Memory Enhancing Activity of Naringin in Unstressed and Stressed Mice: Possible Cholinergic and Nitriergic Modulation

The present study was designed to evaluate the effect of Naringin on memory of unstressed and stressed Swiss young albino mice. Naringin (80?mg/kg, i.p.) and donepezil (10?mg/kg) were administered for 21 successive days to separate groups of unstressed and stressed mice. The nootropic activity was evaluated using elevated plus maze and Hebbs Williams Maze. Brain acetylcholinesterase (AChE), brain nitrite and plasma corticosterone levels were also estimated. unpredictable chronic mild stress was produced by using different stressors. Naringin (80?mg/kg) and donepezil significantly showed memory enhancing activity in both unstressed and stressed mice. Naringin significantly reduced brain AChE activity and brain nitrite levels in both unstressed and stressed mice. Naringin (80?mg/kg) significantly reversed scopolamine-induced amnesia in unstressed and stressed mice. 7-Nitroindazole [a neuronal nitric oxide synthase (NOS) inhibitor] and aminoguanidine (an inducible NOS inhibitor) significantly enhanced memory improving activity and brain nitrite decreasing effect of naringin in unstressed and stressed mice respectively. Plasma corticosterone levels were significantly decreased by naringin (80?mg/kg) in stressed mice as compared to its control. Thus, naringin showed memory enhancing activity in unstressed mice probably by decreasing brain AChE activity and by inhibition of neuronal NOS. The memory enhancing activity of naringin in stressed mice might be due to decrease in brain AChE activity, inhibition of inducible NOS and also by decreasing the elevated plasma corticosterone levels.     

Nitric oxide impairs baroreflex gain during acute psychological stress

Psychological stress can suppress baroreflex function, but the mechanism has not been fully elucidated. Nitric oxide in the brain and in the adrenal cortex, as well as plasma glucocorticoids, increases during stress and has been shown to suppress reflex gain in unstressed animals. Therefore, the purpose of this study was to test the hypothesis that stress, caused by exposure to a novel environment, decreases baroreflex gain in rabbits through the actions of nitric oxide to increase corticosterone release. Baroreflex control of heart rate and plasma corticosterone levels was quantified before and after blockade of nitric oxide synthase (NOS) with N(omega)-nitro-L-arginine (L-NNA; 20 mg/kg iv) in conscious rabbits exposed to a novel environment and in the same rabbits once they had been conditioned to the environment. Stress significantly reduced baroreflex gain from -23.4 +/- 2 to -12.2 +/- 1.6 beats x min(-1) x mmHg(-1) (P < 0.05) and increased plasma corticosterone levels from 5.4 +/- 0.7 to 15.5 +/- 5.0 ng/ml (P < 0.05). NOS blockade increased gain in stressed animals (to -27.2 +/- 5.4 beats x min(-1) x mmHg(-1), P < 0.05) but did not alter gain in unstressed rabbits (-26.8 +/- 4.9 beats x min(-1) x mmHg(-1)) such that gain was equalized between the two states. NOS blockade increased plasma corticosterone levels in unstressed animals (to 14.3 +/- 2.1 ng/ml, P < 0.05) but failed to significantly alter levels in stressed rabbits (14.0 +/- 3.9 ng/ml). In conclusion, psychological stress may act via nitric oxide, independently of increases in corticosterone, to decrease baroreflex gain.     

Protective effects of gallic acid on hepatic lipid peroxide metabolism, glycoprotein components and lipids in streptozotocin-induced type II diabetic Wistar rats

We evaluated the protective effects of gallic acid (3,4,5-trihydroxybenzoic acid) on hepatic lipid peroxidation products, antioxidants, glycoprotein components, and lipids in streptozotocin-induced type II diabetic rats. To induce type II diabetes, rats were injected with streptozotocin intraperitoneally at a single dose of 40 mg/kg. Gallic acid (10 and 20 mg/kg) treatment was given to diabetic rats orally using an intragastric tube daily for 21 days. Streptozotocin-induced diabetic rats showed a significant increase in the levels of blood glucose, hepatic lipid peroxidation products, glycoprotein components, lipids, and the activity of HMG-CoA reductase and a significant decrease in the levels of plasma insulin and liver glycogen. In addition to this, the activities/levels of hepatic antioxidants were decreased in diabetic rats. Gallic acid (10 and 20 mg/kg) treatment showed significant protective effects on all the biochemical parameters studied in diabetic rats. Thus, our study shows the antihyperglycemic, antilipid peroxidative, antioxidant, and antilipidemic effects of gallic acid in streptozotocin-induced type II diabetic rats. A diet containing gallic acid may be beneficial to type II diabetic patients.     

