Effects of felbamate on brain polyamine changes following transient cerebral ischemia in the Mongolian gerbil.

We sought to determine whether treatment with felbamate was capable to reduce the accumulation of putrescine induced by transient forebrain ischemia in the Mongolian gerbil. Gerbils underwent 10 min ligation of common carotid arteries followed by recirculation. Immediately after the release of the arterial occlusion, felbamate (75 and 150 mg kg(-1) i.p.) was administered. Putrescine and polyamine levels were measured in hippocampus and striatum at 1, 8, 24 and 48 h after recirculation. Putrescine levels appeared enhanced already 8 h after the release of the arterial occlusion and kept increasing up to 48 h in the hippocampus and striatum. No significant changes in spermidine levels during recirculation were detected. Conversely, spermine appeared to decrease in the hippocampus while it did not show changes in the striatum. Felbamate significantly reduced the ischemia induced changes in putrescine brain content only at the dose of 150 mg kg(-1) i.p.

Direct viable count as test for toxicity assessment: the effects of four metals on a Salmonella enteritidis strain.

The toxicity of synthetic sewage containing increasing concentrations of arsenic (.125, .25, .5, 1.0 mg L-1), cadmium (.02, .05, .1, .2 mg L-1), lead (.2, .5, 1.0, 2.0 mg L-1) and nickel (.5, 1.0, 2.0, 4.0 mg L-1) has been investigated by determining the total direct count (TDC) and the direct viable count (DVC) of Salmonella enteritidis by means of an immunofluorescence technique (IFA). This has been done in order to evaluate the possibility of using the IFA technique to estimate the toxicity of complex effluents. Arsenic, cadmium and nickel produced a concentration-dependent reduction in the number of viable bacterial cells. This was more clear when the viable bacterial cells were considered than when only the culturable part was used. Lead did not show a concentration-dependent and reproducible effect. At the highest concentrations allowed by the Italian wastewater regulations, lead, cadmium, arsenic and nickel reduced the viable/total bacterial cells ratio to 74.5%, 68.5%, 28.4% and 6.9%, respectively. The toxic effects of the metals were also tested using the standard Microtox assay.

Oral toxicity of bis(2-ethylhexyl) phthalate during pregnancy and suckling in the Long-Evans rat.

Bis(2-ethylhexyl) phthalate (DEHP) is a compound widely used in plastics technology to impart flexibility to rigid polymers. We sought to determine whether the oral exposure of female rats to DEHP during gestation and suckling produces alterations in the litter. Female rats were exposed to different concentrations of DEHP suspended in drinking water (32.5 and 325 microl/litre) from day 1 of pregnancy to day 21 after delivery. Pup body weight gain and kidney, liver and testes weight was measured at different times (21, 28, 35, 42 and 56 days) after birth. Plasma concentrations of DEHP and histopathological alterations in kidneys, liver and testes were also studied. In addition, the ability of female pups (1 month of age) to perform a learned avoidance test, the 'beam walking' test, was evaluated. Perinatal exposure to DEHP produced no statistically significant changes in the body weight gain of offspring. Conversely, it produced a significant decrease in kidney and testes relative weight (organ/body weight) with a significant increase in relative liver weight. Signs of histological damage in kidneys, liver, and particularly testes, were observed. Pups exposed perinatally to the highest concentration of DEHP elicited a significant increase in the time necessary to perform the beam walking test.

Interaction between pefloxacin and aminophylline in genetically epilepsy-prone rats.

The effects of a chronic treatment with pefloxacin on aminophylline-induced seizures in genetically epilepsy-prone rat have been investigated. Two series of experiments were performed. In the first, animals received pefloxacin orally twice a day for five days, then were administered aminophylline intraperitoneally and the occurrence of seizures was evaluated. In the second series of experiments, theophylline serum concentration was evaluated in rats subject to the same experimental protocol. Pefloxacin significantly, and in a dose-dependent manner, increased the occurrence of seizure phases induced by aminophylline, but did not influence theophylline serum levels measured at different times after the injection of aminophylline. We suggest that additive neurotoxic effects of both pefloxacin and aminophylline might contribute to the increased severity of seizure score. The possible role of GABA-benzodiazepine, excitatory amino acid and purinergic mechanism, and the role of pharmacokinetic factors are discussed.

