cyclic-gmp and Brain-Ischemia

Endothelial dysfunction is a hallmark of cerebrovascular disease, including ischemic stroke. Modulating endothelial signalling by cyclic nucleotides, cAMP and cGMP, is a potential therapeutic target in stroke. Inhibitors of the cyclic nucleotide degrading phosphodiesterase (PDE) enzymes may restore cerebral endothelial function. Current knowledge on PDE distribution and function in cerebral endothelial cells is sparse. This review explores data on PDE distribution and effects of PDEi in cerebral endothelial cells and identifies which PDEs are potential treatment targets in stroke.. We performed a systematic search of electronic databases (Medline and Embase). Our search terms were cerebral ischaemia, cerebral endothelial cells, cyclic nucleotide, phosphodiesterase and phosphodiesterase inhibitors.. We found 23 publications which described effects of selective inhibitors of only three PDE families on endothelial function in ischemic stroke. PDE3 inhibitors (PDE3i) (11 publications) and PDE4 inhibitors (PDE4i) (3 publications) showed anti-inflammatory, anti-apoptotic or pro-angiogenic effects. PDE3i also reduced leucocyte infiltration and MMP-9 expression. Both PDE3i and PDE4i increased expression of tight junction proteins and protected the blood-brain barrier. PDE5 inhibitors (PDE5i) (6 publications) reduced inflammation and apoptosis. In preclinical models, PDE5i enhanced cGMP/NO signalling associated with microvascular angiogenesis, increased cerebral blood flow and improved functional recovery. Non-specific PDEi (3 publications) had mainly anti-inflammatory effects.. This review demonstrates that non-selective and selective PDEi of PDE3, PDE4 and PDE5 modulated endothelial function in cerebral ischemic stroke by regulating processes involved in vascular repair and neuroprotection and thus reduced cell death and inflammation. Of note, they promoted angiogenesis, microcirculation and improved functional recovery; all are important in stroke prevention and recovery, and effects should be further evaluated in humans.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Brain Ischemia; Cyclic AMP; Cyclic GMP; Endothelial Cells; Humans; Neovascularization, Physiologic; Neuroprotection; Phosphodiesterase Inhibitors; Recovery of Function; Stroke

Stroke remains the leading cause of adult disability. Thus, it is imperative to develop restorative therapies for ischemic stroke designed specifically to treat the intact brain tissue to stimulate functional benefit. Therapies targeting amplification of brain repair processes with nitric oxide (NO) donors and phosphodiesterase type 5 (PDE5) inhibitors in preclinical studies are emerging and showing improvement of functional recovery after stroke.. This review will mainly cover the effect of NO donors, which produce NO, and PDE5 inhibitors, which elevate cyclic guanosine 3',5'-monophosphate (cGMP), on neural restorative events in ischemic brain and highlight mechanisms underlying their restorative therapeutic activity.. During stroke recovery, interwoven restorative events occur in ischemic brain, which include angiogenesis, neurogenesis, oligodendrogenesis, astrogliosis and neurite outgrowth. Emerging preclinical data indicate that restorative therapies targeting multiple parenchymal cells including neural stem cells, cerebral endothelial cells, astrocytes, oligodendrocytes, neurons would be more effective than agents with a single cell target. Preclinical data suggest that elevated cGMP levels induced by NO donors and PDE5 inhibitors act on cerebral endothelial cells, neural stem cells and oligodendrocyte progenitor cells to enhance stroke-induced angiogenesis, neurogenesis and oligodendrogenesis, respectively. These interacting remodeling events collectively improve neurological function after stroke.

Topics: Animals; Brain Ischemia; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Evaluation, Preclinical; Neovascularization, Physiologic; Neurogenesis; Neurons; Nitric Oxide; Nitric Oxide Donors; Phosphodiesterase 5 Inhibitors; Stroke

Sphingolipids represent a major class of lipids in which selected family members act as bioactive molecules that control diverse cellular processes, such as proliferation, differentiation, growth, senescence, migration and apoptosis. Emerging evidence reveals that sphingomyelinase/ceramide pathway plays a pivotal role in neurodegenerative diseases that involve mitochondrial dysfunction, oxidative stress and apoptosis. Minocycline, a semi-synthetic second-generation tetracycline derivative in clinical use for infection control, is also considered an effective protective agent in various neurodegenerative diseases in pre-clinical studies. Acting via multiple mechanisms, including anti-inflammatory, anti-oxidative and anti-apoptotic effects, minocycline is a desirable candidate for clinical trials in both acute brain injury as well as chronic neurodegenerative disorders. This review is focused on the anti-apoptotic and anti-oxidative mechanisms of minocycline against neurotoxicity induced by sphingomyelinase/ceramide in relation to neurodegeneration, particularly Alzheimer's disease and cerebral ischemia.

Topics: Alzheimer Disease; Antioxidants; Apoptosis; Brain Ischemia; Ceramides; Cyclic GMP; Humans; Minocycline; Mitochondria; Nitric Oxide; Oxidative Stress; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Sphingomyelin Phosphodiesterase; Thioredoxins

Ischemic stroke is the third cause of death and the most common cause of neurological disability. A main target of treatment is the still salvageable tissue surrounding the core of infarction and called "ischemic penumbra". Up to now the only drug approved for the treatment of acute ischemic stroke is recombinant tissue plasminogen activator to achieve early arterial recanalization and hypoxic tissue reperfusion and improve neural function. However, thrombolytic therapy has to be administered soon after the event since its efficacy is time dependent. This intervention also carries an increased risk of hemorrhagic transformation. In the rescue of poorly perfused cerebral regions an important role is played by collateral blood supply through the circle of Willis and through small pial vessels surrounding the lesion. The extent of collateralization is variable and at least in part regulated by the modulation of arteriolar nitric oxide (NO)-dependent endothelial function. Drugs that can improve endothelial function and cerebrovascular reactivity could have a role in collateral formation and infarct volume limitation. Statins affect endothelial NO production demonstrating their potential to influence endothelial NO synthase (eNOS) and in treating stroke. Phosphodiesterase (PDE) inhibitors improve functional recovery after stroke in rats enhancing neuro and synapto genesis and increasing guanosine 3,5-cyclic monophosphate (cGMP). The aim of this review is to highlight the potential of these two classes of drugs in the treatment of acute ischemic stroke by analysing their pharmacological effects and involvement in the NO and cGMP pathways.

Topics: Acute Disease; Animals; Brain Infarction; Brain Ischemia; Cerebral Cortex; Collateral Circulation; Cyclic GMP; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Microcirculation; Nitric Oxide; Phosphodiesterase Inhibitors; Stroke

Topics: Animals; Brain Ischemia; Cyclic GMP; Hippocampus; Mice; N-Methylaspartate; Nitric Oxide; Nitric Oxide Donors; Taurine

Targeted disruption of the neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) genes has led to knockout mice that lack these isoforms. These animal models have been useful to study the roles of nitric oxide (NO) in physiologic processes. nNOS knockout mice have enlarged stomachs and defects in the inhibitory junction potential involved in gastrointestinal motility. eNOS knockout mice are hypertensive and lack endothelium-derived relaxing factor activity. When these animals are subjected to models of focal ischemia, the nNOS mutant mice develop smaller infarcts, consistent with a role for nNOS in neurotoxicity following cerebral ischemia. In contrast, eNOS mutant mice develop larger infarcts, and show a more pronounced hemodynamic effect of vascular occlusion. The knockout mice also show that nNOS and eNOS isoforms differentially modulate the release of neurotransmitters in various regions of the brain. eNOS knockout mice respond to vessel injury with greater neointimal proliferation, confirming that reduced NO levels seen in endothelial dysfunction change the vessel response to injury. Furthermore, eNOS mutant mice still show a protective effect of female gender, indicating that the mechanism of this protection cannot be limited to upregulation of eNOS expression. The eNOS mutant mice also prove that eNOS modulates the cardiac contractile response to ss-adrenergic agonists and baseline diastolic relaxation. Atrial natriuretic peptide, upregulated in the hearts of eNOS mutant mice, normalizes cGMP levels and restores normal diastolic relaxation.

Topics: Animals; Brain; Brain Ischemia; Cyclic GMP; Endothelium, Vascular; gamma-Aminobutyric Acid; Glutamic Acid; Mice; Mice, Knockout; Myocardial Contraction; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Tunica Intima

Evidence has steadily accumulated to indicate that the rapid fluctuations in cyclic nucleotides during primary and secondary stroke are more than epiphenomena of the disease. During acute phases of ischemia, anoxia or hypoxia cyclic AMP rapidly accumulates in cerebral tissue, cerebrospinal fluid (CSF) and venous plasma, while cyclic GMP either remains unchanged or declines. The massive release of transmitters (catecholamines and adenosine) or ionic fluxes (Na+ and K+) may account for these observations. If reflow is established through a previously occluded vessel cyclic AMP content rises even higher in conjunction with a sharp rise in cyclic GMP. It is during this reflow period subsequent to longer term stroke (30-60 min) that the synaptic membrane enzyme, adenylate cyclase, is especially vulnerable. Presumably the cause of injury to cell membrane systems results from excess lactic acid accumulation and/or Ca++ entry through the damaged blood-brain barrier. The latter initiates breakdown of membrane phospholipids with resultant synthesis of vasoactive prostaglandins and formation of free radicals causing further insult to membrane phospholipids. Thus drugs acting to inhibit formation of prostaglandins, scavenge free radicals, reduce lactate formation, inhibit Ca++ entry or stabilize cell membranes have been shown to possess varying degrees of protective action toward adenylate cyclase. Moreover, cyclic AMP has been found to reverse stroke-induced vasospasm in central vessels. Reduced cyclic AMP content in CSF has been used to monitor the severity of coma, whereas clinical improvement was associated with predictable increases in the cyclic nucleotide. Therefore, cyclic nucleotides and related membrane enzyme systems might be used as target molecules in which to develop future therapeutic strategies for prevention or treatment of stroke.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Adenosine; Adenylyl Cyclases; Animals; Brain; Brain Ischemia; Brain Neoplasms; Capillaries; Cerebrovascular Disorders; Cyclic AMP; Cyclic GMP; gamma-Aminobutyric Acid; Guanylate Cyclase; Humans; Hypoxia, Brain; In Vitro Techniques; Lactates; Lactic Acid; Norepinephrine; Phospholipids; Protein Kinases; Synaptic Membranes; Tissue Distribution

