Inhibition of extracellular signal-regulated kinase (ERK1/2) activity reverses endotoxin-induced hypotension via decreased nitric oxide production in rats.

Overproduction of reactive oxygen and nitrogen species leads to oxidative stress and decreased total antioxidant capacity, which is responsible for high mortality from several inflammatory diseases such as endotoxic shock. Among reactive nitrogen species, nitric oxide (NO) produced by inducible NO synthase (iNOS) during endotoxemia is the major cause of vascular hyporeactivity, hypotension and multiple organ failure. This study was conducted to determine if mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK1/2) contributes to endotoxin-induced hypotension as well as vascular inflammation and oxidative stress via NO production. In conscious male Wistar rats, injection of endotoxin (10 mg kg(-1), i.p.) caused a decrease in mean arterial pressure (MAP) for 4h and increased levels of nitrite in serum, aorta and mesenteric artery. These effects of endotoxin were prevented by selective inhibition of ERK1/2 phosphorylation by MAPK kinase (MEK1/2) with U0126 (5 mg kg(-1), i.p.; 1h after endotoxin). Endotoxin also caused an increase in protein levels of phosphorylated ERK1/2 in aorta which was abolished by U0126. Selective inhibition of iNOS with phenylene-1,3-bis[ethane-2-isothiourea] dihydrobromide (1,3-PBIT) (10 mg kg(-1), i.p.; 1h after endotoxin) did not change the endotoxin-induced increase in ERK1/2 activity. Myeloperoxidase activity was increased in aorta and decreased in mesenteric artery by endotoxin, which was reversed by U0126. Endotoxin-induced decrease in one of the products of lipid peroxidation, malonedialdehyde (MDA) was prevented by U0126 in mesenteric artery; however, U0126 caused a further decrease in the levels of MDA in aorta. These data suggest that increased phosphorylation of ERK1/2 by MEK1/2 contributes to the endotoxin-induced hypotension via NO production rat aorta and mesenteric artery. It is likely that ERK1/2 mediates the effect of endotoxin on MPO activity in a different degree in the tissues suggesting possible involvement of any mediator and/or mechanism which also causes neutrophil infiltration during inflammatory response at least in mesenteric artery. Moreover, ERK1/2 seems to be involved in the endotoxin-induced increase in total antioxidant capacity in mesenteric artery.

Temporal variation of oxidant stress in critically ill patients.

AIM: Our aim was to investigate indicators of lipid peroxidation via observing temporal changes or daily fluctuations in cytoprotective enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), and serum components possessing antioxidant activity against free radicals and malondialdehyde (MDA) such as uric acid. This study was conducted in a small number of critically ill patients versus healthy volunteers in order to design an effective antioxidant therapy regimen under oxidative stress. METHODS: Six critically ill patients and 6 young healthy volunteers were recruited. Blood samples were collected 6 times a day with 4 h intervals starting from 8 a.m. From the blood samples, SOD and GSH-PX activities and uric acid and MDA levels were determined. One-way ANOVA and unpaired t-test were used to assess differences within and between the groups, respectively. A two dimensional table curve cosine formulation was performed to elucidate rhythmycity. RESULTS: No significant differences were found in SOD and GSH-PX activities or uric acid levels within the 24 h period or between the groups. MDA levels were significantly higher in the study group at 8 p.m. than that of control group (P<0.05), but no significant difference was found within the 24 h period. We showed that GSH-PX activities in control and study groups revealed temporal variation, whereas uric acid levels varied temporally only in the study group. CONCLUSION: We concluded that there are signs of oxidative stress in ICU patients that vary in time but further studies are required in order to design appropriate antioxidant treatments.

Involvement of calcium/calmodulin-dependent protein kinase II to endotoxin-induced vascular hyporeactivity in rat superior mesenteric artery.

