Role of nitric oxide in catalepsy and hyperthermia in morphine-dependent rats

The possible involvement of nitric oxide (NO) in morphine-induced catalepsy and hyperthermia was studied in morphine-dependent rats. Four days repeated injection regimen was used to induce morphine dependence, which was assessed by naloxone challenge (0.5 mg x kg(-1), s.c.). Pretreatment of rats with the NO synthase inhibitor, N(G)-nitro-L-arginine (L-NA, 8 mg x kg(-1) twice daily, i.p.) potentiated the cataleptic response of morphine as shown by a rightward shift in the morphine-log dose-response curve. Prior treatment of rats with the NO precursor, L-arginine (200 mg x kg(-1), twice daily, i.p.) abolished the potent effect of L-NA and restored the cataleptic scores to levels similar to those of morphine-dependent rats. The same dose of L-NA significantly blocked morphine-induced hyperthermia at the dose levels of morphine (15-105 mg x kg(-1)) and this effect was reversed by L-arginine. These data provide the first experimental evidence that NO is involved in morphine induced catalepsy and hyperthermia and demonstrated that blockade of NO synthesis may suggest a dangerous interaction with opioids in the control of motor function.     

Nitric oxide synthetase inhibition hinders facilitation of active avoidance learning by nicotine in rats

Nicotine produces dose-dependent enhancement of performance in an active avoidance test, and also increases the levels of NO2- and NO3-, which are stable metabolites of nitric oxide (NO), in various brain regions of rats. On the basis of these two observations, we hypothesized that the beneficial effect of nicotine on learning could result from increased NO in relevant brain regions. We therefore tested active avoidance performance in rats given L-Nomega-nitroarginine (L-NA) to inhibit NO synthetase (NOS) prior to nicotine administration. Male Sprague-Dawley rats received L-NA (30 or 50 mg/kg), nicotine (0.4 mg/kg), saline or combinations of these treatments before learning trials. Rats were also tested on the inclined plane, to assess the possible effects due to impairment of motor function by drug treatments on active avoidance learning. L-NA treatment impaired the acquisition of active avoidance learning, and this defect was partially overcome by the co-administration of nicotine. Nicotine facilitated learning and significantly increased the number of correct responses. The threshold for the effect of NOS inhibition on performance exceeded 30 mg/kg L-NA, whereas 50 mg/kg impaired learning and also eliminated the nicotine-induced enhancement of learning. On the fifth day of learning trials, no facilitation of learning by nicotine was observed in rats receiving either dose of L-NA. Our results suggest that NO is involved in the facilitation of active avoidance learning by nicotine.     

Endogenous nitric oxide decreases hippocampal levels of serotonin and dopamine in vivo

Nitric oxide (NO) modulates the levels of various neurotransmitters in the CNS. Here we determined whether the specific nitric oxide synthase (NOS) inhibitor 7-nitroindazole (7-NI), the non-selective inhibitor of guanylate cyclase (GC) and NOS, methylene blue (MB), the NO-precursor L-arginine (L-Arg), and the selective soluble GC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) affect extracellular levels of serotonin (5-HT), dopamine (DA), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) in the rat ventral hippocampus by using microdialysis in freely moving animals. Local perfusion of 7-NI (1 mM) and MB (1 mM) significantly increased extracellular level of 5-HT, whereas DA was increased by 7-NI only. Systemic administration of 7-NI (50 mg kg(-1)) and MB (30 mg kg(-1)) increased the extracellular levels of 5-HT and DA. Extracellular levels of 5-HIAA was not influenced by local or systemic MB or 7-NI. In contrast, extracellular level of HVA was decreased by systemic MB and retrodialyzed MB, but was not influenced by 7-NI. Retrodialysis of L-Arg (2 mM) decreased the levels of 5-HT, DA, 5-HIAA and HVA in the hippocampus. Systemic administration of L-Arg (250 mg kg(-1)) decreased the level of 5-HT, but failed to influence DA, 5-HIAA and HVA. Local perfusion of ODQ (400 microM) did not affect 5-HT overflow in the hippocampus. We conclude that NOS inhibitors increased extracellular levels of 5-HT and DA in the rat ventral hippocampus after local or systemic administration, whereas the NO precursor L-Arg had the opposite effect. Thus, endogenous NO may exert a negative control over the levels of 5-HT and DA in the hippocampus. However, this effect is probably not mediated by cyclic GMP.     