A new cerebral ischemic injury model in rats,preventive effect of gallic acid and in silico approaches

Current study was designed multiple occlusions and reperfusion of bilateral carotid arteries induced cerebral injury model and evaluated the protective effect of gallic acid on it. In silico study was involved to study gallic acid binding affinity on cerebrotonic proteins compared with standard drugs using Autodoc vina tool. Cerebral ischemia was induced by occlusion of bilateral common carotid arteries for 10 mins followed by 10 reperfusions (1 cycle), cycle was continued to 3 cycles (MO/RCA), then pathological changes were observed by estimation of brain antioxidants as superoxide dismutase, glutathione, catalase, oxidants like malonaldehyde, cerebral infarction area, histopathology, and study gallic acid treatment against cerebral injury. Gallic acid exhibited a strong binding affinity on targeted cerebrotoxic proteins. MO/RCA rat brain antioxidant levels were significantly decreased and increased MDA levels (p < 0.0001), Infarction size compared to sham rats. Gallic acid treatment rat brain MDA levels significantly decreased (p < 0.4476) and increased SOD (p < 0.0001), CAT (p < 0.0001), GSH (p < 0.0001), cerebral infarction area when compared to MO/RCA group. Developed model showed significant cerebral ischemic injury in rats, injury was ameliorated by Gallic acid treatment and in silico approaches also inhibit the cerebrotoxic protein function by targeting on active sites.     

Investigation of the possible protective role of gallic acid on paraoxanase and arylesterase activities in livers of rats with acute alcohol intoxication

Gallic acid, a polyphenyl class natural product from gallnut and green tea, is known to be antioxidant, anti‐inflammatory and radical scavenger. In this study, we aimed to investigate the possible protective effects of gallic acid on paraoxonase and arylesterase activities in liver exposed to acute alcohol intoxication. Paraoxonase and arylesterase activities in liver tissue and serum aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase levels were measured. Histological investigations were also made. In our study, we observed a significant increase of serum alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase activities, which are indicators of liver damage after acute ethanol consumption. Gallic acid therapy has significantly reduced the increase in these biomarkers, indicating a possible hepatoprotective effect of gallic acid. Ethanol consumption caused a significant decrease in liver paraoxonase activity (P < 0.001). Gallic acid treatment partly restored this decreased paraoxonase activity, which resulted from ethanol administration. A gallic acid dose of 100 mg/kg was observed as highest restoring effect for paraoxonase activity (P < 0.05). The activity of arylesterase was decreased in the ethanol group as compared with the control group, but this was not significant. However, 50 mg/kg of gallic acid treatment restored the loss of this activity due to ethanol exposure (P < 0.001). We observed that gallic acid ameliorates the liver damage caused by excessive alcohol consumption in a dose‐dependent way. Our results in this study showed that gallic acid might have a protective effect against alcoholic liver disease. Copyright © 2012 John Wiley & Sons, Ltd.     

Nitric oxide- and oxygen-derived free radical generation from control and lipopolysaccharide-treated rat polymorphonuclear leukocyte.