Endotoxin causes impaired vascular contractility proposed to be mediated mainly by induction of inducible nitric oxide synthase (iNOS). Evidence suggests that calcium/calmodulin dependent protein kinase II (CaMKII) may lead to activation of cytosolic phospholipase A(2alpha) (cPLA(2alpha))/inducible cyclooxygenase (COX-2) pathway in response to endotoxin in vascular smooth muscle cells. This study was conducted to determine if CaMKII is involved in the endotoxin-induced vascular hyporeactivity by activating of iNOS and/or cPLA(2alpha)/COX-2 enzymes in rat isolated superior mesenteric artery with endothelium. Incubation with endotoxin (100 microg ml(-1)) for 4h caused vascular hyporeactivity to norepinephrine which was completely abolished by phenylene-1,3-bis[ethane-2-isothiourea] dihydrobromide (1,3-PBIT), a selective iNOS inhibitor, methyl arachidonyl fluorophosphonate (MAFP), a selective 85kDa cPLA(2alpha) inhibitor, DFU, a selective COX-2 inhibitor, and KN-93, a selective CaMKII inhibitor. Endotoxin-induced increase in tissue nitrite production was decreased by 1,3-PBIT and DFU, and further increased by MAFP. MAFP, DFU and KN-93 reversed the endotoxin-induced decrease in tissue 6-keto-PGF(1alpha). These data suggest that reversal of the endotoxin-induced vascular hyporeactivity by inhibition of CaMKII in rat superior mesenteric artery may be related to increased production of vasodilator arachidonic acid products by cPLA(2alpha)/COX-2 pathway rather than prostacyclin and nitric oxide.

Nitric oxide reverses endotoxin-induced inflammatory hyperalgesia via inhibition of prostacyclin production in mice.

We examined whether nitric oxide (NO), derived from constitutive NO synthase (NOS) and/or inducible NOS (iNOS), could contribute to endotoxin-induced inflammatory hyperalgesia via interacting with nuclear factor-kappaB (NF-kappaB), inducible cyclooxygenase (COX-2) and/or polyADP-ribose synthase (PARS). Injection of endotoxin (10 mg kg(-1), i.p.) to mice elicited hyperalgesia, determined by hot plate test, which is prevented by NO precursor (L-arginine), cNOS/iNOS inhibitor (N(G)-nitro-L-arginine methyl ester; L-NAME), NF-kappaB inhibitor (N-acetylserotonin), COX inhibitor (indomethacin), COX-2 inhibitor (DFU) and PARS inhibitor (3-aminobenzamide). Endotoxin caused a decrease in serum nitrite levels prevented by N-acetylserotonin, L-arginine, indomethacin, DFU or 3-aminobenzamide. Endotoxin increased serum 6-keto-PGF(1alpha) levels diminished by L-arginine or aminoguanidine (iNOS inhibitor). L-Arginine, L-NAME, aminoguanidine, DFU or 3-aminobenzamide prevented endotoxin-induced decrease in heart, lungs, kidneys and brain nitrite and malonedialdehyde levels and myeloperoxidase activity. In conclusion, NO reverses endotoxin-induced inflammatory hyperalgesia via inhibition of prostacyclin production, and also contributes to the analgesic effect of NF-kappaB, COX or PARS inhibitors.

Comparison of second controller medications in addition to inhaled corticosteroid in patients with moderate asthma.

The objective of this study was to compare the efficacy and safety of the second controller medications (long-acting beta2-agonist, leukotriene receptor antagonist and sustained-release theophylline) used in addition to inhaler corticosteroid treatment in moderate persistent asthma. A total of 64 patients with asthma, in the moderate persistent asthma category, were divided into three groups. Patients, all of whom were concurrently using inhaled corticosteroid (Budesonide 400 microg twice daily), were treated for 3 months with either inhaled formoterol 9 microg twice daily (first group), oral zafirlukast 20 mg twice daily (second group), or sustained-release theophylline 400 mg once daily (third group). All of the patients were subjected to assessments on the subject of peak expiratory flow (PEF) variability, forced expiratory volume in 1 sec (FEV1), asthma symptom scores (daytime and night-time), supplemental terbutalin use, asthma exacerbations and adverse events. Over the 3-month treatment period. In all of the three groups, significant improvements were recorded in the lung function, asthma symptom scores and supplemental terbutalin use criteria, as a result oftreatments applied. Formoterol treatment resulted in significantly greater and earlier improvements compared with the other two groups in several criteria: PEF variability (17.9 +/- 2.5; 21.9 +/- 3.2; 23.7 +/- 3.3; P < 0.001); asthma symptom score (daytime) (1.6 +/- 0.5; 1 +/- 0.5; 2.0 +/- 0,5; P < 0.05); asthma symptom score (night-time) (1.2 +/- 0.4; 2.2 +/- 0.5; 16 +/- 0.6; P < 0001); and supplement alter butalin use (1.2 +/- 0.3; 1.8 +/- 0.5; 1.7 +/- 0.5; P < 0.05). However, at the end of the treatment, in all of the three groups studied, improvements were attained in overall asthma control and there was no statistical difference among the groups. Although there were no side effects which required the discontinuation of the treatment, it was observed that the maximum side effect was in the second group (20%, 31.6% and 20%, respectively). In conclusion, in patients who still have symptoms on treatment with inhaled corticosteroids, the addition of a long-acting beta2-agonist, leukotriene antagonists or sustained-release theophylline to the treatment is a logical approach, and, in addition to inhaled corticosteroids, any one of these second controller medications may be chosen in patients with moderate asthma.

