Cysteinyl leukotriene receptor 1 is involved in N-methyl-D-aspartate-mediated neuronal injury in mice

AIM: To determine whether cysteinyl leukotriene receptor 1 (CysLT1 receptor) is involved in N-methyl-D-aspartate (NMDA)-induced excitotoxic injury in the mouse brain. METHODS: Brain injury was induced by NMDA microinjection (50-150 nmol in 0.5 microL) into the cerebral cortex. The changes in CysLT1 receptor expression 24 h after NMDA injection and the effects of a CysLT1 receptor antagonist, pranlukast (0.01 and 0.1 mg/kg), an NMDA receptor antagonist, ketamine (30 mg/kg), and an antioxidant, edaravone (9 mg/kg) were observed. RESULTS: In the NMDA-injured brain, the CysLT1 receptor mRNA, and protein expression were upregulated, and the receptor was mainly localized in the neurons and not in the astrocytes. Pranlukast, ketamine and edaravone decreased NMDA-induced injury; pranlukast (0.1 mg/kg) and ketamine inhibited the upregulated expression of the CysLT1 receptor. CONCLUSION: CysLT1 receptor expression in neurons is upregulated after NMDA injection, and NMDA-induced responses are inhibited by CysLT1 receptor antagonists, indicating that the increased CysLT1 receptor is involved in NMDA excitotoxicity.     

Pranlukast, a cysteinyl leukotriene receptor 1 antagonist, protects mice against brain cold injury

We have reported the neuroprotective effect of cysteinyl leukotriene receptor 1 (CysLT1) antagonists on cerebral ischemia. Here, we further determined the protective effect of pranlukast, a CysLT1 receptor antagonist, on brain cold injury in mice. Brains were injured by placing a cooled metal probe on the skull surface for 30 s. We found that pranlukast significantly reduced cold-induced lesion volume (0.3 mg/kg) and the percentage increase in lesioned hemisphere volume (0.03-0.3 mg/kg) 24 h after injury, but did not show any effect 72 h after injury. Pranlukast also significantly inhibited neuron loss 24 h (0.1 mg/kg) and 72 h (0.1-0.3 mg/kg) after injury, and decreased the density of degenerated neurons 24 h (0.01-0.3 mg/kg) and 72 h (0.03-0.3 mg/kg) after injury. In addition, pranlukast (0.1-0.3 mg/kg) significantly reduced endogenous IgG exudation both 24 h and 72 h after injury. Thus, this study indicates the protective effect of pranlukast on brain cold injury.     

Montelukast, a cysteinyl leukotriene receptor-1 antagonist, dose- and time-dependently protects against focal cerebral ischemia in mice

Our previous studies showed that cysteinyl leukotriene receptor-1 (CysLT1) antagonist pranlukast has a neuroprotective effect on cerebral ischemia in rats and mice. However, whether the neuroprotective effect of pranlukast is its special action or a common action of CysLT1 receptor antagonists remains to be clarified. This study was performed to determine whether montelukast, another CysLT1 receptor antagonist, has the neuroprotective effect on focal cerebral ischemia in mice, and to observe its dose- and time-dependent properties. Permanent focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Montelukast was injected intraperitoneally either as multiple doses (once a day for 3 days and 30 min before MCAO) or as a single dose (at 30 min before, 30 min after, or 1 h after MCAO), respectively, and pranlukast and edaravone were used as controls. The neurological deficits, infarct volumes, brain edema, neuron density, and Evans blue extravasation in the brain were determined 24 h after MCAO. Pretreatments with multiple doses or a single dose of montelukast (0.1 and 1.0 mg/kg) before MCAO significantly attenuated all the ischemic insults. Post-treatment with a single dose of montelukast (0.1 and 1.0 mg/kg) at 30 min after MCAO also significantly decreased brain edema and infarct volume, but not neurological deficits. However, post-treatment with a single dose of montelukast at 1 h after MCAO had no significant effect. Pranlukast showed the same effects as montelukast, but edaravone attenuated the ischemic insults only with multiple doses before MCAO. Thus, montelukast has a dose- and time-dependent neuroprotective effect on permanent focal cerebral ischemia in mice, with an effective dose range of 0.1-1.0 mg/kg and a therapeutic window of 30 min. These findings further support the therapeutic potential of CysLT1 receptor antagonists in the treatment of cerebral ischemia at earlier phases.     

