Neuronal Nitric Oxide Synthase Messenger Research Articles

Tadalafil improves bladder dysfunction and object recognition in rats with pelvic venous congestion.

To examine the effects of tadalafil on bladder function and object recognition ability in rats with alterations in urinary frequency and locomotor activity as a result of pelvic venous congestion. A total of 48 female rats were divided into three groups (sham, pelvic venous congestion and pelvic venous congestion/tadalafil groups). In the pelvic venous congestion and pelvic venous congestion/tadalafil groups, the bilateral common iliac veins and uterine veins were ligated under anesthesia. Rats in the pelvic venous congestion/tadalafil group received a diet containing tadalafil, and the other rats were fed a normal diet. After 4weeks, rats underwent analysis of voiding behavior, locomotor activity, a novel object recognition test, continuous cystometry, measurement of plasma monoamines, and measurement of plasma and urinary nitric oxide metabolites. Expression of nitric oxide synthase messenger ribonucleic acid in the bladder wall was also assessed, along with histological examination of the bladder. Rats with pelvic venous congestion showed a higher urinary frequency, lower locomotor activity, and lower plasma and urinary nitric oxide levels than sham rats. The bladder wall endothelial nitric oxide synthase messenger ribonucleic acid level was low and object recognition was impaired. Pelvic venous congestion/tadalafil rats showed improvement in locomotor activity, bladder function and object recognition compared with pelvic venous congestion rats, as well as elevation of plasma and urinary nitric oxide, plasma monoamines, and bladder neuronal nitric oxide synthase messenger ribonucleic acid expression. Bladder wall vascularity was greater in pelvic venous congestion/tadalafil rats compared with sham rats. In rats with pelvic venous congestion, tadalafil might improve bladder function and the general condition by increasing blood flow to the bladder and brain, and by increasing dopamine levels.

Anaemia and the brain

This article reviews the physiological and pathophysiological effects of anaemia on the brain, focusing on the hypothesis that anaemia-induced cerebral hypoxia contributes to anaemic cerebral dysfunction and injury. It also reviews evidence that the regulated increase in cerebral blood flow observed during anaemia represents a compensatory neuroprotective mechanism invoked to optimize cerebral oxygen delivery, thereby protecting the brain from hypoxic injury. Severe anaemia, or low haematocrit, has been associated with cognitive dysfunction, impaired cerebral vascular regulation, neurological injury, and increased mortality, which suggests that the brain is vulnerable to anaemia-induced injury. Reduced cerebral tissue oxygen tension has been measured directly at haemoglobin concentrations near 35 g/l, suggesting that hypoxia may contribute to anaemic cerebral injury. A demonstration of increased hypoxic cerebral gene expression, including neuronal nitric oxide synthase, may provide a more sensitive means of determining the minimum haemoglobin concentration at which anaemia-induced cerebral hypoxia can be detected. The measurement of increased cerebral cortical neuronal nitric oxide synthase messenger RNA and protein levels in rats, at haemoglobin concentrations between 50 and 60 g/l, suggests that cerebral hypoxia occurred at these higher haemoglobin concentrations. Mechanisms regulating anaemic cerebral vasodilation and increased cerebral oxygen delivery, including nitric oxide, require further elucidation to establish their role in protecting the brain during anaemia. Characterization of mechanisms of anaemia-induced cerebral injury will contribute to the development of optimal therapeutic strategies for anaemic patients. Such strategies would include a clearer definition of transfusion triggers based on physiological endpoints. The overall goal of these efforts would be to minimize morbidity and mortality associated with anaemia.

Alteration of expression levels of neuronal nitric oxide synthase and haem oxygenase-2 messenger RNA in the hippocampi and cortices of young adult and aged cognitively unimpaired and impaired Long–Evans rats

Neuronal nitric oxide synthase and haem oxygenase-2 are postulated to be important enzymes involved in neuronal transmission and modulation of free radical levels in neurons. Hippocampal and cortical neuronal nitric oxide synthase and haem oxygenase-2 expressions were compared in young adult (6 months) and aged (24–26 months) Long–Evans rats. Aged rats were assigned as either cognitively unimpaired or impaired based on their performances in the Morris water maze behavioural task. In situ hybridization revealed increased neuronal nitric oxide synthase messenger RNA levels in selected regions of the hippocampi and cortices of aged rats. Moreover, aged cognitively impaired animals showed significantly higher neuronal nitric oxide synthase messenger RNA expression than aged cognitively unimpaired animals in several brain regions. For haem oxygenase-2 mRNA expressions, both young and aged cognitively impaired rats showed increased expressions in hippocampi compared with aged cognitively unimpaired rats, while no difference was found in cortices between all three animal groups. The increase in neuronal nitric oxide synthase messenger RNA expression levels in the aged animals may be related to increased free radical production occurring in ageing. Alternatively, elevated neuronal nitric oxide synthase and haem oxygenase-2 messenger RNA expressions may represent compensatory responses to oxidative stress and age-related changes in neuronal functions. Regarding cognitive status, aged cognitively impaired rats showed significant spatial memory deficits relative to young and aged cognitively unimpaired rats. Our data suggest a correlation between age-related cognitive impairment and change in messenger RNA expressions for the neuronal nitric oxide synthase and haem oxygenase-2 systems in brain areas implicated in learning and memory processes.