Different effects of nitric oxide synthase inhibitors on convulsions induced by nicotine in mice

Acute intraperitoneal (i.p.) administration of N(G)-nitro-L-arginine (NNA, 10, 20 and 40 mg/kg), a non-selective nitric oxide synthase (NOS) inhibitor, significantly and dose-dependently decreased the incidence of convulsions induced by i.p. nicotine (NIC) in mice, whereas 7-nitroindazole (7NI, 50 and 100 mg/kg i.p.), a selective neuronal NOS inhibitor, had a proconvulsant effect. Aminoguanidine (100 mg/kg ip), a specific inducible NOS inhibitor, remained without an effect on convulsive behavior. L-arginine, a nitric oxide (NO) precursor, which independently has no effect on convulsions, markedly reversed the anticonvulsant effect of NNA; yet only partially reversed the proconvulsant effect of 7NI when injected at 500 mg/kg i.p.. Convulsions evoked by intracerebroventricular injection of NIC were significantly suppressed by ip NNA(40 mg/kg i.p.) and enhanced by i.p. 7NI (100 mg/kg i.p.); however, these effects of NNA and 7NI were less potent than those seen when NIC was administered i.p.. The present study revealed essential differences in the action of NOS inhibitors in NIC-induced convulsions. It appears that only NO produced by constitutive NOS is involved in the mechanism of NIC-induced convulsions. The proconvulsant effect of 7NI may result from the mechanisms unrelated to NOS inhibition.     

Protective effects of chitosan oligosaccharide on paraquat-induced nephrotoxicity in rats

We investigated the apoptotic pathway during paraquat (PQ)-induced nephrotoxicity as well as renoprotective effects of chitosan oligosaccharide (COS) in male Sprague-Dawley rats because increasing evidences suggest that antioxidants may prevent PQ-induced apoptosis. Animals were pretreated with normal saline or COS (500 mg/kg, p.o.) 3 days before PQ (60 mg/kg, i.p.) administration, and were sacrificed at scheduled times after PQ administration. Rats administered PQ showed increased serum PQ concentrations, blood urea nitrogen, and creatinine levels in a time-dependent manner and creatinine clearance was decreased compared with control rats. All of these parameters were reversed significantly by COS pretreatment. After the PQ injection, cell deaths occurred in the proximal renal tubules with increased APE, PUMA, and cleaved caspase-3 expression, while APE and cleaved caspase-3 were immunolocalized mainly in the proximal tubules of control kidneys. COS-pretreated rat kidneys showed increased expression of the above parameters before PQ injection. APE and cleaved caspase-3 were immunolocalized ubiquitously in the renal cortex of COS-pretreated rats until 24 h after the PQ injection. These results showed that PQ-induced nephrotoxicity may be caused by apoptosis in rat kidneys and that COS could protect kidneys from PQ-induced toxicity in association with the basal higher level of APE.     

Role of nitric oxide in systemic effect of theophylline on mouse body temperature

