Effect of GABA-negative preparations on the anxiolytic and sedative effects of diazepam

Experiments on rats have shown that bicuculline (2 mg/kg) and picrotoxin (2 mg/kg) abolish the anxiolytic action of diazepam (2.5 mg/kg). Bicuculline (2 and 4 mg/kg) decreases while picrotoxin transforms the sedative effect of diazepam to the anxiolytic one. Picrotoxin (2 mg/kg) reduces the sedative action of gamma-acetylenic GABA (100 mg/kg) but does not favour the manifestation of its anxiolytic effect. It is suggested that the GABA-ergic mechanisms play an important role in the sedative effect of diazepam.     

Endogenous hyperlactatemia and insulin secretion]

In the normal anesthetized dog, the endogenous hyperlactatemia induced either by intense muscular work or by a high dose of phenformin (20 mg/kg subtucaneously) is followed by an increase in the pancreaticoduodenal insulin output. A previous perfusion of sodium dichloroacetate (50 mg/kg. h) opposes the hyperlactatemia, and reduces or suppresses the increase in insulin output.     

Effect of piperine,the active ingredient of black pepper,on intestinal secretion in mice

We have investigated the effect piperine on castor oil-stimulated fluid accumulation in the mouse small intestine. Piperine (2.5-20 mg/kg, i.p.) dose-dependently reduced castor oil-induced intestinal fluid accumulation. The inhibitory effect of piperine (10 mg/kg i.p.) was strongly attenuated in capsaicin (75 mg/kg in total, s.c.)-treated mice but it was not modified by the vanilloid receptor antagonist capsazepine (30 mg/kg i.p.). Pretreatment of mice with hexamethonium (1 mg/kg i.p.), naloxone (2 mg/kg i.p.), yohimbine (1 mg/kg i.p.) or the cannabinoid CB(1) receptor antagonist SR141716A (0.3 mg/kg i.p.) did not modify the inhibitory effect of piperine (10 mg/kg i.p.). These results suggest that piperine reduces castor oil-induced fluid secretion with a mechanism involving capsaicin-sensitive neurons, but not capsazepine-sensitive vanilloid receptors.     

Low molecular weight catalytic metalloporphyrin antioxidant AEOL 10150 protects lungs from fractionated radiation

The objective of this study was to determine whether administration of a catalytic antioxidant, Mn(III) tetrakis(N,N'-diethylimidazolium-2-yl) porphyrin, AEOL10150, reduces the severity of long-term lung injury induced by fractionated radiation (RT). Fisher 344 rats were randomized into five groups: RT+AEOL10150 (2.5 mg/kg BID), AEOL10150 (2.5 mg/kg BID) alone, RT+ AEOL10150 (5 mg/kg BID), AEOL10150 (5 mg/kg BID) alone and RT alone. Animals received five 8 Gy fractions of RT to the right hemithorax. AEOL10150 was administered 15 min before RT and 8 h later during the period of RT treatment (5 days), followed by subcutaneous injections for 30 days, twice daily. Lung histology at 26 weeks revealed a significant decrease in lung structural damage and collagen deposition in RT+AEOL10150 (5 mg/kg BID) group, in comparison to RT alone. Immunohistochemistry studies revealed a significant reduction in tissue hypoxia (HIF1alpha, CAIX), angiogenic response (VEGF, CD-31), inflammation (ED-1), oxidative stress (8-OHdG, 3-nitrotyrosine) and fibrosis pathway (TGFbeta1, Smad3, p-Smad2/3), in animals receiving RT+ AEOL10150 (5 mg/kg BID). Administration of AEOL10150 at 5 mg/kg BID during and after RT results in a significant protective effect from long-term RT-induced lung injury. Low dose (2.5 mg/kg BID) delivery of AEOL10150 has no beneficial radioprotective effects.     

