Effects of early monocular enucleation on cortical spreading depression in well-nourished and malnourished adult rats.

Sensory development is a complex process that can influence physiological and pathological factors. In laterally-eyed mammals, monocular enucleation (ME) during development and the subsequent lack of external sensory stimuli can result in permanent morphological and physiological changes. Malnutrition, especially in early life, also can cause permanent morphofunctional changes due to inadequate nutrient intake in both hemispheres. This study investigated the effects of early (postnatal day 7) ME and malnutrition during the suckling period on cortical excitability in adulthood (110-140 days of life). For this, we compared the speed propagation of cortical spreading depression in the occipital and parietal cortex of malnourished and well-nourished adult rats, previously suckled small-sized litters with three pups (L3/dam) medium-sized litters with six pups (L6/dam), and large-sized litters with twelve pups (L12/dam). The CSD velocity was augmented by the ME in the contralateral side of the removed eye in the parietal and occipital cortex. These findings suggest that visual sensory input deprivation is associated with permanent functional changes in the visual pathways, which can alter cortical excitability and lead to modifications in CSD propagation.

Maternal voluntary physical exercise in the adult rat: evidence of exercise-associated differences in maternal food intake, and in brain effects on the progeny.

Objectives: Maternal physical activity may impact behavioral and electrophysiological aspects of brain function, with short- and long-term effects on pre- and postnatal neurodevelopment of the offspring. This study evaluated in the rat the effects of maternal voluntary physical activity (MVPA) on food intake and weight gain in the dams, as well as anxiety-like behavior, short-term memory and the brain excitability-related phenomenon known as cortical spreading depression (CSD) on the mother-pup dyad.Methods: Female Wistar rats (n=33) were individually housed in cages containing a running wheel for a 30-days adaptation period before mating. Rats were classified as inactive (I); active (A) or very active (VA) according to the distance spontaneously travelled daily. During gestation, the dams continued to have access to the running wheel. Mothers and their respective pups (1 pup per mother) were evaluated in the open field test (OFT), object recognition test (ORT), elevated plus maze test (EPMT) and the CSD propagation features.Results: MVPA was directly associated with increased food intake and weight gain during gestation, and maternal anxiolytic-like behavioral responses in the OFT. Pups from VA mothers showed a high discrimination index for shape recognition memory (ORT) and decreased propagation velocities of CSD, when compared with the inactive group.Discussion: The data suggest that MVPA during the gestational period induces neuroplasticity and may modulate the brain functions in the mother-infant dyad in the rat.

Lactation in large litters influences anxiety, memory, and spreading depression in adult male rats that were chronically subjected to a non-convulsive pilocarpine dose.

Objectives: Unfavorable lactation influences brain excitability and behavioral reactions in adults. Administration early in life of the cholinergic agonist, pilocarpine, even at non-convulsive doses, alters the brain excitability-related phenomenon known as cortical spreading depression (CSD), and produce anxiogenic-like behavior. However, the influence of unfavorable lactation on the CSD- and memory-effects of pilocarpine administration late in life has not been investigated. Herein, we analyzed the ponderal, electrophysiological (CSD), and behavioral effects of chronic treatment with a non-convulsive dose of pilocarpine, in adult rats suckled under favorable and unfavorable conditions.Methods: Wistar rats were suckled in litters with 9 or 15 pups (groups L9 and L15, respectively). A very low dose of pilocarpine (45/mg/kg/day) was chronically administered in mature rats from postnatal day (PND) 69-90. Behavioral tests occurred at PND91 [elevated plus maze (EPM)], PND93 [open field (OF)], and PND94-95 [object recognition memory (ORM)]. CSD was recorded between PND96-120.Results: Pilocarpine-treated rats performed worse in the anxiety and memory tests, and displayed lower CSD propagation velocity when compared with saline-treated controls. In addition, L15 rats showed an increase in the distance traveled and a decrease in the immobility time in the EPM, impaired ORM, and accelerated CSD propagation when compared with L9 rats (p ≤ 0.05).Discussion: These data suggest that sub-convulsive pilocarpine treatment in adult rats can affect behavioral and excitability-related reactions. In addition, unfavorable lactation increases the ambulatory effects of pilocarpine. Further studies should investigate the possible cholinergic molecular mechanisms involved in these effects.

