Júlia Dubois Moreira

Caffeine improves adult mice performance in the object recognition task and increases BDNF and TrkB independent on phospho-CREB immunocontent in the hippocampus.

Caffeine is one of the most psychostimulants consumed all over the world that usually presents positive effects on cognition. In this study, effects of caffeine on mice performance in the object recognition task were tested in different intertrial intervals. In addition, it was analyzed the effects of caffeine on brain derived neurotrophic factor (BDNF) and its receptor, TrkB, immunocontent to try to establish a connection between the behavioral finding and BDNF, one of the neurotrophins strictly involved in memory and learning process. CF1 mice were treated during 4 consecutive days with saline (0.9g%, i.p.) or caffeine (10mg/kg, i.p., equivalent dose corresponding to 2-3 cups of coffee). Caffeine treatment was interrupted 24h before the object recognition task analysis. In the test session performed 15min after training session, caffeine-treated mice recognized more efficiently both the familiar and the novel object. In the test session performed 90min and 24h after training session, caffeine did not change the time spent in the familiar object but increased the object recognition index, when compared to control group. Western blotting analysis of hippocampus from caffeine-treated mice revealed an increase in BDNF and TrkB immunocontent, compared to their saline-matched controls. Phospho-CREB immunocontent did not change with caffeine treatment. Our results suggest that acute treatment with caffeine improves recognition memory, and this effect may be related to an increase of the BDNF and TrkB immunocontent in the hippocampus.

Exercise Increases Insulin Signaling in the Hippocampus: Physiological Effects and Pharmacological Impact of Intracerebroventricular Insulin Administration in Mice

Increasing evidence indicates that physical exercise induces adaptations at the cellular, molecular, and systemic levels that positively affect the brain. Insulin plays important functional roles within the brain that are mediated by insulin‐receptor (IR) signaling. In the hippocampus, insulin improves synaptic plasticity, memory formation, and learning via direct modulation of GABAergic and glutamatergic receptors. Separately, physical exercise and central insulin administration exert relevant roles in cognitive function. We here use CF1 mice to investigate (i) the effects of voluntary exercise on hippocampal insulin signaling and memory performance and (ii) whether central insulin administration alters the effects of exercise on hippocampal insulin signaling and memory performance. Adult mice performed 30 days of voluntary exercise on running wheel and afterward both, sedentary and exercised groups, received intracerebroventricular (icv) injection of saline or insulin (0.5–5 mU). Memory performance was assessed using the inhibitory avoidance and water maze tasks. Hippocampal tissue was measured for [U‐14C] glucose oxidation and the immunocontent of insulin receptor/signaling (IR, pTyr, pAktser473). Additionally, the phosphorylation of the glutamate NMDA receptor NR2B subunit and the capacity of glutamate uptake were measured, and immunohistochemistry was used to determine glial reactivity. Exercise significantly increased insulin peripheral sensitivity, spatial learning, and hippocampal IR/pTyrIR/pAktser473 immunocontent. Glucose oxidation, glutamate uptake, and astrocyte number also increased relative to the sedentary group. In both memory tasks, 5 mU icv insulin produced amnesia but only in exercised animals. This amnesia was associated a rapid (15 min) and persistent (24 h) increase in hippocampal pNR2B immunocontent that paralleled the increase in glial reactivity. In conclusion, physical exercise thus increased hippocampal insulin signaling and improved water maze performance. Overstimulation of insulin signaling in exercised animals, however, via icv administration impaired behavioral performance. This effect was likely the result of aberrant phosphorylation of the NR2B subunit.

Omega-3 fatty acids deprivation affects ontogeny of glutamatergic synapses in rats: relevance for behavior alterations.

