The regional effect of serum hormone levels on cerebral blood flow in healthy nonpregnant women.

Sex hormones estrogen (EST) and progesterone (PROG) have received increased attention for their important physiological action outside of reproduction. While studies have shown that EST and PROG have significant impacts on brain function, their impact on the cerebrovascular system in humans remains largely unknown. To address this, we used a multi-modal magnetic resonance imaging (MRI) approach to investigate the link between serum hormones in the follicular phase and luteal phase of the menstrual cycle (MC) with measures of cerebrovascular function (cerebral blood flow [CBF]) and structure (intracranial artery diameter). Fourteen naturally cycling women were recruited and assessed at two-time points of their MC. CBF was derived from pseudo-continuous arterial spin labeling while diameters of the internal carotid and basilar artery was assessed using time of flight magnetic resonance angiography, blood samples were performed after the MRI. Results show that PROG and EST had opposing and spatially distinct effects on CBF: PROG correlated negatively with CBF in anterior brain regions (r = -.86, p < .01), while EST correlations were positive, yet weak and most prominent in posterior areas (r = .78, p < .01). No significant correlations between either hormone or intracranial artery diameter were observed. These results show that EST and PROG have opposing and regionally distinct effects on CBF and that this relationship is likely not due to interactions with large intracranial arteries. Considering that CBF in healthy women appears tightly linked to their current hormonal state, future studies should consider assessing MC-related hormone fluctuations in the design of functional MRI studies in this population.

Identification of intima-to-media signals for flow-induced vascular remodeling using correlative gene expression analysis.

Changes in blood flow can induce arterial remodeling. Intimal cells sense flow and send signals to the media to initiate remodeling. However, the nature of such intima-media signaling is not fully understood. To identify potential signals, New Zealand white rabbits underwent bilateral carotid ligation to increase flow in the basilar artery or sham surgery (n = 2 ligated, n = 2 sham). Flow was measured by transcranial Doppler ultrasonography, vessel geometry was determined by 3D angiography, and hemodynamics were quantified by computational fluid dynamics. 24 h post-surgery, the basilar artery and terminus were embedded for sectioning. Intima and media were separately microdissected from the sections, and whole transcriptomes were obtained by RNA-seq. Correlation analysis of expression across all possible intima-media gene pairs revealed potential remodeling signals. Carotid ligation increased flow in the basilar artery and terminus and caused differential expression of 194 intimal genes and 529 medial genes. 29,777 intima-media gene pairs exhibited correlated expression. 18 intimal genes had > 200 medial correlates and coded for extracellular products. Gene ontology of the medial correlates showed enrichment of organonitrogen metabolism, leukocyte activation/immune response, and secretion/exocytosis processes. This demonstrates correlative expression analysis of intimal and medial genes can reveal novel signals that may regulate flow-induced arterial remodeling.

Methyl palmitate modulates the nicotine-induced increase in basilar arterial blood flow.

Methyl palmitate (MP) is a fatty acid methyl ester. Our recent study indicated that adrenergic nerve-dependent functional sympathetic-sensory nerve interactions were abolished by MP in mesenteric arteries. However, the effect of MP on perivascular nerves and cerebral blood flow remains unclear. In this study, the increase in basilar arterial blood flow (BABF) after the topical application of nicotinic acetylcholine receptor agonists was measured using laser Doppler flowmetry in anesthetized rats. The choline (a selective α7-nicotinic acetylcholine receptor agonist)-induced increase in BABF was abolished by tetrodotoxin (a neurotoxin), NG -nitro-L-arginine (a nonselective NO synthase inhibitor), α-bungarotoxin (a selective α7-nicotinic acetylcholine receptor inhibitor), and chronic sympathetic denervation. In addition, the nicotine (a nicotinic acetylcholine receptor agonist)-induced increase in BABF was inhibited by MP in a concentration-dependent manner. The acetylcholine-induced increase in BABF was not affected by MP. The myography results revealed that nicotine-induced vasorelaxation was significantly inhibited by MP, but was reversed by chelerythrine (a protein kinase C inhibitor). MP-induced vasodilation was significantly greater in BA rings without endothelium compared to those with endothelium. Meanwhile, MP did not affect baseline BABF. Our results indicate that MP acts as a neuromodulator in the cerebral circulation where it activates the PKC pathway and causes a diminished nicotine-induced increase in blood flow in the brainstem, and that the vasorelaxation effect of MP may play a minor role.

