Rivelilson Mendes de Freitas

Oxidative stress in the hippocampus after pilocarpine‐induced status epilepticus in Wistar rats

The role of oxidative stress in pilocarpine‐induced status epilepticus was investigated by measuring lipid peroxidation level, nitrite content, GSH concentration, and superoxide dismutase and catalase activities in the hippocampus of Wistar rats. The control group was subcutaneously injected with 0.9% saline. The experimental group received pilocarpine (400 mg·kg−1, subcutaneous). Both groups were killed 24 h after treatment. After the induction of status epilepticus, there were significant increases (77% and 51%, respectively) in lipid peroxidation and nitrite concentration, but a 55% decrease in GSH content. Catalase activity was augmented 88%, but superoxide dismutase activity remained unaltered. These results show evidence of neuronal damage in the hippocampus due to a decrease in GSH concentration and an increase in lipid peroxidation and nitrite content. GSH and catalase activity are involved in mechanisms responsible for eliminating oxygen free radicals during the establishment of status epilepticus in the hippocampus. In contrast, no correlations between superoxide dismutase and catalase activities were observed. Our results suggest that GSH and catalase activity play an antioxidant role in the hippocampus during status epilepticus.

The systems containing clays and clay minerals from modified drug release: A review

Clays are materials commonly used in the pharmaceutical industry, either as ingredients or as active ingredients. It was observed that when they are administered concurrently, they may interact with drugs reducing their absorption. Therefore, such interactions can be used to achieve technological and biopharmaceutical advantages, regarding the control of release. This review summarizes bibliographic (articles) and technological (patents) information on the use of systems containing clays and clay minerals in modified drug delivery. In this area, formulations such natural clay, commercial clay, synthetic clay, composites clay-polymers, nanocomposites clay-polymers, films and hidrogels composites clay-polymers are used to slow/extend or vectorize the release of drugs and consequently they increase their bioavailability. Finally, this review summarizes the fields of technology and biopharmaceutical applications, where clays are applied.

Effects of the vitamin E in catalase activities in hippocampus after status epilepticus induced by pilocarpine in Wistar rats

Experimental manipulations suggest that in vivo administration of exogenous antioxidants agents decreases the concentration of free radical in the brain. Neurochemical studies have proposed a role for catalase in brain mechanisms responsible by development to status epilepticus (SE) induced by pilocarpine. The present study was aimed at was investigating the changes in catalase activities after pilocarpine-induced SE. Animals were treated with vitamin E (VIT E) 200 mg/kg (intraperitoneally (i.p.)) and, 30 min later, they received pilocarpine hydrochloride, 400 mg/kg, subcutaneous (s.c.) (P400). Other three groups received VIT E (200 mg/kg, i.p.), pilocarpine (400 mg/kg, s.c.) or 0.9% NaCl (control) alone. Animals were closely observed for behavioral changes, tremors, stereotyped movements, seizures, SE and death, for 24 h following the pilocarpine injection. The brains were dissected after decapitation. The results have shown that pilocarpine administration and resulting SE produced a significant increase in hippocampal catalase activity of (88%). In the group pre-treated which VIT E in hippocampal catalase activity was increase of 67% and 214% when compared with P400 and control group, respectively. Our results demonstrated a direct evidence of an increase in the activity of the hippocampal catalase of rat adults during seizure activity and after the pre-treated which VIT E that could be responsible by regulation of free radical levels during the establishment of SE.

Vitamin C antioxidant effects in hippocampus of adult Wistar rats after seizures and status epilepticus induced by pilocarpine.

Vitamin C (VIT C) is an exogenous antioxidant able to alter the brain oxidative stress. Antioxidant properties have been showed in seizures and status epilepticus (SE) induced by pilocarpine in adult rats. This present study was aimed at was investigating the VIT C effects on latency to first seizure, in percentage of seizures, mortality rate, as well as hippocampal lipid peroxidation levels and catalase activity after seizures and SE. The VIT C effects were investigated after the pretreatment with dose 250 mg/kg, i.p., 30 min before pilocarpine administration (400mg/kg, s.c., pilocarpine group (P400)). The VIT C increase the latency to first seizure and decrease the mortality rate and lipid peroxidation levels. In P400+VIT C and VIT C groups were observed an increase in hippocampal catalase activity. Our results suggests that the vitamin C can exert antioxidant and anticonvulsive effects in adult rats, suggesting that this vitamin can be able by reduction of lipid peroxidation content and increased of catalase enzymatic activity which cerebral compensatory mechanisms in free radical formation during SE.