The role of L-arginine/nitric oxide pathway in the antinociceptive activity of pyridoxine in mouse.

In the present study the role of L-arginine/nitric oxide (NO)/cGMP pathway in the antinociceptive activity of pyridoxine in p-benzoquinone-induced abdominal constriction test in mouse was investigated. Pyridoxine (CAS 58-56-0) displayed dose-dependent antinociceptive activity at 0.0625-1 mg/kg (s.c.) doses. L-arginine (CAS 1119-34-2), a NO precursor, displayed a triphasic pattern as antinociception-nociception-antinociception (61.8 +/- 7.8, -36.5 +/- 12.7 and 17.0 +/- 4.3%, 5, 40 and 50 mg/kg, s.c., respectively). The antinociceptive effect of pyridoxine at ED50 dose (0.43 mg/kg, s.c.) (47.7 +/- 3.9%) was significantly decreased by L-arginine at 40 and 50 mg/kg doses (4.1 +/- 9.3 and 37.8 +/- 1.6%, respectively) while 5 mg/kg dose of L-arginine significantly potentiated the pyridoxine analgesia. On the other hand, pyridoxine reversed the L-arginine-induced nociception to antinociception (4.1 +/- 9.3%) and augmented the antinociceptive effect of L-arginine (37.8 +/- 1.6%). L-NG-nitroarginine methyl ester (CAS 51298-62-5), a NO synthase inhibitor, at 75 mg/kg, s.c. produced antinociception and significantly increased the antinociceptive effect of pyridoxine (63.7 +/- 1.2%). Methylene blue (CAS 61-73-4, MB), a guanylyl cyclase and/or NO synthase inhibitor, was antinociceptive and nociceptive at 5 and 40 mg/kg doses, respectively, 5 mg/kg dose of MB significantly increased the antinociceptive effect of pyridoxine, but did not change it at 40 mg/kg dose. On the other hand, pyridoxine significantly decreased the antinociceptive effect of MB and reversed the MB-induced nociception to antinociception. Combination of pyridoxine and morphine (CAS 57-27-2) (ED50: 0.13 mg/kg, s.c.) at 49.8 +/- 1.9% revealed a significant antinociceptive potentiation (69.1 +/- 1.8%). The findings of the present study emphasise the contribution of central and/or peripheral L-arginine/NO/cGMP nociceptive processes in pyridoxine-induced antinociception.

Role of L-arginine/nitric oxide pathway in the antinociceptive activities of morphine and mepyramine in mice.

The p-benzoquinone (PBQ)-induced abdominal constriction test was used to assess the involvement of L-arginine/nitric oxide (NO) pathway in the antinociceptive activity of the subcutaneously administered H1-receptor antagonist, mepyramine (CAS 59-33-6), and an opioid receptor agonist, morphine (CAS 57-27-2), in mice. Mepyramine (ED50: 5.6 mg/kg) and morphine (ED50: 0.13 mg/kg) produced antinociceptive effects. The NO precursor L-arginine (CAS 1119-34-2) (50 mg/kg) also produced antinociception similar to mepyramine, but significantly less than morphine. The NO synthase (NOS) inhibitor L-NG-monomethylarginine (L-NMMA) (CAS 53308-83-1) (50 mg/kg) did not significantly change p-benzoquinone-induced abdominal constrictions. L-arginine significantly increased the antinociceptive effects of morphine and mepyramine. The antinociceptive activity of morphine, but not that of mepyramine, was completely abolished when combined with L-NMMA. L-NMMA also significantly decreased the antinociception induced by morphine or mepyramine in combination with L-arginine. The present results suggest that morphine and mepyramine could produce peripheral antinociception by the involvement of L-arginine/NO cascade or other related pathways of nociceptive processes induced by NO.

