Malnutrition increases dentate granule cell proliferation in immature rats after status epilepticus

Rotated nursing environment with underfeeding: A form of early-life adversity with sex- and age-dependent effects on coping behavior and hippocampal neurogenesis

We investigated how a unique form of early-life adversity (ELA), caused by rotated nursing environment to induce underfeeding, alters anxiety-like and stress-coping behaviors in male and female Sprague Dawley rats in adolescence and adulthood. Adult female rats underwent either thelectomy (thel; surgical removal of teats), sham surgery, or no surgery (control) before mating. Following parturition, litters were rotated between sham and thel rats every 12 h to generate a group of rats that experienced ELA (rotated housing, rotated mother, and 50% food restriction) from postnatal day 0 to 26. Control litters remained with their natal, nursing dams. Regardless of age and sex, ELA reduced activity in the periphery of the open field. ELA increased immobility in the forced swim test, particularly in adults. We used doublecortin immunohistochemistry to identify immature neurons in the hippocampus. ELA increased the number and density of immature neurons in the dentate gyrus of adolescent males (but not females) and reduced the density of immature neurons in adult males (but not females). This research indicates that a unique form of ELA alters stress-related passive coping and hippocampal neurogenesis in an age- and sex-dependent manner.

Undernourishment and recurrent seizures early in life impair Long-Term Potentiation and alter NMDAR and AMPAR expression in rat hippocampus

Undernourishment is a global issue, especially in developing countries, affecting newborns and children in a vulnerable period of brain development. Previous studies of undernourishment models suggested a relationship between undernourishment and epilepsy. The exposure to both undernourishment and recurrent seizures early in life appears to have detrimental effects on the developing brain. This study aims to investigate the neurobiological consequences of undernourishment and recurrent seizures exposure early in life, investigating Long-Term Potentiation (LTP) induction and gene expression of NMDA receptor subunits in the hippocampus during adulthood (P60). Animals were exposed to maternal deprivation protocol from P2 to P15 to control food intake in rat pups and Flurothyl-induced seizures from P7 to P10. Electrophysiological records of hippocampal slices were recorded and gene expression of NR1A, NR2A, NR2B, NR2C, NR2D and BDNF were investigated. Animals exposed to undernourishment or recurrent seizures failed to promote LTP after stimulation. Furthermore, seizure exposure early in life led to increased expression of hippocampal NR1A, NR2A, NR2B, NR2C and NR2D when compared to controls. Interestingly, when animals were exposed to undernourishment paradigm early in life, this upregulation of NDMA subunits was absent. In conclusion, our study showed impaired LTP after undernourishment and recurrent seizures early in life, together with differential expression of NDMA expression in the hippocampus during adulthood.

Sex-specific consequences of early life seizures

Seizures are very common in the early periods of life and are often associated with poor neurologic outcome in humans. Animal studies have provided evidence that early life seizures may disrupt neuronal differentiation and connectivity, signaling pathways, and the function of various neuronal networks. There is growing experimental evidence that many signaling pathways, like GABAA receptor signaling, the cellular physiology and differentiation, or the functional maturation of certain brain regions, including those involved in seizure control, mature differently in males and females. However, most experimental studies of early life seizures have not directly investigated the importance of sex on the consequences of early life seizures. The sexual dimorphism of the developing brain raises the question that early seizures could have distinct effects in immature females and males that are subjected to seizures. We will first discuss the evidence for sex-specific features of the developing brain that could be involved in modifying the susceptibility and consequences of early life seizures. We will then review how sex-related biological factors could modify the age-specific consequences of induced seizures in the immature animals. These include signaling pathways (e.g., GABAA receptors), steroid hormones, growth factors. Overall, there are very few studies that have specifically addressed seizure outcomes in developing animals as a function of sex. The available literature indicates that a variety of outcomes (histopathological, behavioral, molecular, epileptogenesis) may be affected in a sex-, age-, region-specific manner after seizures during development. Obtaining a better understanding for the gender-related mechanisms underlying epileptogenesis and seizure comorbidities will be necessary to develop better gender and age appropriate therapies.

Does epilepsy cause a reversion to immature function?

Seizures have variable effects on brain. Numerous studies have examined the consequences of seizures, in light of the way that these may alter the susceptibility of the brain to seizures, promote epileptogenesis, or functionally alter brain leading to seizure-related comorbidities. In many -but not all- situations, seizures shift brain function towards a more immature state, promoting the birth of newborn neurons, altering the dendritic structure and neuronal connectivity, or changing neurotransmitter signaling towards more immature patterns. These effects depend upon many factors, including the seizure type, age of seizure occurrence, sex, and brain region studied. Here we discuss some of these findings proposing that these seizure-induced immature features do not simply represent rejuvenation of the brain but rather a de-synchronization of the homeostatic mechanisms that were in place to maintain normal physiology, which may contribute to epileptogenesis or the cognitive comorbidities.