Topics: Acidosis; Animals; Biological Transport, Active; Brain Ischemia; Calcium; Cell Membrane; Cerebrovascular Disorders; Cyclic GMP; Electrophysiology; Energy Metabolism; Epilepsy; Fatty Acids, Nonesterified; Free Radicals; Glutathione; Hypoglycemia; Hypoxia, Brain; Ions; Lactates; Lactic Acid; Microscopy, Electron; Mitochondria; Neuroglia; Neurons; Phospholipids; Time Factors

Cardiac arrest results in significant mortality after initial resuscitation due in most cases to ischemia-reperfusion induced brain injury and to a lesser degree myocardial dysfunction. Nitrite has previously been shown to protect against reperfusion injury in animal models of focal cerebral and heart ischemia. Nitrite therapy after murine cardiac arrest improved 22 h survival through improvements in myocardial contractility. These improvements accompanied transient mitochondrial inhibition which reduced oxidative injury to the heart. Based on preliminary evidence that nitrite may also protect against ischemic brain injury, we sought to test this hypothesis in a rat model of asphyxia cardiac arrest with prolonged survival (7d). Cardiac arrest resulted in hippocampal CA1 delayed neuronal death well characterized in this and other cardiac arrest models. Nitrite therapy did not alter post-arrest hemodynamics but did result in significant (75%) increases in CA1 neuron survival. This was associated with increases in hippocampal nitrite and S-nitrosothiol levels but not cGMP shortly after therapy. Mitochondrial function 1h after resuscitation trended towards improvement with nitrite therapy. Based on promising preclinical data, the first ever phase I trial of nitrite infusions in human cardiac arrest survivors has been undertaken. We present preliminary data showing low dose nitrite infusion did not result in hypotension or cause methemoglobinemia. Nitrite thus appears safe and effective for clinical translation as a promising therapy against cardiac arrest mediated heart and brain injury.

Topics: Animals; Blood Pressure; Brain Ischemia; CA1 Region, Hippocampal; Cyclic GMP; Double-Blind Method; Heart Arrest; Heart Rate; Humans; Male; Methemoglobin; Mitochondria; Neuroprotective Agents; Random Allocation; Rats; Rats, Sprague-Dawley; S-Nitrosothiols; Sodium Nitrite

Ischemic stroke is one of the leading causes of mortality worldwide. The available treatments are not effective. Phosphodiesterase 9A (PDE9A) is an intracellular cyclic guanosine monophosphate (cGMP) hydrolase considered to be a promising therapeutic target for brain diseases. This study explored neuroprotective effects and the underlying mechanism of LW33, a novel PDE9A inhibitor, on ischemic stroke in vitro and in vivo.. A middle cerebral artery occlusion (MCAO) model was established in adult male Sprague-Dawley rats and an oxygen-glucose deprivation/reoxygenation (OGD/R) model was established in human SH-SY5Y cells to mimic ischemia-reperfusion injury in vitro.. LW33 increased cell viability, reduced lactate dehydrogenase activity, and OGD/R-induced apoptosis of SH-SY5Y cells. The protective effects of LW33 against stroke occurred in the recovery phase. LW33 administration significantly reduced cerebral infarction volume in MCAO rats, without causing significant deformation or necrosis of neurons in the cortex. LW33 also improved learning and cognitive dysfunction and reduced other pathological changes in MCAO rats in the recovery period. Moreover, LW33 stimulated the cGMP/PKG/CREB pathway and up-regulated the expression of the apoptosis-related proteins, and this effect was reversed by KT5823 treatment.. LW33 inhibited cell apoptosis and promoted neuronal repair to alleviate OGD/R and MCAO induced pathological alterations via the cGMP/PKG/CREB pathway, indicating that LW33 may be a promising therapeutic target for ischemic stroke.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Brain Ischemia; Cyclic GMP; Glucose; Infarction, Middle Cerebral Artery; Ischemic Stroke; Male; Neuroprotective Agents; Oxygen; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Signal Transduction

Gastrodin, which is extracted from the Chinese herbal medicine Gastrodia elata Blume, can ameliorate neurogenesis after cerebral ischemia. However, it's possible underlying mechanisms remain still elusive. PDE9-cGMP-PKG signaling pathway is involved in the proliferation of neural stem cells (NSCs) after cerebral ischemia. In this study, we investigated whether the beneficial effect of gastrodin on hippocampal neurogenesis after cerebral ischemia is correlated with the PDE9-cGMP-PKG signaling pathway. Bilateral common carotid artery occlusion (BCCAO) in mice and oxygen-glucose deprivation/reoxygenation (OGD/R) in primary cultured hippocampal NSCs were used to mimic brain ischemic injury. The Morris water maze (MWM) test was executed to detect spatial learning and memory. Proliferation, differentiation, and mature neurons were examined using immunofluorescence. The survival and proliferation of NSCs were assessed by CCK-8 assay and BrdU immunofluorescence staining, respectively. ELISA and western blot were used to detect the level of the PDE9-cGMP-PKG signaling pathway. In BCCAO mice, administering gastrodin (50 and 100 mg/kg) for 14 d restored cognitive behaviors; meanwhile, neurogenesis in hippocampus was stimulated, and PDE9 was inhibited and cGMP-PKG was activated by gastrodin. Consistent with the results, administering gastrodin (from 0.01-1 μmol/L) for 48 h dose-dependently ameliorated the cell viability and promoted greatly the proliferation in primary hippocampal NSCs exposed to OGD/R. Gastrodin further decreased PDE9 activity and up-regulated cGMP-PKG level. KT5823, a PKG inhibitor, markedly abrogated the protective effects of gastrodin on OGD/R-injured NSCs, accompanied by the down-regulation of PKG protein expression, but had no effects on PDE9 activity and cGMP level. Gastrodin could accelerate hippocampal neurogenesis after cerebral ischemia, which is mediated, at least partly, by PDE9-cGMP-PKG signaling pathway.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Animals, Newborn; Benzyl Alcohols; Brain Ischemia; Cells, Cultured; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Gastrodia; Glucosides; Hippocampus; Male; Maze Learning; Mice; Mice, Inbred C57BL; Neurogenesis; Rats; Rats, Sprague-Dawley; Signal Transduction

This study aimed to investigate the protective effect of salvinorin A on the cerebral pial artery after forebrain ischemia and explore related mechanisms. Thirty Sprague-Dawley rats received forebrain ischemia for 10 min. The dilation responses of the cerebral pial artery to hypercapnia and hypotension were assessed in rats before and 1 h after ischemia. The ischemia reperfusion (IR) control group received DMSO (1 µL/kg) immediately after ischemia. Two different doses of salvinorin A (10 and 20 µg/kg) were administered following the onset of reperfusion. The 5th, 6th, and 7th groups received salvinorin A (20 µg/kg) and LY294002 (10 µM), L-NAME (10 μM), or norbinaltorphimine (norBIN, 1 μM) after ischemia. The levels of cGMP in the cerebrospinal fluid (CSF) were also measured. The phosphorylation of AKT (p-AKT) was measured in the cerebral cortex by western blot at 24 h post-ischemia. Cell necrosis and apoptosis were examined by hematoxylin-eosin staining (HE) and TUNEL staining, respectively. The motor function of the rats was evaluated at 1, 2, and 5 days post-ischemia. The dilation responses of the cerebral pial artery were significantly impaired after ischemia and were preserved by salvinorin A treatment. In addition, salvinorin A significantly increased the levels of cGMP and p-AKT, suppressed cell necrosis and apoptosis of the cerebral cortex and improved the motor function of the rats. These effects were abolished by LY294002, L-NAME, and norBIN. Salvinorin A preserved cerebral pial artery autoregulation in response to hypercapnia and hypotension via the PI3K/AKT/cGMP pathway.

Topics: Animals; Brain Ischemia; Cerebral Arteries; Chromones; Cyclic GMP; Disease Models, Animal; Diterpenes, Clerodane; Male; Morpholines; Naltrexone; NG-Nitroarginine Methyl Ester; Phosphatidylinositol 3-Kinases; Pia Mater; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Signal Transduction

Infants on chronic peritoneal dialysis (PD) have an increased risk of developing neurological morbidities; however, the underlying biological mechanisms are poorly understood. In this clinical study, we investigated whether PD-mediated impairment of nitric oxide (NO) bioavailability and signaling, in patients with persistently low systolic blood pressure (SBP), can explain the occurrence of cerebral ischemia.. Repeated blood pressure measurements, serial neuroimaging studies, and investigations of systemic nitrate and nitrite levels, as well as NO signaling, were performed in ten pediatric patients on PD. We consistently observed the loss of both inorganic nitrate (-17 ± 3%, P < 0.05) and nitrite (-34 ± 4%, P < 0.05) during PD, which may result in impairment of the nitrate-nitrite-NO pathway. Indeed, PD was associated with significant reduction of cyclic guanosine monophosphate levels (-59.4 ± 15%, P < 0.05). This reduction in NO signaling was partly prevented by using a commercially available PD solution supplemented with l-arginine. Although PD compromised nitrate-nitrite-NO signaling in all cases, only infants with persistently low SBP developed ischemic cerebral complications.. Our data suggests that PD impairs NO homeostasis and predisposes infants with persistently low SBP to cerebral ischemia. These findings improve current understanding of the pathogenesis of infantile cerebral ischemia induced by PD and may lead to the new treatment strategies to reduce neurological morbidities.