Pranlukast dose-and time-dependently protects against ischemic neuronal damage in the rat hippocampus

Objective Our previous studies showed that the neuroprotective effect of pranlukast,a cysteinyl leukotriene receptor-1(CysLT1)antagonist,on global cerebral ischemia in rats.This study was performed to evaluate dose-and time-dependent properties of pranlukast on CA1 neuron loss following transient global ischemia in rats.Methods Brain injury was induced by an improved four-vessel occlusion(4-VO)in rats.pranlukast(0.03-0.30 mg·kg-1)was injected intraperitoneally either as multiple doses(before or after ischemia)or as a single dose(30 min before ischemia),respectively.Physiological variables were monitored and neuron count was measured by computer-assisted imaging.Results The 4-VO model produced continuing postischemic neuronal death in CA1 region.Administration of pranlukast(0.1 and 0.3 mg·kg-1,30 min before ischemia and 1,24,48 and 72 h after ischemia)markedly reduced CA1 death.Treatment with a single dose of pranlukast(0.1 mg·kg-1,30 min before ischemia)also resulted in a significant increase in the number of healthy CA1 neurons at 3 days.Of interest is the finding that pranlukast(0.1 mg·kg-1)rescued CA1 neurons from ischemic death even when treatment was delayed until 30 min or 1 h after ischemia.Conclusions The present study confirms pranlukast has a dose-and time-dependent cerebroprotective effects on CA1 neuron loss following transient global ischemia in rats,with an effective dose range of 0.1-0.3 mg·kg-1 and a therapeutic window of 1 h.These findings further support the therapeutic potential of CysLT1 receptor antagonists in the treatment of global cerebral ischemia.     

ONO-1078 reduces NMDA-induced brain injury and vascular cell adhesion molecule-1 expression in rats

Aim: To determine whether ONO-1078 (pranlukast), a potent cysteinyl leukotriene receptor 1 （CysLT1） antagonist, has an effect on N-methyl-D-aspartate (NMDA)-induced brain injury and vascular cell adhesion molecule-1 (VCAM-1) expression in rats. Methods: Brain injury was induced by direct microinjection of NMDA (0.3μmol in 1μL of sterile 0.1mol/L PBS, pH 7.4) into the cerebral cortex. The lesion volume (area), brain edema and neuron density were assessed by an image analyzer and the expression of VCAM-1 in the cortex was detected by Western blot 24h after NMDA injection. ONO-1078(0.03, 0.1, or 0.3mg/kg) and edaravone (MCI-186, 10mg/kg), a neuroprotective agent, were ip injected 30min before and after NMDA injection. Results: NMDA microinjection produced well-defined focal lesions (Figure 1) dose- and time-dependently. ONO-1078(0.1, 0.3mg/kg) and edaravone (10mg/kg) decreased the total lesion volume, lesion area and brain edema induced by NMDA. Furthermore, ONO-1078 (0.1, 0.3mg/kg) significantly inhibited the enhanced expression of VCAM-1 in the injured cortices, but edaravone did not have this effect. Conclusion: CysLT1 receptor antagonist ONO-1078 attenuates NMDA-induced brain damage in rats, and this might relate to the attenuation of NMDA receptor-dependent neurotoxicity and the inhibition of the upregulation of VCAM-1 expression.     

Pranlukast reduces neutrophil but not macrophage/microglial accumulation in brain after focal cerebral ischemia in mice

AIM: To determine whether pranlukast, a cysteinyl leukotriene receptor-1 antagonist, exerts an anti-inflammatory effect on focal cerebral ischemia in mice. METHODS: Focal cerebral ischemia in mice was induced by permanent middle cerebral artery occlusion (MCAO). In addition to neurological deficits, infarct volume, degenerated neurons and endogenous IgG exudation, we detected accumulation of neutrophils and macrophage/microglia in the ischemic brain tissue 72 h after MCAO. Pranlukast was ip injected 30 min before and after MCAO. RESULTS: Pranlukast significantly attenuated neurological deficits, infarct volume, neuron degeneration and IgG exudation. Importantly, pranlukast (0.01 and 0.1 mg/kg) inhibited myeloperoxidase-positive neutrophil, but not CD11b-positive macrophage/microglial accumulation in the ischemic cortical tissue. CONCLUSION: Pranlukast exerts an anti-inflammatory effect on focal cerebral ischemia in the subacute phase that is limited to neutrophil recruitment through the disrupted blood-brain barrier.     