In the present study, the interaction of nitric oxide synthase (NOS) inhibitors, L-NAME (N(G)-nitro-L-arginine methyl ester HCl) and L-NA (N(omega)-nitro-L-arginine), and its precursor, L-arginine (2-(S)-2-amino-5-[(aminoiminomethyl)amino] pentatonic acid), with theophylline on mouse body temperature was studied. Intraperitoneal (i.p.) injection of different doses of theophylline altered body temperature. Lower doses of theophylline (12.5 and 25 mg/kg) increased, but a higher dose (100 mg/kg) reduced, the animals' body temperature. The combination of L-arginine (20 and 40 mg/kg) with the highest dose of theophylline potentiated the hypothermic effect induced by the latter drug, while L-arginine by itself did not alter body temperature. L-NAME (10-80 mg/kg) or L-NA (10 mg/kg) plus a lower dose of theophylline (12.5 mg/kg) reduced the theophylline-induced hyperthermic response. L-NA (1, 5, and 10 mg/kg) in combination with the high dose of theophylline (100 mg/kg) also induced greater hypothermia. Both L-NAME and L-NA by themselves reduced body temperature. It is concluded that nitric oxide (NO) may be involved in the effects of theophylline on body temperature in mice.     

Role of nitric oxide in maintenance of basal oral tissue blood flow in anesthetized cats.

Experiments were undertaken to determine if nitric oxide (NO) plays a role in regulation of basal blood flow in the oral cavity of pentobarbital anesthetized cats and, if so, to quantify this effect using dose-response relationships. Blood flow was continuously measured from the surface of the tongue and mandibular gingiva (laser-Doppler flowmetry) and from the lingual artery (ultrasonic flowmetry). Cardiovascular parameters also were recorded. Administration of the nonselective inhibitor of nitric oxide synthase (NOS), L-NAME (0.08-20 mg/kg i.v.), produced a dose-related increase of blood pressure associated with decreases of blood flow at all three measurement sites. Maximal blood flow depression of 50-60% was seen 30-60 min after administration of 1.25 mg/kg of L-NAME. D-NAME (1.25 mg/kg i.v.) was inactive at all sites. Subsequent administration of L-arginine partially reversed effects of L-NAME in the lingual artery and tongue, but not in the gingival circulation. The neuronally selective NOS inhibitor, 7-nitroindazole (7-NI, 30 mg/kg i.p.), was devoid of effect on any of the measured parameters. These results suggest that endothelial (but not neuronally derived) NO plays an important role in control of basal blood flow in oral tissues of the cat.     

The spinal nitric oxide involved in the inhibitory effect of midazolam on morphine-induced analgesia tolerance

Previous studies had shown that pretreatment with midazolam inhibited morphine-induced tolerance and dependence. The present study was to investigate the role of spinal nitric oxide (NO) in the inhibitory effect of midazolam on the development of morphine-induced analgesia tolerance. Subcutaneous injection of 100 mg/kg morphine to mice caused an acute morphine-induced analgesia tolerance model. To develop chronic morphine tolerance in mice, morphine was injected for three consecutive days (10, 20, 50 mg/kg sc on Day 1, 2, 3, respectively). In order to develop chronic tolerance model in rats, 10 mg/kg of morphine was given twice daily at 12 h intervals for 10 days. Midazolam was intraperitoneally injected 30 min prior to administration of morphine. Tail-flick test, hot-plate and formalin test were conducted to assess the nociceptive response. Immunocytochemistry, histochemistry and western blot were performed to determine the effect of midazolam on formalin-induced expression of Fos protein, nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and nitric oxide synthase (NOS) in chronic morphine-tolerant rats, respectively. The results showed that pretreatment with midazolam significantly inhibited the development of acute and chronic morphine tolerance in mice, which could be partially reversed by intrathecal injection of NO precursor L-arginine (L-Arg). In chronic morphine-tolerant rats, pretreatment with midazolam significantly decreased the formalin-induced expression of Fos and Fos/NADPH-d double-labeled neurons in the contralateral spinal cord and NADPH-d positive neurons in the bilateral spinal cord. Both inducible NOS (iNOS) and neuronal NOS (nNOS) protein levels in the spinal cord were significantly increased after injection of formalin, which could be inhibited by pretreatment with midazolam. The above results suggested that the decrease of the activity and expression of NOS contributed to the inhibitory effect of midazolam on the development of morphine tolerance.     