Evaluation of basilar artery and cerebrospinal fluid dynamics using phase-contrast MRI: Comparison between mannitol and isotonic saline solution.

Increased intracranial pressure (ICP) can cause irreversible pathological changes in the canine brain and can be life-threatening, so prompt diagnosis and therapeutic responses are warranted. The purposes of this prospective experimental study were to evaluate phase-contrast MRI (PC-MRI) as a non-invasive method for quantifying cerebrospinal fluid (CSF) and basilar artery flow, and to assess effects of intravenous administration of hypertonic fluid. A PC-MRI scan was acquired for six healthy Beagle dogs at the level of the mesencephalic aqueduct. Either 1.0 g/kg mannitol or isotonic saline solution was administered intravenously for 15 min each at a matched dose volume of 5 mL/kg. Basilar artery and CSF flow rates were measured and their values compared between mannitol and isotonic saline solution groups before administration, and subsequently every 15 min for 2 h post-administration. The CSF dynamics were further assessed by measuring repeat flow from the caudal to rostral direction and the rostral to caudal direction as the number of waves. No significant difference was observed in basilar or and CSF flow velocity between the two groups (P > .05). However, administration of isotonic saline solution tended to increase basilar artery velocity slightly over time, while CSF velocity remained unchanged. In the mannitol group, CSF wave forms tended to be reduced at 60 and 75 min (P > .05). Findings from this preliminary study indicated that it is feasible to measure the dynamics of CSF and basilar artery flow by PC-MRI, but no flow differences could be detected for mannitol versus isotonic saline administration.

Epac-mediated relaxation in murine basilar arteries depends on membrane permeability of cyclic nucleotide analogues and endothelial aging.

Cerebral blood supply is finely tuned by regulatory mechanisms depending on vessel caliber the disruption of which contributes to the development of diseases such as vascular dementia, Alzheimer's and Parkinson 's diseases. This study scopes whether cAMP-mimetic-ligands relax young and aged murine cerebral arteries, whether this relates to the activation of PKA or Epac signaling pathways and is changed with advanced age. The hormone Urocortin-1 relaxed submaximally contracted young and old basilar arteries with a similar pD2 and DMAX (~ -8.5 and ~ 90% in both groups). In permeabilized arteries, PKA activation by 6-Bnz-cAMP or Epac activation by 8-pCPT-2'- O-Me-cAMP also induced relaxation with pD2 of -6.3 vs. -5.8 in old for PKA-ligands, and -4.4 and -4.0 in old for Epac-ligands. Furthermore, aging significantly increased submaximal Ca2+-induced force. The effect of 8-pCPT-2'-O-Me-cAMP on intact arteries was attenuated by aging or nitric oxide synthase inhibition. No relaxing effect in both age-groups was observed after treatment with PKAactivator, Sp-6-Phe-cAMPS. In conclusion, our results suggest that in intact basilar arteries relaxation induced by cAMP-mimetics refers only to the activation of Epac and is impaired by smooth muscle and endothelial aging. The study presents an interesting option allowing therapeutic discrimination between both pathways, possibly for the exclusive activation of Epac in brain circulatory system.

Anti-high mobility group box-1 antibody attenuated vascular smooth muscle cell phenotypic switching and vascular remodelling after subarachnoid haemorrhage in rats.