Topics: Arginine; Blood Pressure; Brain; Brain Ischemia; Cerebrovascular Circulation; Cyclic GMP; Female; Homeostasis; Humans; Hypotension; Infant; Infant, Newborn; Male; Nitrates; Nitric Oxide; Nitrites; Peritoneal Dialysis

Carbon monoxide (CO) is an accepted cytoprotective molecule. The extent and mechanisms of protection in neuronal systems have not been well studied. We hypothesized that delivery of CO via a novel releasing molecule (CORM) would impart neuroprotection in vivo against ischemia-reperfusion injury (IRI)-induced apoptosis of retinal ganglion cells (RGC) and in vitro of neuronal SH-SY5Y-cells via activation of soluble guanylate-cyclase (sGC).. To mimic ischemic respiratory arrest, SH-SY5Y-cells were incubated with rotenone (100 nmol/L, 4 h) ± CORM ALF186 (10-100 µmol/L) or inactivated ALF186 lacking the potential of releasing CO. Apoptosis and reactive oxygen species (ROS) production were analyzed using flow-cytometry (Annexin V, mitochondrial membrane potential, CM-H2DCFDA) and Western blot (Caspase-3). The impact of ALF186± respiratory arrest on cell signaling was assessed by measuring expression of nitric oxide synthase (NOS) and soluble guanylate-cyclase (sGC) and by analyzing cellular cGMP levels. The effect of ALF186 (10 mg/kg iv) on retinal IRI in Sprague-Dawley rats was assessed by measuring densities of fluorogold-labeled RGC after IRI and by analysis of apoptosis-related genes in retinal tissue.. ALF186 but not inactivated ALF186 inhibited rotenone-induced apoptosis (Annexin V positive cells: 25 ± 2% rotenone vs. 14 ± 1% ALF186+rotenone, p<0.001; relative mitochondrial membrane potential: 17 ± 4% rotenone vs. 55 ± 3% ALF186+rotenone, p<0.05). ALF186 increased cellular cGMP levels (33±5 nmol/L vs. 23±3 nmol/L; p<0.05) and sGC expression. sGC-inhibition attenuated ALF186-mediated protection (relative mitochondrial membrane potential: 55±3% ALF186+rotenone vs. 20 ± 1% ODQ + ALF186+rotenone, p<0.05). ALF186 protected RGC in vivo (IRI 1255 ± 327 RGC/mm(2) vs. ALF186 + IRI 2036 ± 83; p<0.05) while sGC inhibition abolished the protective effects of ALF186 (ALF186 + IRI 2036 ± 83 RGC/mm(2) vs. NS-2028 + ALF186 + IRI 1263 ± 170, p<0.05).. The CORM ALF186 inhibits IRI-induced neuronal cell death via activation of sGC and may be a useful treatment option for acute ischemic insults to the retina and the brain.

Topics: Animals; Apoptosis; Brain Ischemia; Carbon Monoxide; Cell Line, Tumor; Coordination Complexes; Cyclic GMP; Dose-Response Relationship, Drug; Female; Gene Expression Regulation, Enzymologic; Guanylate Cyclase; Humans; Male; Molybdenum; NADPH Oxidases; Neurons; Neuroprotective Agents; Organometallic Compounds; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptors, Cytoplasmic and Nuclear; Reperfusion Injury; Retinal Ganglion Cells; Rotenone; Signal Transduction; Soluble Guanylyl Cyclase

Striatal medium-sized spiny neurons (MSNs) are highly vulnerable to ischemia. A brief ischemic insult, produced by oxygen and glucose deprivation (OGD), can induce ischemic long-term potentiation (i-LTP) of corticostriatal excitatory postsynaptic response. Since nitric oxide (NO) is involved in the pathophysiology of brain ischemia and the dopamine D1/D5-receptors (D1-like-R) are expressed in striatal NOS-positive interneurons, we hypothesized a relation between NOS-positive interneurons and striatal i-LTP, involving D1R activation and NO production. We investigated the mechanisms involved in i-LTP induced by OGD in corticostriatal slices and found that the D1-like-R antagonist SCH-23390 prevented i-LTP in all recorded MSNs. Immunofluorescence analysis confirmed the induction of i-LTP in both substance P-positive, (putative D1R-expressing) and adenosine A2A-receptor-positive (putative D2R-expressing) MSNs. Furthermore, i-LTP was dependent on a NOS/cGMP pathway since pharmacological blockade of NOS, guanylate-cyclase, or PKG prevented i-LTP. However, these compounds failed to prevent i-LTP in the presence of a NO donor or cGMP analog, respectively. Interestingly, the D1-like-R antagonism failed to prevent i-LTP when intracellular cGMP was pharmacologically increased. We propose that NO, produced by striatal NOS-positive interneurons via the stimulation of D1-like-R located on these cells, is critical for i-LTP induction in the entire population of MSNs involving a cGMP-dependent pathway.

Topics: Animals; Benzazepines; Brain Ischemia; Corpus Striatum; Cyclic GMP; Glucose; Guanylate Cyclase; Interneurons; Long-Term Potentiation; Male; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Donors; Oxygen; Rats; Rats, Wistar; Receptor, Adenosine A2A; Receptors, Dopamine D1; Receptors, Dopamine D5; Synaptic Transmission

Nitric oxide (NO) is an intercellular retrograde messenger involved in several physiological processes such as synaptic plasticity, hippocampal long-term potentiation (LTP), and learning and memory. Moreover NO signaling is implicated in the pathophysiology of brain ischemia. In this study, we have characterized the role of NO/cGMP signaling cascade in the induction and maintenance of post-ischemic LTP (iLTP) in rat brain slices. Moreover, we have investigated the possible inhibitory action of zonisamide (ZNS) on this pathological form of synaptic plasticity as well as the effects of this antiepileptic drug (AED) on physiological activity-dependent LTP. Finally, we have characterized the possible interaction between ZNS and the NO/cGMP/PKG-dependent pathway involved in iLTP. Here, we provided the first evidence that an oxygen and glucose deprivation episode can induce, in CA1 hippocampal slices, iLTP by modulation of the NO/cGMP/PKG pathway. Additionally, we found that while ZNS application did not affect short-term synaptic plasticity and LTP induced by high-frequency stimulation, it significantly reduced iLTP. This reduction was mimicked by bath application of NO synthase inhibitors and a soluble guanyl cyclase inhibitor. The effect of ZNS was prevented by either the application of a NO donor or drugs increasing intracellular levels of cGMP and activating PKG. These findings are in line with the possible use of AEDs, such as ZNS, as a possible neuroprotective strategy in brain ischemia. Moreover, these findings strongly suggest that NO/cGMP/PKG intracellular cascade might represent a physiological target for neuroprotection in pathological forms of synaptic plasticity such as hippocampal iLTP.

Topics: Animals; Anticonvulsants; Brain Ischemia; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Hippocampus; Isoxazoles; Long-Term Potentiation; Male; Neuroprotective Agents; Nitric Oxide; Organ Culture Techniques; Rats; Rats, Wistar; Signal Transduction; Zonisamide

Cerebral ischemia resulting from transient or permanent cerebral artery occlusion leads to neuronal cell death, and eventually causes neurological impairments. Tadalafil (Cialis)is a long-acting phosphodiesterase type-5 (PDE-5) inhibitor used to treat erectile dysfunction. The therapeutic effects of PDE-5 inhibitors on chronic obstructive pulmonary disease, prostate hyperplasia, hypertension, and coronary heart disease have been reported. The present study investigated the effects of tadalafil on short-term memory, cyclic guanosine monophosphate (cGMP) level, apoptotic neuronal cell death, and cell proliferation in the hippocampus following transient global ischemia in gerbils. For this study, a step-down avoidance task, cGMP assay, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and immunohistochemistry for caspase-3 and 5-bromo-2'-deoxyuridine were performed. The results revealed that ischemic injury increased apoptotic neuronal cell death in the hippocampal CA1 region, impaired short-term memory, and decreased cGMP level. Ischemic injury enhanced cell proliferation in the hippocampal dentate gyrus. Tadalafil treatment improved short-term memory by suppressing ischemia-induced apoptotic neuronal cell death in the hippocampal CA1 region, and decreased cGMP level. Also, tadalafil suppressed the ischemia-induced increase in cell proliferation in the hippocampal dentate gyrus. We showed that tadalafil can overcome ischemia-induced apoptotic neuronal cell death, thus facilitates recovery following ischemic cerebral injury.

Topics: Animals; Antimetabolites; Apoptosis; Avoidance Learning; Brain Ischemia; Bromodeoxyuridine; Carbolines; Caspase 3; Cyclic GMP; Dentate Gyrus; Gerbillinae; Hippocampus; Immunohistochemistry; In Situ Nick-End Labeling; Memory, Short-Term; Neurons; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Tadalafil

The present study was designed to explore the mechanisms involved in the anti-ischemic action of lumbrokinase (LK) in brain. The enzyme immunoassay, spectrofluorimeter and flow cytometry were used to detect the level of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP), the Ca(2+) mobilization, and human platelet surface antigen expression in order to elucidate the anti-platelet action involved in LK cerebroprotection. RT-PCR and western blot were used to identify the role of Intercellular adhesion molecule-1 (ICAM-1) and Janus Kinase1/Signal Transducers and Activators of Transcription1 (JAK1/STAT1) pathway in protecting brain against ischemic injury by anti-thrombosis and anti-apoptosis. Results showed that LK significantly potentiated the activity of adenylate cyclase (AC), increased the cAMP level in vivo, remarkably inhibited the rise of rat platelet intracellular Ca(2+) ([Ca(2+)](i)), and attenuated the expression of Glycoprotein IIB/IIIA (GPIIB/IIIA) and P-selectin in human platelet stimulated by thrombin in vitro. Furthermore, the expressions of ICAM-1 and JAK1/STAT1 were remarkably regulated by LK in Human Umbilical Vein Endothelial Cell (HUVEC) and ischemic cerebral tissues. These data indicated that the anti-ischemic activity of LK was due to its anti-platelet activity by elevating cAMP level and attenuating the calcium release from calcium stores, the anti-thrombosis action due to inhibiting of ICAM-1 expression, and the anti-apoptotic effect due to the activation of JAK1/STAT1 pathway.

Topics: Animals; Blood Platelets; Brain Ischemia; Cells, Cultured; Cyclic AMP; Cyclic GMP; Endopeptidases; Endothelial Cells; Integrin beta3; Intercellular Adhesion Molecule-1; Male; Neuroprotective Agents; Platelet Membrane Glycoprotein IIb; Rats; Rats, Wistar; Thrombin

Taurine has been thought to be essential for the development and survival of neural cells and to protect them under cell-damaging conditions. In the brain stem taurine regulates many vital functions, including cardiovascular control and arterial blood pressure. We have recently characterized the release of taurine in the adult and developing brain stem under normal conditions. Now we studied the properties of preloaded [3H]taurine release under various cell-damaging conditions (hypoxia, hypoglycemia, ischemia, the presence of metabolic poisons and free radicals) in slices prepared from the mouse brain stem from developing (7-day-old) and young adult (3-month-old) mice, using a superfusion system. Taurine release was greatly enhanced under these cell-damaging conditions, the only exception being the presence of free radicals in both age groups. The ischemia-induced release was characterized to consist of both Ca2+-dependent and -independent components. Moreover, the release was mediated by Na+-, Cl--dependent transporters operating outwards, particularly in the immature brain stem. Cl- channel antagonists reduced the release at both ages, indicating that a part of the release occurs through ion channels, and protein kinase C appeared to be involved. The release was also modulated by cyclic GMP second messenger systems, since inhibitors of soluble guanylyl cyclase and phosphodiesterases suppressed ischemic taurine release. The inhibition of phospholipases also reduced taurine release at both ages. This ischemia-induced taurine release could constitute an important mechanism against excitotoxicity, protecting the brain stem under cell-damaging conditions.