白三烯受体拮抗剂ONO—1078对大鼠局灶性脑缺血的神经保护作用

AIM: To determine whether ONO-1078 (pranlukast), a potent leukotriene receptor antagonist, has neuroprotective effect on focal cerebral ischemia in the rat. METHODS: Focal cerebral ischemia was induced by 30 min of middle cerebral artery (MCA) occlusion and followed by 24 h reperfusion. ONO-1078 (0.003-1.0 mg/kg) or vehicle (saline 1 mL/kg) was ip injected 30 min before MCA occlusion and 2 h after reperfusion. The neurological score, infarct volume, neuron density (in cortex, hippocampus, and striatum), brain edema, and albumin exudation around the vessels were determined 24 h after reperfusion. RESULTS: ONO-1078 slightly improved the neurological deficiency, and dramatically decreased infarct volume and neuron loss which showed a bell shaped dose response effect with highest effect at doses of 0.01-0.3 mg/kg. Enlargement of the ischemic hemisphere and albumin exudation were inhibited at doses of 0.01-1.0 mg/kg. CONCLUSION: ONO-1078 has the protective effect on focal cerebral ischemia in rats, which is partially attributed to the inhibition of brain edema. This may represent a novel approach to the treatment of acute cerebral ischemia with cysteinyl leukotriene receptor antagonists.     

Synergistic effects of pranlukast and leukotriene B4 receptor antagonist on antigen-induced pulmonary reaction.

We now attempted to differentiate effects of cysteinyl-leukotrienes and leukotriene B4 on antigen-induced pulmonary reaction by using a selective leukotriene D4/E4 (CysLT1) receptor antagonist and a selective LTB4 (BLT) receptor antagonist in rats. An intratracheal challenge with ovalbumin to Brown-Norway rats actively sensitized with ovalbumin produced two phases of airway responses which were estimated based on airway resistance, the immediate-type airway response within 30 min, and the delayed-type airway response beginning from 4 to 6 h after the challenge. Pretreatment of the rats with a CysLT1 receptor antagonist (pranlukast) failed to reduce the elevation of airway resistance, and pretreatment with a BLT receptor antagonist (ONO-4057; 5-[2-(2-carboxyethyl)-3-[6-(4-methoxyphenyl)-5E-hexenyl]- oxyphenoxy] valeric acid) also produced no decrease. In contrast, combined pretreatment of the rats with pranlukast and ONO-4057 did not reduce the amplitude of the immediate-type airway response, but did allow the elevated airway resistance to return to its baseline level and also significantly inhibited the delayed-type airway response. Histological examination at 6 h after ovalbumin challenge showed infiltration of inflammatory cells with a predominance of neutrophils and scattered eosinophils in the bronchial submucosa. While pretreatment with neither pranlukast nor with ONO-4057 inhibited the infiltration of inflammatory cells in the bronchial submucosa, pretreatment with the two antagonists combined significantly inhibited the infiltration of granulocytes into the bronchial submucosa. On the contrary, intratracheal administration of either leukotriene D4 or leukotriene B4 up to 10 microg resulted in the infiltration of granulocytes into the bronchial submucosa, but no synergism for the infiltration of granulocytes was observed after combined administration. These results suggest that leukotriene B4 appears to play a significant role in the antigen-induced pulmonary reaction in association with cysteinyl-leukotrienes. Accordingly, the combined antagonism at the CysLT1 receptor and BLT receptor may be a useful intervention for the treatment of bronchial asthma.     