Essential omega-3 polyunsaturated fatty acids (omega3) are crucial to brain development and function, being relevant for behavioral performance. In the present study we examined the influence of dietary omega3 in the development of the glutamatergic system and on behavior parameters in rats. Female rats received isocaloric diets, either with omega3 (omega3 group) or a omega3 deficient diet (D group). In ontogeny experiments of their litters, hippocampal immunocontent of ionotropic NMDA and AMPA glutamatergic receptors subunits (NR2 A\B and GluR1, respectively) and the alpha isoform of the calcium-calmodulin protein kinase type II (alphaCaMKII) were evaluated. Additionally, hippocampal [(3)H]glutamate binding and uptake were assessed. Behavioral performance was evaluated when the litters were adult (60 days old), through the open-field, plus-maze, inhibitory avoidance and flinch-jump tasks. The D group showed decreased immunocontent of all proteins analyzed at 02 days of life (P2) in comparison with the omega3 group, although the difference disappeared at 21 days of life (except for alphaCaMKII, which content normalized at 60 days old). The same pattern was found for [(3)H]glutamate binding, whereas [(3)H]glutamate uptake was not affected. The D group also showed memory deficits in the inhibitory avoidance, increased in the exploratory pattern in open-field, and anxiety-like behavior in plus-maze. Taken together, our results suggest that dietary omega3 content is relevant for glutamatergic system development and for behavioral performance in adulthood. The putative correlation among the neurochemical and behavioral alterations caused by dietary omega3 deficiency is discussed.

Dietary omega-3 fatty acids attenuate cellular damage after a hippocampal ischemic insult in adult rats ☆

The role of omega-3 polyunsaturated fatty acids (3PUFAs) on brain function is increasingly demonstrated. Here, the effect of dietary deprivation of essential 3PUFAs on some parameters related to neuroprotection was investigated. Rats were fed with two different diets: omega-3 diet and omega-3-deprived diet. To assess the influence of 3PUFAs on brain responses to ischemic insult, hippocampal slices were subjected to an oxygen and glucose deprivation (OGD) model of in vitro ischemia. The omega-3-deprived group showed higher cell damage and stronger decrease in the [(3)H]glutamate uptake after OGD. Moreover, omega-3 deprivation influenced antiapoptotic cell response after OGD, affecting GSK-3beta and ERK1/2, but not Akt, phosphorylation. Taken together, these results suggest that 3PUFAs are important for cell protection after ischemia and also seem to play an important role in the activation of antiapoptotic signaling pathways.

Risks of dietary acrylamide exposure: A systematic review

Acrylamide (AA) is a probable human carcinogen found in carbohydrate-rich foods that have been heated to high temperatures. AA dietary exposure has been associated to development of health problems. We perform a systematic review to elucidate the association of dietary AA exposure and human health problems. Articles were screened by reading titles and abstracts before the full text of eligible articles was read (κ=0.824). Data were harvested by two reviewers and checked by a third. Forty-one articles were analyzed and assessment of dietary exposure proved to be far from uniform and suffered from limitations that possibly impact on the validity of outcomes with relation to human health. Risk assessment of dietary acrylamide exposure is in need of high quality methods for evaluating dietary exposure and validated acrylamide content databases.

Effects of chronic guanosine treatment on hippocampal damage and cognitive impairment of rats submitted to chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion contributes to a cognitive decline related to brain disorders. Its experimental model in rats is a permanent bilateral common carotid artery occlusion (2VO). Overstimulation of the glutamatergic system excitotoxicity due to brain energetic disturbance in 2VO animals seems to play a pivotal role as a mechanism of cerebral damage. The nucleoside guanosine (GUO) exerts extracellular effects including antagonism of glutamatergic activity. Accordingly, our group demonstrated several neuroprotective effects of GUO against glutamatergic excitotoxicity. Therefore, in this study, we evaluated a chronic GUO treatment effects in rats submitted to 2VO. We evaluated the animals performance in the Morris water maze and hippocampal damage by neurons and astrocytes immunohistochemistry. In addition, we investigated the cerebrospinal fluid (CSF) brain derived neurotrophic factor (BDNF) and serum S100B levels. Additionally, the purine CSF and plasma levels were determined. GUO treatment did not prevent the cognitive impairment promoted by 2VO. However, none of the 2VO animals treated with GUO showed differences in the hippocampal regions compared to control, while 20% of 2VO rats not treated with GUO presented loss of pyramidal neurons and increased glial labeling cells in CA1 hippocampal region. In addition, we did not observe differences in CSF BDNF nor serum S100B levels among the groups. Of note, both the 2VO surgery and GUO treatment changed the purine CSF and plasma profile. In conclusion, GUO treatment did not prevent the cognitive impairment observed in 2VO animals, but our data suggest that GUO could be neuroprotective against hippocampal damage induced by 2VO.

Metabolic and behavioral effects of chronic olanzapine treatment and cafeteria diet in rats.

