Cognition Enhancing Activity of Sulforaphane Against Scopolamine Induced Cognitive Impairment in Zebra Fish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Several epidemiological studies have shown that consumption of large quantities of vegetables especially cruciferous vegetables (Broccoli and Brussels sprouts) can protect against chronic diseases. Sulforaphane, an isothiocynate found in cruciferous vegetables has been demonstrated to have neuroprotective effects in several experimental paradigms. This study was undertaken to examine the effect of sulforaphane on cognitive impairment in zebra fish model using a novel method of fear conditioning. Initially, the normal behaviour of zebra fishes was studied in light-dark tank for 10 min daily for 10 days. Fishes were then divided into seven groups of twelve in each. Group I served as normal, group II served as fear conditioned control, group III and group IV were sulforaphane (25 µM/L) and piracetam (200 mg/L) treated respectively. Group V served as scopolamine (400 µM/L) induced memory impairment fishes. Group VI and VII were sulforaphane (25 µM/L) and piracetam (200 mg/L) treated scopolamine induced memory impairment groups respectively. In normal behavioural analysis, fishes preferred to stay in dark compartment. The average number of entries into the dark and time spent in dark were significantly more. Fishes in group II to VII were individually subjected to fear conditioning passive avoidance task and evaluated for learned task memory. It was observed that the average number of entries into dark and time spent in dark were significantly decreased. After exposure to respective treatment fishes in group III to VII were subjected to cognitive evaluation. There was no significant difference in cognition of group III and IV fishes exposed to sulforaphane and piracetam alone respectively. Fishes exposed to scopolamine showed a significant cognitive impairment. Sulforaphane exposure prior to scopolamine significantly retained the memory of learned task. These findings suggest that sulforaphane might be a promising therapeutic agent for cognitive enhancement in Alzheimer’s disease.     

Long-Term Methionine Exposure Induces Memory Impairment on Inhibitory Avoidance Task and Alters Acetylcholinesterase Activity and Expression in Zebrafish (Danio rerio)

Hypermethioninemic patients exhibit a variable degree of neurological dysfunction. However, the mechanisms involved in these alterations have not been completely clarified. Cholinergic system has been implicated in many physiological processes, including cognitive performances, as learning, and memory. Parameters of cholinergic signaling have already been characterized in zebrafish brain. Since zebrafish is a small freshwater teleost which is a vertebrate model for modeling behavioral and functional parameters related to human pathogenesis and for clinical treatment screenings, in the present study we investigated the effects of short- and long-term methionine exposure on cognitive impairment, AChE activity and gene expression in zebrafish. For the studies, animals were exposed at two methionine concentrations (1.5 and 3.0 mM) during 1 h or 7 days (short- or long-term treatments, respectively). We observed a significant increase in AChE activity of zebrafish brain membranes after long-term methionine exposure at 3.0 mM. However, AChE gene expression decreased significantly in both concentrations tested after 7 days of treatment, suggesting that post-translational events are involved in the enhancement of AChE activity. Methionine treatment induces memory deficit in zebrafish after long-term exposure to this amino acid, which could be related, at least in part, with cognitive impairment observed in hypermethioninemia. Therefore, the results here presented raise a new perspective to use the zebrafish as a complementary vertebrate model for studying inborn errors of metabolism, which may help to better understand the pathophysiology of this disease.     

A simple spatial alternation task for assessing memory function in zebrafish

A series of studies was initiated to examine learning and memory function in the zebrafish (Danio rerio) by using a simple spatial alternation paradigm for a food reward. Fish were fed on alternating sides of a divided fish tank, with a red card displayed on one side serving as a visual means of orientation. Although responses were recorded at cue (light tap on the tank), 5 s after cue (as food was delivered), and 5 s after food delivery, the learning test was choice of a correct side of the tank to receive food. Therefore, an accurate level of an animal's achievement of the spatial task was represented by responses at food delivery. Data collected from 11 separate experiments indicated that zebrafish learned to alternate for a food reward. Further, statistical analysis showed that the zebrafish learned the task in the first half of the experiment as exhibited by a calculated t1/2 of 13.9 trials. Zebrafish could recall the task after a short period of 10 days with no testing. The alternating behavior was extinguished by withholding the food reward. Thus, the spatial alternation task can be learned easily by zebrafish, and may be useful in addressing learning and memory functions in vertebrate animals using zebrafish as a model organism.     