半胱氨酰白三烯受体拮抗剂pranlukast对小鼠局灶性脑缺血的治疗作用

目的　观察半胱氨酰白三烯受体拮抗剂pranlukast(ONO 10 78)在小鼠局灶性脑缺血后的治疗作用。方法　采用大脑中动脉阻塞造成小鼠持续性局灶性脑缺血 ,缺血后1、6、2 4h分别给小鼠腹腔注射 pranlukast或依达拉奉 ,观察药物对缺血 2 4、4 8h后的神经功能缺损症状 ,4 8h后的脑梗死体积、两侧大脑半球比值、神经元密度的影响。结果　Pranlukast 0 1、0 2mg·kg-1及依达拉奉 3、10mg·kg-1均能减轻神经症状、减小脑梗死体积、降低缺血侧 /非缺血侧大脑半球比值、减轻海马CA1区、皮层和纹状体的神经元密度降低。结论　Pranlukast脑缺血后给药对脑损伤有治疗作用 ,提示有治疗缺血性脑卒中的临床前景。     

Neuroprotective effect of ONO-1078, a leukotriene receptor antagonist, on transient global cerebral ischemia in rats

AIM: To determine whether ONO-1078 {pranlukast, 4-oxo-8-[p-(4-phenylbutyloxy)benzoyl-amono]-2-(tetrazol-5-yl)-4H-1-benzopyran hemihydrate}, a potent leukotriene receptor antagonist, possesses a neuroprotective effect on global cerebral ischemia in rats, and to explore its possible mechanism of action. METHODS: Transient global cerebral ischemia was induced by four-vessel occlusion for 10 min and followed by 72-h reperfusion. ONO-1078 (0.03-0.3 mg/kg) and edaravone (MCI-186, 3-methyl-1-phenyl-2-pyrazolin-5-one, a neuroprotective agent) 10 mg/kg were ip injected 30 min before ischemia and 1 h after reperfusion, and once a day afterward. Neurological outcome was evaluated before ischemia and 24, 48, 72 h after reperfusion. Neuron density, the expressions of N-methyl-Daspartate (NMDA) receptor subunit proteins (NR1, NR2A, NA2B) and vascular cell adhesion molecule 1(VCAM-1) in the cerebral cortex and hippocampus were measured at 72 h after reperfusion. RESULTS: ONO-1078 (0.1, 0.3 mg/kg) and edaravone (10 mg/     

西洛他唑对脑缺血后神经元损伤的保护作用

目的：观察西洛他唑对小鼠持续性局灶性脑缺血后神经元损伤的剂量依赖性保护作用。方法：以大脑中动脉阻塞诱导小鼠持续性局灶性脑缺血。缺血前30min腹腔注射西洛他唑（3～30mg/kg）和普鲁司特（0.1mg/kg）。观察药物对缺血后神经元形态、密度的影响。结果：脑缺血损伤后,神经元密度降低,变性神经元密度增加。西洛他唑（3～10mg/kg）和普鲁司特能明显增加缺血侧存活神经元密度,减少变性神经元密度。结论：西洛他唑对小鼠持续性局灶性脑缺血后神经元损伤有保护作用。     

Montelukast, a cysteinyl leukotriene receptor-1 antagonist, attenuates chronic brain injury after focal cerebral ischaemia in mice and rats

Objectives Previously we demonstrated the neuroprotective effect of montelukast, a cysteinyl leukotriene receptor‐1 (CysLT₁) antagonist, on acute brain injury after focal cerebral ischaemia in mice. In this study, we have determined its effect on chronic brain injury after focal cerebral ischaemia in mice and rats. Methods After transient focal cerebral ischaemia was induced by middle cerebral artery occlusion, montelukast was intraperitoneally injected in mice or orally administered to rats for five days. Behavioural dysfunction, brain infarct volume, brain atrophy and neuron loss were determined to evaluate brain lesions. Key findings Montelukast (0.1 mg/kg) attenuated behavioural dysfunction, brain infarct volume, brain atrophy and neuron loss in mice, which was similar to pranlukast, another CysLT₁ receptor antagonist. Oral montelukast (0.5 mg/kg) was effective in rats and was more effective than edaravone, a free radical scavenger. Conclusion Montelukast protected mice and rats against chronic brain injury after focal cerebral ischaemia, supporting the therapeutic potential of CysLT₁ receptor antagonists.     