The Role of nitric oxide in convulsions induced by lindane in rats

Lindane is an organochloride pesticide and scabicide. It evokes convulsions mainly trough the blockage of GABA_A receptors. Nitric oxide (NO), gaseous neurotransmitter, has contradictor role in epileptogenesis due to opposite effects of l-arginine, precursor of NO syntheses (NOS), and L-NAME (NOS inhibitor) observed in different epilepsy models. The aim of the current study was to determine the effects of NO on the behavioral and EEG characteristics of lindane-induced epilepsy in male Wistar albino rats.The administration of l-arginine (600, 800 and 1000 mg/kg, i.p.) in dose-dependent manner significantly increased convulsion incidence and severity and shortened latency time to first convulsion elicited by lower lindane dose (4 mg/kg, i.p.). On the contrary, pretreatment with L-NAME (500, 700 and 900 mg/kg, i.p.) decreased convulsion incidence and severity and prolonged latency time to convulsion following injection with a convulsive dose of lindane (8 mg/kg, i.p.). EEG analyses showed increase of number and duration of ictal periods in EEG of rats receiving l-arginine prior to lindane and decrease of this number in rats pretreated with L-NAME.These results support the conclusion that NO plays a role of endogenous convulsant in rat model of lindane seizures.     

Serotonergic mediation of the antidepressant-like effects of nitric oxide synthase inhibitors

Recent studies indicate that nitric oxide (NO) synthase inhibitors have antidepressant-like potential in various animal models. In the present study the behavioural activity of the NO synthase inhibitors, N(G)-nitro-L-arginine (L-NA) and 7-nitroindazole (7-NI), were assessed in a modified rat forced swimming test (FST). Both L-NA and 7-NI, dose dependently reduced immobility and increased swimming behaviour in the rat FST. This behavioural profile parallels the one previously shown with selective serotonin re-uptake inhibitors and serotonergic agonists. Thus, we examined the role of serotonin mediating the behavioural effects of L-NA and 7-NI in the rat FST. Depletion of endogenous serotonin using para-chlorophenylalanine (pCPA; 3 x 150 mg/kg, i.p.) completely blocked L-NA (20 mg/kg, i.p.) and 7-NI (20 mg/kg, i.p.)-induced reductions in immobility and increases in swimming behaviour during the FST. In conclusion these observations suggest that NO synthase inhibitors elicit their antidepressant-like activity in the modified swimming test through a serotonin dependent mechanism.     

Dual effect of nitric oxide in articular inflammatory pain in zymosan-induced arthritis in rats

The contribution of nitric oxide (NO) to articular pain in arthritis induced by zymosan (1 mg, intra articular) in rats was assessed by measuring articular incapacitation (AI). Systemic treatment with the non-selective NO synthase (NOS) inhibitor L-NAME (10 - 100 mg kg(-1) i.p.) or with the selective iNOS inhibitors aminoguanidine (AG; 10 - 100 mg kg(-1) i.p.) or 1400W (0.5 - 1 mg kg(-1) s.c.) inhibited the AI induced by injection of zymosan 30 min later. Local (intra articular) treatment with the NOS inhibitors (L-NAME or AG, 0.1 - 1 micromol; 1400W, 0.01 (micromol) 30 min before zymosan also inhibited the AI. Systemic or local treatment with the NOS inhibitors (L-NAME; AG, 100 mg kg(-1) i.p. or 0.1 micromol joint(-1); 1400W, 1 mg kg(-1) s.c. or 0.01 micromol joint(-1)), 2 h after zymosan did not affect the subsequent AI. Local treatment with the NO donors SNP or SIN-1, 2 h after zymosan did inhibit AI. L-NAME and AG, given i.p. inhibited nitrite but not prostaglandin E(2) (PGE(2)) levels in the joints. L-NAME (100 mg kg(-1)) but not AG (100 mg kg(-1)) increased mean arterial blood pressure. Neither L-NAME, AG nor the NO donor SIN-1 altered articular oedema induced by zymosan. In conclusion, inhibitors of iNOS decrease pain in zymosan arthritis only when given before the zymosan. This was not due to inhibition of articular PGE(2) release or oedema. NO donors also promoted antinociception in zymosan arthritis without affecting oedema.     