Effects of fructose-1,6-biphosphate on microsphere-induced cerebral ischemia in the rat.

Fructose-1,6-bisphosphate has been shown to exert beneficial effects in different experimental models of cerebral ischemia. In view of this evidence, we have determined whether the compound protects the brain during microsphere-induced ischemia. One thousand two hundred microspheres were injected into female rats through a catheter inserted into the right common carotid artery and, 15 minutes and again 24 hours later, we intravenously treated the animals with 333 mg Kg(-1) of fructose-1,6-bisphosphate. The injection of microspheres produced significant changes in the rats' gross behavior, in their performance in the beam walking test, and in their brain lactate concentrations. The treatment with fructose-1,6-bisphosphate significantly attenuated the behavioral alterations induced by microsphere ischemia, but not in reducing brain accumulation of lactate. Moreover, the compound was shown to ameliorate the blood-brain barrier dysfunction, produced 2 and 4 hours after microsphere injection, evaluated by the Evans blue method. These results suggest that fructose-1,6-bisphosphate possesses salutary properties against the damages induced by microsphere ischemia.

Effect of 2,6-diisopropylphenol on the delayed hippocampal cell loss following transient forebrain ischemia in the gerbil.

We examined the protective activity of 2,6-diisopropylphenol on mortality and delayed hippocampal cell death induced by transient cerebral ischemia in the gerbil. Forebrain ischemia was produced by bilaterally occluding the common carotid arteries for 10 minutes; then the blood supply to the brain was restored. The number of survivors was counted for 8 days, and the histopathological damage in the CA1 region of the hippocampus was scored according to the semiquantitative scale of Rudolphi and Colleagues. When intraperitoneally injected immediately after the ischemic attack, 2,6-diisopropylphenol (25, 50, 100 mg kg-1) produced no significant reduction in the rate of mortality in comparison with its vehicle. However, the survivors that had received the compound at the dose of 50 and 100 mg kg-1 elicited a significant increase in the number of viable pyramidal cells in the CA1 hippocampal region. Moreover, we obtained similar results by injecting the compound 30 minutes after the release of the carotid artery occlusion. These results suggest that 2,6-diisopropylphenol, although it does not show any capability of improving the rate of survival, it elicits protective properties against the transient forebrain ischemia-induced delayed hippocampal neuronal death.

Increased cardiovascular responsiveness to central cholinergic stimulation in the genetically epilepsy-prone rat.

We sought to determine whether differences in cardiovascular responsiveness to central stimulation of the cholinergic system existed between the genetically epilepsy-prone and outbred Sprague-Dawley rats. We treated the unanaesthetized, restrained rats with the indirect cholinergic agonist physostigmine (25, 50, 100 and 200 micrograms kg-1, i.v.) and the direct muscarine agonist arecoline (50, 100 and 200 micrograms kg-1, i.v.). Blood pressure and heart rate were evaluated. Genetically epilepsy-prone rats demonstrated to be more susceptible to the action of physostigmine than the outbred Sprague-Dawley rats. Conversely, we did not note any difference between the two strains in the extent of the pressor response induced by arecoline. Moreover, we treated both strains with hemicholinium-3 (34.8 nmol, i.c.v.) to deplete endogenous stores of acetylcholine. This treatment did not affect the pressor response to arecoline, whereas it greatly reduced the response to physostigmine. The present results support an increased cardiovascular responsiveness to central cholinergic stimulation in the genetically epilepsy-prone rat which appears to be related to a pre-synaptic rather than a post-synaptic component.

Effects of fructose-1,6-bisphosphate on brain polyamine biosynthesis in a model of transient cerebral ischemia.