The GABA-ergic system and brain edema

It has been shown in rats with experimental toxic and traumatic edemas that picrotoxin (1 mg/kg) removes the antiedematous action of diazepam, phenazepam, phenibut and amizyl and reduces the action of phentolamine. When the dose of picrotoxin is minimized to 0.5 mg/kg such an effect is not observed. Prolonged daily administration of picrotoxin in a dose of 1 mg/kg results in the development of brain edema. It is recommended that GABA-positive drugs be included into a complex of treatment measures for edema.     

The radiation-modifying capacity of xenogenic apotransferrin for the number of endogenous colony forming units in the spleen of irradiated mice

After intraperitoneal injection of 100 or 198 mg/kg of human serum apotransferrin (apo TF) to mice 1 day before acute exposure to 6 Gy of gamma-radiation, the number of endogenous CFU in spleen (CFUs) increased 2.5 or 2.6 times respectively. At a dose fo 10 mg/kg of the protein only an increasing tendency was found, whereas a dose of 1 mg/kg was inefficient. A dose of 100 mg/kg of BSA did not show any effect suggesting that non-specific immune response to alien antigen did not contribute to apo TF radiomodifying action. The following mechanisms of the apoTF radiomodifying effect are discussed: 1) the ability of the protein to inactivate Fe3+ ions that reduces the consequences of radiation oxidative stress; 2) the stimulation of proliferation of the exposed bone marrow cells by activation of Fe3+ transport or by Ca2+ mediated mechanism of mitogen signal transduction; 3) changing in the content and ratio of cyclic nucleotides by apo TF stimulation of Ca-calmodulin-dependent phosphodiesterase.     

Low molecular weight catalytic metalloporphyrin antioxidant AEOL 10150 protects lungs from fractionated radiation

The objective of this study was to determine whether administration of a catalytic antioxidant, Mn(III) tetrakis(N,N^′-diethylimidazolium-2-yl) porphyrin, AEOL10150, reduces the severity of long-term lung injury induced by fractionated radiation (RT). Fisher 344 rats were randomized into five groups: RT+AEOL10150 (2.5 mg/kg BID), AEOL10150 (2.5 mg/kg BID) alone, RT+AEOL10150 (5 mg/kg BID), AEOL10150 (5 mg/kg BID) alone and RT alone. Animals received five 8 Gy fractions of RT to the right hemithorax. AEOL10150 was administered 15 min before RT and 8 h later during the period of RT treatment (5 days), followed by subcutaneous injections for 30 days, twice daily. Lung histology at 26 weeks revealed a significant decrease in lung structural damage and collagen deposition in RT+AEOL10150 (5 mg/kg BID) group, in comparison to RT alone. Immunohistochemistry studies revealed a significant reduction in tissue hypoxia (HIF1α, CAIX), angiogenic response (VEGF, CD-31), inflammation (ED-1), oxidative stress (8-OHdG, 3-nitrotyrosine) and fibrosis pathway (TGFβ1, Smad3, p-Smad2/3), in animals receiving RT+AEOL10150 (5 mg/kg BID). Administration of AEOL10150 at 5 mg/kg BID during and after RT results in a significant protective effect from long-term RT-induced lung injury. Low dose (2.5 mg/kg BID) delivery of AEOL10150 has no beneficial radioprotective effects.     

Quebrachitol-induced gastroprotection against acute gastric lesions: Role of prostaglandins, nitric oxide and KATP channels