Topical cortical application of ovarian hormones and modulation of brain electrical activity: analysis of spreading depression in well-nourished and malnourished female rats.

Objectives - Clinical and experimental evidence indicates that both ovarian hormones and nutritional condition can affect several brain functions, including those depending on excitability mechanisms. Nutritional deficiency, on the other hand, is capable of disturbing brain structure and function of mammals. We have previously demonstrated that ovariectomy decelerates [Accioly NE, Benevides R, Costa B, Guedes RCA. Ovariectomy in the developing rat decelerates cortical spreading depression in adult brain. Internat J Develop Neurosci. 2012;30:405-410.], whereas systemic hormone administration accelerates the excitability-dependent phenomenon known as cortical spreading depression (CSD; [Accioly NE, Guedes RCA. Neonatal treatment with ovarian hormones and suckling among distinct litter sizes: Differential effects on recognition memory and spreading depression at adulthood. Nutr Neurosci. 2017;1-11. doi:10.1080/1028415X.2017.1358472.]). In this study we investigated the interaction between topical cortical treatment with ovarian hormones and malnutrition during lactation on CSD parameters. Methods - Female Wistar rats were suckled in litters with 6-9 or 12-15 pups (L9 and L15 groups; normal size- and large size litters, respectively). At postnatal days 90-120, estradiol (5, 10 and 20 mg/ml solutions) and progesterone (66 mg/ml, 132 mg/ml and 264 mg/ml solutions) were topically applied during a CSD recording session. CSD parameters (propagation velocity, and amplitude and duration of the CSD DC-shift) were calculated before and after CSD. Results - Topical applications of estradiol and progesterone reversibly and dose- dependently accelerated CSD, and decreased duration and increased amplitude of the CSD DC-shift (p < 0.05); furthermore, unfavorable lactation (L15) accelerated CSD in adulthood. Discussion - In support of our previous studies with systemic hormone treatment, topical cortical application of ovarian hormones modulates CSD in the adult brain, suggesting a cortically-based mechanism for this effect, which might be related to the hormonal action on synaptic transmission with consequent modulation of brain excitability.

Neonatal treatment with ovarian hormones and suckling among distinct litter sizes: Differential effects on recognition memory and spreading depression at adulthood.

OBJECTIVES: Ovarian hormones (OH) and early malnutrition may affect the developing brain, with repercussions on behavioral and excitability-dependent processes. However, the possible synergistic effects of both factors have not been analyzed. In this study, we investigated the effect of treatment in early life with OH and suckling among distinct litter sizes on recognition memory, anxiety behavior, and the excitability-dependent phenomenon known as cortical spreading depression (CSD). METHODS: Female Wistar rats were suckled under favorable and unfavorable lactation, corresponding to litters with 9 and 15 pups (L9 and L15 groups, respectively). From postnatal days (P) 7 to 21, the animals received 50 µg/kg of ß-estradiol or progesterone. From P80 to P84, we tested behavioral reactions. From P90 to P120, we analyzed CSD parameters. RESULTS: Compared with the corresponding L9 groups, the OH-treated L15 groups performed worse in recognition memory tasks. No intergroup difference in the anxiety parameters was observed. Compared with naive and vehicle-treated controls, OH-treated groups displayed higher CSD velocities and amplitudes and shorter CSD durations. DISCUSSION: Early treatment with OH facilitates recognition memory and CSD, and in association with unfavorable lactation (L15) impaired recognition memory, but not anxiety behavior, in the adult brain. OH treatment and L15 lactation condition seem to interact regarding OH action on memory, but not on CSD. Data suggest a long-lasting differential effect that might be related to the lasting hormonal action on brain excitability. We postulate and discuss the possibility that these findings may be implicated in human neurological diseases.