Peroxynitrite produces relaxations on the rat anococcygeus muscle.

Effects of peroxynitrite (ONOO-), its stable product 3-nitrotyrosine (NT) and sodium nitroprusside (SNP) on isolated rat anococcygeus muscle were investigated. Administration of 0.1-1.0 mM ONOO- or 0.01-100.0 microM SNP produced concentration-dependent relaxations on the phenylephrine (2 microM)-precontracted muscle. Time courses of these relaxations to ONOO- and SNP were not similar and decomposed ONOO- caused a biphasic response composed of an initial contraction followed by a relaxation. NT (0.01-0.1 mM) either incubated for 20 min prior to precontraction or given during precontraction plateau did not attenuate precontraction or ONOO(-)-induced relaxations. Results of the present study demonstrate that ONOO- relaxes rat anococcygeus muscle specifically while its stable metabolite NT has no effect.

Effects of econazole on receptor-operated and depolarization-induced contractions in rat isolated aorta.

In our previous study, econazole caused a decrease in serum nitrite levels in septic mice in vivo, but it enhanced the mortality rate. The aim of the study was to investigate the in vitro effects of econazole on receptor-operated and depolarization-induced contractions on endothelium-intact and -denuded rat isolated aorta. Econazole (0.1, 1 and 10 microM) significantly inhibited receptor-operated (phenylephrine, Phe) and depolarization (KCl)-induced contractions of endothelium-intact or -denuded rings in a noncompetitive and concentration-dependent manner. Removal of endothelium changed the pD'2 values only for KCl-induced responses. The pD'2 values of L-type calcium channel blocker nifedipine were significantly higher than the econazole on Phe concentration-response curves in endothelium-intact and -denuded rings. Econazole caused a biphasic response in precontracted by Phe or KCl in endothelium-intact and -denuded rings, first a transient contraction following sustained relaxation. Removal of endothelium did not affect the contractile responses induced by Phe. The contractile responses induced by 10 microM econazole in the KCl-precontracted rings were antagonized by the treatment of alpha-adrenergic receptor antagonist, phentolamine (10 microM). Deendothelization was significantly increased the IC50 values of econazole obtained from Phe- and KCl-precontractions. The relaxations induced by 10 microM econazole in endothelium-intact rings precontracted with Phe or KCl were not changed by NO synthase inhibitor, L-N(G)-nitroarginine (100 microM). The IC50 values of econazole were significantly higher than nifedipine in endothelium-intact and -denuded rings. These results suggest that econazole is a noncompetitive antagonist on alpha1-adrenoceptor-mediated and depolarization-induced contractions in rat isolated aorta by inhibiting Ca2+ entry through L-type calcium channels, and the endothelium seems to modulate vascular responses induced by this agent. The vascular effects of econazole may limit the usage of this agent in septic shock.

Participation of the components of L-arginine/nitric oxide/cGMP cascade by chemically-induced abdominal constriction in the mouse.

The purpose of this study was to investigate the role of the L-arginine/nitric oxide (NO)/cGMP pathway in p-benzoquinone-induced writhing model in mouse. L-arginine, a NO precursor, displayed antinociceptive effects at the doses of 0.125-1.0 mg/kg. When the doses of L-arginine were increased gradually to 10-100 mg/kg, a dose-dependent triphasic pattern of nociception-antinociception-nociception was obtained. The NO synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) (18.7515 mg/kg), possessed antinociceptive activity. Methylene blue (MB), a guanylyl cyclase and/or NOS inhibitor, (5-160 mg/kg) also produced a dose-dependent triphasic response. When L-arginine (50 mg/ kg) was combined with L-NAME (75 mg/kg). L-arginine-induced antinociception did not change significantly. Cotreatment of L-arginine with 5 mg/kg MB significantly decreased MB-induced antinociception and reversed the nociception induced by 40 mg/kg MB to antinociception. It is concluded that the components of L-arginine/nitric oxide/cGMP cascade may participate in nociceptive processes both peripherally and centrally by a direct effect on nociceptors or by the involvement of other related pathways of nociceptive processes induced by NO.

Role of guanylyl cyclase activation via thiamine in suppressing chemically-induced writhing in mouse.