The effect of Quebrachitol (2-O-methyl-l-inositol), a bioactive component from Magonia glabrata fruit extract was investigated against gastric damage induced by absolute ethanol (96%, 0.2 ml/animal) and indomethacin (30 mg/kg, p.o.), in mice. Quebrachitol at oral doses of 12.5, 25, and 50 mg/kg markedly attenuated the gastric lesions induced by ethanol to the extent of 69%, 64%, and 53% and against indomethacin by 55%, 59%, and 26%, respectively. While pretreatment with TRPV1 antagonist capsazepine (5 mg/kg, i.p.) failed to block effectively the gastroprotective effect of quebrachitol (25 mg/kg) against ethanol damage, the non-selective cyclooxygenase inhibitor indomethacin (10 mg/kg, p.o.), almost abolished it. Furthermore, quebrachitol effect was significantly reduced in mice pretreated with l-NAME, or glibenclamide, the respective inhibitors of nitric oxide synthase and K⁺_ATP channel activation. Thus we provide the first evidence that quebrachitol reduces the gastric damage induced by ethanol and indomethacin, at least in part, by mechanisms that involve endogenous prostaglandins, nitric oxide release, and or the activation of K⁺_ATP channels.     

Effect of taurine on the glycemia level and the activity of hydrolases in the intestinal mucosa in carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

Upon a single injection, taurine (50 and 300 mg/kg) and its amide derivative taurepar (50 mg/kg), irrespective of diet and kinds of stress, as a rule, slightly influence the glycemia level in carp. A long-term load of taurine (a total dose of 1250 mg/kg) significantly reduces the glucose concentration in the blood of fishes kept on a carbohydrate diet. Both preparations existentially change the ratio of proteolytic (PA) and amylolitic (AA) activities in all studied fish. As a result, the G/P coefficient increases considerably. It is suggested that the increase in glycosidase activity under taurine injections has an adaptive significance for benthophagous carp, a large part of the diet of which consists of carbohydrate components.     

Enterostatin (VPDPR) and its peptide fragment DPR reduce serum cholesterol levels after oral administration in mice

We found that enterostatin (VPDPR), an anorexigenic peptide for a high-fat diet, significantly reduces serum cholesterol levels after oral administration of 100 mg/kg for 3 days in mice fed a high cholesterol-cholic acid diet. DPR, a peptide fragment of VPDPR, also had hypocholesterolemic activity at a dose of 50 mg/kg. Food intake was not suppressed under these dietary conditions. Fecal excretion of cholesterol and bile acids was increased significantly by both VPDPR and DPR. Interestingly, DPR induced hypocholesterolemic effects just two hours after a single oral administration at a dose of 100 mg/kg.     

Enterostatin (VPDPR) and Its Peptide Fragment DPR Reduce Serum Cholesterol Levels after Oral Administration in Mice

We found that enterostatin (VPDPR), an anorexigenic peptide for a high-fat diet, significantly reduces serum cholesterol levels after oral administration of 100 mg/kg for 3 days in mice fed a high cholesterol-cholic acid diet. DPR, a peptide fragment of VPDPR, also had hypocholesterolemic activity at a dose of 50 mg/kg. Food intake was not suppressed under these dietary conditions. Fecal excretion of cholesterol and bile acids was increased significantly by both VPDPR and DPR. Interestingly, DPR induced hypocholesterolemic effects just two hours after a single oral administration at a dose of 100 mg/kg.     

Caffeine-induced locomotor activity: Possible involvement of GABAergic-dopaminergic-adenosinergic interaction

Caffeine (10–40 mg/kg, p.o.) enhanced locomotor activity (LA). Administration of GABA antagonist, bicuculline (0.5–1.0 mg/kg, i.p.), potentiated this caffeine-induced increase of LA, as well as LA of control rats. Treatment with the GABA agonist, muscimol (0.25–1 mg/kg, i.p.) or dopaminergic antagonist, haloperidol (0.25–1 mg/kg, i.p.) or muscarinic receptor blocker, atropine (3.75–5 mg/kg, i.p.), or inhibitor of acetylcholine esterase physostigmine (0.05–0.30 mg/kg, i.p.) or nicotine (0.5–1.5 mg/kg, i.p.) an nicotinic receptor agonist all decreased the LA of both caffeinetreated and control rats. Haloperidol-induced reduction in caffeine-induced increase in LA was found to be withdrawn with higher dose of caffeine. The dopamine agonist L-Dopa (75–150 mg/kg, p.o.) along with carbidopa (10 mg/kg, p.o.) increased the LA in control rats and potentiated the LA of caffeine treated rats. The haloperidol attenuated the bicuculline-induced increase in LA and atropine or physostigmine attenuated the bicuculline or L-Dopa+carbidopa-induced increase in LA in both caffeine treated and control rats when those drugs were administered concomitantly with bicuculline or L-Dopa+carbidopa. These results suggest that (a) the GABAergic system has direct role in the regulation of LA, and (b) caffeine potentiates LA by antagonism of the adenosine receptor and activation of the dopaminergic system which, in turn, reduces GABAergic activity through the reduction of cholinergic system.     