Effects of hypoxic preconditioning on memory evaluated using the T-maze behavior test

Perioperative brain ischemia and stroke are leading causes of morbidity and mortality. Brief hypoxic preconditioning is known to have protective effects against hypoxic-ischemic insult in the brain. Current studies on the neuroprotective effects of ischemic preconditioning are based on histologic findings and biomarker changes. However, studies regarding effects on memory are rare. To precondition zebrafish to hypoxia, they were exposed to a dissolved oxygen (DO) concentration of 1.0?±?0.5?mg/L in water for 30?s. The hypoxic zebrafish were then exposed to 1.0?±?0.5?mg/L DO until the third stage of hypoxia, for 10 min?±?30?s. Zebrafish were assessed for memory retention after the hypoxic event. Learning and memory were tested using the T-maze, which evaluates memory based on whether or not zebrafish moves to the correct target compartment. In the hypoxic preconditioning group, infarct size was reduced compared with the hypoxic-only treated zebrafish group; memory was maintained to a degree similar to that in the hypoxia-untreated group. The hypoxic-only group showed significant memory impairments. In this study, we used a hypoxic zebrafish model and assessed the effects of ischemic preconditioning not only on histological damages but also on brain function, especially memory. This study demonstrated that a brief hypoxic event has protective effects in hypoxic brain damage and helped maintain memory in zebrafish. In addition, our findings suggest that the zebrafish model is useful in rapidly assessing the effects of ischemic preconditioning on memory.     

Embelin Attenuates Intracerebroventricular Streptozotocin-Induced Behavioral,Biochemical, and Neurochemical Abnormalities in Rats

Embelin, the main active constituent of Embelia ribes, has been reported to possess various pharmacological actions, including anti-inflammatory, antioxidant, anticonvulsant, and neuroprotective. The present study was designed to investigate neuroprotective mechanisms and therapeutic potential of embelin against intracerebroventricular streptozotocin (ICV-STZ)-induced experimental sporadic dementia in rats. STZ was infused bilaterally at the dose of (3 mg/kg/1 μl/1 min) ICV on day first and third. Spatial and non-spatial memory was evaluated using Morris water maze and object recognition task in rats. Embelin (2.5, 5, and 10 mg/kg, i.p.) was administrated for 14 days from seventh day onwards after first ICV-STZ infusion in rats. On day 22, rats were sacrificed and hippocampal brain regions were used to identify biochemical, neurochemical, and neuroinflammatory alterations. STZ-infused rats showed significant learning and memory deficit which was associated with an increase in oxidative stress (lipid peroxidation and nitrite), compromised antioxidant defense (reduced glutathione), neurotransmitter alterations (AChE, dopamine, noradrenaline, 5-hydroxytryptamine, gama amino butyric acid, and glutamate), and elevation in neuroinflammatory cytokine (IL-1 β, IL-6, and TNF-α) levels. Embelin dose dependently attenuated STZ-induced cognitive deficit and biochemical alterations and restored hippocampal neurochemical levels. The observed protective effect might be attributed to the antioxidant and anti-inflammatory potential of embelin and its ability to restore hippocampal neurochemistry. Thus, the outcomes of the current study suggest therapeutic potential of embelin in cognitive disorders such as sporadic Alzheimer’s disease (SAD).     

Attenuation of NF-κβ mediated apoptotic signaling by tocotrienol ameliorates cognitive deficits in rats postnatally exposed to ethanol

