Effects of tannery wastewater exposure on adult Drosophila melanogaster.

Our aim was to evaluate the effects of exposure to tannery wastewater on mortality and/or antioxidant enzyme system in adult wild-type Canton-S Drosophila melanogaster. Exposure to tannery wastewater induced a concentration-dependent lethality in adult Canton-S flies. Tannery wastewater was able to alter antioxidant enzyme activities, specifically glutathione peroxidase-like and glutathione S-transferase, in adult Canton-S D. melanogaster. We conclude that D. melanogaster is a reliable model to evaluate the toxicity induced by tannery wastewater.

Effect of tannery effluent on oxidative status of brain structures and liver of rodents.

Oxidative stress has been considered as a central mechanism of toxicity induced by xenobiotics. Previously, it was demonstrated that mice exposed to tannery effluent showed an anxiety-like behavior, without any comparable behavioral effects in rats. The aim of the present study was to investigate the impact of tannery wastewater on oxidative status in in vitro and in vivo assays with two mammal species, mice and rats. Specifically, homogenates of two brain areas and the liver were incubated with tannery wastewater; reactive species and lipid peroxidation levels and antioxidant enzyme activities were detected. In addition, the effects of in vivo exposure of mice to tannery effluents on and lipid peroxidation levels and the total reactive antioxidant capacity in brain areas and liver. Brain areas, the hippocampus and frontal cortex, and the liver of mice exposed to tannery wastewater showed oxidative stress. Our data suggest that divergent species-dependent hepatic enzymes adaptations, such as glutathione peroxidase and glutathione S-transferase activities, induced by tannery effluent could explain previous behavioral findings.

An evaluation of aversive memory and hippocampal oxidative status in streptozotocin-induced diabetic rats treated with resveratrol.

The present study evaluated the effects of streptozotocin (STZ)-induced diabetes on aversive memory, free radical content and enzymatic antioxidant activity in the hippocampus of adult Wistar rats submitted to oral treatment with resveratrol. Animals were divided into eight groups: non-diabetic rats treated with saline (ND SAL), non-diabetic rats treated with resveratrol at a dose 5mg/kg (ND RSV 5), non-diabetic rats treated with resveratrol at a dose 10mg/kg (ND RSV 10), non-diabetic rats treated with resveratrol at a dose 20mg/kg (ND RSV 20), diabetic rats treated with saline (D SAL), diabetic rats treated with resveratrol at a dose 5mg/kg (D RSV 5), diabetic rats treated with resveratrol at a dose 10mg/kg (D RSV 10) and diabetic rats treated with resveratrol at a dose 20mg/kg (D RSV 20). The animals received oral gavage for 35days. The contextual fear conditioning task was performed to evaluate aversive-based learning and memory. The oxidative status was evaluated in the hippocampus, by measuring the free radical content - using a 2',7'-dichlorofluorescein diacetate probe - and enzymatic antioxidant activities, such as superoxide dismutase and glutathione peroxidase. Our main behavioral results demonstrated that rats from the D RSV 10 and D RSV 20 groups showed an increase in freezing behavior when compared, respectively, to the ND RSV 10 (p<0.01) and ND RSV 20 (p<0.05). Oxidative stress parameters remained unchanged in the hippocampus of all the experimental groups. In contrast to previous experimental findings, our study was unable to detect either cognitive impairments or oxidative stress in the hippocampus of the diabetic rats. We suggest additional long-term investigations be conducted into the temporal pattern of STZ-induced diabetic disruption in memory and hippocampal oxidative status, as well as the effects of resveratrol on these parameters, in a time and dose-dependent manner.

Antiepileptogenic, antioxidant and genotoxic evaluation of rosmarinic acid and its metabolite caffeic acid in mice.