Suckling in litters with different sizes, and early and late swimming exercise differentially modulates anxiety-like behavior, memory and electrocorticogram potentiation after spreading depression in rats.

OBJECTIVE: Analyze the hypothesis that swimming exercise, in rats suckled under distinct litter sizes, alters behavioral parameters suggestive of anxiety and recognition memory, and the electrocorticogram potentiation that occurs after the excitability-related phenomenon that is known as cortical spreading depression (CSD). METHODS: Male Wistar rats were suckled in litters with six or 12 pups (L6 and L12 groups). Animals swam at postnatal days (P) 8-23, or P60-P75 (early-exercised or late-exercised groups, respectively), or remained no-exercised. Behavioral tests (open field - OF and object recognition - OR) were conducted between P77 and P80. Between P90 and P120, ECoG was recorded for 2 hours. After this 'baseline' recording, CSD was elicited every 30 minutes over the course of 2 hours. RESULTS: Early swimming enhanced the number of entries and the percentage of time in the OF-center (P < 0.05). In animals that swam later, this effect occurred in the L6 group only. Compared to the corresponding sedentary groups, OR-test showed a better memory in the L6 early exercised rats, and a worse memory in all other groups (P < 0.05). In comparison to baseline values, ECoG amplitudes after CSD increased 14-43% for all groups (P < 0.05). In the L6 condition, early swimming and late swimming, respectively, reduced and enhanced the magnitude of the post-CSD ECoG potentiation in comparison with the corresponding L6 no-exercised groups (P < 0.05). DISCUSSION: Our data suggest a differential effect of early- and late-exercise on the behavioral and electrophysiological parameters, suggesting an interaction between the age of exercise and the nutritional status during lactation.

Monosodium glutamate and treadmill exercise: Anxiety-like behavior and spreading depression features in young adult rats.

OBJECTIVES: The route of administration is an important factor in determining the action of some drugs. We previously demonstrated that subcutaneous monosodium glutamate (MSG) accelerated cortical spreading depression (CSD) in the rat and that treadmill exercise attenuated this effect. This study evaluated whether other routes of administration exert the same action by testing orogastric (gavage) and topical cortical MSG administration in treadmill-exercised and sedentary rats. Additionally, in the orogastric treatment we tested anxiety-like behavior. METHODS: Exercised and sedentary rats received per gavage water or MSG (1 or 2 g/kg) daily from postnatal (P) day 7 to 27. Behavioral tests (open field and elevated plus-maze) occurred at P53 ± 3. At P56 ± 3, we analyzed CSD parameters (velocity, amplitude, and duration of the negative potential change). Other three groups of rats received an MSG solution (25, 50 or 75 mg/ml) topically to the intact dura mater during CSD recording. RESULTS: MSG-gavage increased anxiety-like behavior and the CSD velocities compared with water-treated controls (P < 0.05). Exercise decelerated CSD. In contrast to gavage, which accelerated CSD, topical MSG dose-dependently and reversibly impaired CSD propagation, reduced CSD amplitude and increased CSD duration (P < 0.05). CONCLUSIONS: The exercise-dependent attenuation of the effects of MSG confirms our previous results in rats treated subcutaneously with MSG. CSD results suggest two distinct mechanisms for gavage and topical MSG administration. Additionally, data suggest that exercise can help protect the developing and adult brain against the deleterious actions of MSG.

Behavioral and electrophysiological brain effects of aspartame on well-nourished and malnourished rats.