Although cerebral vascular smooth muscle cell (VSMC) phenotypic switching is involved in the vascular dysfunction after subarachnoid haemorrhage (SAH), the precise mechanisms are still unclear. High mobility group box-1 (HMGB1) has been identified as a modulator in VSMC proliferation. The purpose of this study was to investigate the potential role of HMGB1 in the VSMC phenotypic switching following SAH. An endovascular perforation SAH model was used in our experiments. The expression levels of HMGB1, α-smooth muscle actin (α-SMA), osteopontin (OPN), smooth muscle myosin heavy chain (SM-MHC), embryonic smooth muscle myosin heavy chain (Smemb), TXA2, PAR-1 and AT1 receptor were evaluated by Western blot analyses. Iba1-positive cells and apoptotic cells were determined by immunofluorescence staining and TUNEL staining, respectively. Vasoconstriction of the isolated basilar artery was stimulated by thrombin and KCl. We found that HMGB1 expression was markedly increased following SAH, and anti-HMGB1 mAb significantly reversed VSMC phenotypic switching and vascular remodelling in rats. However, the effects of HMGB1 on VSMC phenotypic switching were partly blocked in the presence of SC79, a potent activator of phosphatidylinositol-3-kinase-AKT (PI3K/AKT). Furthermore, the enhanced vasoconstriction and decreased cerebral cortical blood flow induced by SAH were reversed by anti-HMGB1 mAb. Finally, we found that anti-HMGB1 mAb attenuated microglial activation and brain oedema, ameliorating neurological dysfunction. These results indicated that HMGB1 is a useful regulator of VSMC phenotypic switching and vascular remodelling following SAH and might be exploited as a novel therapeutic target for delayed cerebral ischaemia.

Vessel shape alterations of the vertebrobasilar arteries in Mucopolysaccharidosis type IVa (Morquio A) patients.

PURPOSE: Main symptom of mucopolysaccharidosis type IVa (MPS IVa) is progressive systemic skeletal dysplasia. This is routinely monitored by cerebral and spinal MRI. The vascular system is generally not in the primary focus of interest. In our population of MPS IVa patients we observed vessel shape alterations of the vertebrobasilar arteries, which has not been described before. MATERIAL AND METHODS: MRI-datasets of 26 patients with MPS IVa acquired between 2008 and 2015 were eligible for retrospective analysis of the vertebrobasilar arteries. The vessel length and angle of the basilar artery (BA) and both vertebral arteries (VA) were analyzed. A deflection angle between 90° and 130° in the vessel course was defined as tortuosity, less than 90° as kinking. The results were compared to a matched control group of 23 patients not suffering from MPS. RESULTS: The deflection angle [°] of the VA and BA was significantly decreased in the majority (85%) of MPS IVa patients compared to the control group: BA 132±24 vs. 177±6, BA/VA transition 113±21 vs. 152±13, right VA 108±23 vs. 156±13, left VA 110± 22 vs. 157±14 (all p<0.005). Likewise, vessels of MPS IVa patients were significantly longer compared to the control group: BA 27±4 vs. 21±2, right VA 20±6 vs. 10±1, left VA 18±5 vs. 11±2 (all p<0.005). CONCLUSION: MPS IVa is associated with significantly increased tortuosity of vertebrobasilar arteries. Therefore the vascular system of MPS IVa patients should be monitored on routinely basis, as vessel shape alterations had been associated with dissections, leading to a higher risk of cerebrovascular events.

Vascular territorial segmentation and volumetric blood flow measurement using dynamic contrast enhanced magnetic resonance angiography of the brain.

This study proposes a method for territorial segmentation and volumetric flow rate (VFR) distribution measurement of cerebral territories based on time-resolved contrast enhanced magnetic-resonance-angiography (MRA). The method uses an iterative region-growing algorithm based on bolus-arrival-time with increased temporal resolution. Eight territories were segmented: (1) right and (2) left internal carotid arteries, including the middle cerebral artery (ICA+MCA), excluding the anterior cerebral arteries (ACA); (3) right and left ACA (R+L-ACA); (4) right and (5) left external carotid arteries (ECA); (6) right and (7) left posterior cerebral arteries (PCA); and (8) vertebrobasilar territory. VFR percentage, relative to the entire brain (rVFR), was measured based on territorial volume as a function of time. Mean rVFR values of fifteen healthy subjects were: ICA+MCA = 23 ± 2%, R + L-ACA = 17 ± 3%, ECA = 4 ± 2%, PCA = 12 ± 2%, and vertebrobasilar territory = 31 ± 4%. Excluding the ECA-rVFR, which is underestimated, these values are comparable to previously reported values. Six subjects were scanned twice, demonstrating comparable and even higher reproducibility than previously reported using phase-contrast, yet with faster scan time (∼1 min). This method was implemented in one patient with MCA occlusion and one with Moyamoya syndrome scanned before and after bypass surgery, demonstrating its clinical potential for quantitative assessment of the degree of occlusion and the effect of surgery.