Previous studies from this lab have shown NO-mediated modulation of free radical generation from polymorphonuclear leukocytes (PMNs), following hypoxic-reoxygenation as well as in the normoxic cells. The present study is an attempt to investigate further the regulation of NO and free radical generation in the lipopolysaccharide (LPS)-treated PMNs. PMNs were isolated from the rat blood and peritoneal cavity, 4 h after LPS (1 mg/kg, i.p.) treatment. Nitric oxide synthase (NOS) activity and nitrite content were increased in the peripheral and peritoneal PMNs following LPS treatment. An increase in the apparent V(max) for l-arginine uptake was also observed in the LPS-treated peripheral PMNs, while peritoneal PMNs exhibited increase in both apparent V(max) and affinity for l-arginine. Synthesis of nitrite did not augment after increasing the availability of substrate to control PMNs, however, peripheral and peritoneal PMNs from LPS-treated rats utilized l-arginine more efficiently for nitrite synthesis. NOS activity, l-arginine uptake, and its utilization were maximal in the peritoneal PMNs. Arachidonic acid (AA, 1 x 10(-6) M)-induced free radical generation from PMNs was also enhanced significantly after LPS treatment. Preincubation of PMNs with nitrite elevated the free radical generation and myeloperoxidase (MPO) release. MPO and antioxidant enzyme activity in the PMNs was significantly augmented after LPS treatment. NOS inhibitors, aminoguanidine and 7-nitroindazole, inhibited arachidonic acid-induced free radical generation from LPS treated PMNs. The results obtained thus indicate that augmentation of free radical generation from rat PMNs following LPS treatment appears to be regulated by NO and MPO.     

Role of nitric oxide in the nicotine-induced pituitary-adrenocortical response.

Nitric oxide (NO) is a major signaling molecule and biological mediator of the hypothalamic-pituitary-adrenal (HPA) axis. We investigated the role of NO formed by endothelial (e), neuronal (n) and inducible (i) nitric oxide synthase (NOS) in the stimulatory effect of nicotine on the HPA axis in rats under basal conditions. Also possible interaction of NOS systems with endogenous prostaglandins (PG) in that stimulation was assessed. NOS and cyclooxygenase inhibitors were administered i.p. 15 min prior to nicotine (2, 5 mg/kg i.p.). Plasma ACTH and serum corticosterone levels were measured 1 h after nicotine injection. NOS blockers given alone did not markedly affect the resting ACTH and corticosterone levels. L-NAME (2-10 mg/kg), a broad spectrum NOS inhibitor considerably and dose dependently enhanced the nicotine-induced ACTH and corticosterone secretion. L-NNA (2 mg/kg) and 7-nitroindazole (7-NI 20 mg/kg), neuronal NOS inhibitors in vivo also significantly augmented the nicotine-induced ACTH and corticosterone levels. L-arginine greatly impaired the nicotine-induced hormone responses and reversed the L-NNA elicited enhancement of the nicotine-evoked ACTH and corticosterone response. In contrast to the constitutive eNOS and nNOS antagonists, an inducible NOS antagonist guanethidine (50-100 mg/kg i.p.) did not substantially affect the nicotine-elicited pituitary-adrenocortical responses. Indomethacin (2 mg/kg i.p.), a non-selective cyclooxygenase blocker abolished the L-NAME and L-NNA-induced enhancement of the nicotine-evoked ACTH and corticosterone response. These results indicate that NO is an inhibitory mediator in the HPA axis activity. Inhibition of its generation by eNOS and nNOS significantly enhances the nicotine-induced HPA response. Under basal conditions iNOS is not involved in the nicotine-induced ACTH and corticosterone secretion. Prostaglandins play an obligatory role in the response of HPA axis to systemic nicotine administration.     

Retinoic acid and host-pathogen interactions: effects on inducible nitric oxide synthase in vivo

Vitamin A and its metabolite retinoic acid modulate the host response to pathogens through poorly characterized mechanisms. In vitro studies have suggested that retinoic acid decreases inducible NO synthase (NOS2, or iNOS) expression, a component of innate immunity, in several cell types stimulated with lipopolysaccharide (LPS) or cytokines. This study investigated the effect of retinoic acid on LPS-stimulated NOS2 expression in vivo. Wistar-Kyoto rats received all-trans retinoic acid (RA, 10 mg/kg) or vehicle intraperitoneally daily for 5 days followed by LPS (4 mg/kg) or saline intraperitoneally and were killed 6 h later. NOS2 activation was estimated by mRNA (RT-PCR) and protein (Western-blot) expression and plasma nitrate/nitrite accumulation. In sharp contrast to previous in vitro study reports, RA significantly enhanced NOS2 mRNA, protein expression, and plasma nitrate/nitrite concentration in LPS-injected rats but not in saline-injected rats. This was associated with increased expression of interleukin-2, interferon (IFN)-gamma and IFN regulatory factor-1 mRNAs in several organs and increased IFN-gamma plasma concentration. RA significantly increased mortality in LPS-injected rats. The NOS inhibitor aminoguanidine (50 mg/kg before LPS injection) significantly attenuated the RA-mediated increase in mortality. These results demonstrate for the first time that RA supplementation in vivo enhances activation of the LPS-triggered NOS2 pathway.     