The non-caloric sweetener aspartame can be potentially harmful to the developing brain, as some studies suggest an association between aspartame intake and adverse neural effects. This study aimed to evaluate the possible effects of aspartame, with or without associated early nutritional deficiency, on behavioral parameters suggestive of anxiety and electrophysiological features of the excitability-related phenomenon known as cortical spreading depression (CSD). Newborn Wistar rats (n = 80) were suckled under favorable (L9; n = 40) or unfavorable lactation conditions (L15; n = 40), consisting of litters with 9 or 15 pups, respectively. In each lactation condition, animals were divided into 4 groups that received per gavage, from postnatal day 8 to 28, 75 mg/kg/d or 125 mg/kg/d aspartame (groups ASP75 and ASP125), or water (vehicle group), or no treatment (naive group). Behavioral tests (elevated plus-maze [EPM]) were performed at postnatal days 86-95 and CSD was recorded between postnatal days 96-115. Compared to the control groups, aspartame dose-dependently reduced body weight, suggesting a negative impact on animal development; aspartame also caused behavioral changes suggestive of anxiety (shorter stay in the open arms in the EPM) and decelerated CSD (lower propagation speed). Some of these parameters were more affected in L15 animals, suggesting an interaction among aspartame and lactation condition. We concluded that early consumption of aspartame adversely affects development of the organism (weight loss), with actions on behavioral (anxiety-like) and cerebral electrophysiological (CSD) parameters. The data suggest caution in aspartame consumption by lactating mothers and their infants.

The facilitating effect of unfavorable lactation on the potentiation of electrocorticogram after spreading depression in awake and anesthetized adult rats.

OBJECTIVES: Cortical spreading depression (CSD) is a brain excitability-related phenomenon that can be affected by unfavorable conditions of lactation and by anesthetic agents. We have previously demonstrated that after CSD the electrocorticogram (ECoG) amplitude increases significantly (ECoG potentiation). Here, we investigated this potentiation in awake and anesthetized adult rats that were previously suckled among different lactation conditions. METHODS: Newborn rats were suckled in litters with 6 pups or 12 pups (L6 or L12 condition, respectively). At adulthood, we evaluated the ECoG potentiation after CSD at two cortical points (one point near, and another remote to the CSD-eliciting site). The amplitude of the ECoG waves was averaged with the support of an algorithm implemented in Matlab™ software. In both L6 and L12 condition, awake animals were compared with anesthetized groups that received either tribromoethanol- or urethane + chloralose-anesthesia. RESULTS: L12 rats presented significantly lower body- and brain weights than L6 rats (P < 0.01), indicating a nutritional deficiency. The anesthetized L6 groups presented with ECoG potentiation (P < 0.05) only in the near cortical recording point (28.0% and 32.6% increase for the tribromoethanol and urethane + chloralose groups, respectively), whereas the L12 groups displayed ECoG potentiation in both near (67.0% and 55.0%) and remote points (37.0% and 20.0%), in comparison with the baseline values (before CSD). DISCUSSION: The results suggest a facilitating effect of unfavorable lactation on the potentiation of ECoG after spreading depression in anesthetized adult rats. The potential implications for the human neurological health remain to be investigated.

Neonatal L-glutamine modulates anxiety-like behavior, cortical spreading depression, and microglial immunoreactivity: analysis in developing rats suckled on normal size- and large size litters.

In mammals, L-glutamine (Gln) can alter the glutamate-Gln cycle and consequently brain excitability. Here, we investigated in developing rats the effect of treatment with different doses of Gln on anxiety-like behavior, cortical spreading depression (CSD), and microglial activation expressed as Iba1-immunoreactivity. Wistar rats were suckled in litters with 9 and 15 pups (groups L 9 and L 15; respectively, normal size- and large size litters). From postnatal days (P) 7-27, the animals received Gln per gavage (250, 500 or 750 mg/kg/day), or vehicle (water), or no treatment (naive). At P28 and P30, we tested the animals, respectively, in the elevated plus maze and open field. At P30-35, we measured CSD parameters (velocity of propagation, amplitude, and duration). Fixative-perfused brains were processed for microglial immunolabeling with anti-IBA-1 antibodies to analyze cortical microglia. Rats treated with Gln presented an anxiolytic behavior and accelerated CSD propagation when compared to the water- and naive control groups. Furthermore, CSD velocity was higher (p < 0.001) in the L 15 compared to the L 9 condition. Gln treatment increased Iba1 immunolabeling both in the parietal cortex and CA1 hippocampus, indicating microglial activation. The Gln effect was dose-dependent for anxiety-like behavior and CSD in both litter sizes, and for microglial activation in the L 15 groups. Besides confirming previous electrophysiological findings (CSD acceleration after Gln), our data demonstrate for the first time a behavioral and microglial activation that is associated with early Gln treatment in developing animals, and that is possibly operated via changes in brain excitability.