17β-Estradiol attenuates secondary injury through activation of Akt signaling via estrogen receptor alpha in rat brain following subarachnoid hemorrhage

BACKGROUND

Apoptosis is implicated in vasospasm and the long-term sequelae of subarachnoid hemorrhage (SAH). This study tested the hypothesis that attenuation of SAH-induced apoptosis after 17β-estradiol (E2) treatment is associated with an increase in phosphorylation of Akt via estrogen receptor-α (ER-α) in rats.

MATERIALS AND METHODS

We examined the expression of phospho-Akt, ERα and ERβ, and apoptosis in cerebral cortex, hippocampus, and dentate gyrus in a two-hemorrhage SAH model in rats. We subcutaneously implanted other rats with a silicone rubber tube containing E2; they received daily injections of nonselective estrogen receptor antagonist (ICI 182,780), selective ERα-selective antagonist (methyl-piperidino-pyrazole), or ERβ-selective antagonist (R,R-tetrahydrochrysene) after the first hemorrhage.

RESULTS

At 7 d after the first SAH, protein levels of phospho-Akt and ERα were significantly decreased and caspase-3 was significantly increased in the dentate gyrus. The cell death assay revealed that DNA fragmentation was significantly increased in the dentate gyrus. Those actions were reversed by E2 and blocked by ICI 182,780 and methyl-piperidino-pyrazole, but not R,R-tetrahydrochrysene. However, there were no significant changes in the expression of the protein levels of phospho-Akt, ERα, ERβ, and caspase-3, and DNA fragmentation after SAH.

CONCLUSIONS

The present study shows that a beneficial effect of E2 in attenuating SAH-induced apoptosis is associated with activation of the expression of phospho-Akt and ERα, and alteration in caspase-3 protein expression via an ERα-dependent mechanism in the dentate gyrus. These data support further the investigation of E2 in the treatment of SAH in humans.

Rapamycin has age-, treatment paradigm-, and model-specific anticonvulsant effects and modulates neuropeptide Y expression in rats

PURPOSE

  Rapamycin (RAP) has certain antiepileptogenic features. However, it is unclear whether these effects can be explained by the anticonvulsant action of RAP, which has not been studied. To address this question, we tested potential anticonvulsant effects of RAP in immature and adult rats using different seizure models and treatment paradigms. In addition, we studied changes in the expression of neuropeptide Y (NPY) induced by RAP, which may serve as an indirect target of the RAP action.

METHODS

  A complex approach was adopted to evaluate the anticonvulsant potential of RAP: We used flurothyl-, pentylenetetrazole (PTZ)-, N-methyl-D-aspartate (NMDA)-, and kainic acid (KA)-induced seizures to test the effects of RAP using different pretreatment protocols in immature and adult rats. We also evaluated expression of NPY within the primary motor cortex, hippocampal CA1, and dentate gyrus (DG) after different pretreatments with RAP in immature rats.

KEY FINDINGS

  We found the following: (1) RAP administered with short-term pretreatment paradigms has a weak anticonvulsant potential in the seizure models with compromised inhibition. (2) Lack of RAP efficacy correlates with decreased NPY expression in the cortex, CA1, and DG. Specifically in immature rats, a single dose of RAP (3 mg/kg) 4 or 24 h before seizure testing had anticonvulsant effects against PTZ-induced seizures. In the flurothyl seizure model only the 4-h pretreatment with RAP was anticonvulsant in the both age groups. Short-term pretreatments with RAP had no effects against NMDA- and KA-induced seizures tested in immature rats. Long-term pretreatments with RAP over 8 days did not show beneficial effect in all tested seizure models in developing rats. Moreover, the long-term pretreatment with RAP had a slight proconvulsant effect on KA-induced seizures. In immature rats, any lack of anticonvulsant effect (including proconvulsant effect of multiple doses of RAP) was associated with downregulation of NPY expression in the cortex and DG. In immature animals, after a single dose of RAP with 24 h delay, we found a decrease of NPY expression in DG, and CA1 as well.

SIGNIFICANCE

  Our data show weak age-, treatment paradigm-, and model-specific anticonvulsant effects of RAP as well as loss of those effects after long-term RAP pretreatment associated with downregulation of NPY expression. These findings suggest that RAP is a poor anticonvulsant and may have beneficial effects only against epileptogenesis. In addition, our data present new insights into mechanisms of RAP action on seizures indicating a possible connection between mammalian target of rapamycin (mTOR) signaling and NPY system.