Ethanol-induced damage in the developing brain may result in cognitive impairment including deficits on neuropsychological tests of learning, memory and executive function, yet the underlying mechanisms remain elusive. In the present study we investigated the protective effect of tocotrienol against cognitive deficit, neuroinflammation and neuronal apoptosis in rat pups postnatally exposed to ethanol. Pups were administered ethanol (5g/kg, 12% v/v) by intragastric intubation on postnatal days 7, 8 and 9. Ethanol-exposed pups showed significant memory impairment in Morris water maze task as evident from increase in escape latency and total distance travelled to reach the hidden platform. Time spent in target quadrant, % total distance traversed in target quadrant and frequency of appearance in target quadrant was also significantly decreased in ethanol exposed pups in probe trial. Poor memory retention was exhibited by ethanol-exposed pups in elevated plus maze test also. Impaired cognition was associated with significantly enhanced acetylcholinesterase activity, increased neuroinflammation (oxidative-nitrosative stress, TNF-α, IL-1β and TGF-β1) and neuronal apoptosis (NF-κβ and Caspase-3) in different brain regions of ethanol-exposed pups. Co-administration with tocotrienol significantly ameliorated all the behavioral, biochemical and molecular alterations in the different brain regions of ethanol exposed pups. The current study thus demonstrates the possible involvement of NF-κβ mediated apoptotic signaling in cognitive deficits associated with postnatal ethanol exposure in rats and points to the potential of tocotrienol in the prevention of cognitive deficits in children with fetal alcohol spectrum disorders (FASDs).     

An ameliorative effect of recovery sleep on total sleep deprivation-induced neurodegeneration

Neurodegenerative changes following sleep deprivation (SD) result in debilitating behavioral and cognitive dysfunction. SD causes gradual cognitive impairment and later results in neurodegeneration. These changes are thought to be the consequences of cellular disorganization and degeneration in selected brain areas – the hippocampus, prefrontal cortex, amygdala, and hypothalamus. We investigated the histological changes in mice exposed to 6 days SD and to the effects of 2 days of recovery sleep in the brain regions listed above. Cytological changes, total viable cell count in hippocampal subregions, Bcl-2 expression, and degenerative changes like cell morphology and membrane integrity of neurons were evaluated. Results demonstrated that prolonged SD decreased the count of viable and healthy cells and caused a decrease in Bcl-2 positive cells and an increase in degenerated cells with pyknotic morphology, chromatolysis and darkly stained cytoplasm. Degenerative changes were ameliorated by 2 days of recovery sleep or rehabilitation after SD. Data suggest that chronic SD constitutes a severe threat to the brain and leads to neurodegeneration, while rehabilitation or recovery sleep ameliorates or protects the brain from neurodegenerative challenges.     

Chronic and acute alcohol administration induced neurochemical changes in the brain: comparison of distinct zebrafish populations

The zebrafish is increasingly utilized in the analysis of the effects of ethanol (alcohol) on brain function and behavior. We have shown significant population-dependent alcohol-induced changes in zebrafish behavior and have started to analyze alterations in dopaminergic and serotoninergic responses. Here, we analyze the effects of alcohol on levels of selected neurochemicals using a 2 × 3 (chronic × acute) between-subject alcohol exposure paradigm randomized for two zebrafish populations, AB and SF. Each fish first received the particular chronic treatment (0 or 0.5 vol/vol % alcohol) and subsequently the acute exposure (0, 0.5 or 1.0 % alcohol). We report changes in levels of dopamine, DOPAC, serotonin, 5HIAA, glutamate, GABA, aspartate, glycine and taurine as quantified from whole brain extracts using HPLC. We also analyze monoamine oxidase and tyrosine hydroxylase enzymatic activity. The results demonstrate that compared to SF, AB is more responsive to both acute alcohol exposure and acute alcohol withdrawal at the level of neurochemistry, a finding that correlates well with prior behavioral observations and one which suggests the involvement of genes in the observed alcohol effects. We discuss correlations between the current results and prior behavioral findings, and stress the importance of characterization of zebrafish strains for future behavior genetic and psychopharmacology studies.     

Adding preferred color to a conventional reward method improves the memory of zebrafish in the T-maze behavior model

Zebrafish have become a useful model for studying behavior and cognitive functions. Recent studies have shown that zebrafish have natural color preference and the ability to form associative memories with visual perception. It is well known that visual perception enhances memory recall in humans, and we suggest that a similar phenomenon occurs in zebrafish. This study proposes that adding a visual perception component to a conventional reward method would enhance memory recall in zebrafish. We found that zebrafish showed greater preference for red cellophane over yellow in the training session but could not remember the preferred place in the memory test. However, the test memory recall was greater when the zebrafish were exposed to the red cellophane with a food reward during the training session, when compared with the use of food reward only. Furthermore, the red cellophane with food reward group showed more predictable memory recall than the food reward only group. These results propose that visual perception can increase memory recall by enhancing the consolidation processes. We suggest that color-cued learning with food reward is a more discriminative method than food reward alone for examining the cognitive changes in the zebrafish.