Olanzapine and highly palatable diets can alter metabolism and brain function. We investigated the interaction of chronic treatment (4 months) with olanzapine and a cafeteria diet on metabolic parameters, memory tasks (spatial and aversive), the elevated plus maze and locomotor activity induced by d-amphetamine. Male Wistar rats were separated into the following groups: standard diet vehicle, standard diet and olanzapine, cafeteria diet vehicle and cafeteria diet and olanzapine. Olanzapine was administered in the drinking water (approximately 1.5 mg/kg/day), and after 3 days of treatment, the rats exhibited an expected anxiolytic effect and reduced amphetamine-induced hyperlocomotion. After 4 months of treatment, cafeteria diet vehicle and cafeteria diet olanzapine rats exhibited an increased body weight and heavier fat pads compared with the standard diet groups. Olanzapine increased only the epididymal and mesenteric fat pads. The cafeteria diet and olanzapine group showed greater glucose intolerance compared with all other groups. The cafeteria diet altered the effects of chronic olanzapine on the performance in the water maze and inhibitory avoidance tasks. Chronic olanzapine treatment failed to affect amphetamine-induced locomotion and to produce anxiolytic effects in the elevated plus maze task, regardless of the diet. Our results suggest that chronic olanzapine caused an increase in fat pads, which is putatively involved in the etiology of many metabolic diseases. Rats on the cafeteria diet were overweight and exhibited glucose intolerance. We did not observe these effects with olanzapine treatment with the standard diet. Moreover, the chronic treatment regimen caused tolerance to the antipsychotic and anxiolytic effects of olanzapine and seemed to potentiate some of the metabolic effects of the cafeteria diet. The cafeteria diet also modified the effects of chronic treatment with olanzapine on cognitive tasks, which may represent an undesirable effect of poor diets in psychiatric patients.

Evidence that Hyperprolinemia Alters Glutamatergic Homeostasis in Rat Brain: Neuroprotector Effect of Guanosine

This study investigated the effects of acute and chronic hyperprolinemia on glutamate uptake, as well as some mechanisms underlying the proline effects on glutamatergic system in rat cerebral cortex. The protective role of guanosine on effects mediated by proline was also evaluated. Results showed that acute and chronic hyperprolinemia reduced glutamate uptake, Na+, K+-ATPase activity, ATP levels and increased lipoperoxidation. GLAST and GLT-1 immunocontent were increased in acute, but not in chronic hyperprolinemic rats. Our data suggest that the effects of proline on glutamate uptake may be mediated by lipid peroxidation and disruption of Na+, K+-ATPase activity, but not by decreasing in glutamate transporters. This probably induces excitotoxicity and subsequent energy deficit. Guanosine was effective to prevent most of the effects promoted by proline, reinforcing its modulator role in counteracting the glutamate toxicity. However, further studies are needed to assess the modulatory effects of guanosine on experimental hyperprolinemia.

Short-term alterations in hippocampal glutamate transport system caused by one-single neonatal seizure episode: implications on behavioral performance in adulthood.

Impairment in the activity and expression of glutamate transporters has been found in experimental models of epilepsy in adult animals. However, there are few studies investigating alterations on glutamate transporters caused by epilepsy in newborn animals, especially in the early periods after seizures. In this study, alterations in the hippocampal glutamate transporters activity and immunocontent were investigated in neonatal rats (7 days old) submitted to kainate-induced seizures model. Glutamate uptake, glutamate transporters (GLT-1, GLAST, EAAC1) and glutamine synthetase (GS) were assessed in hippocampal slices obtained 12 h, 24 h, 48 h, 72 h and 60 days after seizures. Immunoreactivity for hippocampal GFAP, NeuN and DAPI were assessed 24 h after seizure. Behavioral analysis (elevated-plus maze and inhibitory avoidance task) was also investigated in the adult animals (60 days old). The decrease on glutamate uptake was observed in hippocampal slices obtained 24 h after seizures. The immunocontent of GLT-1 increased at 12 h and decreased at 24 h (+62% and -20%, respectively), while GLAST increased up to 48 h after seizures. No alterations were observed for EAAC1 and GS. It should be mentioned that there were no long-term changes in tested glutamate transporters at 60 days after kainate treatment. GFAP immunoreactivity increased in all hippocampal subfields (CA1, CA3 and dentate gyrus) with no alterations in NeuN and DAPI staining. In the adulthood, kainate-treated rats showed anxiety-related behavior and lower performance in the inhibitory avoidance task. Our findings indicate that acute modifications on hippocampal glutamate transporters triggered by a single convulsive event in early life may play a role in the behavioral alterations observed in adulthood.