Epilepsy, poverty and early under-nutrition in rural Ethiopia

PURPOSE

The incidence of epilepsy in Ethiopia is high compared with industrialised countries, but in most cases the cause of epilepsy is unknown. Childhood malnutrition remains widespread. We performed a case-control study to determine whether epilepsy is associated with poverty and markers of early under-nutrition.

METHODS

Patients with epilepsy (n=112), aged 18-45years, were recruited from epilepsy clinics in and around two towns in Ethiopia. Controls with a similar age and gender distribution (n=149) were recruited from patients and relatives attending general outpatient clinics. We administered a questionnaire to define the medical and social history of cases and controls, and then performed a series of anthropometric measurements. Unconditional logistic regression was used to estimate multivariate adjusted odds ratios. Multiple linear regression was used to estimate adjusted case-control differences for continuously distributed outcomes.

RESULTS

Epilepsy was associated with illiteracy/low levels of education, odds ratio=3.0 (95% confidence interval: 1.7-5.6), subsistence farming, odds ratio=2.6 (1.2-5.6) and markers of poverty including poorer access to sanitation (p=0.009), greater overcrowding (p=0.008) and fewer possessions (p<0.001). Epilepsy was also associated with the father's death during childhood, odds ratio=2.2 (1.0-4.6). Body mass index was similar in cases and controls, but patients with epilepsy were shorter and lighter with reduced sitting height (p<0.001), bitrochanteric diameter (p=0.029) and hip size (p=0.003). Patients with epilepsy also had lower mid-upper arm circumference (p=0.011) and lean body mass (p=0.037).

CONCLUSION

Epilepsy in Ethiopia is strongly associated with poor education and markers of poverty. Patients with epilepsy also had evidence of stunting and disproportionate skeletal growth, raising the possibility of a link between early under-nutrition and epilepsy.

Malnutrition in infancy as a susceptibility factor for temporal lobe epilepsy in adulthood induced by the pilocarpine experimental model

Malnutrition during the earliest stages of life may result in innumerable brain problems. Moreover, this condition could increase the chances of developing neurological diseases, such as epilepsy. We analyzed the effects of early-life malnutrition on susceptibility to epileptic seizures induced by the pilocarpine model of epilepsy. Wistar rat pups were kept on a starvation regimen from day 1 to day 21 after birth. At day 60, 16 animals (8 = well-nourished; 8 = malnourished) were exposed to the pilocarpine experimental model of epilepsy. Age-matched well-nourished (n = 8) and malnourished (n = 8) rats were used as controls. Animals were video-monitored over 9 weeks. The following behavioral parameters were evaluated: first seizure threshold (acute period of the pilocarpine model); status epilepticus (SE) latency; first spontaneous seizure latency (silent period), and spontaneous seizure frequency during the chronic phase. The cell and mossy fiber sprouting (MFS) density were evaluated in the hippocampal formation. Our results showed that the malnourished animals required a lower pilocarpine dose in order to develop SE (200 mg/kg), lower latency to reach SE, less time for the first spontaneous seizure and higher seizure frequency, when compared to well-nourished pilocarpine rats. Histopathological findings revealed a significant cell density reduction in the CA1 region and intense MFS among the malnourished animals. Our data indicate that early malnutrition greatly influences susceptibility to seizures and behavioral manifestations in adult life. These findings suggest that malnutrition in infancy reduces the threshold for epilepsy and promotes alterations in the brain that persist into adult life.

Effects of intra-uterine and early extra-uterine malnutrition on seizure threshold and hippocampal morphometry of pup rats

We evaluate the influence of different malnutrition paradigms (intra-uterine × extra-uterine) in body and brain weight, in seizure threshold and in hippocampus morphometry, in developing rats. Intra-uterine malnutrition model consisted in reduction by half of the ration offered to pregnant female; extra-uterine malnutrition consisted of progressive limitation of lactation, from P2 to P15. Seizure induction was accomplished by exposure to flurothyl, at P15. At the same day animals were sacrificed. Morphometric analysis was based on hippocampal pyramidal and granular cells estimate number, through volume calculation and cellular density. Extra-uterine malnutrition significantly reduced pups body and brain weight, seizure threshold and neuronal number in CA4 region only. Intra-uterine malnutrition reduced neuronal number in CA2, CA4 and DG regions regarding well-nourished and extra-uterine malnourished animals. In CA3, CA4 and dentate gyrus, a significant cell increase was observed in groups exposed to seizures, regarding similar control groups.