Role of glucocorticoids in the stress-induced suppression of testicular steroidogenesis in adult male rats.

We have examined the role of glucocorticoids in the stress-induced inhibition of testicular steroidogenesis. Immobilization (3 hr) reduced plasma testosterone (T) levels to 24% of control values but did not affect plasma LH levels. This reduction was partially reversed by in vivo injections of the antiglucocorticoid, RU486, prior to the stress session at a dose of 10 mg/kg BW, but not at 1.0 or 50 mg/kg BW. Stressed rats that were treated with 10 mg/kg BW RU486 had twofold higher plasma T levels than vehicle-treated stressed animals. Injections of RU486 did not affect plasma LH levels in control or stressed rats and did not affect T levels of unstressed rats. Stressed rats had eightfold higher plasma corticosterone levels than controls, and RU486 had no effect on control or stress levels of corticosterone. The possible role of glucocorticoids in mediating the effect of stress on testicular T production was investigated also in vitro by incubating testicular interstitial cells from unstressed rats for 3 hr with corticosterone (0, 0.01, 0.1, or 1.0 microM) or dexamethasone (0, 0.001, 0.01, or 0.1 microM), followed by an additional 2 hr with hCG (0, 25, 50, or 100 microIU). Both corticosterone and dexamethasone inhibited hCG-stimulated T production in a dose-dependent manner. Cells incubated with the highest concentration of either of the glucocorticoids showed significantly reduced responses to hCG stimulation. In the absence of hCG, in vitro T production was not affected by dexamethasone or 0.01 and 0.1 microM corticosterone. However, the highest dose of corticosterone (1.0 microM) produced a 63% elevation in basal T production. Coincubation of testicular interstitial cells with corticosterone (1.0 microM) or dexamethasone (0.1 microM) and RU486 (0.01, 0.1, and 1.0 microM) reversed the glucocorticoid-induced suppressions of T production in a dose-dependent manner. Our results suggest that during stress increases in plasma levels of glucocorticoids in male rats act via glucocorticoid receptors on testicular interstitial cells to suppress the testicular response to gonadotropins, and that the decline of testosterone production during immobilization stress is in part mediated by a direct action of glucocorticoids on the testis.     

Role of nitric oxide in obsessive–compulsive behavior and its involvement in the anti-compulsive effect of paroxetine in mice

In view of the reports that nitric oxide modulates the neurotransmitters implicated in obsessive–compulsive disorder, patients with obsessive–compulsive disorder exhibit higher plasma nitrate levels, and drugs useful in obsessive–compulsive disorder influence nitric oxide, we hypothesized that nitric oxide may have some role in obsessive–compulsive behavior. We used marble-burying behavior of mice as the animal model of obsessive–compulsive disorder, and nitric oxide levels in brain homogenate were measured using amperometric nitric oxide-selective sensor method. Intraperitoneal administration of nitric oxide enhancers viz. nitric oxide precursor—l-arginine (800 mg/kg), nitric oxide donor—sodium nitroprusside (3 mg/kg) or phosphodiesterase type 5 inhibitor—sildenafil (3 mg/kg) significantly increased marble-burying behavior as well as brain nitrites levels, whereas treatment with 7-nitroindazole—neuronal nitric oxide synthase inhibitor (20–40 mg/kg, i.p.) or paroxetine—selective serotonin reuptake inhibitor (5–10 mg/kg, i.p.) dose dependently attenuated marble-burying behavior and nitrites levels in brain. Further, co-administration of sub-effective doses of 7-nitroindazole (10 mg/kg) and paroxetine (2.5 mg/kg) significantly attenuated marble-burying behavior. Moreover, pretreatment with l-arginine (400 mg/kg, i.p.), sodium nitroprusside (2.0 mg/kg, i.p.) or sildenafil (2.0 mg/kg, i.p.) significantly attenuated the inhibitory influence of 7-nitroindazole (40 mg/kg) or paroxetine (10 mg/kg) on marble-burying behavior as well as on brain nitrites levels. None of the above treatment had any significant influence on locomotor activity. In conclusion, obsessive compulsive behavior in mice appears related to nitric oxide in brain, and anti-compulsive effect of paroxetine appears to be related to decrease central levels of nitric oxide.     