Cytological characterization of a pituitary folliculo-stellate-like cell line, Tpit/F1, with special reference to adenosine triphosphate-mediated neuronal nitric oxide synthase expression and nitric oxide secretion.

An immortal nonhormone-producing cell line with a characteristic star-shaped morphology, named Tpit/F1, was derived from an anterior pituitary gland of a temperature-sensitive large T antigen transgenic mouse. To characterize Tpit/F1 cells, we performed cytological studies, which revealed that Tpit/F1 cells express the messenger RNAs of neruonal nitric oxide (NO) synthase, S-100 protein, basic fibroblast growth factor, and pituitary-restricted transcription factor. The Tpit/F1 cells response to pituitary adenylate cyclase-activating peptide comprised the stimulated secretion of interleukin-6. Furthermore, glucocorticoids stimulate glutamine synthase production by Tpit/F1 cells. Considering these cytological characteristics together with their morphology, we deduced that Tpit/F1 cells are derived from pituitary folliculo-stellate (FS) cells. Our cytophysiological analyses of Tpit/F1 cells revealed that intracellular Ca2+ increased dose dependently on ATP administration (0-100 microM), and that this effect did not require the presence of extracellular Ca2+ and was not abolished by treatment with gadolinium, a Ca2+ channel blocker. The ATP-induced increase in intracellular Ca2+ ([Ca2+]i) was completely abolished by treatment with the Ca2+-adenosine triphosphatase (Ca2+-ATPase) inhibitor thapsigargin, which suggests that ATP increases [Ca2+]i by mobilizing internally stored Ca2+ followed by an influx of Ca2+. Moreover, UTP was equipotent with ATP in causing the [Ca2+]i increase in Tpit/F1 cells. Also, the Ca2+ response was prevented by the phospholipase C inhibitor, U-73122, but not by its inactive analog, U-73343. From these results we therefore concluded that ATP acts on Tpit/F1 cells via P2Y2-purinoceptors. Interestingly, both neuronal nitric oxide synthase messenger RNA and NO secretion were increased by ATP administration (10 and 100 microM). These results suggest the biological significance of the topological colocalization of FS cells and endocrine cells. Namely, ATP is cosecreted with hormones from endocrine cells and stimulates NO production by FS cells, and the released NO may regulate neighboring endocrine cell and blood vessels.

Nitric oxide and nitric oxide synthase in the early phase of perinatal asphyxia of the rat

The role of nitric oxide, a compound involved in neurotransmission and regulation of cerebral blood flow, in cerebral ischemia is still not fully elucidated yet. Although well studied in adult systems of cerebral ischemia/hypoxia, information on nitric oxide in perinatal asphyxia is limited and, in particular, no direct evidence for its generation has been provided. We therefore decided to study nitric oxide generation in brain of asphyctic rat pups by biophysical and biochemical methods. We used a simple, non-invasive rat model resembling the clinical situation in perinatal asphyxia: rat pups delivered by Caesarean section were placed into a water bath at 37°C still in patent membranes for various asphyctic periods (up to 20 min). Brain pH, cerebral blood flow, neuronal nitrix oxide synthase messenger RNA (by northern and dot blot analysis), immunoreactive protein (by western blot analysis) and nitric oxide synthase activity were determined; generation of nitric oxide was evaluated directly by electron paramagnetic resonance spectroscopy. Neuronal nitric oxide synthase messenger RNA activity and nitric oxide generation were unaffected, whereas neuronal nitric oxide synthase-immunoreactive protein of 150,000 mol. wt was decreased and of 136,000 mol. wt was increased with the length of the asphyctic period. This is the first report on direct evidence for the generation of nitric oxide in perinatal asphyxia and we demonstrate that nitric oxide production remains unaffected even by 20 min of asphyxia, at a time-point when cerebral blood flow was increased four-fold and severe acidosis was present. However, it was found that levels of immunoreactive neuronal nitric oxide synthase of 136,000 mol. wt were increased paralleling the length of asphyxia. Levels of the 150,000 mol. wt immunoreactive neuronal nitric oxide synthase protein decreased, suggesting a different regulation pattern. Thus, the present biochemical and biophysical results form the basis for further investigations on nitric oxide in perinatal asphyxia.