Alpha-Tocopherol Counteracts the Effect of Ethanol on Cortical Spreading Depression in Rats of Various Ages, With and Without Ethanol Abstinence.

BACKGROUND: We previously demonstrated that acute and chronic treatment with ethanol (EtOH), respectively, decelerated and accelerated the propagation of cortical spreading depression (CSD) in rats and that the antioxidant carotenoid astaxanthin counteracted these effects. Here, we investigated whether noncarotenoid antioxidants exert the same action by testing α-tocopherol in rats of various ages, with and without 5 to 10 days of EtOH abstinence. METHODS: Male Wistar young adult (60 to 80 days old) and mature adult (150 to 180 days old) rats received per gavage acute (1 day) or chronic (21 days) treatment with 3 g/kg/d EtOH combined with acute (300 mg/kg) or chronic (85 mg/kg/d) treatment with α-tocopherol or vehicle-only treatment (olive oil and water for α-tocopherol and EtOH, respectively). CSD was recorded over 4 hours and the velocity of CSD propagation was calculated. On both ages, animals under chronic EtOH treatment were subjected to CSD recording immediately after EtOH treatment or after a 5- to 10-day period of EtOH abstinence. RESULTS: In both age groups, acute and chronic EtOH exposure decelerated and accelerated CSD, respectively, versus the corresponding control groups. Addition of α-tocopherol counteracted the effects of EtOH on CSD, returning CSD velocities to levels in control groups (p < 0.05). Chronic α-tocopherol (85 mg/kg/d) did not alter CSD. CONCLUSIONS: Our data reinforce the counteracting role of antioxidants on brain processes involved in the action of EtOH on CSD and suggest that this role is not a particular property of carotenoids; furthermore, this general feature of antioxidants is not substantially influenced by age or by 5 to 10 days of EtOH abstinence.

Omega-3 deficiency and neurodegeneration in the substantia nigra: involvement of increased nitric oxide production and reduced BDNF expression.

BACKGROUND: Our previous study demonstrated that essential fatty acid (EFA) dietary restriction over two generations induced midbrain dopaminergic cell loss and oxidative stress in the substantia nigra (SN) but not in the striatum of young rats. In the present study we hypothesized that omega-3 deficiency until adulthood would reduce striatum's resilience, increase nitric oxide (NO) levels and the number of BDNF-expressing neurons, both potential mechanisms involved in SN neurodegeneration. METHODS: Second generation rats were raised from gestation on control or EFA-restricted diets until young or adulthood. Lipoperoxidation, NO content, total superoxide dismutase (t-SOD) and catalase enzymatic activities were assessed in the SN and striatum. The number of tyrosine hydroxylase (TH)- and BDNF-expressing neurons was analyzed in the SN. RESULTS: Increased NO levels were observed in the striatum of both young and adult EFA-deficient animals but not in the SN, despite a similar omega-3 depletion (~65%) in these regions. Increased lipoperoxidation and decreased catalase activity were found in both regions, while lower tSOD activity was observed only in the striatum. Fewer TH- (~40%) and BDNF-positive cells (~20%) were detected at the SN compared to the control. CONCLUSION: The present findings demonstrate a differential effect of omega-3 deficiency on NO production in the rat's nigrostriatal system. Prolonging omega-3 depletion until adulthood impaired striatum's anti-oxidant resources and BDNF distribution in the SN, worsening dopaminergic cell degeneration. GENERAL SIGNIFICANCE: Omega-3 deficiency can reduce the nigrostriatal system's ability to maintain homeostasis under oxidative conditions, which may enhance the risk of Parkinson's disease.

Neonatal taurine and alanine modulate anxiety-like behavior and decelerate cortical spreading depression in rats previously suckled under different litter sizes.