The possible role of L-arginine/nitric oxide (L-arginine/NO) pathway in the antinociceptive activity of thiamine (vitamin B1) in p-benzoquinone-induced mouse writhing model was investigated. Thiamine (ED50, 0.11 mg/kg), L-arginine (50 mg/kg), NG-nitro L-arginine methyl ester (L-NAME, 75 mg/kg) and morphine (ED50: 0.13 mg/kg) displayed antinociceptions following s.c. administrations (52.4 +/- 5.5%, 36.8 +/- 7.7%, 27.8 +/- 11.1%, 66.1 +/- 3.5%, respectively). However, methylene blue (MB, 40 mg/kg, s.c.) produced a nociception (-32.1 +/- 9.9%). Coadministration of B1 with L-arginine did not significantly change L-arginine-induced antinociception (48.9 +/- 3.7%). Cotreatment of thiamine with L-NAME and MB significantly increased the L-NAME-induced antinociception (53.9 +/- 3.9%) and reversed the MB-induced nociception to antinociception (46.0 +/- 4.2%). L-Arginine and L-NAME-induced antinociceptions were significantly increased (55.9 +/- 3.9% and 61.1 +/- 5.0%, respectively) by morphine. MB-induced nociception significantly reversed to antinociception by the concomitant administration of morphine (41.6 +/- 8.9%). Thiamine and morphine coadministration displayed antinociception (46.0 +/- 4.2%). The present results suggest that thiamine could produce antinociception by the activation of guanylyl cyclase mediated by cyclic guanosine monophosphate (cGMP) that may trigger the possible involvement of central and/or peripheral L-arginine/NO/cGMP pathway.

Temporal variation in serum nitrite levels in rats and mice.

Although considerable evidence implicates involvement of nitric oxide (NO) in circadian regulation, little is known about possible 24 h variations in basal NO metabolism. In this study, daily variations in serum nitrite levels were studied in locally bred mice and rats during the months of September and October. The serum was separated from blood samples obtained at six different times of the day and night (1 h, 5 h, 9 h, 13 h, 17 h, and 21 h after lights off [HALO] from male albino mice and rats). As an index of in vivo NO generation, serum nitrite levels (determined by the diazotization method) in rats exhibited significant temporal fluctuation (unpaired Student t test), with the concentration highest at 5 HALO and 21 HALO and lowest at 9 HALO. No such temporal variation was detected in mice in these studies conducted on locally bred animals in the autumn.

Effects of nitric oxide synthase inhibition in lipopolysaccharide-induced sepsis in mice.

In the present study, we have investigated the effects of nitric oxide (NO) synthase inhibition on mortality in lipopolysaccharide (LPS)-induced sepsis in mice. Serum nitrite levels peaked at 15 h after an injection of LPS (10 mg kg-1, i.p.). Aminoguanidine, a selective inducible NO synthase (iNOS) inhibitor, at a dose of 100 mg kg-1 significantly reduced the LPS-induced increase in nitrite levels and improved mortality. Econazole, iNOS inhibitor, calmodulin antagonist, 5-lipoxygenase and a specific thromboxane synthase inhibitor, at a 1 mg kg-1 dose significantly decreased the LPS-induced increase in nitrite levels, but increased mortality 4. 9-fold when compared to the LPS group (control). Indomethacin, a putative iNOS and non-selective cyclo-oxygenase (COX) inhibitor, of 1, 10 and 100 mg kg-1, dose dependently decreased the LPS-induced increase in nitrite levels. This decrease was significantly different from the control at 10 and 100 mg kg-1 dose levels. When indomethacin (100 mg kg-1) was combined with aminoguanidine (100 mg kg-1), LPS-induced nitrite levels were significantly attenuated. NO precursor, L-arginine, was added to this combination in order to test the inhibition of iNOS activity which resulted in no change in nitrite levels. An indomethacin and aminoguanidine combination increased mortality twofold when compared to the control. The addition of L-arginine to the combination enhanced the mortality rate to 1.5-fold. These results suggest that NO appears to play a role in the LPS-induced septic shock model in mice. The improvement in sepsis-induced mortality enhanced by aminoguanidine by the inhibition of iNOS but not with the other agents or combinations should be re-evaluated in order to make an appropriate choice of the therapeutic target. In addition, it may also suggest that other mediators, such as arachidonic acid products and cytokines play a role in septic shock pathogenesis as well. (c) 1998 The Italian Pharmacological Society.

