑屏障模型进行染毒,分别比较0、2、4、6和8 h不同染毒时间对血脑屏障通透性的改变。结果芦丁吸光值检测显示:与0μmol/L纳米氧化铝组相比,125μmol/L组差异无统计学意义,250和500μmol/L组血脑屏障通透性均明显增加(P<0.05)。与0 h组相比,2、4、6和8 h组血脑屏障通透性均明显增加(P<0.05)。结论体外血脑屏障模型实验研究结果显示,纳米氧化铝可以损伤血脑屏障,引起血脑屏障通透性增加。     

Ethanol enhancement of blood-brain barrier permeability to catecholamines in chicks

The effect of ethanol (EtOH) on permeability of the blood-brain barrier (BBB) to parenteral catecholamines was investigated in neonate chicks. Animals simulataneously administered EtOH, 2 g/kg, and norepinephrine (NE), 5 mg/kg, or epinephrine (E), 5 mg/kg, entered a roosting state which was more pronounced than that observed after either amine alone. Roosting chicks were killed 2 min after NE + EtOH and 10 min after E + EtOH for whole brain amine analysis. NE + EtOH treatment resulted in a 220% increase in whole brain NE over controls receiving this amine alone, whereas E + EtOH produced a 29% increase in brain E. EtOH alone did not alter endogenous levels of either amine in brain. Results indicate that EtOH, a solvent whose solubility characteristics allow it to penetrate easily both aqueous and lipoid membrane components, facilitates entry of E and NE into the brain of the neonate chick across an imperfect BBB present at hatching.     

Enhancement of blood-brain barrier permeability by sodium caprate.

We examined the effect of sodium caprate on the integrity of the tight junctions of brain capillary endothelial cells, using a modified in-situ brain perfusion technique. Model hydrophilic compounds used were [3H]mannitol, [14C]sucrose, [3H]PEG900, [3H]PEG4000, FITC-dextran 4000, FITC-dextran 20000 and FITC-dextran 70000. The brain distribution volume of [14C]sucrose was significantly increased by sodium caprate in a concentration-dependent manner. The effective minimum concentration was 10mM. Furthermore, the effects of sodium caprate on the distribution volumes of hydrophilic compounds, [3H]mannitol, [14C]sucrose, [3H]PEG900, [3H]PEG4000, FITC-dextran 4000, FITC-dextran 20000 and FITC-dextran 70000, showed a molecular weight dependence. A plot of apparent permeation clearance against diffusion coefficient values suggested that 20 mM sodium caprate induced pores so large that the above compounds could pass through the blood-brain barrier with negligible friction within the pore. Our results showed that intracarotid sodium caprate perfusion could enhance the permeation of hydrophilic compounds through the blood-brain barrier.     

大鼠放射性脑损伤所致血脑屏障通透性改变与EBA 及 VEGF 表达的相关性研究

摘要： 目的 探究脑皮质内皮屏障抗原 （EBA） 及血管内皮生长因子 （VEGF） 在放射性血脑屏障损害条件下的动态变化规律, 为临床提供参考。方法 使用随机数字表法将 48 只清洁级雄性 SD 大鼠分为对照组和放射性脑损伤后 7、 14 和 28 d 4 组, 每组 12 只。采用 X 线电子计算机断层扫描设备制备大鼠放射性脑损伤模型。大鼠按照 3 mL/kg的剂量尾静脉注射 3%伊文思蓝 （EB）, 开颅并暴露脑皮质血管, 放于微循环显微镜下观察 EB 渗出情况, 并借助微循环显微成像系统评估血脑屏障通透性; 使用免疫组化染色的方法来检测各组大鼠脑皮质 EBA 和 VEGF 的表达。结果 与对照组相比, 损伤组大鼠脑皮质微血管 EB 外渗量和 VEGF 的表达水平于伤后 7、 14、 28 d 均有不同程度升高（均 P＜0.05）, 从伤后 7 d 至 28 d 逐渐降低, 损伤各亚组之间差异均有统计学意义（均 P＜0.05）, 二者呈正相关（r=0.898, P < 0.001）; EBA 表达水平于伤后各个时间点均下降 （均 P＜0.05）, 从伤后 7 d 至 28 d 逐渐升高, 损伤各亚组之间差异均有统计学意义 （均 P＜0.05）, 与 EB 外渗量呈负相关 （r=-0.866, P < 0.001）。结论 大鼠放射性脑损伤后血脑屏障通透性增加与 EBA 表达减少、 VEGF 表达增加具有重要关联性。     

Aluminum alters the permeability of the blood-brain barrier to some non-peptides

The effect of aluminum administered intraperitoneally (i.p.) on the levels of peripherally injected 99mTc labelled red blood cells in brain and on the penetration of the blood-brain barrier by radioiodinated serum albumin (RISA), thyroxine, iodide, cortisol, N-Tyr-delta sleep-inducing peptide (N-Tyr-DSIP), growth hormone, thyroid stimulating hormone (TSH), prolactin and human and rat luteinizing hormone was examined. Treatment with aluminum did not alter the brain/blood ratio for either 99mTc red blood cells or RISA, although it did increase the blood levels of RISA. These results show that aluminum caused a contraction in the volume of plasma without altering the vascular space of the brain, disrupting the blood-brain barrier, or increasing the "leakiness" of the blood-brain barrier. Aluminum enhanced the permeability of the blood-brain barrier to labelled prolactin, thyroxine, cortisol, growth hormone, N-Tyr-DSIP and rat luteinizing hormone, but not to labelled TSH, iodide, or human luteinizing hormone, a substance with an octanol coefficient markedly different from that of luteinizing hormone from the rat. Incubation of the peptide with aluminum before injection did not increase penetration, demonstrating that aluminum did not increase the permeability of the blood-brain barrier by acting directly on the peptide. Aluminum, administered intraperitoneally, increased the accuracy of lipophilicity as a predictor of penetration of the blood-brain barrier, but the greatest increase in penetration was seen with thyroxine, a substance which crosses the blood-brain barrier by carrier-mediated transport.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of P-glycoprotein inhibition in the rat blood-brain barrier

This article describes the experimental set-up and pharmacokinetic modeling of P-glycoprotein function in the rat blood-brain barrier using [(11)C]verapamil as the substrate and cyclosporin A as an inhibitor of P-gp. [(11)C]verapamil was administered to rats as an i.v. bolus dose followed by graded infusions to obtain steady-state concentrations in the brain during 70 min. CsA was administered as a bolus followed by a constant infusion 20 min after the start of the [(11)C]verapamil infusion. The brain uptake of [(11)C]verapamil over 2 h was portrayed in a sequence of PET scans in parallel with measurement of [(11)C]verapamil concentrations in blood and plasma and CsA concentrations in blood. Mixed effects modeling in NONMEM was used to build a pharmacokinetic model of CsA-induced P-gp inhibition. The brain pharmacokinetics of [(11)C]verapamil was well described by a two-compartment model. The effect of CsA on the uptake of [(11)C]verapamil in the brain was best described by an inhibitory indirect effect model with an effect on the transport of [(11)C]verapamil out of the brain. The CsA concentration required to obtain 50% of the maximal inhibition was 4.9 microg/mL (4.1 microM). The model parameters indicated that 93% of the outward transport of [(11)C]verapamil was P-gp mediated.