Time-Dependent Variations in Serum Nitrite, 6-Keto-Prostaglandin F1α and Thromboxane B2 Levels Induced by Lipopolysaccharide in Mice

Clinical features of certain immuno-inflammatory disorders exhibit time-dependent fluctuations, which could be related to circadian rhythmicity of proinflammatory mediator production. Many biologically active substances including nitric oxide (NO) and eicosanoids are released into the circulation in sepsis. Increased NO and eicosanoid levels have been reported to be responsible from death in septic shock. The aim of this study was to investigate the variations in the NO and eicosanoid production and mortality induced by bacterial endotoxin, lipopolysaccharide (LPS) injected either in the morning or in the evening. Experiments were performed on mice synchronised to 12 h light and 12 h dark (lights on at 09:00 h). Animals were injected intraperitoneally with LPS (10 mg/kg) at 09:00 (morning) and 21:00 h (evening) alone or in combination with aminoguanidine (NO synthase (NOS) inhibitor) (100 mg/kg) or indomethacin (cyclooxygenase (COX) inhibitor) (100 mg/kg). The serum was separated from blood samples obtained at nine different time points. Nitrite (stable product of NO), 6-keto-prostaglandin F_1α (6-keto-PGF_1α, stable product of prostacyclin) and thromboxane B₂ (TxB₂, stable product of thromboxane) concentrations in serum samples were measured. Serum nitrite levels showed a 24 h circadian rhythmicity depending on LPS injection time. Morning injection caused a peak after 15 h, while evening injection had two peaks after 9 and 18 h. The peak values obtained from morning and evening injections were significantly decreased by aminoguanidine and indomethacin. When LPS injected to mice in the morning and in the evening, it gradually increased the mortality rate within 24 h which could be abolished by aminoguanidine, but not indomethacin. Indomethacin-induced inhibition on LPS-induced nitrite levels was higher in the morning than in the evening. 6-keto-PGF_1α and TxB₂ levels were decreased by indomethacin when injected with LPS at both injection times, but not aminoguanidine. These results showed that there is an interaction between NO and eicosanoids, and LPS may produce different effects on NOS activity, but not eicosanoid production and mortality, depending on injection time in the experimental septic shock model in mice. Chronopharmacological manipulations of NOS and COX pathways and interactions between them could lead to novel therapeutic approaches for the treatment of septic shock.     

Immunoenhancing effects of alprazolam in mice

The GABA/benzodiazepine receptor chloride channel complex has been proposed to play a modulatory role in immune function. The effects of alprazolam, a triazolobenzodiazepine with high affinity for "central" benzodiazepine receptors, were examined on several parameters of immune function in mice. Natural killer cell activity, mixed leukocyte reactivity and mitogen-induced lymphocyte proliferation were all significantly increased two hr after administration of low doses (0.02-1.0 mg/kg) of alprazolam. Twenty four hr later, similar but less robust immunoenhancing effects were observed. Higher doses of alprazolam (5-10 mg/kg) did not affect these measures of immune function. The immunoenhancing effects of alprazolam did not appear related to corticosterone levels. In contrast, vehicle injection caused a profound suppression of these immune parameters two hr later, which was no longer apparent 24 hr later. This immunosuppression appeared to correlate with a concurrent rise in serum corticosterone levels. These data support the hypothesis that the GABA/benzodiazepine receptor chloride channel complex modulates immune function. Use of low doses of alprazolam may be of potential clinical importance when immunoenhancement is required.     