Abbreviations: WM: working memory; LTM: long-term memory     

Il1-β Involvement in Cognitive Impairment after Sepsis

Sepsis is defined as the host's reaction to infection and characterised by a systemic inflammatory response with important clinical implications. Central nervous system dysfunction secondary to sepsis is associated with local generation of pro- and anti-inflammatory cytokines, impaired cerebral microcirculation, an imbalance of neurotransmitters, apoptosis and cognitive impairment. It's known that the IL-1β is one of the first cytokines to be altered. Thus, the objective of this study was to evaluate the role of IL-1β in cognitive parameters in brain tissue through the use of an IL-1β (IL-1ra) receptor antagonist up to 10 days and to assess blood–brain barrier permeability, cytokine levels, oxidative parameters and energetic metabolism up to 24 h, after sepsis induction. To this aim, we used sham-operated Wistar rats or submitted to the cecal ligation and perforation (CLP) procedure. Immediately after, the animals received one dose of 10 μg of IL-1ra. After 24 h, the rats were killed and were evaluated for biochemical parameters in the pre-frontal cortex, hippocampus and striatum. After 10 days, the animals were submitted to the habituation to the open field and step-down inhibitory avoidance task. We observed that the use of IL-1ra reverted the increase of blood–brain barrier permeability in the pre-frontal cortex, hippocampus and striatum; the increase of IL-1β, IL1-6 and TNF-α levels in the pre-frontal cortex and striatum; the decrease of complex I activity in the pre-frontal, hippocampus and striatum; the increase of oxidative parameters in pre-frontal cortex, hippocampus and striatum; and cognitive impairment. In conclusion, the results observed in this study reinforce the role of acute brain inflammatory response, in particular, the IL1β response, in the cognitive impairment associated with sepsis.     

Environmental Circadian Disruption Worsens Neurologic Impairment and Inhibits Hippocampal Neurogenesis in Adult Rats After Traumatic Brain Injury

Circadian rhythms modulate many physiologic processes and behaviors. Therefore, their disruption causes a variety of potential adverse effects in humans and animals. Circadian disruption induced by constant light exposure has been discovered to produce pathophysiologic consequences after brain injury. However, the underlying mechanisms that lead to more severe impairment and disruption of neurophysiologic processes are not well understood. Here, we evaluated the effect of constant light exposure on the neurobehavioral impairment and survival of neurons in rats after traumatic brain injury (TBI). Sixty adult male Sprague–Dawley rats were subjected to a weight-drop model of TBI and then exposed to either a standard 12-/12-h light/dark cycle or a constant 24-h light/light cycle for 14 days. Our results showed that 14 days of constant light exposure after TBI significantly worsened the sensorimotor and cognitive deficits, which were associated with decreased body weight, impaired water and food intake, increased cortical lesion volume, and decreased neuronal survival. Furthermore, environmental circadian disruption inhibited cell proliferation and newborn cell survival and decreased immature cell production in rats subjected to the TBI model. We conclude that circadian disruption induced by constant light exposure worsens histologic and neurobehavioral impairment and inhibits neurogenesis in adult TBI rats. Our novel findings suggest that light exposure should be decreased and circadian rhythm reestablished in hospitalized TBI patients and that drugs and strategies that maintain circadian rhythm would offer a novel therapeutic option.     