We evaluated the effects on cerebral ischemia of a treatment with fructose-1,6-bisphosphate, a compound known to possess protective effects on acute ischemic injury in a variety of different tissues. We investigated the ability of the compound, administered either 15 minutes before or 15 minutes after the ischemic insult, in reducing the ischemia-induced changes in polyamine brain levels. The experiments were performed in adult, chloral hydrate-anesthetized Mongolian gerbils that underwent a 15 minutes ligation of the common carotid arteries followed by recirculation. Animals were sacrificed 1, 8 and 24 hours and immediately after the release of the occlusion. Polyamine brain levels were not modified during ischemia. Putrescine began to increase after eight hours from the release of the occlusion and we found it significantly increased after 24 hours in the hippocampus and striatum. We did not detect any significant changes in spermidine brain levels either during ischemia or during recirculation. Conversely, spermine appeared to decrease in the hippocampus while it did not show changes in striatum and medulla-pons. The activity of ornithine decarboxylase, a key enzyme in the biosynthesis of polyamines, resulted enhanced at the end of the ischemic period in all the brain regions tested and showed a peak at eight hours of recirculation in striatum and hippocampus whereas returned to control values in the medulla-pons. Fructose-1,6-bisphosphate significantly reduced the ischemia induced changes in polyamine brain content when administered before the ischemic insult while did not show protective properties when administered post-ischemically.

Neuroprotective activity of fructose-1,6-bisphosphate following transient forebrain ischemia in the Mongolian gerbil.

We examined the protective activity of fructose-1,6-bisphosphate (FBP) on mortality and delayed hippocampal cell death induced by transient cerebral ischemia in the Mongolian gerbil. Forebrain ischemia was produced by bilaterally occluding the common carotid arteries for 15 min using microaneurysm clips; then the blood supply to the brain was restored. The number of survivors was counted for 8 days, and the histopathological damage in the CA1 region of the hippocampus was scored according to the semiquantitative scale of Rudolphi and colleagues. When injected 15 min before the ischemic insult, FBP (100 and 333 mg/kg, i.v.) significantly reduced the rate of mortality during the 8-day observation period. Equivalent doses of fructose and fructose monophosphate did not improve survival, and neither did low doses (33 mg/kg) of FBP. FBP also produced a significant degree of protection against the CA1 pyramidal cell loss in comparison with its vehicle (distilled water). Conversely, when we administered the compound, at the same dose, 15 min after the release of the arterial occlusion, we observed neither a significant reduction of mortality nor significant protection against hippocampal CA1 pyramidal cell loss. These results suggest that FBP possesses salutary properties against the damages induced by transient cerebral ischemia, although they are evident only when the compound is administered before the resolution of the ischemic injury.

Anticonvulsant effects of U-54494A and U-50488H in genetically epilepsy-prone rats and DBA/2 mice: a possible involvement of glycine/NMDA receptor complex.

1. The effects of U-54494A and U-50488H on convulsions produced by sound have been studied in genetically epilepsy-prone DBA/2 mice and genetically epilepsy-prone rats. 2. Both compounds showed a dose-dependent anticonvulsant activity. U-54494A was less potent as an anticonvulsant than U-50488H in genetically epilepsy-prone rats and elicited a similar potency to that of U-50488H in DBA/2 mice when administered intracerebroventricularly or intraperitoneally. 3. Similar sedative and hypothermic effects were observed after the highest dose of U-54494A and U-50488H in DBA/2 mice. U-50488H seems to exhibit a greater sedative effect and to affect the rotarod test in rats much more than U-54494A. U-54494A elicited a better therapeutic index than U-50488H. 4. The anticonvulsant properties of both compounds are antagonized by high doses of naloxone and nor-binaltorphimine, a selective kappa-opioid antagonist. 5. The effects of U-50488H and U-54494A in DBA/2 mice were also antagonized by the glycine/NMDA receptor antagonist D-serine. 6. The present results suggest a possible interaction between kappa-opioid and the glycine/NMDA receptors during epileptic phenomena.

Repeated treatment with quinolones potentiates the seizures induced by aminophylline in genetically epilepsy-prone rats.