Neuroprotective actions of vitamin C related to decreased lipid peroxidation and increased catalase activity in adult rats after pilocarpine-induced seizures

In the present study, we examined the neuroprotective effects of vitamin C in adult rats after pilocarpine-induced seizures. Vitamin C is an exogenous antioxidant that can be used in treatment of seizures. It can alter oxidative stress and damage neuronal induced by seizures. Its antioxidant properties can be proved in epilepsy models, such as pilocarpine-induced seizures in adult rats. In order to investigate neuroprotective effects of vitamin C, adult male rats (2 months-old) were pretreated with vitamin C (VIT C 250 mg/kg, i.p.) 30 min before receiving pilocarpine (400 mg/kg, s.c., P400 group). The other three groups were treated with vitamin C (VIT C group) and saline 0.9 (control group) alone. The pretreatment with vitamin C increased the latency to first seizures and reduced mortality rate after pilocarpine-induced seizures. Pretreatment with vitamin C alone decrease lipid peroxidation levels when compared to pilocarpine group and P400+VIT C. In P400, P400+VIT C and VIT C groups were observed an increased hippocampal catalase activity when compared to control group. Our results can suggest that neuroprotective effects of vitamin C in adult rats can be the result of reduced lipid peroxidation levels and increase of catalase activity after seizures and status epilepticus induced by pilocarpine.

Antinociceptive and Antioxidant Activities of Phytol In Vivo and In Vitro Models.

The objective of the present study was to evaluate the antinociceptive effects of phytol using chemical and thermal models of nociception in mice and to assess its antioxidant effects in vitro. Phytol was administered intraperitoneally (i.p.) to mice at doses of 25, 50, 100, and 200 mg/kg. In the acetic acid-induced writhing test, phytol significantly reduced the number of contortions compared to the control group (P < 0.001). In the formalin test, phytol reduced significantly the amount of time spent in paw licking in both phases (the neurogenic and inflammatory phases), this effect being more pronounced in the second phase (P < 0.001). Phytol also provoked a significant increase in latency in the hot plate test. These antinociceptive effects did not impaire the motor performance, as shown in the rotarod test. Phytol demonstrated a strong antioxidant effect in vitro in its capacity to remove hydroxyl radicals and nitric oxide as well as to prevent the formation of thiobarbituric acid reactive substances (TBARS). Taken as a whole, these results show the pronounced antinociceptive effects of phytol in the nociception models used, both through its central and peripheral actions, but also its antioxidant properties demonstrated in the in vitro methods used.

Pilocarpine-induced status epilepticus in rats: lipid peroxidation level, nitrite formation, GABAergic and glutamatergic receptor alterations in the hippocampus, striatum and frontal cortex.

The aim of the study was to investigate the lipid peroxidation levels, nitrite formation, GABAergic and glutamatergic receptor densities in the hippocampus, frontal cortex and striatum of Wistar rats after seizures and status epilepticus (SE) induced by pilocarpine. The control group was treated with 0.9% saline and sacrificed 1 h after the treatment. One group of rats was administered with pilocarpine (400 mg/kg sc) and sacrificed 1 h after treatment. The result shows that pilocarpine administration and the resulting SE produced a significant increase of lipid peroxidation level in the hippocampus (46%), striatum (25%) and frontal cortex (21%). In nitrite formation, increases of 49%, 49% and 75% in hippocampus, striatum and frontal cortex, respectively, was observed. Pilocarpine treatment induced down-regulation of GABAergic receptors in the hippocampus (38%), striatum (15%) and frontal cortex (11%). However, with regard to glutamatergic receptor densities, increases in the hippocampus (11%), striatum (17%) and frontal cortex (14%) was observed during the observation period. These results show a direct evidence of lipid peroxidation and nitrite formation during seizure activity that could be responsible for the GABAergic and glutamatergic receptor concentration changes during the establishment of SE induced by pilocarpine.