<Emphasis Type="Italic">Arbutus andrachne</Emphasis> L. Reverses Sleep Deprivation-Induced Memory Impairments in Rats

Sleep deprivation (SD) is associated with cognitive deficits. It was found to affect the hippocampus region of the brain by impairing memory formation. This impairment is suggested to be caused by elevation in oxidative stress in the body, including the brain during SD. It was hypothesized that the methanolic extract of the fruits of Arbutus andrachne L. (Ericaceae) will prevent chronic SD-induced impairment of hippocampal memory via its antioxidative properties. The methanolic extract of the fruits of A. andrachne was evaluated for its beneficial properties to reverse SD-induced cognitive impairment in rats. Animals were sleep deprived for 8 weeks using a multiple platform model. The extract was administered i.p. at three doses (50, 200, and 500 mg/kg). Behavioral studies were conducted to test the spatial learning and memory using radial arm water maze (RAWM). In addition, the hippocampus was dissected to analyze the following oxidative stress markers: glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, glutathione peroxidase (GPx), and catalase. Chronic SD impaired short- and long-term memories (P < 0.05). Treatment of animals with A. andrachne fruit extract at all doses prevented long-term memory impairment induced by SD while such treatment prevented short-term memory impairment only at 200 and 500 mg/kg dose levels. Moreover, A. andrachne fruit extract normalized the reduction in the hippocampus GSH/GSSG ratio and activity of GPx, and catalase (P < 0.05) induced by chronic sleep deprivation. Chronic sleep deprivation impaired both short- and long-term memory formation, while methanolic extract of A. andrachne fruits reversed this impairment, probably through normalizing oxidative stress in the hippocampus.     

Analysis of Skeletal Muscle Defects in Larval Zebrafish by Birefringence and Touch-evoke Escape Response Assays

Zebrafish (Danio rerio) have become a particularly effective tool for modeling human diseases affecting skeletal muscle, including muscular dystrophies^1-3, congenital myopathies^4,5, and disruptions in sarcomeric assembly^6,7, due to high genomic and structural conservation with mammals⁸. Muscular disorganization and locomotive impairment can be quickly assessed in the zebrafish over the first few days post-fertilization. Two assays to help characterize skeletal muscle defects in zebrafish are birefringence (structural) and touch-evoked escape response (behavioral).Birefringence is a physical property in which light is rotated as it passes through ordered matter, such as the pseudo-crystalline array of muscle sarcomeres⁹. It is a simple, noninvasive approach to assess muscle integrity in translucent zebrafish larvae early in development. Wild-type zebrafish with highly organized skeletal muscle appear very bright amidst a dark background when visualized between two polarized light filters, whereas muscle mutants have birefringence patterns specific to the primary muscular disorder they model. Zebrafish modeling muscular dystrophies, diseases characterized by myofiber degeneration followed by repeated rounds of regeneration, exhibit degenerative dark patches in skeletal muscle under polarized light. Nondystrophic myopathies are not associated with necrosis or regenerative changes, but result in disorganized myofibers and skeletal muscle weakness. Myopathic zebrafish typically show an overall reduction in birefringence, reflecting the disorganization of sarcomeres.The touch-evoked escape assay involves observing an embryo''s swimming behavior in response to tactile stimulation^10-12. In comparison to wild-type larvae, mutant larvae frequently display a weak escape contraction, followed by slow swimming or other type of impaired motion that fails to propel the larvae more than a short distance¹². The advantage of these assays is that disease progression in the same fish type can be monitored in vivo for several days, and that large numbers of fish can be analyzed in a short time relative to higher vertebrates.     

Effects of amyloid beta peptide (25-35) on the behavior of rats in a radial maze

Impairment of cognitive functions, particularly long-term (episodic) and working memory, is one of the earliest prognostic symptoms of Alzheimer's disease, both cognitive impairment and neurodegeneration being mediated by amyloid-beta neurotoxicity. Effects of intracerebroventricular administration of amyloid-beta peptide (25-35) [A beta(25-35)] to rats on the retention of previously learned task in an 8-armed radial maze was studied. A beta(25-35) was injected bilaterally, at doses of 15 or 30 nmol/rat, 7 days after the preliminary learning. The performance in the maze was tested 60 days after the surgery. A beta(25-35) impaired the short-term memory, with no significant effect on the long-term memory. No dose dependence could be demonstrated.     