1. The effects of a chronic treatment with several quinolone derivatives on on the aminophylline-induced convulsions in the genetically epilepsy-prone rat have been investigated. 2. Two series of experiments have been performed: in the first one animals received the quinolone twice a day for 5 days, then were given aminophylline (80-140 mg.kg-1, i.p.); in the second series of experiments the rats were treated once a day with the quinolone plus 120 mg.kg-1 of aminophylline for 5 days. The changes induced by both treatment protocols on electrocortical activity and on the occurrance of seizures have been evaluated. 3. Enoxacin reduced the dose of aminophylline necessary for the induction of seizures in a higher degree with respect to the other quinolone derivatives. The derivatives which showed minor proconvulsant properties were ofloxacin, ciprofloxacin and cinoxacin. The potentiation of seizures induced by quinolones appeared a dose-dependent phenomenon which was more evident when high doses of quinolones were used. 4. The chronic treatment carried out daily with quinolones and aminophylline suggests that additive neurotoxic effects of both classes of drugs may contribute to the increase of severity of seizure scores. 5. The possible role of GABA-benzodiazepine, excitatory amino acid, purinergic mechanisms as well as the role of pharmacokynetic factors are discussed.

Effects of captopril on the development of rat doxorubicin nephropathy.

The effects of a daily administration of an anti-converting enzyme inhibitor. Captopril (CPT) (100 mg/kg/orally), on the development of functional and morphological alterations induced in rats by a single injection (7.5 mg/kg/iv) of Doxorubicin (DXR) (Adriamycin*), were investigated. Twenty-four-hour protein excretion, urine output, food intake, water intake, and body weight gain were measured weekly for 30 days. Transmission and scanning electron microscopy observations were performed on kidney samples after 30 days. Four groups were studied. Group 1 were control rats. Group 2 were rats injected with DXR. Group 3 were rats injected with DXR and treated with CPT for 30 days. Group 4 were rats injected with DXR and treated with CPT for 15 days (CPT treatment started 15 days after DXR injection). Group 1 did not show significant functional or morphological changes. Group 2 showed severe proteinuria, significant increase in urinary volume within 2 weeks, significant body weight reduction and diffuse morphological changes. These changes mainly consisted of podocyte swelling, severe foot process fusion, and presence of casts within tubular lumen. Group 3, with respect to group 2, showed a significant reduction of the 24 h protein excretion and urine output. This group displayed morphological changes similar to those observed in group 2, but with a focal distribution. Group 4 showed functional and morphological changes comparable with those of group 2. It is concluded that CPT partially inhibits the development of the functional and morphological damage induced by DXR in the rat kidney. However, CPT did not influence the natural development of nephropathy when treatment started 15 days after DXR injection.

Effects of some calcium antagonists upon the activity of common antiepileptic compounds on sound-induced seizures in DBA/2 mice.

1. Flunarizine (2.65 mumol/kg, i.p.) and nimodipine (5.25 mumol/kg, i.p.) potentiated the anticonvulsant properties of phenytoin, phenobarbital and valproate against audiogenic seizures in DBA/2 mice. 2. Diltiazem (5.25 mumol/kg, i.p.) was able to potentiate the antiseizure activity of phenytoin but was not effective against the anticonvulsant action of phenobarbital and valproate. 3. Verapamil (5.25 mumol/kg, i.p.) was unable to potentiate the anticonvulsant properties of all antiepileptic drugs studied. 4. Bay K 8644 (1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluorophenyl)-pyridine- 5-carboxylic acid), a calcium agonist at a dose of 2.65 mumol/kg, i.p., induced a reduction of anticonvulsant potency of phenytoin, phenobarbital and valproate. 5. None of the calcium antagonists used significantly increased the plasma levels of antiepileptic compounds or significantly affected the body temperature changes induced by anticonvulsant drugs. 6. It may be concluded that some calcium antagonists enhance the anticonvulsant properties of some antiepileptic drugs against audiogenic seizures. A pharmacokinetic interaction does not seem responsible for these effects.

Changes in urine volume and urinary electrolyte excretion after intracerebroventricular injection of arecoline and hemicholinium-3.

Activation of cholinergic neurons in specific brain regions evokes a hypernatriuretic response, which appears to be atropine-sensitive and, perhaps, independent from the renal innervation. However the role of cholinergic neurons in central control of renal function is not well understood. The purpose of this study was to further investigate whether brain acetylcholine stores are able to influence kaliuresis and natriuresis in conscious rats. Therefore, the renal response to cholinergic drugs was examined in Wistar rats which underwent to a 0.15 M NaCl solution (saline) load administered by gavage. Central injection of arecoline, a muscarinic agonist, produced a dose-dependent reduction in water diuresis and a highly significant increase in sodium excretion within two hours from the oral saline load. An intracerebroventricular (ICV) injection of methylatropine completely blocked both the antidiuretic and the natriuretic response induced by arecoline. Hemicholinium-3 (HC), centrally administered at a dose (34.8 nmol) known to be capable of inducing a maximal depletion of brain acetylcholine, elicited a time-dependent antidiuretic effect accompanied by a highly significant reduction in potassium and sodium urinary excretion. Therefore, we suggest that brain cholinergic neurons are involved in the regulation of the electrolyte balance.