Relaxant Effects of the Selective Estrogen Receptor Modulator, Bazedoxifene, and Estrogen Receptor Agonists in Isolated Rabbit Basilar Artery.

We have previously shown that the selective estrogen receptor modulator, bazedoxifene, improves the consequences of ischemic stroke. Now we aimed to characterize the effects and mechanisms of action of bazedoxifene in cerebral arteries. Male rabbit isolated basilar arteries were used for isometric tension recording and quantitative polymerase chain reaction. Bazedoxifene relaxed cerebral arteries, as 17-ß-estradiol, 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol [estrogen receptor (ER) α agonist], and G1 [G protein-coupled ER (GPER) agonist] did it (4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol > bazedoxifene = G1 > 17-ß-estradiol). 2,3-Bis(4-hydroxyphenyl)-propionitrile (ERß agonist) had no effect. Expression profile of genes encoding for ERα (ESR1), ERß (ESR2), and GPER was GPER > ESR1 > ESR2. As to the endothelial mechanisms, endothelium removal, N-nitro-L-arginine methyl ester, and indomethacin, did not modify the relaxant responses to bazedoxifene. As to the K channels, both a high-K medium and the Kv blocker, 4-aminopyridine, inhibited the bazedoxifene-induced relaxations, whereas tetraethylammonium (nonselective K channel blocker), glibenclamide (selective KATP blocker) or iberiotoxin (selective KCa blocker) were without effect. Bazedoxifene also inhibited both Ca- and Bay K8644-elicited contractions. Therefore, bazedoxifene induces endothelium-independent relaxations of cerebral arteries through (1) activation of GPER and ERα receptors; (2) increase of K conductance through Kv channels; and (3) inhibition of Ca entry through L-type Ca channels. Such a profile is compatible with the beneficial effects of estrogenic compounds (eg, SERMs) on vascular function and, specifically, that concerning the brain. Therefore, bazedoxifene could be useful in the treatment of cerebral disorders in which the cerebrovascular function is compromised (eg, stroke).

Inhibition by ketamine and amphetamine analogs of the neurogenic nitrergic vasodilations in porcine basilar arteries.

The abuse of ketamine and amphetamine analogs is associated with incidence of hypertension and strokes involving activation of sympathetic activities. Large cerebral arteries at the base of the brain from several species receive dense sympathetic innervation which upon activation causes parasympathetic-nitrergic vasodilation with increased regional blood flow via axo-axonal interaction mechanism, serving as a protective mechanism to meet O2 demand in an acutely stressful situation. The present study was designed to examine effects of ketamine and amphetamine analogs on axo-axonal interaction-mediated neurogenic nitrergic vasodilation in porcine basilar arteries using techniques of blood-vessel myography, patch clamp and two-electrode voltage clamp, and calcium imaging. In U46619-contracted basilar arterial rings, nicotine (100µM) and electrical depolarization of nitrergic nerves by transmural nerve stimulation (TNS, 8Hz) elicited neurogenic nitrergic vasodilations. Ketamine and amphetamine analogs concentration-dependently inhibited nicotine-induced parasympathetic-nitrergic vasodilation without affecting that induced by TNS, nitroprusside or isoproterenol. Ketamine and amphetamine analogs also concentration-dependently blocked nicotine-induced inward currents in Xenopus oocytes expressing α3ß2-nicotinic acetylcholine receptors (nAChRs), and nicotine-induced inward currents as well as calcium influxes in rat superior cervical ganglion neurons. The potency in inhibiting both inward-currents and calcium influxes is ketamine>methamphetamine>hydroxyamphetamine. These results indicate that ketamine and amphetamine analogs, by blocking nAChRs located on cerebral perivascular sympathetic nerves, reduce nicotine-induced, axo-axonal interaction mechanism-mediated neurogenic dilation of the basilar arteries. Chronic abuse of these drugs, therefore, may interfere with normal sympathetic-parasympathetic interaction mechanism resulting in diminished neurogenic vasodilation and, possibly, normal blood flow in the brainstem.

High dietary fructose does not exacerbate the detrimental consequences of high fat diet on basilar artery function.