The amino acids taurine and alanine play a role in several physiological processes, including behavior and the electrical activity of the brain. In this study, we investigated the effect of treatment with taurine or alanine on anxiety-like behavior and the excitability-dependent phenomenon known as cortical spreading depression (CSD), using rats suckled in litters with 9 and 15 pups (groups L9 and L15). From postnatal days 7 to 27, the animals received per gavage 300 mg/kg/day of taurine or alanine or both. At 28 days, we tested the animals in the elevated plus maze, and at 33-35 days, we recorded CSD and analyzed its velocity of propagation, amplitude, and duration. Compared with water-treated controls, the L9 groups treated with taurine or alanine displayed anxiolytic behavior (higher number of entries in the open arms; p < 0.05), and reduced CSD velocity (p < 0.001). The effect of both amino acids on CSD was also found in the L15 groups and in five additional L9 groups (naïve, water, taurine, alanine, or both) treated at adulthood (90-110 days). The L15 condition resulted in smaller durations and higher CSD velocities compared with the L9 condition. Besides reinforcing previous evidence of behavioral modulation by taurine and alanine, our data are the first confirmation that treatment with these amino acids decelerates CSD regardless of lactation conditions (normal versus unfavorable lactation) or age at amino acid administration (young versus adult). The results suggest a modulating role for both amino acids on anxiety behavior and neuronal electrical activity.

Brain effects of the lectin from Canavalia ensiformis in adult rats previously suckled in favorable and unfavorable conditions: A spreading depression and microglia immunolabeling study.

OBJECTIVE: To evaluate in adult rats, previously suckled under favorable and unfavorable conditions, the brain electrophysiological and microglial effects of the treatment early in life with the lectin (ConA) from Canavalia ensiformis. METHODS: Male Wistar newborn rats (n = 89) were suckled under favorable or unfavorable conditions, represented by litters with 6-7 pups or 12-14 pups (groups N6 and N12, respectively). From postnatal days 5-24, they were treated intraperitoneally with 1 or 10 mg/kg ConA (groups L1 and L10, respectively), or with saline solution (group Sal), or no treatment (group Naïve). At 90-120 days of age, cortical spreading depression (CSD) was recorded at two parietal points for 4 hours, and CSD parameters (velocity of propagation and amplitude and duration of the DC slow potential change) were measured. Fixative-perfused brain sections were reacted with anti-Iba1 antibodies to quantify immunolabeled microglia. RESULTS: Compared with the control groups, ConA-treated animals dose-dependently presented with reduced CSD propagation velocities and increased amplitude and duration of the CSD slow potential change. Microglia Iba-1 immunoreactivity was lower in both nutritional groups treated with ConA, in comparison with the control groups. The CSD hemisphere presented with higher immunoreactivity compared with the CSD-free hemisphere. DISCUSSION: Attenuation in CSD propagation and microglia reaction was associated in adulthood with ConA treatment during brain development, indicating that the lectin can affect the electrophysiological and microglial development, and suggesting long-lasting protective action of the lectin on the rat brain, which is not impeded by the unfavorable suckling condition.

Unraveling the Influence of Litter Size, Maternal Care, Exercise, and Aging on Neurobehavioral Plasticity and Dentate Gyrus Microglia Dynamics in Male Rats.

This study explores the multifaceted influence of litter size, maternal care, exercise, and aging on rats' neurobehavioral plasticity and dentate gyrus microglia dynamics. Body weight evolution revealed a progressive increase until maturity, followed by a decline during aging, with larger litters exhibiting lower weights initially. Notably, exercised rats from smaller litters displayed higher body weights during the mature and aged stages. The dentate gyrus volumes showed no significant differences among groups, except for aged sedentary rats from smaller litters, which exhibited a reduction. Maternal care varied significantly based on litter size, with large litter dams showing lower frequencies of caregiving behaviors. Behavioral assays highlighted the detrimental impact of a sedentary lifestyle and reduced maternal care/large litters on spatial memory, mitigated by exercise in aged rats from smaller litters. The microglial dynamics in the layers of dentate gyrus revealed age-related changes modulated by litter size and exercise. Exercise interventions mitigated microgliosis associated with aging, particularly in aged rats. These findings underscore the complex interplay between early-life experiences, exercise, microglial dynamics, and neurobehavioral outcomes during aging.