Circadian-rhythm-dependent effects of L-NG-nitroarginine methyl ester (L-NAME) on morphine-induced analgesia.

Circadian changes in the interactions between L-NG-nitroarginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, and morphine-induced antinociception were investigated by the mouse hot-plate test. Both the basal pain sensitivity and morphine-induced analgesia undergo significant 24 h variations. L-NAME (40 mg/kg, i.p.) alone did not show any antinociceptive activity, but potentiated morphine-induced analgesia when combined with morphine at all injection times. In terms of percentage absolute potentiation (%AP), L-NAME dramatically augmented the analgesic effect of morphine in the late dark period at 19 hours after lights on (HALO). It is concluded that nitric oxide (NO) is involved in the modulation of the analgesic effect of morphine; thus, the L-NAME and morphine combination might be beneficial in alleviating pain.

Comparison of nitric oxide production by monocyte/macrophages in healthy subjects and patients with active pulmonary tuberculosis.

The aim of the present study was to determine the NO production by human cultured macrophages (m phi) and to compare the NO production between healthy subjects and patients with active pulmonary tuberculosis. The bioassay method was used for assessment of validation. Lipopolysaccharide (125 ng ml-1)-activated m phi from healthy and diseased subjects released a substantial amount of NO. NO synthase inhibitor, NG-nitro-L-arginine methyl ester, (0.1 mmol l-1) suppressed NO synthesis significantly in m phi of healthy subjects. Nitrite formation measured by the diazotization method in the supernatants taken from cultured m phi of tuberculous patients were significantly lower than the healthy subjects. The supernatants obtained in both subjects caused relaxation of guinea-pig aorta reversed by methylene blue (10 mumol l-1). There was a significant difference between relaxations of healthy and diseased supernatants. Nitrite formation measured by the bioassay method in the supernatants taken from cultured m phi of tuberculous patients was significantly higher than the healthy subjects. It was concluded that NO production appeared to be decreased in tuberculosis. The reason for decreased production of NO in tuberculosis may be related to the interaction of several cytokines and/or eicosanoids by means of the disease related induction of immune reactions.

Bradykinin-induced responses in a coaxial bioassay system composed of rat anococcygeus muscle and guinea pig trachea.

1. Epithelium-dependent effects of bradykinin (BK) were investigated in a coaxial bioassay system which consisted of guinea pig trachea as donor organ and rat anococcygeus muscle as test tissue. 2. BK (10(-9) to 10(-5) M) produced concentration-dependent relaxations on the phenylephrine (3 x 10(-6) M)-precontracted rat anococcygeus muscle mounted alone. Relaxations decreased significantly when muscle was mounted in epithelium-intact trachea. There was also a significant difference between the relaxations obtained in the muscle within epithelium-intact and epithelium-denuded trachea (at 10(-7) to 10(-5) M concentrations). 3. Capsaicin (10(-5) M) pretreatment did not change BK (10(-9) to 10(-5) M)-induced relaxations in each preparation compared with vehicle pretreatment. Indomethacin (10(-6) M) in combination with thiorphan (10(-5) M) and atropine (10(-6) M) did not affect the BK-induced relaxations of the muscle within capsaicin-pretreated epithelium-intact or denuded trachea. 4. CGS 8515 (a specific 5-lipoxygenase inhibitor, 10(-6) M) did not change BK (10(-5) M)-induced relaxation on the muscle alone, and caused an increase of BK-induced relaxation on the muscle within epithelium-intact trachea compared with that obtained without CGS 8515. 5. Results showed that epithelial or nonepithelial factors were capable of modulating the responsiveness of rat anococcygeus muscle to BK. The decreased relaxation by BK in anococcygeus muscle did not occur by the release of cyclooxygenase products or tachykinins from tracheal epithelium, but it may have occurred by the contractile action of lipoxygenase product secreted by nonepithelial sources. In addition, BK might stimulate the secretion of an epithelium-derived inhibitory factor from the trachea.

Antinociceptive effect of some amaryllidaceae plants in mice.