The objective of the study was to determine the effects of a high fat (HF) diet alone or with high fructose (HF/F) on functional and structural changes in the basilar arteries and cardiovascular health parameters in rats. Male Sprague Dawley rats were fed either a HF (30%) or HF/F (30/40%) diet for 12 weeks. The basilar artery was cannulated in a pressurized system (90 cm H2O) and vascular responses to KCl (30 - 120 mM), endothelin (10(-11) - 10(-7) M), acetylcholine (ACh) (10(-10) - 10(-4) M), diethylamine (DEA)-NONO-ate (10(-10) - 10(-4) M), and papaverine (10(-10) - 10(-4) M) were evaluated. Rats were also monitored for food intake, body weight, blood lipids, blood pressure, and heart rate. At death, asymmetrical dimethyl arginine level (ADMA) and leptin were assayed in serum. Although there was no significant difference in weight gain and food intake, HF and HF/F diets increased body fat composition and decreased the lean mass. HF/F diet accelerated the development of dyslipidemia. Although resting blood pressure remained unchanged, stress caused a significant elevation in blood pressure and a modest increase in heart rate in HF fed rats. Both HF and HF/F diet resulted in decreased response to endothelium-dependent and -independent relaxation, whereas increased basilar artery wall thickness was observed only in HF group. Serum leptin levels positively correlated with wall thickness. Moreover serum ADMA was increased and eNOS immunofluorescence was significantly decreased with both diets. These data suggest that the presence of high fructose in a HF diet does not exacerbate the detrimental consequences of a HF diet on basilar artery function.

Ischemia as a potential etiologic factor in idiopathic unilateral sudden sensorineural hearing loss: Analysis of posterior circulation arteries.

The association between idiopathic sudden sensorineural hearing loss (ISSNHL) and the radiologic characteristics of the vertebrobasilar artery is unclear. We hypothesized that the degree and direction of vertebrobasilar artery curvature in the posterior circulation contribute to the occurrence of ISSNHL. We consecutively enrolled patients diagnosed with unilateral ISSNHL in two tertiary hospitals. Magnetic resonance images were performed in all patients to exclude specific causes of ISSNHL, such as vestibular schwannoma, chronic mastoiditis, and anterior inferior cerebellar artery infarct. We measured the following parameters of posterior circulation: vertebral and basilar artery diameter, the degree of basilar artery curvature (modified smoker criteria), and vertebral artery dominance. Pure tone audiometries were performed at admission and again 1 week and 3 months later. A total of 121 ISSNHL patients (mean age, 46.0 ± 17.3 years; 48.8% male) were included in these analyses. The proportion of patients with the left side hearing loss was larger than the proportion with the right side hearing loss (left, 57.9%; right, 42.1%). The majority of patients were characterized by a left dominant vertebral artery and right-sided basilar artery curvature. The direction of the basilar artery curvature was significantly associated with hearing loss lateralization (p = 0.036). Age and sex matched multivariable analyses revealed the absence of diabetes and right-sided basilar artery curvature as significant predictors for left sided hearing loss. There was no statistical difference between atherosclerotic cardiovascular risk score (high versus low) and hearing outcomes at 3 months. In ISSNHL, the laterality of hearing loss was inversely associated with the direction of basilar artery curvature. Our results, therefore, indicate the importance of vascular assessment when evaluating ISSNHL.

Pharmacological characterization of the mechanisms involved in the vasorelaxation induced by progesterone and 17ß-estradiol on isolated canine basilar and internal carotid arteries.