Hypercaloric high-lipid diet and brain development: effects on cortical spreading depression in adult rats.

UNLABELLED: Nutritional conditions early in life constitute one of the environmental factors that can influence brain electrophysiology, as evaluated through the phenomenon denominated as cortical spreading depression (CSD). OBJECTIVE: To evaluate the effects of hypercaloric diet intake in different phases of life on CSD features in adult rats. METHODS: Newborn Wistar rats were suckled by dams fed a high-lipid (cafeteria) hypercaloric diet during the lactation period. After suckling, part of the pups remained in the high-lipid diet until the end of the experiment in adulthood (group 'full-life' FL), and the other part received the control (lab chow) diet (group L). A third group received the hypercaloric diet only at adulthood (group Ad). When the animals reached 90-93 days of life, CSD was recorded. RESULTS: CSD propagation velocities (in mm/minute) and CSD amplitudes (in mV) were reduced (P < 0.05) in the groups L (2.77 ± 0.07 and 7.1 ± 2.0 for velocity and amplitude, respectively) and FL (3.05 ± 0.17 and 8.5 ± 1.9), but not in the group Ad (3.36 ± 0.11 and 10.7 ± 2.0), in comparison with a control group (C), fed the lab chow diet during the entire life (3.52 ± 0.18 and 10.8 ± 2.2). DISCUSSION: CSD velocity changes observed in adulthood were associated with the hypercaloric dietary treatment during brain development, constituting evidence in favor of permanent or at least long-lasting electrophysiological effects related to the prevailing nutritional status during the period of brain growth spurt.

Early malnutrition attenuates the impairing action of naloxone on spreading depression in young rats.

OBJECTIVES: Malnutrition early in life can disrupt neurotransmitter systems in the brain, affecting its electrophysiological function. The opioid receptor antagonist naloxone can affect the electroencephalogram (EEG) and behavior in animals and humans, and patients under drug-abuse treatment use it as a therapy. The goal of this work in the rat is to determine whether malnutrition early in life modulates the action of naloxone on the excitability-related phenomenon known as cortical spreading depression (CSD). METHODS: Malnutrition was induced by feeding the dams during the gestation and lactation with a low-protein diet (8% protein). Their male pups received a single daily subcutaneous injection of naloxone (10 mg/kg/day) from the 7th to the 28th postnatal day, and were subsequently (30-40 days of life) submitted to a 4-hours CSD recording session, with electrodes at two points at a fixed distance apart on the parietal cortical surface. RESULTS: Compared to well-nourished rats receiving a 23% protein diet, malnourished animals displayed lower body weights and higher CSD velocities of propagation, confirming the facilitating effect of malnutrition on CSD. Naloxone treatment reduced in well-nourished rats the CSD propagation velocity, as compared to saline-injected controls. In contrast, the naloxone effect was less intense in the malnourished condition, and the CSD velocity difference between malnourished-naloxone and malnourished-saline groups did not reach statistical significance. DISCUSSION: Data strongly support the involvement of opioid-based mechanisms in excitability-related neural processes, which probably influence CSD propagation, and indicate that early malnutrition attenuates the impairing action of naloxone on CSD.

Treadmill Exercise Reverses the Adverse Effects of Intermittent Fasting on Behavior and Cortical Spreading Depression in Young Rats.

Intermittent fasting (IF) and physical exercise (PE) have beneficial psychological and physiological effects, improving memory and anxiety-like behavior. However, the impact of this combination on brain electrophysiological patterns is unknown. We aimed to evaluate the behavior and parameters of a brain excitability-related phenomenon named cortical spreading depression (CSD) in young rats (31-87 days of life) submitted to IF and treadmill PE for eight weeks. Sixty-four male and female Wistar rats aged 24 days were randomized into control, IF, PE, and IF+PE groups. Behavioral tests (open field (OF), object recognition, and elevated plus maze (EPM)) were performed, and the CSD propagation features were recorded. IF caused behavioral responses indicative of anxiety (lower number of entries and time spent in the OF center and EPM open arms). IF also reduced the discrimination index for object recognition memory tests and increased the propagation velocity of CSD. PE rats displayed more entries into the OF center and lowered CSD propagation speed. Data suggest that IF worsens anxiety-like behavior and memory and accelerates CSD in young rats. In contrast, PE reverted the unfavorable effects of IF. The brain effects of IF and PE at younger ages are recommended for study.