Nitric oxide mediates the interleukin-1beta- and nicotine-induced hypothalamic-pituitary-adrenocortical response during social stress.

We investigated the role of nitric oxide (NO) in the interleukin 1beta (IL-1beta) and nicotine induced hypothalamic-pituitary-adrenal axis (HPA) responses, and a possible significance of CRH and vasopressin in these responses under basal and social stress conditions. Male Wistar rats were crowded in cages for 7 days prior to treatment. All compounds were injected i.p., nitric oxide synthase (NOS) inhibitors, alpha-helical CRH antagonist and vasopressin receptor antagonist 15 min before IL-1beta or nicotine. Identical treatment received control non-stressed rats. Plasma ACTH and serum corticosterone levels were measured 1 h after IL-1beta or nicotine injection. L-NAME (2 mg/kg), a general nitric oxide synthase (NOS) inhibitor, considerably reduced the ACTH and corticosterone response to IL-1beta (0.5 microg/rat) the same extent in control and crowded rats. CRH antagonist almost abolished the nicotine-induced hormone responses and vasopressin antagonist reduced ACTH secretion. Constitutive endothelial eNOS and neuronal nNOS inhibitors substantially enhanced the nicotine-elicited ACTH and corticosterone response and inducible iNOS inhibitor, aminoguanidine, did not affect these responses in non-stressed rats. Social stress significantly attenuated the nicotine-induced ACTH and corticosterone response. In crowded rats L-NAME significantly deepened the stress-induced decrease in the nicotine-evoked ACTH and corticosterone response. In stressed rats neuronal NOS antagonist did not alter the nicotine-evoked hormone responses and inducible NOS inhibitor partly reversed the stress-induced decrease in ACTH response to nicotine. These results indicate that NO plays crucial role in the IL-1beta-induced HPA axis stimulation under basal and social stress conditions. CRH and vasopressin of the hypothalamic paraventricular nucleus may be involved in the nicotine induced alterations of HPA axis activity. NO generated by eNOS, but not nNOS, is involved in the stress-induced alterations of HPA axis activity by nicotine.     

Role of prostaglandins and nitric oxide in the lipopolysaccharide-induced ACTH and corticosterone response.

This study was designed to determine the role of endogenous prostaglandins (PG) and nitric oxide (NO) in the lipopolysaccharide (LPS)-induced ACTH and corticosterone secretion in conscious rats. LPS (0.5 and 1 mg/kg) given i.p. stimulated the hypothalamic-pituitary-adrenocortical (HPA) activity measured 2 h later. A non-selective cyclooxygenase inhibitor indomethacin (10 mg/kg i.p.), piroxicam (2 mg/kg i.p.), a more potent antagonist of constitutive cyclooxygenase (COX-1) and compound NS-398 (2 mg/kg i.p.), a selective inhibitor of inducible cyclooxygenase (COX-2) given 30 min before LPS (1 mg/kg i.p.) significantly diminished both the LPS-induced ACTH and corticosterone secretion. COX-2 blocker was the most potent inhibitor of ACTH secretion (72.3%). Nomega-nitro-L-arginine methyl ester (L-NAME 2 and 10 mg/kg i.p.), a non-selective nitric oxide synthase (NOS) blocker given 15 min before LPS did not substantially alter plasma ACTH and corticosterone levels 2 h later. Aminoguanidine (AG 100 mg/kg i.p.), a selective inducible nitric oxide synthase (iNOS) inhibitor, considerably enhanced ACTH and corticosterone secretion induced by a lower dose (0.5 mg/kg) of LPS and did not significantly alter this secretion after a larger dose (1 mg/kg) of LPS. L-NAME did not markedly affect the indomethacin-induced inhibition of ACTH and corticosterone response. By contrast, aminoguanidine abolished the indomethacin-induced reduction of ACTH and corticosterone secretion after LPS. These results indicate an opposite action of PG generated by cyclooxygenase and NO synthesized by iNOS in the LPS-induced HPA-response.     