AIMS: Antioxidant compounds have been extensively investigated as a pharmacological alternatives to prevent epileptogenesis. Rosmarinic acid (RA) and caffeic acid (CA) are compounds with antioxidant properties, and RA has been shown to inhibit GABA transaminase activity (in vitro). Our aim was to evaluate the effect of RA and CA on seizures induced by pentylenotetrazole (PTZ) using the kindling model in mice. MAIN METHODS: Male CF-1 mice were treated once every three days during 16days with RA (1, 2 or 4mg/kg; i.p.), or CA (1, 4 or 8mg/kg; i.p.), or positive controls diazepam (1mg/kg; i.p.) or vigabatrin (600mg/kg; p.o.), 30min before PTZ administration (50mg/kg; s.c.). After the last treatment, animals were sacrificed and the cortex was collected to evaluate free radicals (determined by 2',7'-dichlorofluorescein diacetate probe), superoxide dismutase (SOD) and genotoxic activity (Alkaline Comet Assay). KEY FINDINGS: Rosmarinic acid 2mg/kg increased latency and decreased percentage of seizures, only on the 4th day of observation. The other tested doses of RA and CA did not show any effect. Rosmarinic acid 1mg/kg, CA 4mg/kg and CA 8mg/kg decreased free radicals, but no dose altered the levels of enzyme SOD. In the comet assay, RA 4mg/kg and CA 4mg/kg reduced the DNA damage index. SIGNIFICANCE: Some doses of rosmarinic acid and CA tested showed neuroprotective action against oxidative and DNA damage produced in the kindling epilepsy model, although they did not produce antiepileptogenic effect in vivo.

Treadmill exercise alters histone acetylation differently in rats exposed or not exposed to aversive learning context.

Epigenetic modifications have been linked to memory formation after learning context exposure and to exercise effects on memory performance. The aim of this study was to investigate the effect of treadmill exercise (20 min/day during 2 weeks) on H3K14 acetylation and H3S10 phosphorylation levels in the hippocampi of 3-month-old Wistar rats exposed and not exposed to aversive learning context. Male Wistar rats aged 2-3 months were assigned to non-exercised (sedentary) and exercised (running daily for 20 min for 2 weeks) groups. Single-trial step-down inhibitory avoidance (IA) conditioning was employed as an aversive memory model. Epigenetic parameters were determined 30 min after the IA test. A decrease in the H3K14 acetylation in the hippocampus 24 h after IA training (30 min after test session) was observed. Exercise reversed the IA effect, and no effect was observed in the non-IA exposed group. Our data support the hypothesis that modulation of H3K14 acetylation levels in the hippocampus might be related, at least in part, to exercise effects on aversive memory.

Long-term effects of pre and post-ischemic exercise following global cerebral ischemia on astrocyte and microglia functions in hippocampus from Wistar rats.

Persistent effects of pre- and postischemic exercise on glial cells activation after global cerebral ischemia remains poorly understood. Here, we investigated the effect of both pre and postischemic treadmill exercise protocols (20min/day during 2 weeks) on glial cells immunostaining in the hippocampus of Wistar rats submitted to global ischemia. A synergistic effect between ischemia and postischemic exercise on the astrocytic area was demonstrated. Postischemic exercise partially reversed the ischemia-induced increase on the area occupied by microglia, without any effect of pre-ischemic protocol. In conclusion, postischemic exercise distinctly modulates astrocyte and microglia immunostaining in the hippocampal dentate gyrus following global cerebral ischemia in Wistar rats.

Treadmill exercise alters histone acetyltransferases and histone deacetylases activities in frontal cortices from wistar rats.

Studies have pointed out the relationship between neuroprotective exercise effects and epigenetic mechanisms on the hippocampus. Considering the role of frontal cortex on brain functions, we investigated the impact of different exercise protocols on enzymatic system involved with histone acetylation status, histone acetyltransferases (HATs), and histone desacetylases (HDACs) in frontal cortices from Wistar rats. Male Wistar rats aged 3 months were submitted to a single session or a daily running protocol during 2 weeks. The single session enhanced HAT activity, while the moderate daily exercise protocol reduced the HDAC activity. Our results indicate that frontal cortex is susceptible to epigenetic modulation following exercise and that both exercise protocols seem to induce a histone hyperacetylation condition in this brain area.

Exposition to tannery wastewater did not alter behavioral and biochemical parameters in Wistar rats.