Topics: 2,4-Dinitrophenol; Animals; Brain Ischemia; Brain Stem; Calcium Signaling; Cyclic GMP; Female; Guanylate Cyclase; Hydrogen Peroxide; Hypoglycemia; Ion Channels; Male; Mice; Microtomy; Neuroprotective Agents; Oxidants; Protein Kinase C; Sodium Chloride Symporters; Taurine; Uncoupling Agents

Nitric oxide (NO) mediates pathogenic changes in the brain subsequent to energy deprivation; yet the NO mechanism involved in the early events remains unclear. We examined the acute effects of severe hypoxia and oxygen-glucose deprivation (OGD) on the endogenous NO production and the NO-mediated pathways involved in the intracellular calcium ([Ca(2+)](i)) response in the rat hippocampal neurons. The levels of NO and [Ca(2+)](i) in the CA1 region of the slices rapidly elevated in hypoxia and were more prominent in OGD, measured by the electrochemical method and spectrofluorometry, respectively. The NO and [Ca(2+)](i) responses were enhanced by L-arginine and were reduced by NO synthase inhibitors, suggesting that the endogenous NO increases the [Ca(2+)](i) response to energy deprivation. Nickel and nifedipine significantly decreased the NO and [Ca(2+)](i) responses to hypoxia and OGD, indicating an involvement of L-type Ca(2+) channels in the NO-mediated mechanisms. In addition, the [Ca(2+)](i) responses were attenuated by ODQ or KT5823, inhibitors of the cGMP-PKG pathway, and by acivicin, an inhibitor of gamma-glutamyl transpeptidase for S-nitrosylation, and by the thiol-alkylating agent N-ethylmaleimide (NEM). Moreover, L-type Ca(2+) currents in cultured hippocampal neurons with whole-cell recording were significantly increased by L-arginine and were decreased by L-NAME. Pretreatment with NO synthase inhibitors or NEM but not ODQ abolished the effect of L-arginine on the Ca(2+) currents. Also, vitamin C, which decomposes nitrosothiol but not disulfide by reduction, reversed the change in the Ca(2+) current with L-arginine. Taken together, the results suggest that an elevated endogenous NO production enhances the influx of Ca(2+) via the hippocampal L-type Ca(2+) channel by S-nitrosylation during an initial phase of energy deprivation.

Topics: Animals; Arginine; Brain Ischemia; Calcium; Calcium Channels, L-Type; Cell Hypoxia; Cells, Cultured; Cyclic GMP; Electrophysiology; Enzyme Inhibitors; Fura-2; Hippocampus; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxygen; Rats; Rats, Sprague-Dawley; S-Nitrosothiols

This study was aimed to evaluate the influence of an antagonist of heme oxygenase, zinc protoporphyrin IX (ZnPPIX), on the production of endogenous carbon monoxide (CO) and the secondary cerebral injury after subarachnoid hemorrhage (SAH). Wistar rats were divided into non-SAH, SAH, and ZnPPIX groups. Autologus arterial hemolysate was injected into rat cisterna magna to induce SAH. CO and cyclic guanosine monophosphate (cGMP) levels in the brain, and lactate dehydrogenase (LDH) activity in serum were determined 24 hours and 72 hours after cisternal injection. It was found that 24 hours and 72 hours after SAH, the CO contents in SAH group were increased by 20.76% and 37.36%, respectively. CO content in ZnPPIX group was statistically lower than that in SAH group. No obvious change of cGMP content in SAH group was found. However, cGMP content in ZnPPIX group was lower than that in SAH group. Serum LDH activity increased significantly after induction of SAH. LDH activity in ZnPPIX group increased to a greater extent. It was concluded that ZnPPIX aggravates the cerebral injury secondary to experimental SAH by inhibiting the production of endogenous CO. The activation of HO/CO pathway is an intrinsic protective mechanism against cerebral ischemic injury after SAH.

Topics: Animals; Brain Ischemia; Carbon Monoxide; Cyclic GMP; Heme Oxygenase (Decyclizing); L-Lactate Dehydrogenase; Protoporphyrins; Rats; Rats, Wistar; Subarachnoid Hemorrhage; Time Factors

Inosine is a naturally occurring nucleoside degraded from adenosine. Recent studies have demonstrated that inosine has potent immunomodulatory and neuroprotective effects. In the present study, we further investigated the inhibitory effects of inosine on platelet activation in vitro and in vivo, as well as in attenuating middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia in rats.. Inosine concentration-dependently (0.5 to 6.0 mmol/L) inhibited platelet aggregation stimulated by agonists. Inosine (1.5 and 3.0 mmol/L) inhibited phosphoinositide breakdown, [Ca+2]i, and TxA2 formation in human platelets stimulated by collagen (1 microg/mL). In addition, inosine (1.5 and 3.0 mmol/L) markedly increased levels of cyclic guanylate monophosphate (GMP) and cyclic GMP-induced vasodilator-stimulated phosphoprotein Ser157 phosphorylation. Rapid phosphorylation of a platelet protein of molecular weight 47,000 (P47), a marker of protein kinase C activation, was triggered by collagen (1 microg/mL). This phosphorylation was markedly inhibited by inosine (3.0 mmol/L). Inosine (1.5 and 3.0 mmol/L) markedly reduced hydroxyl radical in collagen (1 microg/mL)-activated platelets. In in vivo studies, inosine (400 mg/kg) significantly prolonged the latency period of inducing platelet plug formation in mesenteric venules of mice, and administration of 2 doses (100 mg/kg) or a single dose (150 mg/kg) of inosine significantly attenuated MCAO-induced focal cerebral ischemia in rats.. Platelet aggregation contributes significantly to MCAO-induced focal cerebral ischemia. The most important findings of this study suggest that inosine markedly inhibited platelet activation in vitro and in vivo, as well as cerebral ischemia. Thus, inosine treatment may represent a novel approach to lowering the risk of or improving function in thromboembolic-related disorders and ischemia-reperfusion brain injury.

Topics: Animals; Brain Ischemia; Calcium; Cell Adhesion Molecules; Collagen; Contrast Media; Cyclic AMP; Cyclic GMP; Fluorescein; Free Radical Scavengers; Humans; Infarction, Middle Cerebral Artery; Inosine; Male; Mice; Microcirculation; Microfilament Proteins; Phosphatidylinositols; Phosphoproteins; Phosphorylation; Platelet Aggregation; Platelet Aggregation Inhibitors; Protein Kinase C; Rats; Rats, Wistar; Thrombosis; Thromboxane B2

Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system and initiates the events leading to ischemic brain damage. Glutamate receptor antagonists are being used to reduce neuronal damage observed after hypoxia and ischemia. The glutamate receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo-(a,d)-cyclohepten-5,10-imine maleate (MK-801) crosses the blood-brain barrier readily and produces a non-competitive use-dependent blockade of the N-methyl-D-aspartate subtype of glutamate receptor. The aim of this study was to investigate effects of MK-801 administered before and just after the onset of ischemia in rats on nitrite and cyclic guanosine monophosphate (cGMP) levels. Focal cerebral ischemia in rats was produced by permanent occlusion of right middle cerebral artery (MCAO). Nitrite and cGMP levels were measured in both cortex and cerebellum at 0, 10, and 60 min following MCAO. The same parameters were measured in rats treated with MK-801 (0.5 mg/kg, i.p.) 30 min before or just after MCAO. Ipsilateral cortical nitrite levels were increased relative to contralateral cortex after MCAO. No significant changes were observed in cerebellum. The cGMP concentrations in both sides of the cortex and cerebellum were increased at 10 and 60 min compared with 0 min values. cGMP level in the ipsilateral cortex was higher than contralateral cortex, whereas the opposite was found for the cerebellum. MK-801 treatment before or just after MCAO decreased significantly nitrite and cGMP production. Our data indicate that MK-801 treatment before or just after focal ischemia prevents the increase in NO and cGMP production.

Topics: Animals; Brain; Brain Ischemia; Cyclic GMP; Disease Models, Animal; Dizocilpine Maleate; Male; Nitrites; Rats; Time Factors

Superfused rat cerebral cortex slices were submitted to a continuous electrical (5 Hz) stimulation and treated with sodium azide (1-10 mM) in the presence of 2 mM 2-deoxyglucose ("chemical ischemia"). Presynaptic cholinergic activity, evaluated as acetylcholine release, was inhibited depending on the sodium azide concentrations and on the length of application (5-30 min). Following a 5-min treatment with 10 mM sodium azide, acetylcholine release was reduced to 45+/-2.3%; simultaneously, there was a 15- and 10-fold increase in glutamate and nitric oxide effluxes, respectively. After restoring normal superfusion conditions, acetylcholine release recovered to 70+/-3.1% of the controls; the N-methyl-D-aspartate receptor antagonist MK-801 (10 microM) as well as the nitric oxide scavengers, haemoglobin (20 microM) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide (150 microM), improved the recovery in presynaptic activity, showing that both glutamate and nitric oxide play detrimental roles in chemical ischemia. On the other hand, the post-ischemic recovery was worsened by the guanylylcyclase inhibitor 1H-[l,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (10 microM), suggesting that the activation of such a pathway plays a neuroprotective role and that the nitric oxide-induced harmful effects depend on different mechanisms. Chemical ischemia-evoked nitric oxide efflux partly derived from its calcium-dependent endogenous synthesis, since both the intracellular calcium chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (1 mM), and the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (100 microM), substantially prevented sodium azide effects. Nitric oxide efflux was only weakly reduced by MK-801 and was not modified by either the L-type calcium channel blocker, nifedipine (10 microM) or the N-type calcium channel blocker omega-conotoxin (0.5 microM), thus suggesting a prevailing intracellular calcium-dependence of nitric oxide production, although a partial extracellular calcium source cannot be ruled out. These findings show that sodium azide plus 2-deoxyglucose treatment is a useful protocol to induce brain ischemia in vitro and underline the involvement of nitric oxide in the complex events following the ischemic insult.