Corticosterone and phenytoin reduce neuronal nitric oxide synthase messenger RNA expression in rat hippocampus

The production and release of the corticosteroids, namely the glucocorticoids and the mineralocorticoids, are regulated by various stimuli, including stress. Previous studies from our laboratory have shown that chronic exposure to stress or to stress levels of glucocorticoids produces atrophy of the apical dendrites of CA3 pyramidal neurons in the hippocampus. This stress-induced dendritic remodeling is blocked by the anti-epileptic drug phenytoin, which suppresses glutamate release, and also by N-methyl- d-aspartate receptor antagonists. These results suggest an interaction between glucocorticoids and excitatory amino acids in the development of stress-induced atrophy of CA3 pyramidal neurons. Since nitric oxide is proposed to play an important role in mediating both the physiological and pathophysiological actions of excitatory amino acids, we examined the regulation of neuronal nitric oxide synthase messenger RNA expression by corticosterone and phenytoin in the rat hippocampus. The expression of neuronal nitric oxide synthase messenger RNA in hippocampal pyramidal neurons and granule neurons of the dentate gyrus was unaffected by 21-day administration of corticosterone (40 mg/kg), phenytoin (40 mg/kg) or the combination of corticosterone and phenytoin. However, in hippocampal interneurons, corticosterone/phenytoin co-administration led to a significant reduction in neuronal nitric oxide synthase messenger RNA levels when compared with vehicle controls. These results suggest that, during exposure to stress levels of corticosterone, phenytoin inhibits glucocorticoid-induced atrophy of CA3 pyramidal neurons by reducing neuronal nitric oxide synthase expression in hippocampal interneurons. Moreover, these results may provide another example of synaptic plasticity in the hippocampus mediated by nitric oxide synthase.

Decreased neuronal nitric oxide synthase messenger RNA and somatostatin messenger RNA in the striatum of Huntington's disease.

The cellular abundance of neuronal nitric oxide synthase and somatostatin messenger RNAs was compared in the caudate nucleus, putamen and sensorimotor cortex of Huntington's disease and control cases. Neuronal nitric oxide synthase messenger RNA was significantly decreased in the caudate nucleus and putamen, but not in the sensorimotor cortex in Huntington's disease; the decrease in neuronal nitric oxide synthase messenger RNA became more pronounced with the severity of the disease. Somatostatin gene expression was significantly decreased in the dorsal putamen in Huntington's disease, but was essentially unchanged in all other regions examined. The density of neurons expressing detectable levels of neuronal nitric oxide synthase messenger RNA was reduced in the striata of Huntington's disease cases with advanced pathology; the density of neurons expressing detectable levels of somatostatin messenger RNA was similar in control and Huntington's disease cases. Neuropeptide Y-, somatostatin- and NADPH-diaphorase-positive neurons were consistently present throughout the striatum across all the grades of the disease. Neuronal nitric oxide synthase and NADPH-diaphorase activity (a histochemical marker for nitric oxide synthase-containing neurons) co-localize with somatostatin and neuropeptide Y in interneurons in the human striatum and cerebral cortex. Although the neurodegeneration associated with Huntington's disease is most evident in the striatum (particularly the dorsal regions), neuronal nitric oxide synthase/neuropeptide Y/somatostatin interneurons are relatively spared. Nitric oxide released by neuronal nitric oxide synthase-containing neurons may mediate glutamate-induced excitotoxic cell death, a mechanism proposed to be instrumental in causing the neurodegeneration seen in Huntington's disease. The results described here suggest that although the population of interneurons containing somatostatin, neuropeptide Y and neuronal nitric oxide synthase do survive in the striatum in Huntington's disease they are damaged during the course of the disease. The results also show that the reduction in neuronal nitric oxide synthase and somatostatin messenger RNAs is most pronounced in the more severely affected dorsal regions of the striatum. Furthermore, the loss of neuronal nitric oxide messenger RNA becomes more pronounced with the severity of the disease; thus implying a down-regulation in neuronal nitric oxide synthase messenger RNA synthesis, and potentially neuronal nitric oxide synthase protein levels, in Huntington's disease.