Oxidative stress in the hippocampus during experimental seizures can be ameliorated with the antioxidant ascorbic acid

Ascorbic acid has many nonenzymatic actions and is a powerful water-soluble antioxidant. It protects low density lipoproteins from oxidation and reduces harmful oxidants in the central nervous system. Pilocarpine-induced seizures have been suggested to be mediated by increases in oxidative stress. Current studies have suggested that antioxidant compounds may afford some level of neuroprotection against the neurotoxicity of seizures. The objective of the present study was to evaluate the neuroprotective effects of ascorbic acid (AA) in rats, against the observed oxidative stress during seizures induced by pilocarpine. Wistar rats were treated with 0.9% saline (i.p., control group), ascorbic acid (500 mg/kg, i.p., AA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), and the association of ascorbic acid (500 mg/kg, i.p.) plus pilocarpine (400 mg/kg, i.p.), 30 min before of administration of ascorbic acid (AA plus pilocarpine group). After the treatments all groups were observed for 6 h. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline and pilocarpine-treated animals. Protective effects of ascorbic acid were also evaluated on the same parameters. In pilocarpine group there was a significant increase in lipid peroxidation and nitrite level. However, no alteration was observed in superoxide dismutase and catalase activities. Antioxidant treatment significantly reduced the lipid peroxidation level and nitrite content as well as increased the superoxide dismutase and catalase activities in hippocampus of adult rats after seizures induced by pilocarpine. Our findings strongly support the hypothesis that oxidative stress in hippocampus occurs during seizures induced by pilocarpine, proving that brain damage induced by the oxidative process plays a crucial role in seizures pathogenic consequences, and also imply that a strong protective effect could be achieved using ascorbic acid.

Evaluation of acute toxicity of a natural compound (+)-limonene epoxide and its anxiolytic-like action

The aim of the study is to determine the acute toxicity and anxiolytic-like effects of a mixture of cis and trans of (+)-limonene epoxide in animal models of anxiety. After acute treatment with (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg (i.p.) no mortality was noted during 14 days of observation. In general, behavior, food and water consumption showed no significant changes. In open field test, (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg, after intraperitoneal administration, significantly decreased the number of crossings, grooming and rearing (p<0.001). All these effects were reversed by the pre-treatment with flumazenil (25 mg/kg, i.p.), similar to those observed with diazepam used as a positive standard. In the elevated-plus-maze test, (+)-limonene epoxide increased the time of permanence and the number of entrances in the open arms. All these effects were reversed by flumazenil, an antagonist of benzodiazepine receptors. In addition, (+)-limonene epoxide (75 mg/kg) also produced a significant inhibition of the motor coordination (p<0.01), that was reversed by flumazenil. In conclusion, the present work evidenced sedative and anxiolytic-like effects of (+)-limonene epoxide, which might involve an action on benzodiazepine-type receptors. These results indicate that the properties of (+)-limonene epoxide should be more thoroughly examined in order to achieve newer tools for management and/or treatment of central nervous system diseases and anxiolytic-like effects. The LD50 obtained for the acute toxicity studies using intraperitoneal route of administration was 4.0 g/kg. These findings suggest that acute administration of the (+)-limonene epoxide exerts an anxiolytic-like effect on mice, and it could serve as a new approach for the treatment anxiety, since it practically does not produce toxic effects.

Effects of lipoic acid on oxidative stress in rat striatum after pilocarpine-induced seizures

The relationship between free radical and scavenger enzymes has been found in the epilepsy and reactive oxygen species have been implicated in seizure-induced neurodegeneration. It has been suggested that pilocarpine-induced seizures is mediated by increases in oxidative stress. Current researches have suggested that antioxidant compounds may afford some level of neuroprotection against the neurotoxicity of seizures in cellular level. The objective of the present study was to evaluate the neuroprotective effects of lipoic acid (LA) in rats, against the observed oxidative stress during seizures induced by pilocarpine. Wistar rats were treated with 0.9% saline (i.p., control group), LA (20mg/kg, i.p., LA group), pilocarpine (400mg/kg, i.p., P400 group), and the association of LA (20mg/kg, i.p.) plus pilocarpine (400mg/kg, i.p.), 30 min before of administration of LA (LA plus P400 group). After the treatments all groups were observed for 1h. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline and pilocarpine-treated animals. Protective effects of LA were also evaluated on the same parameters. In P400 group there was a significant increase in lipid peroxidation, nitrite level and glutathione peroxidase (GPx) activity. However, no alteration was observed in superoxide dismutase (SOD) and catalase activities. Antioxidant treatment significantly reduced the lipid peroxidation level and nitrite content as well as increased the SOD, catalase and GPx activities in rat striatum after seizures. Our findings strongly support the hypothesis that oxidative stress in striatum occurs during seizures induced by pilocarpine, proving that brain damage induced by the oxidative process plays a crucial role in seizures pathogenic consequences, and also imply that strong protective effect could be achieved using LA.