Topics: Acetylcholine; Animals; Antimetabolites; Brain Ischemia; Catalase; Cyclic GMP; Deoxyglucose; Energy Metabolism; Glutamic Acid; Guanylate Cyclase; In Vitro Techniques; Male; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Sprague-Dawley; Sodium Azide; Vasodilator Agents

Guanosine 3', 5'-cyclic monophosphate (cGMP) acts as a relaxant second messenger in the cerebral vessels. cGMP-specific phosphodiesterase type 5 (PDE5) inhibitor increases intracellular cGMP levels. This study investigated the effect of the PDE5 inhibitor on the ischemic brain.. Regional cerebral blood flow (rCBF), cGMP concentration, and infarction volume were measured in the rat middle cerebral artery occlusion model. Ten minutes after ischemia, the animals received an intravenous (i.v.) infusion of vehicle (phosphate-buffered saline), PDE5 inhibitor, zaprinast (10 mg/kg), or nitric oxide donor, S-nitroso-N-acetyl-penicillamine (SNAP, 100 microg/kg). rCBF was measured continuously by laser-Doppler flowmetry in the ischemic penumbra of the ischemic and contralateral sides under continuous blood pressure monitoring. cGMP concentrations were determined using the enzyme immunoassay and infarct volumes were estimated by 2,3,5-triphenyltetrazolium chloride staining.. The administration of zaprinast significantly increased rCBF in the ischemic brain compared with the pre-drug control value despite the decreased mean blood pressure, whereas it did not affect rCBF in the contralateral side. The cGMP concentration was significantly higher in the ischemic cortex compared with the contralateral side. SNAP infusion increased the cGMP concentration in the bilateral cortices to a similar extent. The volume of cerebral infarction was significantly decreased by zaprinast administration.. The PDE5 inhibitor zaprinast may selectively increase CBF in the ischemic brain via increased cGMP levels, thus providing a new strategy against acute cerebral infarction.

Topics: Analysis of Variance; Animals; Blood Circulation Time; Blood Pressure; Brain Ischemia; Cerebrovascular Circulation; Cyclic GMP; Disease Models, Animal; Functional Laterality; Immunoenzyme Techniques; Infarction, Middle Cerebral Artery; Laser-Doppler Flowmetry; Male; Nitric Oxide Donors; Penicillamine; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Wistar; Regional Blood Flow; Tetrazolium Salts; Time Factors

An 8-amino-acid peptide, NAPVSIPQ (NAP), was identified as the smallest active element of activity-dependent neuroprotective protein that exhibits potent neuroprotective action. Potential signal transduction pathways include cGMP production and interference with inflammatory mechanisms, tumor necrosis factor-alpha, and MAC1-related changes. Because of its intrinsic structure, NAP might interact with extracellular proteins and also transverse membranes. NAP-associated protection against oxidative stress, glucose deprivation, and apoptotic mechanisms suggests interference with fundamental processes. This paper identifies p53, a key regulator of cellular apoptosis, as an intracellular target for NAP's activity.

Topics: Alzheimer Disease; Animals; Apoptosis; Brain; Brain Ischemia; Cyclic GMP; Down-Regulation; Encephalitis; Macrophage-1 Antigen; Neuroprotective Agents; Oligopeptides; Oxidative Stress; PC12 Cells; Rats; Tumor Necrosis Factor-alpha; Tumor Suppressor Protein p53

Cortical spreading depression (CSD) is characterised by slowly propagating waves of cellular depolarization and depression and involves transient changes in blood flow, ion balance and metabolism. In cerebral ischaemia, peri-infarct CSD-like depolarization potentiates infarct growth, whereas preconditioning with a CSD episode protects against subsequent ischaemic insult. Thus, many of the long-lasting molecular changes that occur in CSD-affected tissue are presumed to be part of a 'neuroprotective cascade.' 3',5'-Cyclic guanosine monophosphate (cGMP) has been shown to be a neuroprotective mediator and the nitric oxide system, which increases cGMP production by soluble guanylate cyclase, is up-regulated by CSD. Atrial and C-type natriuretic peptide (ANP/CNP) are present in cerebral cortex and their actions are mediated via particulate guanylate cyclase receptors and cGMP production. Therefore, in further efforts to characterise the role of cGMP-related systems in CSD and neuroprotection, this study investigated possible changes in cortical natriuretic peptide expression following acute, unilateral CSD in rats. Using in situ hybridisation, significant 20-80% increases in ANP mRNA were detected in layers II and VI of ipsilateral cortex at 6 h and 1-14 days after CSD. Ipsilateral cortical levels were again equivalent to control contralateral values after 28 days. Assessment of cortical concentrations of ANP immunoreactivity by radioimmunoassay revealed a significant 57% increase at 7 days after CSD. Despite using a sensitive signal-amplification protocol, authentic ANP-like immunostaining was readily detected in subcortical nerve fibres, but was not reliably detected in normal or CSD-affected neocortex, suggesting the presence of very low levels, and/or active or differential processing of the peptide. Cortical CNP mRNA levels are not altered by CSD, indicating the specificity of the observed effects.Overall, these novel findings demonstrate a prolonged increase in cortical ANP expression after an acute episode of CSD. The overlap between the described time course of CSD-induced protection against ischaemic insult and demonstrated increases in ANP levels, suggest that ANP (like nitric oxide) may contribute to CSD-induced neuroprotection, via effects on cGMP production and other signal-transduction pathways.

Topics: Animals; Atrial Natriuretic Factor; Brain Ischemia; Cell Survival; Cerebral Cortex; Cerebral Infarction; Cortical Spreading Depression; Cyclic GMP; Gene Expression; Ischemic Preconditioning; Male; Neurons; Potassium Chloride; Rats; Rats, Sprague-Dawley; Reaction Time; RNA, Messenger; Signal Transduction; Up-Regulation

Nitrates exhibit a selectivity of action in different tissue types not fully recognized: in particular, the neuromodulatory and cardiovascular properties can be dissociated. A novel nitrate showed relatively weak systemic effects, but in the middle cerebral artery occlusion rat model of focal ischemia, reduced the cerebral infarct by 60-70% when administered 4 h after the onset of ischemia.

Topics: Animals; Blood Pressure; Brain; Brain Ischemia; Cyclic GMP; Dose-Response Relationship, Drug; Guanylate Cyclase; In Vitro Techniques; Infarction, Middle Cerebral Artery; Muscle Relaxation; Muscle, Smooth, Vascular; Neuroprotective Agents; Nitrates; Nitroglycerin; Propane; Rats; Vasodilator Agents

N-methyl-D-aspartate receptors (NMDARs) mediate ischemic brain damage but also mediate essential neuronal excitation. To treat stroke without blocking NMDARs, we transduced neurons with peptides that disrupted the interaction of NMDARs with the postsynaptic density protein PSD-95. This procedure dissociated NMDARs from downstream neurotoxic signaling without blocking synaptic activity or calcium influx. The peptides, when applied either before or 1 hour after an insult, protected cultured neurons from excitotoxicity, reduced focal ischemic brain damage in rats, and improved their neurological function. This approach circumvents the negative consequences associated with blocking NMDARs and may constitute a practical stroke therapy.

Topics: Amino Acid Sequence; Animals; Brain; Brain Ischemia; Calcium; Cells, Cultured; Cerebral Infarction; Cyclic GMP; Disks Large Homolog 4 Protein; Guanylate Kinases; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; N-Methylaspartate; Nerve Tissue Proteins; Neurons; Patch-Clamp Techniques; Peptides; Protein Binding; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Recombinant Fusion Proteins; Signal Transduction; Synaptic Transmission

Excitotoxicity has been implicated in the etiology of ischemic stroke and chronic neurodegenerative disorders. Hence, the development of novel neuroprotectant molecules that ameliorate excitotoxic brain damage is vigorously pursued. We used a neuroprotection-based cellular assay to screen a synthetic combinatorial library of N-alkylglycine trimers. Two compounds (6-1-2 and 6-1-10) that efficiently prevented excitotoxic neurodegeneration in vitro and in vivo were identified. Both molecules protected primary cultures of cerebellar neurons against glutamate-induced neuronal death with an efficiency equivalent to N-methyl-D-aspartate (NMDA) receptor antagonists. These trialkylglycines did not block appreciably the NMDA receptor channel, or attenuated glutamate-induced increase of Ca(2+), or affect the glutamate-nitric oxide-cGMP pathway. Intraperitoneal injection of both peptoids in mice attenuated > or = 80% ammonia-induced, NMDA receptor-mediated animal death. Furthermore, these two molecules reduced by > or = 50% the neurodegeneration in striatum in a rat model of cerebral ischemia. Neuroprotection against ischemia was associated with decreased activation of caspase-3, reflecting prevention of apoptotic neuronal death. Collectively, the results reported indicate that these trialkylglycines are new neuroprotectant leads with important in vivo activity against excitotoxicity, and that they act on a novel, yet-unrecognized cellular target. These lead compounds may become tolerated drugs for the treatment of acute and chronic neurodegenerative diseases with fewer side effects than NMDA receptor antagonists.

Topics: Ammonia; Animals; Apoptosis; Brain Ischemia; Calcium; Caspase 3; Caspases; Cell Death; Cells, Cultured; Combinatorial Chemistry Techniques; Cyclic GMP; Excitatory Amino Acid Antagonists; Excitatory Amino Acids; Glutamic Acid; Injections, Intraperitoneal; Mice; Neurons; Neuroprotective Agents; Oligopeptides; Peptoids; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Silver Staining

Nitric oxide (NO) may act as a toxin in several neuropathologies, including the brain damage resulting from cerebral ischaemia. Rat striatal slices were used to determine the mechanism of enhanced NO release following simulated ischaemia and, for estimating the NO concentrations, the activity of guanylyl cyclase served as a biosensor. Exposure of the slices for 10 min to an oxygen- and glucose-free medium caused a 70% fall in cGMP levels. On recovery, cGMP increased 2-fold above basal, where it remained for 40 min before declining. The pattern of changes matched those of cGMP or NO oxidation products measured during and after brain ischaemia in vivo. The increase observed during the recovery period was blocked by inhibition of NO synthase or NMDA receptors and was curtailed by tetrodotoxin, implying that it was caused by glutamate release leading to activation of the NMDA receptor-NO synthase pathway. Calibration of the cGMP levels against NO-stimulated guanylyl cyclase yielded a basal NO concentration of 0.6 nm. The peak NO concentration achieved on recovery from simulated ischaemia was estimated as 0.8 nm. These values are compatible with the low micromolar concentrations of NO oxidation products (chiefly nitrate) found by microdialysis in vivo, providing the NO inactivation rate (forming nitrate) is accounted for. NO at a concentration around 1 nm is unlikely to be toxic to cells. However, if the NO inactivation mechanism were to fail (as it can) the NO production rate normally providing only subnanomolar NO could readily generate toxic (microM) NO concentrations.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Arginine; Biosensing Techniques; Brain Ischemia; Cyclic GMP; Guanylate Cyclase; NADPH Dehydrogenase; Neostriatum; Neurons; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury

Although the macrolide immunosuppressant tacrolimus (FK506) is neuroprotective in animal models of focal and global cerebral ischaemia, the mechanism of this action is not known. FK506 inhibits the protein phosphatase calcineurin, whose substrates can include nitric oxide synthase (NOS), and the neuroprotective effect of FK506 has been attributed to inhibition of NOS activity. We have examined nitric oxide-mediated cyclic guanosine monophosphate (cGMP) accumulation in neonatal rat cerebellar prisms. As expected, N-methyl-D-aspartate (NMDA) induced a rapid, concentration dependent accumulation of cGMP that was inhibited by the NMDA receptor antagonist dizocilpine (MK801) and the NOS inhibitor L-nitro-arginine methyl ester. Phosphoserine immunopositivity following NMDA exposure was increased in the presence of FK506, confirming inhibition of calcineurin. However, FK506 had no effect on NMDA-stimulated cGMP accumulation. These findings suggest that the neuroprotective effect of FK506 may be mediated by mechanisms other than increased NOS phosphorylation.