Preventive role of gallic acid on alcohol dependent and cysteine protease-mediated pancreas injury

In order to investigate an association between alcohol consumption and lysosomal cysteine protease induced pancreatic injury and preventive effect of gallic acid as dose-dependent, we determined myeloperoxidase and malondialdehyde levels, serum amylase activities and cathepsin B and L activities in the cytosolic and lysosomal fractions of pancreatic tissue in the ethanol (8?g/kg) and ethanol plus gallic acid (at different doses 50, 100 and 200?mg/kg) given rats. Absolute ethanol (8?g/kg) was given by oral gavage. Gallic acid was dissolved in the saline (2?ml/kg) and administered before 30?min the oral administration of ethanol. Pancreatic myeloperoxidase and also malondialdehyde levels and serum amylase activities were measured. Besides, histological investigations were made. Cathepsin B activities in the cytosolic fraction were decreased by gallic acid (200?mg/kg) and increased in ethanol given rats. Cytosolic/lysosomal ratio of cathepsin B and L were found to be low in the all doses of gallic acid as compared to ethanol group. Serum amylase, pancreatic myeloperoxidase activities and malondialdehyde levels in the ethanol group were higher than in the control group. These were not statistically significant for myeloperoxidase and malondialdehyde. Also, our histopathologic results indicated that ethanol administration increased pancreatic tissue injury. Gallic acid especially at 200?mg/kg improved ethanol-mediated pancreatic tissue damage.In conclusion, gallic acid treatments were decreased release of lysosomal cathepsin B and L enzymes into cytoplasmic fraction and prevented alcohol mediated pancreatic tissue injury. Preventive effect of gallic acid might be dose-dependent.     

Blockade of Nitric Oxide Overproduction and Oxidative Stress by <Emphasis Type="Italic">Nigella sativa</Emphasis> Oil Attenuates Morphine-Induced Tolerance and Dependence in Mice

The effects of Nigella sativa oil on morphine-induced tolerance and dependence in mice and possible mechanism(s) of these effects were investigated, for the first time, in this study. Repeated administration of Nigella sativa oil (4 ml/kg, p.o.) along with morphine (5 mg/kg, s.c.) attenuated the development of tolerance, as measured by the hot plate test, and dependence, as assessed by naloxone (5 mg/kg, i.p.)-precipitated withdrawal manifestations. Concomitantly, nitric oxide overproduction and increase in brain malondialdehyde level induced by repeated administration of morphine to mice or by administration of naloxone to morphine-dependent mice were inhibited by co-administration of the oil. Also, the decrease in brain intracellular reduced glutathione level and glutathione peroxidase activity induced by both treatments were inhibited by co-administration of the oil. The increase in brain glutamate level induced by both treatments was not inhibited by concurrent administration of the oil. The inhibitory effect of the oil on morphine-induced tolerance and dependence and on naloxone-induced biochemical alterations in morphine-dependent mice was enhanced by concurrent i.p. administration of the NMDA receptor antagonist, dizocilpine (0.25 mg/kg). Similarly, concurrent i.p. administration of the NO synthase inhibitors; L-N (G)-nitroarginine methyl ester (10 mg/kg), aminoguanidine (20 mg/kg) and 7-nitroindazole (25 mg/kg) or the antioxidant, N-acetylcysteine (50 mg/kg) enhanced this inhibitory effect of the oil. On the other hand, this effect was antagonized by concurrent i.p. administration of the nitric oxide precursor, L-arginine (300 mg/kg). These results provide evidence that Nigella sativa oil, through inhibition of morphine-induced NO overproduction and oxidative stress, appears to have a therapeutic potential in opioid tolerance and dependence.     

Ex Vivo Measurement of Brain Tissue Nitrite and Nitrate Accurately Reflects Nitric Oxide Synthase Activity In Vivo