Dexamethasone Reduced Clonidine-induced Hypoactivity in Mice

Reduced clonidine anti-nociception in mice given low doses of dexamethasone has encouraged us to investigate the effects of dexamethasone pretreatment on locomotor hypoactivity, another example of clonidine-induced behaviour in mice. Dexamethasone administered intraperitoneally (0.1, 1.0, 10 mg kg^?1) 30 min before clonidine reduced clonidine-induced locomotor hypoactivity in the activity cage to an extent which was dose-dependent. Dexamethasone administered centrally (10 ng/mouse) 30 min before clonidine was also able to reduce clonidine-induced locomotor hypoactivity. Cycloheximide administered at a dose of 10 mg kg^?1 2 h before clonidine did not change the effects of clonidine but was able to prevent the effects of dexamethasone on clonidine-induced hypoactivity. The glucocorticoid receptor antagonist RU38486 administered centrally at the dose of 1 ng/mouse did not change the effects of clonidine, whereas it was able to block the effects of dexamethasone on clonidine-induced locomotor hypoactivity. These results suggest that the effects of dexamethasone on clonidine-induced locomotor hypoactivity depend on the stimulating effects that dexamethasone exerts on the protein synthesis via the glucocorticoid receptor in the brain.     

白三烯受体拮抗剂ONO-1078对大鼠短暂性全脑缺血的神经保护作用

AIM: To determine whether ONO-1078 {pranlukast, 4-oxo-8-[p-(4-phenylbutyloxy)benzoyl-amono]-2-(tetrazol-5-yl)-4H-1-benzopyran hemihydrate), a potent leukotriene receptor antagonist, possesses a neuroprotective effect on global cerebral ischemia in rats, and to explore its possible mechanism of action. METHODS: Transient global cerebral ischemia was induced by four-vessel occlusion for 10 min and followed by 72-h reperfusion. ONO-1078(0.03-0.3mg/kg) and edaravone (MCI-186, 3-methyl-1-phenyl-2-pyrazolin-5-one, a neuroprotective agent) 10 mg/kg were ip injected 30 rain before ischemia and 1 h after reperfusion, and once a day afterward. Neurological outcome was evaluated before ischemia and 24, 48, 72 h after reperfusion. Neuron density, the expressions of N-methyl-D-aspartate (NMDA) receptor subunit proteins (NR1, NR2A, NA2B) and vascular cell adhesion molecule 1 (VCAM-1) in the cerebral cortex and hippocampus were measured at 72h after reperfusion. RESULTS: ONO-1078 (0.1,0.3mg/kg) and edaravone (10 mg/kg) improved ischemia-induced neurological deficiency and reduced neuron death.ONO-1078 (0.1, 0.3mg/kg) significantly inhibited the enhanced expression of NMDA receptor subunit protein NR2A in the cortex and VCAM-1 in the hippocampus of ischemic rats. CONCLUSION: ONO-1078 possesses a neuroprotective effect on global cerebral ischemia in rats, and its mechanism may be partly related to the inhibition of the upregulation of NR2A and VCAM- 1 in different regions of the brain.     

Studies on the experimental allergic rhinitis induced by Japanese cedar pollen--role of cysteinyl leukotrienes in nasal allergic symptoms