Ribavirin-induced behavioral, body temperature and electrocortical spectra effects in the rat.

Behavioral, electrocortical spectra and body temperature effects, following a single intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) injection of ribavirin, were studied in male adult rats. Ribavirin, when administered i.p., induced squatting posture, sedation, electrocortical synchronization, piloerection and a slight decrease of tactile and/or auditory stimuli/responses lasting from 45 min to 16 hr, as well as a longer lasting hypothermic effect. Following i.c.v. administration, ribavirin (50, 100 and 200 micrograms) elicited a soporific effect and produced changes in the electrocortical spectra. Pretreatment, 15 min before, with either prazosin (10 mg/kg, i.p.), an alpha 1-adrenoceptor blocker, or piperoxan (20 mg/kg, i.p.) and yohimbine (1 mg/kg, i.p.), two alpha 2-adrenoceptor blockers, or naloxone (1 mg/kg, i.p.), an opioid antagonist, did not prevent the hypothermic and behavioral effects induced by i.p. or i.c.v. administration of ribavirin. The present findings exclude an involvement of alpha-adrenergic and opioid neurotransmission in mediating the hypothermic, electrocortical and behavioral effects induced by ribavirin.

Antihypertensive activity of indolepyruvic acid: a keto analogue of tryptophan.

We studied the effect of indole-3-pyruvic acid (IPA) on systolic blood pressure of normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats. Experiments were also carried out in order to investigate whether IPA may influence the development of hypertension in spontaneously hypertensive rats. Age-matched normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats treated with N-methylglucamine, were used as controls. Acute oral (up to 50 mg/kg) and intravenous (5 mg/kg) administration of IPA did not change systolic blood pressure in any models of hypertension. By contrast, a repeated administration of IPA (100 mg/kg/day, by oral gavage for 10 days) significantly decreased systolic blood pressure in all models of hypertension, while it elicited no significant effect in normotensive rats. Moreover, when IPA was given daily to 5-week-old spontaneously hypertensive rats for 7 weeks, it partially inhibited the development of hypertension. In addition, chronic administration of IPA caused enhanced levels of tryptophan and 5-hydroxyindoleacetic acid in the cortex and diencephalon. Brainstem serotonin content in both normotensive and spontaneously hypertensive rats was also enhanced by IPA treatment. Our results suggest that IPA lowers blood pressure in different rat models of hypertension and this effect seems to be correlated with an increase in cerebral serotonin metabolism.

Effects of fructose 1,6-diphosphate on splanchnic artery occlusion shock in the rat.

Splanchnic artery occlusion (SAO) shock, produced by clamping splanchnic arteries for 45 min followed by the release of occlusion, was induced in male rats, treated 15 min before surgery, with fructose 1,6-diphosphate (FDP) or with equivalent doses of fructose or inorganic phosphate. Survival rate, peritoneal macrophage phagocytosis and plasma levels of myocardial depressant factor (MDF) were measured. Shocked animals pretreated with vehicle exhibited 24.6 +/- 0.9% phagocytic activity, 110 +/- 3.9 units/ml MDF plasma levels and 0% survival. Sham animals showed the following values: survival 100%; phagocytosis, 49.5 +/- 1.3%; MDF, 22 +/- 2.9 units/ml. Pretreatment with FDP (25 mg/kg/i.v.) significantly improved survival rate (50%) and macrophage phagocytosis (37.9 +/- 0.4%) and reduced plasma MDF levels (77 +/- 3 units/ml). Equivalent doses of fructose and inorganic phosphate did not improve survival, as well as lower doses of FDP. These results suggest a beneficial effect of FDP in SAO shock.