Topics: Animals; Animals, Newborn; Brain Ischemia; Calcineurin; Calcineurin Inhibitors; Cerebellum; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Female; Immunosuppressive Agents; Male; N-Methylaspartate; Neurons; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Phosphorylation; Phosphoserine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Tacrolimus

Transient ischemia is known to lead to a long-lasting depression of cerebral metabolic rate and blood flow and to an attenuated metabolic and circulatory response to physiological stimuli. However, the corresponding responses to induced seizures are retained, demonstrating preserved metabolic and circulatory capacity. The objective of the present study was to explore how a preceding period of ischemia (15 min) alters the release of free fatty acids (FFAs) and diacylglycerides (DAGs), the formation of cyclic nucleotides, and the influx/efflux of Ca(2+), following intense neuronal stimulation. For that purpose, seizure activity was induced with bicuculline for 30 s or 5 min at 6 h after the ischemia. Extracellular Ca(2+) concentration (Ca(2+)(e)) was recorded, and the tissue was frozen in situ for measurements of levels of FFAs, DAGs, and cyclic nucleotides. Six hours after ischemia, the FFA concentrations were normalized, but there was a lowering of the content of 20:4 in the DAG fraction. Cyclic AMP levels returned to normal values, but cyclic GMP content was reduced. Seizures induced in postischemic animals showed similar changes in Ca(2+)(e), as well as in levels of FFAs, DAGs, and cyclic nucleotides, as did seizures induced in nonischemic control animals, with the exception of an attenuated rise in 20:4 content in the DAG fraction. We conclude that, at least in the neocortex, seizure-induced phospholipid hydrolysis and cyclic cAMP/cyclic GMP formation are not altered by a preceding period of ischemia, nor is there a change in the influx/efflux of Ca(2+) during seizure discharge or in associated spreading depression.

Topics: Animals; Bicuculline; Brain Ischemia; Calcium; Cyclic AMP; Cyclic GMP; Diglycerides; Electroencephalography; Fatty Acids, Nonesterified; Male; Phospholipids; Rats; Rats, Wistar; Seizures

To observe the role of NMDA receptor-Nitric Oxide(NOS)-cGMP pathway in ischemic brain injury.. The common cervical arteries of the rats were transient blocked bilaterally, in association with bleeding from their tails and followed by reperfusion. The procedures were repeated once again as above to establish a stable ischemic brain injury model. 3H-MK801 binding, cNOS activity, iNOS activity, and the cGMP content were measured at different time intervals after ischemic injury.. The results indicated that the change of 3H-MK801 binding varied among the cerebral cortex and hippocampus. cNOS activity began to rise in all parts of the brain 24 hours after operation and reached its peak in 3 days. The regions where iNOS and cNOS activity and cGMP content all increased significantly include the hippocamus, striatum and cortex, especially in hippocampus.. The tendency and degree of increase of those four indixes were cosistent during ischemic injury, indicating an important role of NMDA receptor-NO-cGMP in ischemic injury of the hippocampus.

Topics: Animals; Brain; Brain Ischemia; Cyclic GMP; Female; Hippocampus; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Rats; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury

Heme oxygenase-1 (HO-1, HSP32) is an early gene that is responsive to an array of pathological conditions including, but not limited to, hypoxia and cerebral ischemia. HO-1 cleaves the heme molecule and produces carbon monoxide (CO) and biliverdin (an antioxidant) and is essential for iron homeostasis. The purpose of this study was to investigate, using transgenic (Tg) mice, whether overexpression of HO-1 in the brain augments or attenuates cellular injury caused by ischemic stroke. Homozygous HO-1 Tg mice that overexpress HO-1 under the control of the neuron-specific enolase promoter (characterized previously) were used. Under halothane anesthesia and normothermic conditions, wild-type nontransgenic (nTg; n = 22) and HO-1 Tg (n = 24) mice were subjected to middle cerebral artery occlusion (MCAo). Six hours after induction of ischemia, Tg and nTg mice developed infarcts that were 39 +/- 6 and 63 +/- 9 mm3, respectively (p < 0.01). No significant difference between the two strains was observed in the values of brain edema (11.3 +/- 4% in Tg vs. 14.6 +/- 5% in nTg; p < 0.1). At 24 h after MCAo, Tg mice exhibited significant neuroprotection as determined by the stroke volumes (41 +/- 2 mm3 in Tg vs. 74 +/- 5 mm3 in nTg; p < 0.01) and values of ischemic cerebral edema (21 +/- 6% in Tg vs. 35 +/- 11% in nTg; p < 0.01). Data suggest that neuroprotection in Tg mice was, at least in part, related to the following findings: (a) constitutively up-regulated cyclic GMP and bcl-2 levels in neurons; (b) inhibition of nuclear localization of p53 protein; and (c) antioxidant action of HO-1, as detected by postischemic neuronal expression of ferritin, and decreases in iron staining and tissue lipid peroxidation. We suggest that pharmacological stimulation of HO-1 activity may constitute a novel therapeutic approach in the amelioration of ischemic injury during the acute period of stroke.

Topics: Animals; Arterial Occlusive Diseases; Behavior, Animal; Blotting, Northern; Brain Edema; Brain Ischemia; Cerebral Arterial Diseases; Cerebrovascular Circulation; Cyclic GMP; Ferritins; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Immunohistochemistry; Lipid Peroxidation; Membrane Proteins; Mice; Mice, Transgenic; NADPH Dehydrogenase; Neurons; Proto-Oncogene Proteins c-bcl-2; Stroke Volume; Tumor Suppressor Protein p53

The aim of this study was to investigate the role of nitric oxide in metabolic disturbances induced in brain tissue of fetal guinea pigs by oxygen-glucose deprivation. Experiments were performed on hippocampal slices so as to exclude the effects of nitric oxide on the cardiovascular system. Metabolic disturbances were assessed by measuring changes in energy metabolism and protein synthesis after different periods of oxygen-glucose deprivation (OGD). Ten min after OGD of 40 min duration, the concentration of cGMP in tissue slices rose from 1.35 +/- 0.38 to 18.6 +/- 1.04 pmol/mg protein (P < 0.05). This rise was almost completely inhibited by the addition of 100 microM N-nitro-L-arginine (NNLA), indicating that NO-synthase was strongly activated after OGD in fetal brain tissue. However, addition of NNLA improved neither protein synthesis nor energy metabolism measured 12 h after OGD. Thus, nitric oxide does not appear to contribute directly to processes leading to metabolic disturbances induced by transient ischemia in immature brain tissue.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cell Hypoxia; Cyclic GMP; Energy Metabolism; Fetus; Glucose; Guinea Pigs; Hippocampus; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Organ Culture Techniques; Oxygen

The present study was designed to evaluate the effects of pretreatment with a combination of desmethyl tirilazad (21-aminosteroid) plus dizocilpine maleate (N-methyl-D-aspartate receptor antagonist) and nimodipine (calcium channel antagonist) on constitutive nitric oxide synthase (cNOS) activity and cyclic guanosine monophosphate (cGMP) levels in brain homogenates of rats subjected to global cerebral transient ischemia induced by bilateral clamping of the carotids for 30 min and reduction of arterial pressure (to 50-60 mm Hg) by intravenous infusion of trimethaphan (30 mg/kg). Our results show that cerebral ischemia produced an increase in cNOS activity and cGMP levels in brain homogenates. Pretreatment with desmethyl tirilazad or dizocilpine maleate or nimodipine individually significantly suppressed (p < 0.01) the increase in cNOS activity and cGMP levels induced by cerebral ischemia, which may be related to their neuroprotective effect. Similar results were obtained with pretreatment by a combination of desmethyl tirilazad plus dizocilpine maleate plus nimodipine.

Topics: Animals; Brain; Brain Ischemia; Cyclic GMP; Dizocilpine Maleate; Enzyme Inhibitors; Male; Neuroprotective Agents; Nimodipine; Nitric Oxide Synthase; Pregnatrienes; Rats; Rats, Wistar

In this study, the N-Methyl-D-Aspartate (NMDA) receptor-dependent nitric oxide and cyclic GMP (cGMP) synthesis in the course of reperfusion after 5 min of ischemia in gerbil brain hemispheres and cerebellum were investigated. Moreover, the role of the neuronal isoform of nitric oxide (NO) synthase (nNOS) in liberation of NO in postischemic brain and the involvement of NO in membrane lipoperoxidations activated during reperfusion were evaluated. Enhancement of Ca2+/calmodulin-regulated NOS activity and cGMP level in brain hemispheres and in cerebellum during reperfusion was found to be coupled to the activation of the NMDA receptor. cGMP concentration 40% above the control level was observed to persist up to 7 days after ischemia. The amount of conjugated double bounds in membrane lipids and the level of thiobarbituric acid reactive substances were increased exclusively in brain hemispheres, indicating activation of lipid peroxidation. The NMDA receptor antagonist, MK-801, eliminated, and a rather selective nNOS inhibitor, 7-Nitroindazole (7-NI) attenuated, NMDA receptor-evoked enhancement of NOS activity and cGMP level in brain hemispheres and in cerebellum during reperfusion. Moreover, 7-NI decreased significantly membrane lipid peroxidation during the early time of reperfusion. Histological examination demonstrated that 7-NI protects against death a selected population of neuronal cells in CA1 layer of hippocampus. It is suggested that NMDA receptor dependence of NO release during reperfusion is responsible for the degeneration of some populations of neurons and that the effect is mediated by activation of free radical formation and lipid peroxidation. Moreover, in cerebellum, ischemia-evoked activation of glutamatergic system stimulates NO-dependent signal transmission. Our results indicated that 7-NI has a significant ameliorating effect on biochemical alterations evoked by ischemia, suggesting nNOS inhibitors as a potential therapeutic agents in reperfusion injury.