Cardiotoxicity reduction induced by halofantrine entrapped in nanocapsule devices

The main objective of the present study was to evaluate the reduction in halofantrine (Hf) toxicity, an antimalarial drug frequently associated with QT interval prolongation in electrocardiogram, by its entrapment in poly-epsilon-caprolactone nanocapsules (NC). The acute lethal dose (LD(100)) of Hf.HCl experimentally observed was 200 mg/kg whereas the calculated LD(50) was 154 mg/kg. In contrast, the LD(100) for Hf-NC was 300 mg/kg with a longer mean time to death than Hf.HCl. The calculated LD(50) was 249 mg/kg for Hf-NC. The Hf entrapped in PCL NC presented a greater efficacy than PLA-PEG NC and than Hf solution in P. berghei-infected mice at 1 mg/kg. The cardiovascular parameters, ECG and arterial blood pressure, were evaluated in anaesthetized Wistar rats after the IV administration of a single, especially high dose (100 and 150 mg/kg) of halofantrine base loaded-nanocapsules (Hf-NC) or halofantrine chlorhydrate (Hf.HCl) solution. It was observed that Hf solution caused prolongation of the QT and PR intervals of the ECG; however, this effect was significantly (P<0.001) reduced when Hf was administered entrapped in nanocapsules. The treatment with Hf.HCl induced a pronounced bradycardia and severe hypotension leading to death. The effect of Hf-NC upon heart rate was reduced from 58 to 75% for 100 and 150 mg/kg, respectively, when compared with Hf.HCl solution. These findings show that the encapsulation of halofantrine reduces the QT interval prolongation of ECG in rats and suggest that a modification of drug distribution was possible by using nanocapsules. Hf encapsulation was the main factor responsible for the significant reduction in cardiac toxicity observed.     

L-NAME administration prevents the inhibition of nucleotide hydrolysis by rat blood serum subjected to hyperargininemia

Summary. The main objective of the present study was to evaluate the in vivo and in vitro effect of Arg on serum nucleotide hydrolysis. The action of N^ω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, on the effects produced by Arg was also examined. Sixty-day-old rats were treated with a single or a triple (with an interval of 1 h between each injection) intraperitoneal injection of saline (group I), Arg (0.8 g/kg) (group II), L-NAME (2.0 mg/kg or 20 mg/kg) (group III) or Arg (0.8 g/kg) plus L-NAME (2.0 mg/kg or 20 mg/kg) (group IV) and were killed 1 h later. The present results show that a triple Arg administration decreased ATP, ADP and AMP hydrolysis. Simultaneous injection of L-NAME (20 mg/kg) prevented such effects. Arg in vitro did not alter nucleotide hydrolysis. It is suggested that in vivo Arg administration reduces nucleotide hydrolysis in rat serum, probably through nitric oxide or/and peroxynitrite formation. Both are first authors.     