Behavioral effects of bovine lactoferrin administration during postnatal development of rats

We tested the hypothesis that rats consuming bovine lactoferrin (bLf) during postnatal development would show better performance of stressful tasks during adolescence. In the first study, we orally administered bLf (750 mg/kg) once daily between postnatal days 16–34. Rats then underwent a battery of behavioral tests: open field (forced exploration of risky environment), light–dark emergence (voluntary exploration of risky environment), baited holeboard (working and reference memory), food neophobia (preference for familiar versus novel food), forced swim (test for antidepressant efficacy), and shuttle-box escape (learning to escape footshock). bLf-supplemented rats showed less exploration of the risky environment, greater preference for the familiar food odor, and faster escape responses. The effect of bLf on forced-swim behavior depended on sex: immobility increased for males and decreased for females. In the next study, we replaced the forced-swim test with an escape-swim test in which rats learned to use a visual cue to locate an escape platform, and we tested the dose response of bLf on this and the shuttle-box escape test, with subjects receiving vehicle or bLf at 500, 1,000, or 2,000 mg/kg. Under this modified testing battery, improvement of escape from footshock was not observed at any dose. However, males, but not females, showed a significant dose-dependent effect of bLf on acquisition of the water-escape task. On average, males receiving a higher dose mastered the task 20–25 % sooner than rats receiving a lower dose or vehicle. These results offer preliminary evidence that bLf supplementation during development can improve subsequent cognitive performance during stress.     

Hippocampal-dependent spatial memory in the water maze is preserved in an experimental model of temporal lobe epilepsy in rats

Cognitive impairment is a major concern in temporal lobe epilepsy (TLE). While different experimental models have been used to characterize TLE-related cognitive deficits, little is known on whether a particular deficit is more associated with the underlying brain injuries than with the epileptic condition per se. Here, we look at the relationship between the pattern of brain damage and spatial memory deficits in two chronic models of TLE (lithium-pilocarpine, LIP and kainic acid, KA) from two different rat strains (Wistar and Sprague-Dawley) using the Morris water maze and the elevated plus maze in combination with MRI imaging and post-morten neuronal immunostaining. We found fundamental differences between LIP- and KA-treated epileptic rats regarding spatial memory deficits and anxiety. LIP-treated animals from both strains showed significant impairment in the acquisition and retention of spatial memory, and were unable to learn a cued version of the task. In contrast, KA-treated rats were differently affected. Sprague-Dawley KA-treated rats learned less efficiently than Wistar KA-treated animals, which performed similar to control rats in the acquisition and in a probe trial testing for spatial memory. Different anxiety levels and the extension of brain lesions affecting the hippocampus and the amydgala concur with spatial memory deficits observed in epileptic rats. Hence, our results suggest that hippocampal-dependent spatial memory is not necessarily affected in TLE and that comorbidity between spatial deficits and anxiety is more related with the underlying brain lesions than with the epileptic condition per se.     

Modulation of the histaminergic system and behaviour by alpha-fluoromethylhistidine in zebrafish

The functional role of histamine (HA) in zebrafish brains was studied. Zebrafish did not display a clear circadian variation in brain HA levels. Loading of zebrafish with l-histidine increased HA concentration in the brain. A single injection of the histidine decarboxylase (HDC) inhibitor, alpha-fluoromethylhistidine (alpha-FMH), gave rise to a rapid reduction in zebrafish brain HA. Low HDC activity in the brain after injections verified the effect of alpha-FMH. A reduction in the number of histaminergic fibres but not neurones and an increased expression of HDC mRNA was evident after alpha-FMH. Automated behavioural analysis after alpha-FMH injection showed no change in swimming activity, but abnormalities were detected in exploratory behaviour examined in a circular tank. No significant behavioural changes were detected after histidine loading. The time spent for performance in the T-maze was significantly increased in the first trial 4 days after alpha-FMH injections, suggesting that lack of HA may impair long-term memory. The rostrodorsal telencephalon, considered to correspond to the mammalian amygdala and hippocampus in zebrafish, is densely innervated by histaminergic fibres. These results suggest that low HA decreases anxiety and/or affects learning and memory in zebrafish, possibly through mechanisms that involve the dorsal forebrain.     