Nitric oxide synthase mediates delta opioid receptor-induced hypothermia in rats

The role of nitric oxide (NO) production in delta opioid receptor-induced hypothermia has not been reported. The present study investigated the effect of nitric oxide synthase (NOS) inhibitors on the hypothermic effect of (+)-4-[(aR)-a-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC-80), a nonpeptide delta opioid agonist. SNC-80 (35 mg/kg, i.p.) administered to rats caused a significant hypothermia. N-nitro-L-arginine methyl ester (L-NAME) (10, 25 and 50 mg/kg, i.p.), a NOS inhibitor, and 7-nitroindazole (7-NI) (5 and 10 mg/kg, i.p.), a neuronal NOS inhibitor, were ineffective. For combined administration, L-NAME (50 mg/kg, i.p.) or 7-NI (10 mg/kg, i.p.) attenuated SNC-80-evoked hypothermia. To determine the involvement of central NOS, L-NAME (0.25, 0.5 and 1 mg/rat) was administered i.c.v. 30 min prior to SNC-80 (35 mg/kg, i.p.). Experiments revealed that L-NAME (1 mg/rat, i.c.v.) attenuated SNC-80-induced hypothermia. The present data demonstrate that central NO production is necessary for delta opioid receptor-induced hypothermia.     

The involvement of nitric oxide in the antinociception induced by cyclosporin A in mice

Cyclosporin A (CsA) and other immunophilin-binding agents are known to inactivate neuronal nitric oxide synthase (nNOS). Nitric oxide (NO) is involved in the nociception at the spinal level. We evaluated the effect of acute intraperitoneal (i.p.) administration of CsA on the tail-flick response in mice and the involvement of NO and opioid receptors in this effect. CsA (5, 10, 20 and 50 mg/kg i.p.) induced a significant increase in tail-flick response. Nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine (LNNA; 10, 40 and 80 mg/kg i.p.) significantly potentiated the CsA-induced (5 mg/kg) increase in tail-flick latency (TFL). While NOS substrate L-arginine (100, 200, 400 mg/kg i.p.) inhibited the CsA-induced (20 mg/kg) antinociception completely and in a dose-dependent manner. Concomitant administration of L-NNA and L-arginine blocked the inhibition exerted by the latter on the CsA-induced antinociception. The opioid receptor antagonist naloxone (4 mg/kg i.p.) did not alter the CsA effect. These results indicate that acute administration of CsA induces an antinociceptive effect that involves the L-arginine-NO pathway but is not mediated by opioid receptors.     

Regional blood flow responses to acute ANG II infusion: effects of nitric oxide synthase inhibition.