Effect of neonatal melatonin administration on behavioral and brain electrophysiological and redox imbalance in rats.

Introduction: Melatonin (MLT) reportedly has beneficial effects in neurological disorders involving brain excitability (e.g., Epilepsy and Migraine) and behavioral patterns (e.g., Anxiety and Depression). This study was performed to investigate, in the developing rat brain, the effect of early-in-life administration of two different doses of exogenous MLT on behavioral (anxiety and memory) and electrophysiological (CSD analysis) aspects of brain function. Additionally, brain levels of malondialdehyde (MDA) and superoxide dismutase (SOD), both cellular indicators of redox balance status, were evaluated. We hypothesize that MLT differentially affects the behavioral and CSD parameters as a function of the MLT dose. Materials and methods: Male Wistar rats received, from the 7th to the 27th postnatal day (PND), on alternate days, vehicle solution, or 10 mg/kg/or 40 mg/kg MLT (MLT-10 and MLT-40 groups), or no treatment (intact group). To perform behavioral and cognition analysis, from PND30 to PND32, they were tested in the open field apparatus, first for anxiety (PND30) and then for object recognition memory tasks: spatial position recognition (PND31) and shape recognition (PND32). On PND34, they were tested in the elevated plus maze. From PND36 to 42, the excitability-related phenomenon known as cortical spreading depression (CSD) was recorded, and its features were analyzed. Results: Treatment with MLT did not change the animals' body weight or blood glucose levels. The MLT-10 treatment, but not the MLT-40 treatment, was associated with behaviors that suggest less anxiety and improved memory. MLT-10 and MLT-40 treatments, respectively, decelerated and accelerated CSD propagation (speed of 2.86 ± 0.14 mm/min and 3.96 ± 0.16 mm/min), compared with the control groups (3.3 ± 0.10 mm/min and 3.25 ± 0.11 mm/min, for the intact and vehicle groups, respectively; p < 0.01). Cerebral cortex levels of malondialdehyde and superoxide dismutase were, respectively, lower and higher in the MLT-10 group but not in the MLT40 group. Conclusion: Our findings suggest that MLT intraperitoneal administration during brain development may differentially act as an antioxidant agent when administered at a low dose but not at a high dose, according to behavioral, electrophysiological, and biochemical parameters.

Potentiation of spontaneous and evoked cortical electrical activity after spreading depression: in vivo analysis in well-nourished and malnourished rats.

Cortical spreading depression (CSD) is influenced by brain excitability and is related to neurological diseases, such as epilepsy. In vitro evidence indicates that neuronal electrical activity is potentiated after CSD. Malnutrition can cause electrophysiological changes in the brain, both in animals and in humans. Here, we investigated in vivo whether CSD potentiates the amplitude of electrocorticogram (ECoG) and of transcallosal evoked responses in adult well-nourished (W), early-malnourished (M), and food-restricted rats. ECoG amplitudes were compared before and after CSD, at two parietal regions (designated the anterior and posterior regions). In the anterior region, post-CSD amplitudes of the ECoG waves were 13-23% higher (P < 0.05) than the pre-CSD values in all groups. In the posterior region, amplitudes increased 22% in the M group only (P < 0.05). In a fourth CSD-free group, ECoG amplitude did not change during the four recording hours. Transcallosal electrically evoked cortical responses also increased 21.5 ± 9.6% and 41.8 ± 28.5%, after CSD, in the W and M conditions, respectively, as compared to pre-CSD values. The data support the hypothesis of an in vivo CSD potentiation on cortical excitability as recorded by spontaneous and evoked electrical activity and modulation by nutritional status.