The effect of protein synthesis inhibition in the central nervous system on long-term memory formation in some behavioral tasks

The effect of the maximum protein synthesis inhibition in brain and spinal cord on long-term memory formation in extreme situations was studied in various new behavioral tasks in rats. Cycloheximide injected bilaterally into the lateral ventricles three hours before learning suppressed protein synthesis in the central nervous system by 96% during one hour after learning. Forty-four hours after learning in a standard Morris water maze, the information about the platform position was not retained, whereas no memory disorder was observed in case of learning in a simplified Morris maze or a new test learned jump-out-of-water task. A more prolonged suppression of protein synthesis (76%, ten hours after learning) elicited amnesia in five out of eight rats learned in a simplified Morris maze but not disturbed information storage after 48 h and 14 days in the learned jump-out-of-water task. It was concluded that protein synthesis inhibitors are not a universal tool for disrupting formation of long-term memory. It was assumed that under extreme conditions, sometimes procedural long-term (to two weeks) memory is formed without de novo protein synthesis.     

Chronic Treatment with Paraquat Induces Brain Injury,Changes in Antioxidant Defenses System,and Modulates Behavioral Functions in Zebrafish

Paraquat (PQ) administration consists in a chemical model that mimics phenotypes observed in Parkinson’s disease (PD), due to its ability to induce changes in dopaminergic system and oxidative stress. The aim of this study was to evaluate the actions of PQ in behavioral functions of adult zebrafish and its influence on oxidative stress biomarkers in brain samples. PQ (20 mg/kg) was administered intraperitoneally with six injections for 16 days (one injection every 3 days). PQ-treated group showed a significant decrease in the time spent in the bottom section and a shorter latency to enter the top area in the novel tank test. Moreover, PQ-exposed fish showed a significant decrease in the number and duration of risk assessment episodes in the light–dark test, as well as an increase in the agonistic behavior in the mirror-induced aggression (MIA) test. PQ induced brain damage by decreasing mitochondrial viability. Concerning the antioxidant defense system, PQ increased catalase (CAT) and glutathione peroxidase (GPx) activities, as well as the non-protein sulfhydryl content (NPSH), but did not change ROS formation and decreased lipid peroxidation. We demonstrate, for the first time, that PQ induces an increase in aggressive behavior, alters non-motor patterns associated to defensive behaviors, and changes redox parameters in zebrafish brain. Overall, our findings may serve as useful tools to investigate the interaction between behavioral and neurochemical impairments triggered by PQ administration in zebrafish.     

Piracetam Prevents Scopolamine-Induced Memory Impairment and Decrease of NTPDase, 5′-Nucleotidase and Adenosine Deaminase Activities

Piracetam improves cognitive function in animals and in human beings, but its mechanism of action is still not completely known. In the present study, we investigated whether enzymes involved in extracellular adenine nucleotide metabolism, adenosine triphosphate diphosphohydrolase (NTPDase), 5′-nucleotidase and adenosine deaminase (ADA) are affected by piracetam in the hippocampus and cerebral cortex of animals subjected to scopolamine-induced memory impairment. Piracetam (0.02 μmol/5 μL, intracerebroventricular, 60 min pre-training) prevented memory impairment induced by scopolamine (1 mg/kg, intraperitoneal, immediately post-training) in the inhibitory avoidance learning and in the object recognition task. Scopolamine reduced the activity of NTPDase in hippocampus (53 % for ATP and 53 % for ADP hydrolysis) and cerebral cortex (28 % for ATP hydrolysis). Scopolamine also decreased the activity of 5′-nucleotidase (43 %) and ADA (91 %) in hippocampus. The same effect was observed in the cerebral cortex for 5′-nucleotidase (38 %) and ADA (68 %) activities. Piracetam fully prevented scopolamine-induced memory impairment and decrease of NTPDase, 5′-nucleotidase and adenosine deaminase activities in synaptosomes from cerebral cortex and hippocampus. In vitro experiments show that piracetam and scopolamine did not alter enzymatic activity in cerebral cortex synaptosomes. Moreover, piracetam prevented scopolamine-induced increase of TBARS levels in hippocampus and cerebral cortex. These results suggest that piracetam-induced improvement of memory is associated with protection against oxidative stress and maintenance of NTPDase, 5′-nucleotidase and ADA activities, and suggest the purinergic system as a putative target of piracetam.