Topics: Animals; Brain Ischemia; Cerebellum; Cerebral Cortex; Cyclic GMP; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Gerbillinae; Indazoles; Lipid Peroxidation; Male; Membrane Lipids; Neuroprotective Agents; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Prosencephalon; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Signal Transduction; Thiobarbituric Acid Reactive Substances

Experiments were conducted to evaluate the effects of desmethyl tirilazad (10 mg/kg, i.p.), a 21-aminosteroid, on constitutive nitric oxide synthase (cNOS) activity and cyclic guanosine monophosphate (cGMP) levels in brain homogenates of rats subjected to cerebral global transient ischemia induced by bilateral clamping of the carotids for 30 minutes and reduction of arterial pressure (to 50-60 mmHg) by intravenous infusion of 1.5 ml of a solution of trimethaphan (5 mg/ml). Our results show that ischemia induces a rise in cNOS activity (from 62.0 +/- 6.1 to 133.3 +/- 13.3 pmol/min/mg protein) and cGMP levels (from 459.3 +/- 49.6 to 1074.1 +/- 132.1 fmol/mg protein). Pretreatment with desmethyl tirilazad abolishes these increases. These results are in agreement with the neuroprotective efficacy of desmethyl tirilazad in cerebral ischemia.

Topics: Animals; Blood Pressure; Brain Ischemia; Cerebral Cortex; Cyclic GMP; Male; Nitric Oxide Synthase; Pregnatrienes; Rats; Rats, Wistar; Trimethaphan

Glutamate receptor antagonists are protective in animal models of focal cerebral ischemia. Lamotrigine (3,5-diamino-6-[2,3-dichlorophenyl]-1,2, 4-triazine) is an anticonvulsant drug that blocks voltage-gated sodium channels and inhibits the ischemia-induced release of glutamate. Experiments in primary neuronal cultures implicate nitric oxide (NO) as a mediator of glutamatergic neurotoxicity acting via N-Methyl-D-Aspartate (NMDA) receptors. The effect of glutamate release inhibitor, Lamotrigine upon NO and cGMP production has been examined in focal cerebral ischemia in rats. Focal cerebral ischemia was produced by the permanent occlusion of right middle cerebral artery (MCA) in urethane anesthetized rats. A number of indicators of brain NO production (nitrite, cGMP) were determined in ipsilateral and contralateral cerebral cortex and cerebellum after 0, 10, 60 min of focal cerebral ischemia. The same parameters were measured in rats treated with Lamotrigine (20 mg/kg, i.p.) 30 min before or just after the occlusion of the right MCA.

Topics: Animals; Anticonvulsants; Brain Ischemia; Cerebellum; Cerebral Arteries; Cerebral Cortex; Cyclic GMP; Excitatory Amino Acid Antagonists; Functional Laterality; Lamotrigine; Male; Nitric Oxide; Radioimmunoassay; Rats; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Triazines

Recent evidence in primary neuronal cell culture implicates NO as a mediator of glutamatergic neurotoxicity acting via N-methyl-D-aspartate (NMDA) receptors. In this study, we investigated the effects of inhibition of NOsynthase activity in focal cerebral ischemia in rats. Focal cerebral ischemia was produced by permanent occlusion of right MCA in urethane anesthetized rats. A number of indicators of brain NO production, nitrite and cGMP were determined in ipsilateral and contralateral cerebral cortex and cerebellum after 0, 10 and 60 minutes of focal cerebral ischemia. The same parameters were measured in rats pre- and posttreated with the potent Nitric oxide synthase (NOS) inhibitor, NW-nitro-L-arginine methyl ester (L-NAME).

Topics: Animals; Brain Chemistry; Brain Ischemia; Cerebral Arteries; Cyclic GMP; Enzyme Inhibitors; Hearing Loss, Sudden; Labyrinth Diseases; Male; Nerve Tissue Proteins; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Rats

This study was aimed to examine properties and changes in nitric oxide synthase (NOS) activity and cGMP level during reperfusion after 5 min of brain ischemia in gerbils. Animals were treated 5 min before ischemia with NOS inhibitors: N-Nitro-L-arginine (NNLA), or 7-Nitroindazole (7-NI), or with the inhibitor of guanylate cyclase, LY 83583, or with hydrocortisone for 7 days before ischemia. Northern blot analysis was performed using specific cDNA for inducible NOS. It was observed that ischemia significantly enhances NOS activity and cGMP level. During reperfusion, biphasic increase in NOS activity and cGMP level took place with two peaks 15 min and 2 h after ischemia. NNLA, 7-NI, and LY 83583 eliminated enhancements of NOS activity and cGMP level, whereas glucocorticoid remained without effect. There was no activation of gene encoding inducible NOS (iNOS). Our results indicate that ischemia-reperfusion activates constitutive NOS. It is suggested that nitric oxide (NO) production during reperfusion is related to neuronal degeneration and that inhibitor of NOS offers a new therapeutical strategies.

Topics: Animals; Brain; Brain Chemistry; Brain Ischemia; Cyclic GMP; Gerbillinae; Male; Nitric Oxide Synthase; Reperfusion Injury

The stimulation of NMDA receptor activates NO dependent cGMP biosynthesis with dynamic and extent different for hippocampus and brain cortex. The significantly higher NO mediated cGMP level was observed in hippocampus than in brain cortex. NMDA receptor stimulation increases NO mediated cGMP formation about 8 fold in hippocampus and 2.5 fold in brain cortex as compared to basal value (2 mM CaCl2). The activity of NO synthase and the basal level of cGMP in unstimulated slices were only slightly higher in hippocampus then in brain cortex. The CA2+ calmodulin dependent NO synthase was found in brain membrane and cytosol fraction. The enzyme activity was not affected by glucocorticoids, even after 20 days of hydrocortisone treatment in a dose of 40 mg/kg b.w. Brain ischemia induced by ligation of both common carotid arteries in gerbils increases significantly NOS activities as well as the level of cGMP and putrescine but decreases mono-ADP-ribosylation of brain proteins during reperfusion period. The ischemia evoked changes of NOS/cGMP were eliminated by specific inhibitor of neuronal form of NOS, 7-Nitrodazole (7NI) administered in a dose of 25 mg/kg b.w. 5 min. before ischemia. This inhibitor has no effect on the level of putrescine enhanced during ischemia and also biphasically during reperfusion. The inhibitor of guanylate cyclase, LY 83583 administered in a dose of 6 mg/kg b.w. 5 min before ischemia diminishes not only the enhanced level of cGMP but also NOS activity stimulated by ischemia. These results indicate that activation of NMDA receptor stimulates more significantly NO/cGMP production in hippocampus than in brain cortex suggesting the role of NO in neuronal form of NOS and inhibitor of guanylate cyclase protect the brain against excessive production of nitric oxide and cGMP during ischemia-reperfusion. These compounds may offer a new strategy in the therapy of brain ischemia.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Culture Techniques; Cyclic GMP; Hippocampus; Male; Nitric Oxide; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

To determine the role of cerebral vasoconstriction in the delayed hypoperfusion phase in comatose patients after cardiac arrest.. Prospective study.. Medical intensive care unit in a university hospital.. 10 comatose patients (Glasgow Coma Score +/- 6)successfully resuscitated from a cardiac arrest occurring outside the hospital.. We measured the pulsatility index (PI) and mean blood flow velocity (MFV) of the middle cerebral artery, the cerebral oxygen extraction ratio and jugular bulb levels of endothelin, nitrate, and cGMP during the first 24 h after cardiac arrest.. The PI decreased significantly from 1.86 +/- 1.02 to 1.05 +/- 0.22 (p = 0.03). The MFV increased significantly from 29 +/- 10 to 62 +/- 25 cm/s (p = 0.003). Cerebral oxygen extraction ratio decreased also from 0.39 +/- 0.13 to 0.24 +/- 0.11 (p = 0.015). Endothelin levels were high but did not change during the study period. Nitrate levels varied widely and showed a slight but significant decrease from 37.1 mumol/l (median; 25th-75th percentiles: 26.8-61.6) to 31.3 mumol/l (22.1-39.6) (p = 0.04). Cyclic guanosine monophosphate levels increased significantly from 2.95 mumol/l (median; 25th-75th percentiles: 2.48-5.43) to 7.5 mumol/l (6.20-14.0) (p = 0.02).. We found evidence of increased cerebrovascular resistance during the first 24 h after cardiac arrest with persistent high endothelin levels, gradually decreasing nitrate levels, and gradually increasing cGMP levels, This suggests that active cerebral vasoconstriction due to an imbalance between local vasodilators and vasoconstrictors plays a role in the delayed hypoperfusion phase.

Topics: Adult; Aged; Aged, 80 and over; Brain Ischemia; Cardiopulmonary Resuscitation; Cerebrovascular Circulation; Coma; Critical Care; Cyclic GMP; Endothelin-1; Female; Heart Arrest; Humans; Male; Middle Aged; Nitrates; Prospective Studies; Vascular Resistance

Effects of intrauterine hypoxia-ischemia (HI) on brain functional development in the term rat were examined in cerebellar granule cell cultures obtained from an in utero HI model. On gestation d 17, HI conditions were achieved by complete clamping of the uterine vasculature for designated durations followed by removal of the clamps to permit reperfusion. Sham operation (surgery without vasculature clamping) was performed as the control. After surgery, the uterine horns were returned to dam's abdomen to let the pups deliver naturally. Severe HI insult from the surgical manipulation was evident in that the lactate levels of fetal brain increased, and fetal blood pH decreased with the duration of vasculature clamping up to 1 h. The experimental HI insult up to 1 h did not affect fetal survival rate, but retarded growth of fetuses or newborns was observed in the 1 h HI group. N-Methyl-D-aspartate (NMDA)- and kainate (KA)-stimulated cGMP formation and glutamate accumulation were measured in cerebellar granule cell cultures from 8-d-old pups suffering from various durations of antenatal HI insult. NMDA (100 microM)-induced elevation of cGMP was further augmented by a 10-35-min HI insult as compared with the control cells (62.4-78.2 versus 49 pmol/mg protein). In the presence of L-NG-monomethyl-arginine (L-NMMA, 150 microM), a nitric oxide synthase inhibitor, NMDA-induced cGMP formation was blocked, and the blockade of cGMP formation by L-NMMA (10 microM) could be reversed by simultaneous application of 1 mM arginine in both control and HI cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Brain Ischemia; Cells, Cultured; Cerebellar Diseases; Chronic Disease; Cyclic GMP; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Fetal Hypoxia; Gestational Age; Glutamic Acid; Hypoxia, Brain; Kainic Acid; N-Methylaspartate; Nitric Oxide Synthase; omega-N-Methylarginine; Rats; Rats, Sprague-Dawley

To elucidate the mechanisms of ischemic cell damage, biochemical disturbances developing during and following in vitro ischemia of 5, 10 or 15 min duration were compared in hippocampal slices prepared from gerbil and rat brains. During ischemia the release of glutamate from slices into the medium was determined, and after ischaemia and 10 min of recovery slices were analyzed for ATP levels, adenylate energy charge and cGMP content. The release of glutamate into the medium during in vitro ischemia and the recovery of energy metabolism determined after 10 min of recovery was almost identical in slices prepared from gerbil and rat hippocampi. In contrast, cGMP levels measured 10 min following in vitro ischemia were significantly higher in gerbil as compared to rat slices. Since after 10 min of recovery following in vitro ischemia, cGMP levels reflect nitric oxide (NO) synthesis (inhibition by NO synthase blocker), it is concluded that increased NO synthesis may contribute to the higher sensitivity of the gerbil as compared to the rat hippocampus towards transient ischemia.