There are scarce data on the neurotoxicity in mammalian induced by tannery wastewaters. Previously, the anxiogenic effect of tannery wastewater was demonstrated in mice, while wastewater submitted to photoelectrooxidation (PEO) process treatment did not affect the anxiety state. Considering that species may response differently to xenobiotics, the aim of the present work was to study the effects of exposure to tannery wastewaters (non-PEO or PEO-treated) on behavioral and neurochemical markers in another species of laboratory animals, specifically Wistar rats. Male Wistar rats were given free access to water bottles containing non-PEO or PEO-treated tannery wastewaters (0.1, 1 and 5% in drinking water). During the exposure, behavioral tests of anxiety (elevated plus-maze, neophobia, open field and light-dark box), depression (forced swimming) and memory (inhibitory avoidance, novel object and discriminative avoidance) were performed. On the 30th day, brain structures were dissected out to evaluate cellular oxidative state (hippocampus, cerebellum and striatum) and acetylcholinesterase activity (hippocampus and striatum). Exposure to tannery effluent with or without photoelectrochemical treatment did not alter any behavioral and neurochemical parameters evaluated. Our data indicate that Wistar rats may not be an adequate species for ecotoxicological studies involving tannery effluents and that POE treatment did not generate other toxic compounds.

Histone deacetylase activity is altered in brain areas from aged rats.

It has been described that histone acetylation levels are decreased in several cellular and in vivo neurodegeneration models as well as in normal brain aging, although the impact of the aging process on histone deacetylases (HDAC) activity yet remains poorly understood. Therefore, our aim was to evaluate the effect of the aging process on HDAC activity in hippocampi and frontal cortices from 3 and 18-months-old Wistar rats. The animals were decapitated at different times of day, in the early morning and in afternoon. HDAC activity was increased in hippocampus from the aged group. Besides, the hippocampal HDAC activity was also significantly increased in early morning. A significant interaction between age and time of the day was observed in frontal cortices, given that the HDAC activity was higher in early morning in the aged group. These data support the hypothesis that the aging-related dysfunction may be related, at least in part, to acetylation imbalance through HDAC activity in rat brain.

Inflammatory response and oxidative stress in developing rat brain and its consequences on motor behavior following maternal administration of LPS and perinatal anoxia.

Cerebral palsy (CP) is a disorder of locomotion, posture and movement that can be caused by prenatal, perinatal or postnatal insults during brain development. An increased incidence of CP has been correlated to perinatal asphyxia and maternal infections during gestation. The effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) associated or not with perinatal anoxia (PA) in oxidative and inflammatory parameters were examined in cerebral cortices of newborns pups. Concentrations of TNF-α, IL-1, IL-4, SOD, CAT and DCF were measured by the ELISA method. Other newborn rats were assessed for neonatal developmental milestones from day 1 to 21. Motor behavior was also tested at P29 using open-field and Rotarod. PA alone only increased IL-1 expression in cerebral cortex with no changes in oxidative measures. PA also induced a slight impact on development and motor performance. LPS alone was not able to delay motor development but resulted in changes in motor activity and coordination with increased levels of IL-1 and TNF-α expression associated with a high production of free radicals and elevated SOD activity. When LPS and PA were combined, changes on inflammatory and oxidative stress parameters were greater. In addition, greater motor development and coordination impairments were observed. Prenatal exposure of pups to LPS appeared to sensitize the developing brain to effects of a subsequent anoxia insult resulting in an increased expression of pro-inflammatory cytokines and increased free radical levels in the cerebral cortex. These outcomes suggest that oxidative and inflammatory parameters in the cerebral cortex are implicated in motor deficits following maternal infection and perinatal anoxia by acting in a synergistic manner during a critical period of development of the nervous system.

Treadmill exercise induces age-related changes in aversive memory, neuroinflammatory and epigenetic processes in the rat hippocampus.

It has been described that exercise can modulate both inflammatory response and epigenetic modifications, although the effect of exercise on these parameters during the normal brain aging process yet remains poorly understood. Here, we investigated the effect of aging and treadmill exercise on inflammatory and epigenetic parameters specifically pro and anti-inflammatory cytokines levels, activation of NF-kB and histone H4 acetylation levels in hippocampus from Wistar rats. Additionally, we evaluated aversive memory through inhibitory avoidance task. Rats of 3 and 20 months of age were assigned to non-exercised (sedentary) and exercised (running daily for 20 min for 2 weeks) groups. The effect of daily forced exercise in the treadmill was assessed. The levels of inflammatory and epigenetic parameters were determined 1h, 18 h, 3 days or 7 days after the last training session of exercise. It was observed an age-related decline on aversive memory, as well as aged rats showed increased hippocampal levels of inflammatory markers, such as TNFα, IL1-ß and NF-kB and decreased IL-4 levels, an anti-inflammatory cytokine. Moreover, lower levels of global histone H4 acetylation were also observed in hippocampi from aged rats. Interestingly, there was a significant correlation between the biochemical markers and the inhibitory avoidance test performance. The forced exercise protocol ameliorated aging-related memory decline, decreased pro-inflammatory markers and increased histone H4 acetylation levels in hippocampi 20-months-old rats, while increased acutely IL-4 levels in hippocampi from young adult rats. Together, these results suggest that an imbalance of inflammatory markers might be involved to the aging-related aversive memory impairment. Additionally, our exercise protocol may reverse aging-related memory decline through improving cytokine profile.