Cysteinyl leukotrienes (CysLTs: LTC4, LTD4, and LTE4) are a family of potent inflammatory mediators that appear to contribute to the pathophysiologic features of allergic rhinitis. Because treatment with a CysLT1 receptor antagonist and a 5-lipoxygenase inhibitor modified allergen-induced nasal blockage in patients with allergic rhinitis, and CysLTs were detected in nasal cavity lavage fluid, it has been suggested that CysLTs act as significant inflammatory mediators in allergic rhinitis. The role of CysLTs was evaluated in our experimental allergic rhinitis model in sensitized guinea pigs which shows biphasic nasal blockage, sneezing and nasal hyperresponsiveness to LTD4 induced by repetitive inhalation challenge with Japanese cedar pollen. In this model, the CysLT1 receptor antagonist pranlukast suppressed the late-phase nasal blockage but not early blockage and sneezing. Nasal hyperresponsiveness (nasal blockage) to LTD4 was largely blocked by pranlukast, naphazoline, and N omega-nitro-L-arginine-methyl ester. The results demonstrate that nasal blockage induced by CysLTs is mainly due to dilatation of nasal blood vessels, which can be induced by the nitric oxide produced through CysLT1 receptor activation. On the other hand, when pollen inhalation challenge was performed in the presence of nasal hyperresponsiveness, antigen-induced biphasic nasal blockage and sneezing were considerably enhanced and CysLTs contributed to both symptoms, suggesting that nasal hyperresponsiveness induces aggravation of antigen-induced nasal symptoms. The results presented in this study further suggest that our model is a good representative of human allergic rhinitis and offer evidence that CysLTs are chemical mediators mainly responsible for allergic nasal symptoms.     

Montelukast modulates lung CysLT(1) receptor expression and eosinophilic inflammation in asthmatic mice

AIM: To determine the expressions of cysteinyl leukotriene receptors, CysLT1 and CysLT2, in airway eosinophilic inflammation of OVA-induced asthmatic mice and the modulation by montelukast, a CysLT1 receptor antagonist. METHODS: Asthma model was induced by chronic exposure to ovalbumin (OVA) in C57BL/6 mice. The eosino-phils in bronchoalveolar lavage (BAL) fluid and lung tissues were counted, IL-5 level in BAL fluid was measured, and CysLT1 and CysLT2 receptor mRNA expressions were detected by semi-quantitative RT-PCR. RESULTS: Montelukast (6 mg/kg, once per day for 20 d) significantly suppressed the increased eosinophils in BAL fluid and lung tissue, and increased IL-5 level in BAL fluid in OVA challenged mice. OVA challenge increased CysLT1 but decreased CysLT2 receptor mRNA expression. Montelukast inhibited the increased CysLT1 but not the reduced CysLT2 expression after OVA challenge. CONCLUSION: CysLT receptors are modulated immunologically, and montelukast inhibits up-regulation of CysLT1 receptor     

Effect of MK-801 on pilocarpine-evoked seizures in mice exposed to transient incomplete brain ischemia

The aim of the study was to examine the role of NMDA receptors in the modulation of brain tolerance after transient cerebral ischemia. Adult mice were exposed for 30 min to bilateral clamping of common carotid arteries (BCCA) under anaesthesia. The non-competitive NMDA antagonist, MK-801 was administered intraperitoneally (ip) in two experimental paradigms: a) acute: twice at 1.0 mg/kg; 1 h before the clamping of the vessels and 6 h after re-circulation; b) chronic at a dose of 0.1 mg/kg, started 24 h after recirculation and continued once daily for 13 days with the last injection 24 h before the induction of convulsions. Seizures were evoked with pilocarpine (400 mg/kg, ip) 14 days after BCCA. It was found that transient incomplete brain ischemia induced protection against pilocarpine toxicity. The acute treatment with MK-801 did not diminish the anticonvulsant action of the procedure. In contrast, the chronic treatment with the drug led to a marked potentiation of the effect. In conclusion, it can be suggested that studied NMDA receptor antagonist used at relatively low dose may enhance the brain tolerance activated after a transient ischemic episode.     

Lowered brain stimulation reward thresholds in rats treated with a combination of caffeine and N-methyl-D-aspartate but not alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate or metabotropic glutamate receptor-5 receptor antagonists