Abstract: The ex vivo tissue concentration of nitrite and nitrate (NO_x) was found to correlate closely with the activity of nitric oxide synthase (NOS; EC 1.14.13.39) in various brain regions. Systemic administration of the nonselective NOS inhibitor N ^ω-nitro- l -arginine ( l -NA) at doses that completely inhibited both central and peripheral NOS, depleted whole-brain and CSF NO_x by up to 75% but had no effect on plasma NO_x. Selective inhibition of central NOS by intracerebroventricular administration of l -NA methyl ester produced similar decreases in levels of whole-brain NO_x. A residual concentration of NO_x of 10–15 µ M remained in all brain regions even after complete inhibition of brain NOS. Brain NO_x content decreased rapidly and in parallel with the inhibition of brain NOS. The ex vivo measurement of levels of brain NO_x was found to reflect the in vivo efficacy of several different types of NOS inhibitor: l -NA, N ^ω-monomethyl- l -arginine, and 7-nitroindazole. Intraperitoneal administration of the NOS substrate l -arginine increased brain NO_x concentrations by up to 150% of control values. These results demonstrate that the ex vivo measurement of levels of brain tissue NO_x is a rapid, reliable, and straightforward technique to determine NOS activity in vivo. This method can be used to assess both the regional distribution and the degree of inhibition of NOS activity in vivo.     

Expression of nitric oxide synthase isoforms in normal ventilatory and limb muscles

Hussain, Sabah N. A., Qasim El-Dwairi, Mohammed N. Abdul-Hussain, and Dalia Sakkal. Expression of nitric oxidesynthase isoforms in normal ventilatory and limb muscles.J. Appl. Physiol. 83(2): 348-353, 1997.Nitric oxide (NO), an important messenger molecule withwidespread actions, is synthesized by NO synthases (NOS). In thisstudy, we investigated the correlation between fiber type and NOSactivity among ventilatory and limb muscles of various species. We alsoassessed the presence of the three NOS isoforms in normal skeletalmuscles and how various NOS inhibitors influence muscle NOS activity.NOS activity was detected in various muscles; however, NOS activity inrabbits and rats varied significantly among different muscles.Immunoblotting of muscle samples indicated the presence of both theneuronal NOS and the endothelial NOS isoforms but not thecytokine-inducible NOS isoform. However, these isoforms were expressedto different degrees in various muscles. Although the neuronal NOSisoform was detectable in the canine diaphragm, very weak expressionwas detected in rabbit, rat, and mouse diaphragms. The endothelial NOSisoform was detected in the rat and mouse diaphragms but not in thecanine and rabbit diaphragms. We also found thatN^G-nitro-L-arginine methyl ester,7-nitroindazole, andS-methylisothiourea werestronger inhibitors of muscle NOS activity than was aminoguanidine. These results indicate the presence of different degrees ofconstitutive NOS expression in normal ventilatory and limb muscles ofvarious species. Our data also indicate that muscle NOS activity is not determined by fiber type distribution but by other not yet identified factors. The functional significance of this expression remains to beassessed.

     

Antidepressant Like Effect of Ascorbic Acid in Mice: Possible Involvement of NO-sGC-cGMP Signaling

The present study was designed to determine the antidepressant like activity of ascorbic acid (AA) in mice. Further the influence of NO-sGC-cGMP signaling in the antidepressant like effect of AA in mice was determined. Male swiss albino mice were used in the present study. Mice in the control group received saline and fluoxetine (10 mg/kg, i.p.) was used as the standard antidepressant drug. AA (50, 100 and 150 mg/kg, i.p.) was administered to the mice and depression related behavior were determined using tail suspension test (TST) and forced swim test (FST). Further the whole brain nitrite and serotonin levels were also determined. It was observed that the administration of AA (100 mg/kg, i.p.) reversed the depression like behavior in mice in TST and FST. AA (100 mg/kg, i.p.) treatment decreased the level of nitrite and increased the level of serotonin in the brain of mice significantly as compared to control. Further the behavioral and neurochemical effect of AA (50 mg/kg, i.p) was studied in NO modulator [NO donor: L-Arginine (50 mg/kg, i.p); NO-sGC inhibitor: methylene blue (1 mg/kg, i.p.) and cGMP modulator: sildenafil (1 mg/kg, i.p.)] pretreated mice. It was observed that the pretreatment of NO donor and cGMP modulator counteracted the effect conferred by AA (50 mg/kg, i.p). While the pretreatment of NO-sGC inhibitor potentiated the effect conferred by AA (50 mg/kg, i.p). The present study suggested that the AA confer antidepressant like effect in mice and NO-sGC-cGMP signaling pathway influence the antidepressant like effect of AA in mice.