Exercise induces age-dependent changes on epigenetic parameters in rat hippocampus: a preliminary study.

Regular exercise improves learning and memory, including during aging process. Interestingly, the imbalance of epigenetic mechanisms has been linked to age-related cognitive deficits. However, studies about epigenetic alterations after exercise during the aging process are rare. In this preliminary study we investigated the effect of aging and exercise on DNA methyltransferases (DNMT1 and DNMT3b) and H3-K9 methylation levels in hippocampus from 3 and 20-months aged Wistar rats. The animals were submitted to two exercise protocols: single session or chronic treadmill protocol. DNMT1 and H3-K9 methylation levels were decreased in hippocampus from aged rats. The single exercise session decreased both DNMT3b and DNMT1 levels in young adult rats, without any effect in the aged group. Both exercise protocols reduced H3-K9 methylation levels in young adult rats, while the single session reversed the changes on H3-K9 methylation levels induced by aging. Together, these results suggest that an imbalance on DNMTs and H3-K9 methylation levels might be linked to the brain aging process and that the outcome to exercise seems to vary through lifespan.

Effect of landfill leachate on oxidative stress of brain structures and liver from rodents: modulation by photoelectrooxidation process.

The decomposition of solid waste in landfill is responsible for the formation of leachate, a dark liquid with an unpleasant odor; studies investigating its toxicity on mammals are rare. Oxidative stress has been considered as an important biochemical mechanism of the toxicity of several xenobiotics. The aim of this study was to evaluate the effects of landfill leachate on oxidative parameters in striatum, hippocampus and liver homogenates of mice and rats. In order to propose a clean technology for the treatment of leachate, we also investigated the effects of landfill leachate submitted to photoelectrooxidation process (PEO). The homogenates of cerebral structures and liver of Swiss albino mice and Wistar rats were incubated with different concentrations of non-PEO landfill leachate and PEO-treated landfill leachate. After the incubation, the levels of free radicals, determined by 2',7'-dichlorofluorescein diacetate probe, and the lipoperoxidation, quantified by the thiobarbituric acid reactive substances, were evaluated. There was an increase on the levels of free radicals in striatum of both mice and rats when exposed to non-PEO leachate. Moreover, PEO-treated leachate increased the lipoperoxidation in striatum homogenates from rodents. However, both leachates did not alter any of the parameters evaluated in the hippocampus. In the liver, the incubation with leachates induced an augment on levels of free radicals only in samples of mice. In addition, PEO-treated leachate increased the lipoperoxidation indexes in the liver of mice and rats. These results suggest that the landfill leachate can induce an oxidative stress state in the liver and the striatum of rodents. Additionally, the PEO process was unable to efficiently alter the toxic compounds of landfill leachate.

Environmental enrichment prevents behavioral deficits and oxidative stress caused by chronic cerebral hypoperfusion in the rat.

AIMS: The aim of the present study was to evaluate the neuroprotective effects of environmental enrichment (EE), assessed by cognitive activity in the Morris water maze, and on brain oxidative status, through measurement of macromolecules damage, lipid peroxidation levels, total cellular thiols and antioxidant enzymes in hippocampus, striatum and cerebral cortex. MAIN METHODS: Adult male Wistar rats were submitted to the modified permanent bilateral occlusion of the common carotid arteries (2VO) method, with right common carotid artery being first occluded, and tested three months after the ischemic event. Cognitive and physical stimulation, named Environmental Enrichment, consisted of one-hour sessions run 3 times per week during 12weeks, following two different stimulation protocols: pre-ischemia and pre+post-ischemia. Rats were then tested for both reference and working spatial memory tasks in the water maze and later sacrificed for measurement of oxidative stress parameters. KEY FINDINGS: A significant cognitive deficit was found in both spatial tasks after hypoperfusion; this effect was reversed in the 2VO enriched group. Moreover, hippocampal oxidative damage and antioxidant enzyme activity were decreased by environmental enrichment. SIGNIFICANCE: These results suggest that both stimulation protocols exert a neuroprotective effect against the cognitive impairment and the reduction of biomarkers for oxidative damage caused by chronic cerebral hypoperfusion.