Topics: Adenosine Triphosphate; Animals; Arginine; Brain Ischemia; Cyclic GMP; Energy Metabolism; Enzyme Inhibitors; Gerbillinae; Glutamic Acid; Hippocampus; In Vitro Techniques; Male; Nitric Oxide Synthase; Nitroarginine; Rats

Topics: Amino Acid Oxidoreductases; Animals; Arachidonic Acid; Arginine; Brain; Brain Ischemia; Cyclic GMP; Gerbillinae; Glutamates; Male; Membrane Lipids; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Receptors, N-Methyl-D-Aspartate; Signal Transduction

N-Methyl-D-aspartate (NMDA) receptor activation generates nitric oxide (NO) and cyclic GMP (cGMP) and produces 'excitotoxic' neuronal injury. To examine the possible role of cGMP in excitotoxicity, we evaluated the effects of agents that stimulate or inhibit cGMP activity on the release of lactate dehydrogenase from neuron-enriched cortical cultures. cGMP analogs exhibited no toxicity, and inhibitors of guanylate cyclase or of cGMP-dependent enzymes failed to protect cultures from the toxic effects of NMDA or the NO donor sodium nitroprusside. These findings argue against a role for cGMP in the pathogenesis of excitotoxic neuronal injury.

Topics: Animals; Brain Ischemia; Cells, Cultured; Cerebral Cortex; Cyclic GMP; L-Lactate Dehydrogenase; Neurons; Rats; Rats, Inbred Strains

The purpose of this experiment is to study the role of arginine vasopressin (AVP) in acute cerebral ischemic edema in Mongolian gerbils. The results show that intracerebroventricular injection (ICV) of AVP exacerbates acute ischemic brain edema, while ICV of AVP antiserum significantly decreases the ischemic brain edema. Nimodipine (calcium antagonist) cannot block this role of AVP in brain edema. In addition, the cortical Na(+)-K+ ATPase activity is significantly decreased, while the cAMP content of ischemic cortex and hypothalamus and the cGMP content of the hypothalamus are markedly increased after AVP ICV. These suggest that AVP may play an important role in the pathophysiologic process of ischemic brain edema by inhibiting the Na(+)-K+ ATPase activity of the cerebral cell membrane and the AVP receptors mediated by cAMP and cGMP.

Topics: Animals; Arginine Vasopressin; Brain; Brain Edema; Brain Ischemia; Cyclic AMP; Cyclic GMP; Female; Gerbillinae; Injections, Intraventricular; Male; Sodium-Potassium-Exchanging ATPase

Changes in the levels of cyclic AMP (cAMP) and cyclic GMP (cGMP) have been measured in brains of 20-day-old rat fetuses exposed to global intrauterine ischemia. Ischemia of different duration (0.5-30 minutes) did not alter the level of cAMP. In contrast, cGMP levels increased as a result of ischemia. This increase was seen even after a short period of ischemia (less than 5 minutes) and was maximal after 5 minutes, where a threefold increase could be observed. This stimulation was transient: after 30 min of ischemia, cGMP returned to the control level. Accumulation of cGMP can be related to the activation of guanylate cyclase, the activity of which is doubled after 15 minutes of ischemia. Immunoprecipitation of guanylate cyclase after in vivo labeling of the fetal brain with 32Pi revealed a threefold increase in the phosphorylation of the enzyme after 15 minutes of ischemia. The possible role of these modifications in cGMP metabolism during the course of ischemia is discussed.

Topics: Animals; Brain; Brain Ischemia; Cyclic AMP; Cyclic GMP; Fetal Hypoxia; Guanylate Cyclase; Phosphorylation; Protein Kinases; Protein Processing, Post-Translational; Rats; Rats, Inbred Strains

The content of cyclic nucleotides (cAMP and cGMP), hormones (T3, T4, insulin, protein-bound iodine and thyroid-stimulating hormone) and phosphodiesterase activity were examined in the acute period and over time in blood plasma of patients with ischemic stroke. The parameters under study were found to be interrelated. Also, it has been established that the T4/T3 and cAMP/cGMP ratios and the content of insulin may serve as important biochemical criteria for the gravity of ischemic stroke.

Topics: Acute Disease; Brain Ischemia; Cerebral Infarction; Cyclic AMP; Cyclic GMP; Humans; Insulin; Nucleotides, Cyclic; Phosphoric Diester Hydrolases; Thyroxine; Triiodothyronine

The effects of the anti-ischemic agents ifenprodil and its derivative SL 82.0715 ((+/-)-alpha-(4-chlorophenyl)-4-[(4-fluorophenyl) methyl]-1-piperidineethanol] have been analyzed in a number of models indicative of N-methyl-D-aspartate (NMDA) antagonistic potential in vitro and in vivo. Ifenprodil and SL 82.0715 potently and noncompetitively antagonize the stimulatory effects of NMDA on cyclic GMP production in immature rat cerebellar slices (IC50 values, 0.4 and 10 microM, respectively), as well as the NMDA-evoked [3H]acetylcholine release in adult rat striatal slices (IC50 values, 1.6 and 6.6 microM, respectively). Ifenprodil is 10 times more potent than (+/-)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) but less active than the reference noncompetitive NMDA channel blockers [MK 801, ((+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine ], phencyclidine and 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP)] in these models. Ifenprodil and SL 82.0715 partially displace (maximal displacement 40-50% at 10 microM) the NMDA receptor ligand [3H]CPP from its binding site to rat brain membranes (IC50 values, 0.1 and 0.3 microM, respectively) in a noncompetitive manner; in the micromolar range the two agents also partially displace the NMDA channel ligand [3H]TCP from its binding site to rat brain membranes, and noncompetitively antagonize the L-glutamate-induced increase in [3H]TCP binding. Ifenprodil (0.01-1 microM) partially antagonizes the depolarizing effects of NMDA on the immature rat hemisected spinal cord in vitro. In mouse cultured spinal cord neurons, ifenprodil dose-dependently antagonizes the depolarizing effects of micropressure applied NMDA. Inhibition of the effects of NMDA in this model by ifenprodil and SL 82.0715 is noncompetitive. In vivo and after systemic i.p. administration, ifenprodil and SL 82.0715 antagonize the stimulatory effects of intrastriatally dialyzed NMDA on striatal dopamine release in rats (ID50 values, 0.9 and 0.3 mg/kg, respectively), and block the harmaline-evoked increase in cerebellar cyclic GMP production in mice (ID50 values, 3 and 4 mg/kg, respectively). These results indicate that ifenprodil is a noncompetitive NMDA antagonist which has a mechanism of action distinct from either the reference competitive NMDA receptor antagonists (CPP and 2-amino-5-phosphonovalerate) or the noncompetitive NMDA channel blockers (phencyclidine, TCP and MK 801). The potent NMDA antagonistic effects of the ifenprodil c

Topics: Animals; Aspartic Acid; Brain Ischemia; Cells, Cultured; Cerebellum; Corpus Striatum; Cyclic GMP; Dopamine; Harmaline; In Vitro Techniques; Mice; N-Methylaspartate; Phencyclidine; Piperazines; Piperidines; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Spinal Cord

Topics: Animals; Brain Ischemia; Cerebral Cortex; Creatine Kinase; Cyclic AMP; Cyclic GMP; Disease Models, Animal; Female; L-Lactate Dehydrogenase; Male; Rabbits; Sodium

The effect of nimodipine on cerebral metabolism during ischemia and reflow was studied in female mongolian gerbils. Animals were divided into three experimental groups. Group 1 received 1 mg/kg nimodipine i.p. 1 h prior to ischemia. Group 2 received an injection of the vehicle, 5% polyethylene glycol 400. Group 3 received an equal volume of normal saline. Cerebral ischemia was induced by bilateral common carotid artery occlusion for 1, 2, or 5 min. Recirculation was established for 0, 1, or 5 min. Sham-operated animals served as nonischemic controls. Gerbils were killed by microwave irradiation. Regional levels of ATP, phosphocreatine, glucose, glycogen, cyclic AMP, and cyclic GMP were measured in brain extracts using standard assay techniques. Levels of metabolites in sham-operated animals did not differ among Groups 1, 2, and 3. At 1 min of ischemia, cortical and striatal ATP levels were highest in Group 1 (p less than 0.05 and p less than 0.01, respectively). After 5 min of recirculation, cortical and striatal glucose levels were highest in Group 1 (p less than 0.005). Regional levels of the metabolites measured at other times did not differ significantly among the three groups. Pretreatment with nimodipine thus retards the fall in ATP and facilitates the recovery of glucose in mongolian gerbils subjected to common carotid artery occlusion. A regional variability of this effect was observed.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Calcium Channel Blockers; Cerebrovascular Circulation; Cyclic AMP; Cyclic GMP; Female; Gerbillinae; Nicotinic Acids; Nimodipine

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Creatine; Cyclic AMP; Cyclic GMP; Evoked Potentials; Glucose; Guinea Pigs; Hippocampus; Hydrogen-Ion Concentration; In Vitro Techniques; Male; Models, Biological; Oxygen; Perfusion; Phosphocreatine

Topics: Acute Disease; Adaptation, Physiological; Animals; Brain Ischemia; Cerebral Cortex; Cholinergic Fibers; Cyclic AMP; Cyclic GMP; Female; Ganglia, Sympathetic; Male; Rats; Sympathectomy; Time Factors