Previous studies suggested that adenosine A1 and A2A receptor agonists counteract behavioral effects of N-methyl-D-aspartate (NMDA) receptor antagonists while adenosine receptor antagonists may produce opposite effects enhancing the actions of NMDA receptor antagonists. To further evaluate the effects of combined administration of adenosine receptor antagonist caffeine and various NMDA and non-NMDA glutamate receptor antagonists on brain stimulation reward (discrete-trial threshold current intensity titration procedure), rats with electrodes implanted into the ventral tegmental area were tested after pretreatment with NMDA receptor channel blocker MK-801 (0.01-0.3 mg/kg), competitive antagonist D-CPPene (0.3-5.6 mg/kg), glycine site antagonist L-701,324 (1.25-5 mg/kg), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist GYKI-53655 (1-10 mg/kg), metabotropic glutamate receptor 5 (mGluR5) antagonist MPEP (1-10 mg/kg) alone and in combination with caffeine (1-30 mg/kg). MK-801 (0.056 and 0.1 mg/kg) was the only tested glutamate antagonist that lowered self-stimulation thresholds, while D-CPPene (5.6 mg/kg) and MPEP (5.6 and 10 mg/kg) had the opposite effects. Threshold-increasing effects of D-CPPene, but not of MPEP, however, were associated with marked impairment of operant performance, reflected by longer latencies to respond and higher rates of responding during the inter-trial intervals. Operant performance was also disrupted by the highest dose of MK-801 (0.3 mg/kg). For subsequent experiments, caffeine (1-30 mg/kg) was combined with the highest doses of NMDA receptor antagonists that did not lower the brain stimulation reward thresholds and did not impair operant performance. Caffeine had no appreciable effects on self-stimulation behavior when given alone. A low dose of caffeine (3 mg/kg) significantly lowered self-stimulation thresholds only when given together with MK-801 (0.03 mg/kg) or D-CPPene (3 mg/kg). Combined with the same antagonist drugs, higher doses of caffeine (10 and 30 mg/kg) facilitated time-out responding. These results indicate that, within a limited dose range, caffeine in combination with an NMDA receptor channel blocker and a competitive antagonist significantly lowers brain stimulation reward thresholds in rats.     

Distribution of cysteinyl leukotriene receptor 2 in human traumatic brain injury and brain tumors

Aim: To determine the distribution of cysteinyl leukotriene receptor 2 (CysLT2),one of the cysteinyl leukotriene receptors, in human brains with traumatic injury and tumors. Methods: Brain specimens were obtained from patients who underwent brain surgery. CysLT2 in brain tissues was examined using immunohistochemical analysis. Results: CysLT2 was expressed in the smooth muscle cells (not in the endothelial cells) of arteries and veins. CysLT2 was also expressed in the granulocytes in both vessels and in the brain parenchyma. In addition, CysLT2 was detected in neuron- and glial-appearing cells in either the late stages of traumatic injury or in the area surrounding the tumors. Microvessels regenerated 8 d after trauma and CysLT2 expression was recorded in their endothelial cells.Conclusion: CysLT2 is distributed in vascular smooth muscle cells and granulocytes, and brain trauma and tumor can induce its expression in vascular endothelial cells and in a number of other cells.     

Involvement of cysteinyl leukotriene receptors in angiogenesis in rat thoracic aortic rings

Cysteinyl leukotrienes (CysLTs) are potent inflammatory mediators that induce inflammation through the activation of CysLT1 and CysLT2 receptors. It has been reported that inflammatory mediators, such as prostaglandins, play an important role in angiogenesis. However, whether CysLTs and the receptor subtypes are involved in angiogenesis is not clarified. Here, we determined the effects of CysLT receptor agonist leukotriene D4 (LTD4) and antagonists on angiogenesis by rat thoracic aortic ring assay. We found that the microvessel growth in 25% serum-containing cultures was significantly inhibited by the CysLT1 receptor antagonist montelukast (0.1-1 microM), but not by the CysLT2 receptor antagonist BAY cyslt2 (0.1-1 microM). The microvessel growth in serum-free culture was affected neither by montelukast (0.01-1 microM) nor by BAY cyslt2 (0.1-1 microM). Furthermore, LTD4 at 100 nM significantly enhanced the microvessel growth in serum-free culture and LTD4 at 10-100 nM significantly enhanced the microvessel growth in 25% serum-containing cultures. The enhancement was abrogated by both montelukast and BAY cyslt2. Thus, CysLT1 receptors may mediate endogenously regulated microvessel growth in normal culture; whereas the exogenous agonist LTD4 induces angiogenesis through the activation of both CysLT1 and CysLT2 receptors. The CysLT receptor antagonists can be developed as angiogenesis inhibitors.