Progesterone and 17ß-estradiol induce vasorelaxation through non-genomic mechanisms in several isolated blood vessels; however, no study has systematically evaluated the mechanisms involved in the relaxation induced by 17ß-estradiol and progesterone in the canine basilar and internal carotid arteries that play a key role in cerebral circulation. Thus, relaxant effects of progesterone and 17ß-estradiol on KCl- and/or PGF2α-pre-contracted arterial rings were investigated in absence or presence of several antagonists/inhibitors/blockers; the effect on the contractile responses to CaCl2 was also determined. In both arteries progesterone (5.6-180 µM) and 17ß-estradiol (1.8-180 µM): (1) produced concentration-dependent relaxations of KCl- or PGF2α-pre-contracted arterial rings; (2) the relaxations were unaffected by actinomycin D (10 µM), cycloheximide (10 µM), SQ 22,536 (100 µM) or ODQ (30 µM), potassium channel blockers and ICI 182,780 (only for 17ß-estradiol). In the basilar artery the vasorelaxation induced by 17ß-estradiol was slightly blocked by tetraethylammonium (10mM) and glibenclamide (KATP; 10 µM). In both arteries, progesterone (10-100 µM), 17ß-estradiol (3.1-31 µM) and nifedipine (0.01-1 µM) produced a concentration-dependent blockade of the contraction to CaCl2 (10 µM-10mM). These results suggest that progesterone and 17ß-estradiol produced relaxation in the basilar and internal carotid arteries by blockade of L-type voltage dependent Ca(2+) channel but not by genomic mechanisms or production of cAMP/cGMP. Potassium channels did not play a role in the relaxation to progesterone in both arteries or in the effect of 17ß-estradiol in the internal carotid artery; meanwhile KATP channels play a minor role on the effect of 17ß-estradiol in the basilar artery.

Pituitary adenylate cyclase-activating polypeptide (PACAP) induces relaxations of peripheral and cerebral arteries, which are differentially impaired by aging.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a well-known neuropeptide, which also has vasomotor effects. However, little is known regarding its age-related and organ-specific vasomotor effects. We hypothesized that the vasomotor effects of PACAP depend on the tissue origin of the vessels and aging substantially modulates its actions. Thus, carotid (CA) and basilar arteries (BA) were isolated from young (2 months old), middle age (12 months old), and old (30 months old) rats. Their vasomotor responses were measured with an isometric myograph (DMT610M) in response to cumulative concentrations of PACAP1-38 (10(-9)-10(-6) M). PACAP1-38 induced (1) significantly greater concentration-dependent relaxations in CA compared to that of BA of young, middle age, and old rats; (2) relaxations of CA significantly decreased, whereas they did not change substantially in BA, as a function of age; (3) sodium nitroprusside (SNP)-induced relaxation did not change after PACAP1-38 administration in any conditions; and (4) inhibition of PAC1 receptors by selective PAC1 receptor blocker (PACAP6-38) completely diminished the responses to PACAP in all age groups of BA and CA. In conclusion, these findings suggest that PACAP1-38 has greater vasomotor effect in CA than that in BA, whereas aging has less effect on PACAP-induced relaxation of cerebral arteries and BA than that in peripheral arteries and CA suggesting that the relaxation to PACAP is maintained in cerebral arteries even in old age.

Memantine inhibits α3ß2-nAChRs-mediated nitrergic neurogenic vasodilation in porcine basilar arteries.

Memantine, an NMDA receptor antagonist used for treatment of Alzheimer's disease (AD), is known to block the nicotinic acetylcholine receptors (nAChRs) in the central nervous system (CNS). In the present study, we examined by wire myography if memantine inhibited α3ß2-nAChRs located on cerebral perivascular sympathetic nerve terminals originating in the superior cervical ganglion (SCG), thus, leading to inhibition of nicotine-induced nitrergic neurogenic dilation of isolated porcine basilar arteries. Memantine concentration-dependently blocked nicotine-induced neurogenic dilation of endothelium-denuded basilar arteries without affecting that induced by transmural nerve stimulation, sodium nitroprusside, or isoproterenol. Furthermore, memantine significantly inhibited nicotine-elicited inward currents in Xenopous oocytes expressing α3ß2-, α7- or α4ß2-nAChR, and nicotine-induced calcium influx in cultured rat SCG neurons. These results suggest that memantine is a non-specific antagonist for nAChR. By directly inhibiting α3ß2-nAChRs located on the sympathetic nerve terminals, memantine blocks nicotine-induced neurogenic vasodilation of the porcine basilar arteries. This effect of memantine is expected to reduce the blood supply to the brain stem and possibly other brain regions, thus, decreasing its clinical efficacy in the treatment of Alzheimer's disease.

Systemic L-citrulline prevents cerebral vasospasm in haptoglobin 2-2 transgenic mice after subarachnoid hemorrhage.