The antinociceptive effects of ethanolic extracts of Pancratium maritimum L., Narcissus tazetta subspecies tazetta and Leucojum aestivum L. bulbs have been investigated in mice using the p-benzoquinone-induced abdominal constriction and hot-plate tests. In the p-benzoquinone-induced abdominal constriction test the ethanolic extracts of P. maritimum (300, 600 or 1200 mg kg-1, s.c.) and N. tazetta subsp. tazetta (5, 50, 100 or 200 mg kg-1, s.c.) caused dose-dependent inhibition of abdominal constrictions whereas a fluctuating response was obtained from ethanolic extracts of L aestivum (2.5-500 mg kg-1, s.c.). In the hot-plate test P. maritimum and L. aestivum caused a significant increase of latency only at the highest concentrations used (1200 mg kg-1 and 500 mg kg-1, i.p., respectively). However, at these concentrations they also caused significant toxic effects. In contrast with P. maritimum and L. aestivum, N. tazetta subsp. tazetta (5-500 mg kg-1, i.p.) extracts had no antinociceptive effect in this test. These findings indicate that the antinociceptive effect of Amaryllidaceae plants differs depending on the model of nociception investigated.

Effects of platelet-activating factor antagonists WEB 2086 and BN 50730 on digoxin-induced arrhythmias.

Effects of platelet-activating receptor antagonists WEB 2086 (1.0-30.0 mg.kg-1 intravenously) and BN 50730 (10.0 mg.kg-1 intravenously) alone or in combination with CGS 8515 (a specific 5-lipoxygenase inhibitor, 0.3 mg.kg-1 intravenously) and Dazmegrel (a thromboxane synthase inhibitor, 1.0 mg.kg-1.hr-1 intravenous infusion) on digoxin-induced arrhythmias were investigated in anaesthetised guinea-pigs. ECG, mean arterial blood pressure, heart rate and arrhythmias were recorded, starting 30 min. before digoxin administration and continuing for 60 min. afterwards. WEB 2086 (10.0 mg.kg-1 intravenously) reduced the mortality rate and arrhythmia score significantly compared to the control values. However, in combination with CGS 8515, it did not affect the mortality rate. BN 50730 (10.0 mg.kg-1) reduced the incidence of ventricular fibrillation and also arrhythmia score. BN 50730 in combination with Dazmegrel was reduced the arrhythmia score, incidence of ventricular fibrillation and mortality rate significantly, compared to control values. Digoxin-induced acute rise in mean arterial blood pressure was not affected by any of drug treatment except WEB 2086 (10.0 mg.kg-1) in combination with CGS 8515. Heart rate values did not differ between groups. However, pressure-rate index was reduced by WEB 2086 alone or in combination with CGS 8615. Results showed that although two different platelet-activating factor antagonists have different effects on the incidence of ventricular fibrillation and mortality, they improved the digoxin-induced arrhythmias when they were used either separately or in combination with CGS 8515 or Dazmegrel by implicating that platelet-activating factor has a role on digoxin-induced arrhythmias.

Hypoglycaemic effect of Momordica charantia extracts in normoglycaemic or cyproheptadine-induced hyperglycaemic mice.

The hypoglycaemic effect of orally administered extracts of Momordica charantia L. fruits was examined in normoglycaemic or cyproheptadine-induced hyperglycaemic mice. The aqueous extract reduced the fasting glucose levels of hyperglycaemic or normoglycaemic mice. However, the ethanol extract did not affect the fasting or nonfasting glucose levels significantly in both groups of mice. There was no significant difference between the glucose-loaded and glucose-loaded plus aqueous extract given group. On the other hand, oral glucose-loading of the cyproheptadine-induced hyperglycaemic animals reduced the fasting glucose levels significantly. These results showed that aqueous extract of M. charantia fruits has a hypoglycaemic activity without improving the tolerance to glucose in cyproheptadine-induced diabetic mice.

Antinociceptive effects of H1- and H2-antihistaminics in mice.

1. Two methods were used to study the analgesic effects of subcutaneous injections of antihistaminics in mice: the p-benzoquinone(PBQ)-writhing test and caudal compression test. 2. Mepyramine, lupitidine (SKF 93479), and famotidine produced significant antinociceptive effects dose-dependently, during both the PBQ-writhing and caudal compression tests. 3. However, ranitidine did not reveal any antinociceptive effect. 4. Icotidine (SKF 93319) produced significant antinociception and also augmented the analgesic effect of morphine, on the caudal compression test. 5. However, mepyramine, famotidine, and lupitidine did not affect morphine-induced analgesia on the caudal compression test and displayed a nonsignificant potentiation on morphine-induced analgesia in the PBQ-writhing test.