Time-dependent effects of treadmill exercise on aversive memory and cyclooxygenase pathway function.

Exercise induces brain function adaptations and improves learning and memory; however the time window of exercise effects has been poorly investigated. Studies demonstrate an important role for cyclooxygenase-2 (COX-2) pathway function in the mechanisms underlying memory formation. The aim of present work was to investigate the effects of treadmill exercise on aversive memory and COX-2, PGE(2) and E-prostanoid receptors contents in the rat hippocampus at different time points after exercise has ended. Adult male Wistar rats were assigned to non-exercised (sedentary) and exercised (running daily for 20min, for 2weeks) groups. The inhibitory avoidance task was used to assess aversive memory and the COX-2, PGE(2) and E-prostanoid receptors (EP1, EP2, EP3 and EP4) levels were determined 1h, 18h, 3days or 7days after the last training session of treadmill exercise. The step down latency in the inhibitory avoidance, COX-2 and EP4 receptors levels were acutely increased by exercise, with a significant positive correlation between aversive memory performance and COX-2 levels. Increased EP2 content decreased PGE(2) levels were observed 7days after the last running session. The treadmill exercise protocol facilitates inhibitory avoidance memory and induces time-dependent changes on COX-2 pathways function (COX-2, PGE(2) and EP receptors).

Effect of Calea serrata Less. n-hexane extract on acetylcholinesterase of larvae ticks and brain Wistar rats.

Acetylcholinesterase (AChE), an enzyme that hydrolyses acetylcholine (ACh) at cholinergic synapses, is a target for pesticides and its inhibition by organophosphates leads to paralysis and death of arthropods. It has been demonstrated that the n-hexane extract of Calea serrata had acaricidal activity against larvae of Rhipicephalus (Boophilus) microplus and Rhipicephalus sanguineus. The aim of the present study was to understand the mechanism of the acaricidal action of C. serrata n-hexane extract are specifically to investigate the in vitro anticholinesterase activity on larvae of R. microplus and in brain structures of male Wistar rats. The n-hexane extract significantly inhibited in vitro acetylcholinesterase activity in R. microplus larvae and rat brain structures. The results confirm that inhibition of acetylcholinesterase is a possible mechanism of action of hexane extract at C. serrata.

Effects of pre- and postnatal protein malnutrition in hypoxic-ischemic rats.

Neonatal hypoxic-ischemic encephalopathy (HI) is a major cause of nervous system damage and neurological morbidity. Perinatal malnutrition affects morphological, biochemical and behavioral aspects of neural development, including pathophysiological cascades of cell death triggered by ischemic events, so modifying resulting brain damage. Female Wistar rats were subjected to protein restriction during pregnancy and lactation (control group: 25% soybean protein; malnourished group: 7%). Seven days after delivery (PND7), their offspring were submitted to unilateral cerebral HI; rats were then tested for sensorimotor (PND7 and PND60) and memory (PND60) functions. Offspring of malnourished mothers showed marked reduction in body weight starting in lactation and persisting during the entire period of observation. There was a greater sensorimotor deficit after HI in malnourished (M) animals, in righting reflex and in home bedding task, indicating an interaction between diet and hypoxia-ischemia. At PND60, HI rats showed impaired performance when compared to controls in training and test sessions of rota-rod task, however there was no effect of malnutrition per se. In the open field, nourished HI (HI-N) presented an increase in crossings number; this effect was not present in HI-M group. Surprisingly, HI-M rats presented a better performance in inhibitory avoidance task and a smaller hemispheric brain damage as compared to HI-N animals. Our data points to a possible metabolic adaptation in hypoxic-ischemic animals receiving protein malnutrition during pregnancy and lactation; apparently we observed a neuroprotective effect of diet, possibly decreasing the brain energy demand, under a hypoxic-ischemic situation.

Ascorbate uptake is decreased in the hippocampus of ageing rats.