BACKGROUND: Nitric oxide (NO) depletion and periadventitial inflammation contribute to the pathogenesis of cerebral vasospasm. L-Citrulline increases L-arginine levels, thereby raising NO synthesis. Transgenic C57Bl6 mice with a haptoglobin (Hp) 2-2 genotype develop more severe vasospasm than wild-type (Hp 1-1) mice after subarachnoid hemorrhage (SAH). OBJECTIVE: To evaluate the toxicity of systemic L-citrulline and its effect on basilar artery (BA) vasospasm, neurobehavioral scores, and inducible NO synthase (iNOS)/endothelial NO synthase (eNOS) expression after SAH in Hp 2-2 mice. METHODS: The Hp 2-2 genotypes were confirmed by reverse-transcriptase polymerase chain reaction. Toxicity was assessed with escalating L-citrulline doses. To test efficacy, Hp 1-1 and Hp 2-2 mice (n = 64) were divided into 4 groups (n = 32 per genotype): sham surgery (n = 8), SAH with no treatment (n = 8), SAH + vehicle (n = 8), and SAH + L-citrulline (200 mg/kg IP every 8 hours; n = 8). Post-SAH neurobehavioral scores were recorded at 24 hours; animals were perfused; and BAs were processed for analysis. Expression of iNOS and eNOS was determined by reverse-transcriptase polymerase chain reaction. RESULTS: The administration of L-citrulline resulted in higher BA lumen patencies in both genotypes (Hp 1-1: SAH + vehicle, 77.8 ± 3.2% vs SAH + L-citrulline, 91.8 ± 5.9% [mean ± SEM]; P < .05; Hp 2-2: SAH + vehicle, 67.1 ± 2.0% vs SAH + L-citrulline, 86.9 ± 2.2%; P < .001). Neurobehavioral scores were higher in Hp 2-2 mice treated with L-citrulline (SAH + vehicle, 1.2 ± 0.2 vs SAH + L-citrulline, 2.4 ± 0.2; P < .01). Expression of iNOS and eNOS increased in Hp 2-2 mice after L-citrulline treatment, but limited sample sizes prevented further statistical analysis. L-Citrulline was not toxic even at the highest dose. CONCLUSION: L-Citrulline is safe; increases BA patency, neurobehavioral scores, and NOS expression in Hp 2-2 mice after SAH; and is a potential agent for treatment of vasospasm after SAH.

Natural course of the arteriovenous malformations of the brain initially presented by hemorrhage: analysis of a clinical series of 39 patients.

AIM: AVM because of outstanding tendency toward bleeding, even though 20 times more rare then aneurysm on the blood vessels of the brain and her own specific anatomical structure even today represents big neurosurgical challenge. MATERIAL AND METHODS: Series which is shown here consists of 39 patients which were hospitalized in the institute for neurosurgery of the Clinical Center of Serbia in the period between 1995 and 2004. This group was exposed to symptomatic therapy or it was estimated that surgery, embolization and radio surgery. RESULTS: Combined type of venous drainage brings a high risk (p < 0.001) from repeated bleeding. Combined artery bringing from different flows (p < 0.05) contributes to genesis of 'steal phenomenon', in combination with deep venous drainage it presents predisposing anatomical characteristics for repeated bleeding (p < 0.001) according to our results should present AVM with dimensions 2.5 to 5 cm localized in eloquent zone of big brain with combined type of venous drainage and cobined artery bringing from vertebro-basilar flow and carotid flow. CONCLUSION: Perception of natural course of AVM point to certainly more benign pathology in regard to other vascular malformations. Specific anatomical structure requires planning of treatment from case to case, most often combination of embolization, radio surgery and surgical treatment.

Pharmacological evidence that Ca²+ channels and, to a lesser extent, K+ channels mediate the relaxation of testosterone in the canine basilar artery.