Effect of novel nociceptin/orphanin FQ-NOP receptor ligands on ethanol drinking in alcohol-preferring msP rats

Activation of the NOP receptor by the endogenous ligand nociceptin/orphanin FQ (N/OFQ) reduces alcohol consumption in genetically selected alcohol-preferring Marchigian Sardinian (msP) rats. The present study evaluated the effect of three newly synthesized peptidergic and one brain-penetrating heterocyclic NOP receptor agonists on alcohol drinking in the two bottle choice paradigm. MsP rats were intracerebroventricularly (ICV) injected with the NOP receptor agonists OS-462 (0.5 and 1.0 μg), UFP-102 (0.25 and 1.0 μg) or UFP-112 (0.01 and 0.05 μg), or with Ro 64-6198 (0.3 and 1.0 mg/kg) given intraperitoneally (i.p.) and tested for 10% alcohol consumption. Results showed decreased alcohol consumption after treatment with all three peptidergic NOP receptor agonists (OS-462, UFP-102 and UFP-112). OS-462 (at the 1.0 μg dose) and UFP-102 (at the 0.25 μg dose) induced a significant increase in food intake as well. Surprisingly, Ro 64-6198 was ineffective at the 0.3 mg/kg dose, whereas it increased ethanol and food consumption at the 1.0 mg/kg dose. Pre-treatment with the selective μ-receptor antagonist naloxone (0.5 mg/kg, i.p.) reduced these effects of 1.0 mg/kg of Ro 64-6198. These findings confirm that activation of brain NOP receptors reduces alcohol drinking in msP rats and demonstrate that OS-462, UFP-102 and UFP-112 act as potent NOP receptor agonists. On the other hand, Ro 64-6198 increased alcohol drinking, an effect probably induced by a residual agonist activity of this compound at μ-opioid receptors. Overall, the results indicate that OS-462, UFP-102 and UFP-112 may represent valuable pharmacological tools to investigate the functional role of the brain N/OFQ system.     

The short term satiety peptide cholecystokinin reduces meal size and prolongs intermeal interval

Camostat mesilate (or mesylate) releases endogenous cholecystokinin (CCK) or CCK-58, the only detectable endocrine form of CCK in the rat, and reduces cumulative food intake by activating CCK₁ receptor. However, the literature lacks meal pattern analysis and an appropriate dose-response curve for this peptide. Therefore, the current study determines meal size (MS), intermeal interval (IMI) and satiety ratio (SR) by orogastric gavage of camostat (0, 12.5, 25, 50, 100, 200, 300, 400, 800 mg/kg) and compares them to those previously reported by a single dose of CCK-8 (1 nmol/kg, i.p), the most utilized form of CCK. We found that camostat (200, 300, 400 and 800 mg/kg) and CCK-8 reduced cumulative food intake and the size of the first meal, but only camostat prolonged IMI and increased SR. There was no change in the duration of the first two meals or in rated behaviors such as feeding, grooming, standing and resting in response to camostat and CCK-8, but there was more resting during the IMI in response to camostat. This study provides meal pattern analysis and an appropriate dose-response curve for camostat and CCK-8. Camostat reduces food intake by decreasing MS and prolonging IMI, whereas CCK-8 reduces food intake by reducing only meal size.     

The efficacy of diazepam in the treatment of acute iron overload in rats

While conducting studies on the prevention of mortality from acute iron intoxication in rats, diazepam, given to prevent animal suffering, was observed to be associated with reduced mortality in a limited number of animals. The objective was to assess whether diazepam reduces mortality following acute iron intoxication in rats. Survival of rats was compared among groups receiving (i) orally 612 mg/kg iron alone (LD60), (ii) iron with a subcutaneous injection of 2.5 mg/kg diazepam (DZ), or (iii) iron, DZ with 800 mg/kg deferiprone intraperitoneal injections. The administration of DZ decreased mortality from 60 to 16% (p < 0.001). The addition of deferiprone to DZ resulted in zero mortality (p < 0.05 compared with the DZ group) over the study period. The administration of DZ was not associated with decreased iron absorption or increased urinary iron excretion, whereas the administration of deferiprone did result in urinary iron excretion. Microscopic examination suggests that diazepam administration may be associated with lower intracellular accumulation of iron. In conclusion, diazepam reduces mortality from iron overdose in rats through a yet unidentified mechanism, although the drug does not inhibit iron absorption or enhance urinary iron removal.     