We hypothesized that nitric oxide (NO) opposes regional vasoconstriction caused by acute angiotensin II (ANG II) infusion in conscious rats. Mean arterial pressure (MAP), blood flow, and vascular conductance (regional blood flow/ MAP; ml/min/100 g/mm Hg) were measured and/or calculated before and at 2 min of ANG II infusion (0.05 or 1 microg/kg/min, i.a.) in the absence and presence of NO synthase (NOS) inhibition [N(G)-nitro-L-arginine methyl ester (L-NAME), 0.25 or 1 mg/kg, i.a.]. ANG II reduced stomach and hindlimb conductance only after NOS inhibition. For example, whereas 0.05 microg/kg/min ANG II did not attenuate conductance in the stomach (i.e., 1.04+/-0.08 to 0.93+/-0.12 ml/min/100 g/mm Hg), this variable was reduced (i.e., 0.57+/-0.14 to 0.34-/+0.05 ml/min/100 g/mm Hg; p < 0.05) when ANG II was infused after 0.25 mg/kg L-NAME. In addition, whereas hindlimb conductance was similar before and after administering 1 microg/kg/min ANG II (i.e., 0.13+/-0.01 and 0.09+/-0.02, respectively), this variable was reduced (i.e., 0.07+/-0.01 and 0.02+/-0.00, respectively; p < 0.05) when ANG II was infused after 1 mg/kg L-NAME. These findings indicate that NO opposes ANG II-induced vasoconstriction in the stomach and hindlimb. In contrast, whereas both doses of ANG II decreased (p < 0.05) vascular conductance in the kidneys and small and large intestine regardless of whether NOS inhibition was present, absolute vascular conductance was lower (p < 0.05) after L-NAME. For example, 1 microg/kg ANG II reduced renal conductance from 3.34+/-0.31 to 1.22+/-0.14 (p < 0.05). After 1 mg/kg L-NAME, renal conductance decreased from 1.39+/-0.18 to 0.72+/-0.16 (p < 0.05) during ANG II administration. Therefore the constrictor effects of NOS inhibition and ANG II are additive in these circulations. Taken together, our results indicate that the ability of NO to oppose ANG II-induced constriction is not homogeneous among regional circulations.     

Effects of nitric oxide synthase inhibitors and melatonin on the hyperglycemic response to streptozotocin in rats

Recent studies evidence that peroxynitrite is spontaneously formed when nitric oxide (NO) and superoxide coexist and suggest that it is likely to be involved in the destruction of the pancreatic beta cells. We examined whether drugs that inhibit nitric oxide synthase (NOS) or scavenge peroxynitrite could abrogate STZ-induced hyperglycemia in rats. Blood glucose levels were measured before (0 h) and 24, 48, and 72 h following intraperitoneal administration of 60 mg/kg streptozotocin (STZ). The levels of blood sugar in STZ-treated control animals were significantly elevated at all time points of observation with a peak increase at 48 h. The hyperglycemic response of STZ was found to be significantly reduced in animals pretreated with aminoguanidine (50 mg/kg i.p.), an inducible isoform-selective NOS (iNOS) inhibitor with antioxidant property, and by melatonin (6 mg/kg i.p.), an antioxidant that also prevents peroxynitrite formation but not by Nw-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg i.p.), and 7-nitroindazole (7-NI, 50 mg/kg i.p.), the constitutive inhibitors of endothelial and neuronal NOS, respectively. These findings indicate the possible participation of iNOS-derived NO as well as oxygen free radicals in STZ-induced pancreatic beta cell destruction and compounds that act as scavengers of peroxynitrite may offer protection against such a damage.     

Low endotoxemia prevents the reduction of gastric blood flow induced by NSAIDs: role of nitric oxide

1 The role of nitric oxide (NO) in the effects of low endotoxemia on gastric damage and blood flow has been evaluated in indomethacin-treated rats. 2 Pretreatment (-1 h) with endotoxin (40 micro g kg(-1)) reduced gastric damage induced by indomethacin (20 mg kg(-1)) in conscious rats. 3 Endotoxin prevented the reduction in gastric blood flow (laser Doppler flowmetry) induced by indomethacin in pentobarbital-anaesthetised rats. 4 Pretreatment with an NO-synthase (NOS) inhibitor (L-NAME, 1 mg kg(-1)) reversed the protective effect of endotoxin on gastric blood perfusion. 5 Endotoxin did not modify the expression of mRNA for endothelial NOS or inducible NOS in the gastric corpus when evaluated 1 h postinjection. However, a 3.8-fold increase in inducible NOS mRNA and a 61% reduction in endothelial NOS mRNA were observed in the gastric corpus 4 h after endotoxin administration. 6 Evaluation of both total and Ca(2+)-dependent NOS activity by analysing the rate of conversion of L-arginine to L-citrulline in gastric corpus homogenates showed no differences between animals treated with endotoxin and those treated with saline 1 or 4 h beforehand. Ca(2+)-independent NOS activity was almost non-apparent in control as well as in endotoxin-treated rats at all the time points analysed. 7 Low endotoxemia preserves blood perfusion and protects the gastric mucosa against the deleterious effects of indomethacin through the endogenous NO release. NO synthesis in response to endotoxin does not involve the inducible NOS, but probably depends on the post-translational/biochemical regulation in vivo of a Ca(2+)-dependent NOS, most probably endothelial NOS.     