Testosterone induces vasorelaxation through non-genomic mechanisms in several isolated blood vessels, but no study has reported its effects on the canine basilar artery, an important artery implicated in cerebral vasospasm. Hence, this study has investigated the mechanisms involved in testosterone-induced relaxation of the canine basilar artery. For this purpose, the vasorelaxant effects of testosterone were evaluated in KCl- and/or PGF(2α)-precontracted arterial rings in vitro in the absence or presence of several antagonists/inhibitors/blockers; the effect of testosterone on the contractile responses to CaCl2 was also determined. Testosterone (10-180 µM) produced concentration-dependent relaxations of KCl- or PGF(2α)-precontracted arterial rings which were: (i) unaffected by flutamide (10 µM), DL-aminoglutethimide (10 µM), actinomycin D (10 µM), cycloheximide (10 µM), SQ 22,536 (100 µM) or ODQ (30 µM); and (ii) significantly attenuated by the blockers 4-aminopyridine (K(V); 1 mM), BaCl2 (K(IR); 30 µM), iberiotoxin (BK(Ca²+); 20 nM), but not by glybenclamide (K(ATP); 10 µM). In addition, testosterone (31, 56 and 180 µM) and nifedipine (0.01-1 µM) produced a concentration-dependent blockade of the contraction to CaCl2 (10 µM to 10 mM) in arterial rings depolarized by 60mM KCl. These results, taken together, show that testosterone relaxes the canine basilar artery mainly by blockade of voltage-dependent Ca²+ channels and, to a lesser extent, by activation of K+ channels (K(IR), K(V) and BK(Ca²+)). This effect does not involve genomic mechanisms, production of cAMP/cGMP or the conversion of testosterone to 17ß-estradiol.

Characterization of vasoconstrictor-induced relaxation in the cerebral basilar artery.

The vascular endothelium regulates vascular smooth muscle functions by releasing endothelium-derived vasoactive substances. To identify physiological mechanisms mediating the inhibitory effect of the endothelium on vasoconstrictors, the basilar arteries isolated from Wistar rats were used in an organ bath study. In the intact basilar artery (with endothelium), 100 nM serotonin (5-HT) induced phasic contraction (28.7+/-4.1% of 60 mM KCl-induced contraction) followed by profound time-dependent relaxation at 3 min (3.8+/-0.4%). In the denuded artery (without endothelium), the 5-HT-induced contraction was enhanced (51.7+/-16.1%), while the relaxation was abolished. In the intact basilar artery, the contraction was facilitated and the amplitude of the phasic contraction was significantly enhanced (70.1+/-10.3%), but time-dependent relaxation was still manifested at 3 min (25.7+/-10.0%) in the presence of Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME) and indomethacin. Time-dependent relaxation induced by 5-HT was abolished in Ca(2+)-free and in K(+)-free Krebs-Henseleit buffer (KHB). Furthermore, the 5-HT-induced contraction was enhanced by treatment with ouabain (105.6+/-11.8%), tetraethylammonium chloride (133.2+/-7.9%), charybdotoxin with apamin (145.4+/-6.4%) or BaCl(2) (72.2+/-13.8%) at 3 min; also, time-dependent relaxation was abolished by these blockers in the presence of L-NAME and indomethacin. U46619 (100 nM) induced sustained contraction without time-dependent relaxation in normal KHB, but charybdotoxin with apamin did not affect the contraction. The results suggest that time-dependent relaxation is modulated by endothelial sodium-potassium pump (Na(+)/K(+)-ATPase) and Ca(2+)-activated K(+) channel (K(Ca)) activity, especially small- and intermediate-conductance K(Ca)-prominent ionic mechanisms of the so-called endothelium-derived hyperpolarizing factor.

Alpha lipoic acid alleviates oxidative stress and preserves blood brain permeability in rats with subarachnoid hemorrhage.

The neuroprotective effect of alpha lipoic acid (ALA; 100 mg/kg, po), a dithiol antioxidant, on experimentally induced subarachnoid hemorrhage (SAH) was assessed in Wistar albino rats. Neurological examination scores recorded at the 48th h of SAH induction were increased in SAH groups, which were accompanied with significant increases in the formation of reactive oxygen species, DNA fragmentation ratios, malondialdehyde levels and myeloperoxidase activity, while significant decreases in the brain glutathione content and Na(+), K(+)-ATPase activity were observed. On the other hand, ALA treatment reversed all these biochemical indices as well as SAH-induced histopathological alterations. Increased brain edema, impaired blood-brain-barrier permeability and neurological scores were also improved by ALA treatment. The results demonstrate that ALA exerts neuroprotective effects via the enhancement of endogenous antioxidant enzyme activity, the inhibition of neutrophil accumulation and free radical generation, suggesting a therapeutic potential in reducing secondary injury after SAH in patients.