Effect of homologous immunoglobulin with normal anti-tissue antibodies on the development of strontium-90-induced osteosarcomas in rats

In experiments on Wistar rats it was shown that homologous immunoglobulin (a single dose of 25 mg/kg), with normal antitissue antibodies, subcutaneously injected in the following manner: a single injection 90 days or 6 months, or double injection 3 and 6 months after intraperitoneal administration of strontium 90 (11.1 kBq/kg) reduces osteosarcoma occurrence and increases the average lifetime of animals.     

Dietary zinc attenuates renal lead deposition but metallothionein is not directly involved

Chronic lead exposure irreversibly damages the kidneys and may be associated with hypertension and renal insufficiency at sub-clinically toxic levels. Zinc supplementation reduces lead absorption and tissue retention in rodent models but the mechanisms are unknown. Metallothionein (MT) may function in lead detoxification. Our objective was to investigate the effects of marginal zinc (MZ) and supplemental zinc (SZ) intakes on renal lead and zinc accumulation, renal MT immunolocalization and levels. Weanling Sprague Dawley rats were assigned to MZ (8 mg Zn/kg diet), zinc-adequate control (CT; 30 mg Zn/kg), zinc-adequate diet-restricted (DR; 30 mg Zn/kg) or SZ (300 mg Zn/kg) groups, with and without lead acetate-containing drinking water (200 mg Pb/L) for 3 weeks. Kidneys were analyzed for lead and zinc by inductively coupled plasma spectroscopy and MT by immunolocalization and Western blotting. MZ had higher renal lead and lower renal zinc concentrations than CT. SZ was more protective than CT against renal lead accumulation. Renal MT levels reflected dietary intake (SZ ≥ DR ≥ CT ≥ MZ) but lead had no effect on MT staining intensity, distribution, or relative protein amounts. In summary, while SZ lowered renal lead concentration, MT did not appear to function in renal lead accumulation. Future studies should explore alternate mechanisms of renal lead detoxification.     

PRECONVULSIVE CHANGES IN BRAIN GLUCOSE METABOLISM FOLLOWING DRUGS INHIBITING GLUTAMATE DECARBOXYLASE

—Brain glucose and glycogen concentrations have been studied in mice treated with allylglycine, 4-deoxypyridoxine and isoniazid, and the effects compared with the preconvulsive increase in brain glucose and glycogen concentration that follows d , l -methionine sulphoximine treatment. Allylglycine (180 mg/kg), 4-deoxypyridoxine (250 mg/kg), isoniazid (150 mg/kg) and d ,l -methionine sulphoximine (300 mg/kg) when given to mice at room temperature, cause a fall in rectal temperature which can be prevented by maintaining the mice in an incubator at 33-34°C. An increase in brain glucose concentration is seen after allylglycine (+ 133%), d ,l -methionine sulphoximine (+ 113%) and 4-deoxypyridoxine (+ 70%) treatment when mice are kept at room temperature and killed before convulsions occur. This is associated with a rise in blood glucose concentration after allylglycine, but not after the other drugs. Preventing the fall in rectal temperature reduces, but does not abolish, the rise in brain glucose concentration seen after allylglycine, d ,l -methionine sulphoximine and 4-deoxypyridoxine. Brain glycogen concentration increases at room temperature after D,L-methionine sulphoximine and 4-deoxypyridoxine, but in mice with maintained body temperature only 4-deoxypyridoxine produces an increase in brain glycogen. Isoniazid does not increase brain glucose or glycogen at room temperature, but reduces their concentration in mice kept in the incubator. All four drugs are known to act on amino acid metabolism; d ,l -methionine sulphoximine potently inhibits glutamine synthetase whereas 4-deoxypyridoxine, allylglycine and isoniazid inhibit glutamate decarboxylase. The connection, if any, between a block in the further metabolism of glutamate and an increase in brain glucose and glycogen is unknown.