DETA/NONOate, a nitric oxide donor, produces antidepressant effects by promoting hippocampal neurogenesis

RATIONALE: Increasing evidence suggests that depression may be associated with a lack of hippocampal neurogenesis. Our recent study shows that endogenous nitric oxide (NO) contributes to chronic mild stress (CMS)-induced depression by suppressing hippocampal neurogenesis. OBJECTIVES: The aim of this study was to investigate the effects of exogenous NO in CMS-induced depression in young adult mice. RESULTS: In normal mice, administration of a pure NO donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) aminio] diazen-1-ium-1,2-diolate (DETA/NONOate; 0.4 mg/kg, i.p., for 7 days) produced an antidepressant-like effect and significantly increased hippocampal neurogenesis. The mice exposed to CMS exhibited behavioral changes typical of depression and impaired neurogenesis in the hippocampus. Treatment with DETA/NONOate (0.4 mg/kg, i.p., for 7 days) reversed CMS-induced behavioral despair and hippocampal neurogenesis impairment. We treated mice with a telomerase inhibitor 3'-azido-deoxythymidine (AZT; 100 mg/kg, i.p., for 14 days) to disrupt neurogenesis. From day 4 to day 11 of AZT treatment, mice were injected with DETA/NONOate (0.4 mg/kg, i.p., for 7 days). Disrupting hippocampal neurogenesis blocked the antidepressant effect of DETA/NONOate. CONCLUSIONS: Our findings suggest that exogenous NO benefits chronic stress-induced depression by stimulating hippocampal neurogenesis and may represent a novel approach for the treatment of depressive disorders.     

Altered L-arginine/nitric oxide synthase/nitric oxide pathway in the vascular adventitia of rats with sepsis

1. In recent studies, the vascular adventitia has been established as an important source of inducible nitric oxide synthase (iNOS) and subsequent nitric oxide (NO) production, even more powerful than the media in response to certain inflammatory factors, such as lipopolysaccharide (LPS). The adventitia has an independent L-arginine (L-Arg)/NOS/NO pathway and is involved in the regulation of vascular function. In the present study, we explored the changes in and the pathophysiological significance of the L-Arg/NOS/NO pathway in the adventitia of rats with sepsis. 2. Sepsis was induced by caecal ligation and puncture in order to observe changes in L-Arg transport, NOS gene expression and activity and NO generation in the vascular adventitia to determine the mechanism of activation of the L-Arg/NOS/NO pathway. 3. Severe sepsis resulted in severe disturbance of haemodynamic features, with decreased mean arterial blood pressure, brachycardia and inhibited cardiac function (decreased left ventricular +/-dP/dt(max)). Left ventricular end-diastolic pressure was elevated threefold (P < 0.01) under anaesthesia. Rats with sepsis showed severe glucopenia and lacticaemia. Plasma levels of the inflammatory factors macrophage chemoattractant protein-1 and interleukin-8 were increased five- and 29-fold, respectively (P < 0.01). 4. In the adventitia of the thoracic and abdominal aortas, the L-Arg/NO pathway was similarly characterized: the uptake of [(3)H]-L-Arg was Na(+) independent, with the peak occurring at approximately 40 min incubation. Total NOS activity was largely calcium independent (> 90%). The V(max) of L-Arg transport in the sepsis group was increased by 83.5% (P < 0.01), but the K(m) value was not significantly different compared with controls. 5. The mRNA levels of cationic amino acid transporter (CAT)-1 and CAT-2B in the sepsis group were increased by 86 and 62%, respectively (both P < 0.01). Inducible NOS activity was increased 2.8-fold compared with controls (P < 0.01) and iNOS mRNA levels were elevated approximately sixfold (P < 0.01). The NO levels in the plasma and incubation media (incubation for 40 min) in the sepsis group were increased by 144 and 273%, respectively (both P < 0.01). 6. The Arg/NOS/NO pathway was activated in the vascular adventitia of rats with sepsis shock. The L-Arg/NOS/NO pathway in the aortic adventitia may play an important role in the pathogenesis of sepsis and septic shock.     