Protein malnutrition differentially alters the number of glutamic acid decarboxylase-67 interneurons in dentate gyrus and CA1–3 subfields of the dorsal hippocampus

In 30- and 90-day-old rats, using immunohistochemistry for glutamic acid decarboxylase 67 (GAD-67), we have tested whether malnutrition during different periods of hippocampal development produces deleterious effects on the population of GABA neurons in the dentate gyrus (DG) and cornu Ammonis (CA1-3) of the dorsal hippocampus. Animals were under one of four nutritional conditions: well-nourished controls (Con), prenatal protein malnourished (PreM), postnatal protein malnourished (PostM), and chronic protein malnourished (ChroM). We found that the number of GAD-67-positive (GAD-67+) interneurons was higher in the DG than in the CA1-3 areas of both Con and malnourished groups. Regarding the DG, the number of GAD-67+ interneurons was increased in PreM and PostM and decreased in ChroM at 30 days. At 90 days of age the number of GAD-67+ interneurons was increased in PostM and ChroM and remained unchanged in PreM. With respect to CA1-3, the number of labeled interneurons was decreased in PostM and ChroM at 30 days of age, but no change was found in PreM. At 90 days no changes in the number of these interneurons were found in any of the groups. These observations suggest that 1) the cell death program starting point is delayed in DG GAD-67+ interneurons, and 2) protein malnutrition differentially affects GAD-67+ interneuron development throughout the dorsal hippocampus. Thus, these changes in the number of GAD-67+ interneurons may partly explain the alterations in modulation of dentate granule cell excitability, as well as in the emotional, motivational, and memory disturbances commonly observed in malnourished rats.

The influence of gestational age and birth weight in the clinical assesment of the muscle tone of healthy term and preterm newborns

OBJECTIVE: To evaluate the influence of gestational age (GA) and birth weight (BW) in the clinical assessment of the muscle tone of healthy term and preterm newborns. METHOD: Cross sectional study. The muscle tone of healthy 42 preterm and 47 term newborns was quantified and measured with a goniometer (an instrument for measuring angles) respectively between 7th-14th day of life and 24-48 hours of life. Newborns were grouped according to GA and BW and evaluated at fixed time intervals by one examiner. Preterm newborns were matched to term at 40 weeks postconceptional age (PCA). RESULTS: The evolution of muscle tone in the preterm occurred gradually, following PCA, independent of birth weight. Preterm newborns had lower scores in all muscle tone indicators when compared to term at the first assessment. Differences were observed among preterm small for GA and adequate to GA for the indicator heel to ear (p<0.001). When compared at 40 weeks PCA, except for posture, all other indicators were significantly different (p< 0.001) among groups. CONCLUSION: Prematurity and intrauterine malnutrition are influential factors in some indicators of the newborn muscle tone state. Muscle tone assessment of preterm infants does not seem to be influenced by birth weight, however evolution is clearly related to postconceptional age. When we compared term newborns AGA and SGA it seems to have a clear influence of the birth weight on some indicators of the muscle tone. The use of devices such as the goniometer allows the performance of a more objective assessment of muscle tone and helps to quantify findings.

The mossy fiber system of the hippocampal formation is decreased by chronic and postnatal but not by prenatal protein malnutrition in rats

We tested in 70-day-old Sprague-Dawley rats, whether malnutrition imposed during different periods of hippocampal development produced deleterious effects on the total reference volume of the mossy fiber system. Animals were treated under four nutritional conditions: (a) well nourished; (b) prenatal protein malnourished; (c) chronic protein malnourished and (d) postnatal protein malnourished. Timm's stained material was used in coronal hippocampal sections (40 microm) to estimate--using the Principle of Cavalieri--the total reference volume of the mossy fiber system in each experimental group. Our results show that chronic and postnatal protein malnourished, but not prenatal malnourished rats, decrease the mossy fiber system and the total reference volume of the mossy fiber system are selectively vulnerable to the type of dietary restriction. Thus, chronic and posnatal protein malnutrition produce deleterious effects, but only rats under prenatal protein malnutrition were able to reorganize synapses in this plexus. These findings raise the possibility that chronic malnutrition, as a long-term stressful factor, might be an important paradigm to test structural hippocampal changes that produce physiological and pathophysiological effects, or the possibility to recover its function for nutritional rehabilitation.