Ascorbate, an intracellular antioxidant, has been considered critical for neuronal protection against oxidant stress, which is supported especially by in vitro studies. Besides, it has been demonstrated an age-related decrease in brain ascorbate levels. The aims of the present study were to investigate ascorbate uptake in hippocampal slices from old Wistar rats, as well as its neuroprotective effects in in vitro and in vivo assays. Hippocampal slices from male Wistar rats aged 4, 11 and 24 months were incubated with radiolabeled ascorbate and incorporated radioactivity was measured. Hippocampal slices from rats were incubated with different concentrations of ascorbate and submitted to H(2)O(2)-induced injury, cellular damage and S100B protein levels were evaluated. The effect of chronic administration of ascorbate on cellular oxidative state and astrocyte biochemical parameters in the hippocampus from 18-months-old Wistar rats was also studied. The ascorbate uptake was decreased in hippocampal slices from old-aged rats, while supplementation with ascorbate (2 weeks) did not modify any tested oxidative status in the hippocampus and the incubation was unable to protect hippocampal slices submitted to oxidative damage (H(2)O(2)) from old rats. Our data suggest that the decline of ascorbate uptake might be involved in the brain greater susceptibility to oxidative damage with advancing age and both in vitro and vivo assays suggest that ascorbate supplementation did not protect hippocampal cells.

Different intensities of treadmill running exercise do not alter melatonin levels in rats / Diferentes intensidades de exercício de corrida em esteira não alteram os níveis de melatonina em ratos

Background: Regular and moderate exercise has been considered an interesting neuroprotective strategy. Our research group demonstrated that a protocol of moderate exercise on a treadmill reduced, while a protocol of high-intensity exercise increased in vitro ischemic cell damage in Wistar rats. The molecular mechanisms by which physical exercise exerts neuroprotective effects remain unclear. Accumulating evidence suggests that exercise may have short- and long-term effects on melatonin secretion in humans. Melatonin, the main product of the pineal gland, has been shown to have neuroprotective effects in models of brain and spinal cord injury and cerebral ischemia. A dual modulation of melatonin secretion by physical activity has also been demonstrated. This study aimed to investigate the effect of different exercise intensities, moderateand high-intensity exercise, on serum melatonin levels in rats. Methods: Thirty-five adult male Wistar rats were divided into non-exercised (sedentary) and exercised (20- or 60-min sessions) groups. The exercise protocols consisted of two weeks of daily treadmill training. Blood samples were collected approximately 16 hours after the last training session (8:00-10:00) and melatonin levels were assayed by ELISA. Results: The exercise protocols, two weeks of 20 min/day or 60 min/day of treadmill running, did not affect serum melatonin levels. Conclusion: Our data demonstrated that melatonin levels may not be directly involved in the exercise-induced, intensitydependent dual effect on in vitro ischemia.

Introdução: O exercício físico regular e moderado é considerado uma interessante estratégia neuroprotetora. Nosso grupo de pesquisa demonstrou que um protocolo de exercício moderado em esteira reduziu, enquanto um protocolo de intensidade elevada aumentou o dano isquêmico in vitro em ratos Wistar. Os mecanismos moleculares pelos quais o exercício físico exerce neuroproteção ainda não estão claramente elucidados. Várias evidências sugerem que o exercício pode ter efeitos a curto e longo prazo sobre a secreção de melatonina em humanos. A melatonina, o principal produto da glândula pineal, tem demonstrado exercer uma atividade neuroprotetora em modelos de trauma cerebral e medular e isquemia cerebral. Foi demonstrada também uma modulação dual da atividade física sobre a secreção de melatonina. O objetivo deste estudo foi estudar o efeito de diferentes intensidades de exercício, moderado e elevado, sobre os níveis séricos de melatonina de ratos. Métodos: Trinta e cinco ratos Wistar adultos machos foram divididos em não-exercitados (sedentários) ou exercitados (sessões de 20 ou 60 min). Os protocolos de exercício consistiam em duas semanas diárias de treinamento em esteira ergométrica. Os soros foram coletados aproximadamente 16 horas após a última sessão de treino (8:00-10:00) e os níveis de melatonina foram avaliados através da técnica de ELISA. Resultados: Os protocolos de exercício físico, duas semanas de 20 min/dia ou 60 min/dia de corrida em esteira, não alteraram os níveis séricos de melatonina. Conclusão: Nossos dados demonstram que os níveis de melatonina parecem não estar diretamente envolvidos com o efeito dual do exercício físico dependente da intensidade na isquemia in vitro.