Enhancement by escins Ib and IIb of Mg(2+) absorption from digestive tract in mice: role of nitric oxide

The effects of escins Ib and IIb isolated from horse chestnuts on Mg(2+) absorption from the digestive tract and the role of endogenous nitric oxide (NO) were investigated in mice. Test samples were given orally to fasted mice 30, 120, 180, 240 and 300 min before administration of 0.5 M MgSO(4) (10 ml/kg, p.o.). The serum Mg(2+) levels were determined 30, 60, 120 and 180 min after administration of MgSO(4). Escins Ib and IIb (12.5 and 25 mg/kg) significantly increased the serum Mg(2+) by 10.0-27.3%, 30, 120 and 180 min after administration of the samples, and 30, 60, 120 and 180 min after administration of MgSO(4). Escins Ib and IIb (12.5 mg/kg) significantly decreased the Mg(2+) content in the small intestinal fluid in MgSO(4)-loaded mice, but did not increase the serum Mg(2+) levels in normal mice. The effects of escins Ib and IIb (12.5 mg/kg) on serum Mg(2+) levels were attenuated in a dose-related manner by the pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 3-20 mg/kg, i.p., an inhibitor of constitutive and inducible NO synthase), but not with D-NAME (10 mg/kg, i.p., the inactive enantiomer of L-NAME) or dexamethasone (0.05 and 0.5 mg/kg, s.c., an inhibitor of inducible NO synthase). The effect of L-NAME was reversed by L-arginine (600 mg/kg, i.p., a substrate of NO synthase), but not by D-arginine (900 mg/kg, i.p., the enantiomer of L-arginine). These results suggest that escins Ib and IIb enhance Mg(2+) absorption from the digestive tract in mice, in which the constitutive, but not the inducible, NO synthase plays an important role.     

Sodium nitroprusside and L-arginine attenuates ferric nitrilotriacetate-induced oxidative renal injury in rats

The role of nitric oxide (NO) in acute renal failure (ARF) is debatable. In the present study, we investigated the effect of acute administration of NO donor, Sodium nitroprusside (SNP), L-Arginine (L-Arg) and NO synthase inhibitor, N(omega)-L-arginine methyl ester (L-NAME) in Fe-NTA induced renal toxicity. Rats were pretreated with SNP (2.5 mg/kg i.p), L-Arg (125 mg/kg, i.p.) and L-NAME (10 mg/kg, i.p.) prior to administration of Fe-NTA (8 mg iron/kg body weight, i.p.) to determine the urea and creatinine levels along with biochemical analysis of oxidative stress. Fe-NTA administration markedly increased the BUN and serum creatinine level which was coupled with a marked lipid peroxidation, decreased levels of reduced glutathione and total nitric oxide levels of rat kidneys coupled with significant morphological alterations. It also resulted in the significant increase in tumor necrosis factor-alpha (TNF-alpha) in serum. Concomitant treatment with SNP and L-Arg significantly reduced the serum creatinine and BUN levels, reduced lipid peroxidation in a significant manner, restored levels of reduced glutathione, increased total nitric oxide levels and restored the normal morphology. Pretreatment with SNP and L-Arg attenuated the levels of TNF-alpha in serum in a significant manner. Prior administration of L-NAME reversed the protective effects produced by SNP and L-Arg. Present findings strongly suggest that nitric oxide plays a significant role in the pathophysiology of iron-induced renal failure and administration of NO donors can be valuable in the treatment of ARF.