Effect of food deprivation during early development on cognition and neurogenesis in the rat

Food deprivation has been recognized as having pronounced beneficial effects in adult animals, increasing longevity, reducing seizure susceptibility, and enhancing resistance to neurotoxins. It is not known whether food deprivation in developing animals is neuroprotective or harmful. To evaluate the effects of food deprivation on brain development, we evaluated visual-spatial learning and memory and neurogenesis in the dentate gyrus of the hippocampus in food-deprived (FD) and well-fed (WF) rats. To induce food deprivation, pups were removed from their dams for 12 hours per day from Postnatal Day (P) 2 to P19. FD and WF rat pups were then subjected to status epilepticus (SE) induced by lithium-pilocarpine at P20. After SE, neurogenesis was measured, while in another group of P38 rats, learning and memory were evaluated using the Morris water maze. Food deprivation was found to reduce neurogenesis when assessed after the period of food deprivation. Although SE reduced neurogenesis in the WF animals, it had little effect additional to food deprivation on neurogenesis in the FD rats. Compared with the WF group, FD rats had a mild impairment in memory in the water maze testing after SE. Our study demonstrates that food deprivation during the neonatal period in rats is associated with a decrease in neurogenesis and mild impairment of visual-spatial memory. Although SE decreased neurogenesis in the WF group, in FD animals, SE did not reduce neurogenesis more than what was seen with food deprivation alone. Our results suggest that although food deprivation during early development reduces dentate gyrus neurogenesis, the reduced neurogenesis is not a major factor in cognitive impairment after SE in FD rats.

Temporal Lobe Epileptogenesis and Epilepsy in the Developing Brain: Bridging the Gap Between the Laboratory and the Clinic. Progression, But in What Direction?

The origins of human mesial temporal lobe epilepsy and hippocampal sclerosis are still not well understood. Hippocampal sclerosis and temporal lobe epileptogenesis involve a series of pathologies including hippocampal neuronal loss and gliosis, axonal reorganization, and maybe hippocampal neoneurogenesis. However, the causality of these events is unclear as well as their relation to the factors that may precipitate epileptogenesis. Significant differences between temporal lobe epileptogenesis in the adult and immature brain may require differential approaches. Hereditary factors also may participate in some cases of hippocampal sclerosis. The key point is to identify the significance of these age-dependent changes and to design preventive treatments. Novel strategies for the prevention and treatment of mesial temporal lobe epilepsy and hippocampal sclerosis may include rational use of neuroprotective agents, hormonotherapy, immunizations, and immunotherapy.

Nutrition and brain function: a multidisciplinary virtual symposium

A few months ago, the Brazilian Society for Neuroscience and Behavior (SBNeC) promoted a "virtual symposium" (by Internet, under the coordination of R.C.A. Guedes) on "Nutrition and Brain Function". The discussions generated during that symposium originated the present text, which analyzes current topics on the theme, based on the multidisciplinary experience of the authors. The way the brain could be non-homogeneously affected by nutritional alterations, as well as questions like early malnutrition and the development of late obesity and hormone abnormalities were discussed. Also, topics like the role of essential fatty acids (EFAs) on brain development, increased seizure susceptibility and changes in different neurotransmitters and in cognitive performance in malnourished animals, as well as differences between overall changes in nutrient intake and excess or deficiency of specific nutrients (e.g. iodine deficiency) were analyzed. It was pointed out that different types of neurons, possibly in distinct brain structures, might be differently affected by nutritional manipulation, including not only lack-but also excess of nutrient intake. Such differences could help in explaining discrepancies between data on humans and in animals and so, could aid in determining the basic mechanisms underlying lesions or changes in brain function and behavior.

Epileptogenesis during development: injury, circuit recruitment, and plasticity

PURPOSE

To use animal models of variable seizure induction in rats at different developmental stages to determine contributing factors for spontaneous seizures resulting from status epilepticus (SE) early in life.

METHODS

Two models of SE with distinct modes of seizure induction, lithium-pilocarpine (LiPC) and perforant path stimulation (PPS), were used at different ages. Multiple methods of determining neurodegeneration during an acute period and plastic changes in those monitored during the chronic phase were used.

RESULTS

Different modes of seizure induction lead to varying types and extents of damage, dependent on the age of the animals at the time of insult. LiPC resulted in injury to animals as young as 2 weeks and became widespread in animals 3 weeks old, whereas widespread damage after PPS was not seen until P35. Rats at an age with widespread damage in response to seizures also showed extensive immediate-early gene activation and often developed spontaneous seizures and features of hippocampal plasticity seen in the epileptic brain.

CONCLUSIONS

SE early in life results in multiple consequences to the developing brain. These changes, coexisting in the nonepileptic brain, can overlap in a maladaptive combination to result in the diseased state of epilepsy. The consequence of early seizures in immature animals is a function of both the developmental stage and the method of seizure induction.