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.

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.

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.

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.

Effects of maternal low-protein diet and spontaneous physical activity on the transcription of neurotrophic factors in the placenta and the brains of mothers and offspring rats.

Maternal protein restriction and physical activity can affect the interaction mother-placenta-fetus. This study quantified the gene expression of brain-derived neurotrophic factor (BDNF), neurothrophin 4, tyrosine kinase receptor B (TrkB/NTRK2), insulin-like growth factor (IGF-1), and insulin-like growth factor receptor (IGF-1r) in the different areas of mother's brain (hypothalamus, hippocampus, and cortex), placenta, and fetus' brain of rats. Female Wistar rats (n = 20) were housed in cages containing a running wheel for 4 weeks before gestation. According to the distance spontaneously traveled daily, rats were classified as inactive or active. During gestation, on continued access to the running wheel, active and inactive groups were randomized to receive normoprotein diet (18% protein) or a low-protein (LP) diet (8% protein). At day 20 of gestation, gene expression of neurotrophic factors was analyzed by quantitative polymerase chain reaction in different brain areas and the placenta. Dams submitted to a LP diet during gestation showed upregulation of IGF-1r and BDNF messenger RNA in the hypothalamus, IGF-1r and NTRK2 in the hippocampus, and BDNF, NTRK2, IGF-1 and IGF-1r in the cortex. In the placenta, there was a downregulation of IGF-1. In the brain of pups from mothers on LP diet, IGF-1r and NTRK2 were downregulated. Voluntary physical activity attenuated the effects of LP diet on IGF-1r in the hypothalamus, IGF-1r and NTRK2 in the hippocampus, IGF-1 in the placenta, and NTRK2 in the fetus' brain. In conclusion, both maternal protein restriction and spontaneous physical activity influence the gene expression of BDNF, NTRK2, IGF-1, and IGF-1r, with spontaneous physical activity being able to normalize in part the defects caused by protein restriction during pregnancy.

Valeriana officinalis Counteracts Rotenone Effects on Spreading Depression in the Rat Brain in vivo and Protects Against Rotenone Cytotoxicity Toward Rat Glioma C6 Cells in vitro.

Astrocytes can protect neurons against oxidative stress and excitability-dependent disorders, such as epilepsy. Valeriana officinalis has been used as anticonvulsant and can exert an antioxidant effect, which may underlie its opposing action against the toxic effects of the pesticide rotenone. We investigated the V. officinalis /rotenone interaction in the cortical spreading depression (CSD), a phenomenon that depends upon brain excitability (in vivo model). In addition, we analyzed the protective action of V. officinalis against the cytotoxic effects of rotenone in cultures of rat C6 glioma cells (in vitro model). For the CSD study, Wistar rats received either V. officinalis (250 mg/kg/day via gavage for 15 days; n = 8) or 10 mg/kg/day rotenone via subcutaneous injections for 7 days (n = 7), or they received both substances (n = 5). Two control groups received either saline (vehicle for V. officinalis; n = 8) or 1% Tween-80 aqueous solution (vehicle for rotenone; n = 9). After treatment, CSD was recorded for 4 h. The rotenone- and V. officinalis-treated groups presented, respectively, with lower (2.96 ± 0.14 mm/min), and higher CSD propagation velocity (3.81 ± 0.10 mm/min) when compared with the controls (Tween-80, 3.37 ± 0.06 mm/min and saline, 3.35 ± 0.08 mm/min; p < 0.05). The rotenone plus V. officinalis-treated group displayed a CSD velocity (3.38 ± 0.07 mm/min) that was similar to controls. In line with these results, in vitro experiments on rat glioma C6 cells revealed a protective effect (MTT assay) of V. officinalis against rotenone-induced cytotoxicity. These results suggest the therapeutic potential of V. officinalis for treating neurological diseases involving redox imbalance and astrocyte dysfunction.

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.

Taurine/Pilocarpine Interaction in the Malnourished Rat Brain: A Behavioral, Electrophysiological, and Immunohistochemical Analysis.

This study aimed to evaluate the possible protective role of taurine on anxiety-like behavior, brain electrical activity and glial cell immunoreactivity in well-nourished and malnourished rats that were treated with a subconvulsing dose of pilocarpine. Newborn Wistar rats were subjected to normal or unfavorable lactation conditions, represented by the suckling of litters with 9 or 15 pups, resulting in well-nourished and malnourished animals, respectively. Each nutritional group was split into five subgroups that were treated from postnatal day (PND) 35 to 55 with 300 mg/kg/day of taurine + 45 mg/kg/day of pilocarpine (group T + P), taurine only (group T), pilocarpine only (group P), vehicle control (group V), or not treated control (group naïve; Nv). At PND56-58, the groups were subjected to the elevated plus-maze behavioral tests. Glycemia was measured on PND59. Between PND60 and PND65, the cortical spreading depression (CSD) was recorded in the cerebral cortex, and the levels of malondialdehyde and microglial and astrocyte immunoreactivity were evaluated in the cortex and hippocampus. Our data indicate that treatment with taurine and pilocarpine resulted in anxiolytic-like and anxiogenic behavior, respectively, and that nutritional deficiency modulated these effects. Both treatments decelerated CSD propagation and modulated GFAP- and Iba1-containing glial cells. Pilocarpine reduced body weight and glycemia, and administration of taurine was not able to attenuate the effects of pilocarpine. The molecular mechanisms underlying taurine action on behavioral and electrophysiological parameters in the normal and altered brain remain to be further explored.

Stereological Analysis of Early Gene Expression Using Egr-1 Immunolabeling After Spreading Depression in the Rat Somatosensory Cortex.

Early growth response-1 (Egr-1), defined as a zinc finger transcription factor, is an upstream master switch of the inflammatory response, and its expression can be used to investigate the spatial and temporal extent of inflammatory changes in the brain. Cortical spreading depression (CSD) is characterized as a slowly propagating (2-5 mm/min) depolarization wave through neurons and astrocytes in humans that contributes to migraines and possibly to other brain pathologies. In rodents, CSD can be induced experimentally, which involves unilateral depolarization that is associated with microglial and astrocyte responses. The impact of CSD on structures beyond the affected hemisphere has not been explored. Here, we used an optical fractionator method to investigate potential correlations between the number of and period of the eletrophysiologic record of CSD phenomena and Egr-1 expression in ipsilateral and contralateral hemispheres. CSD was elicited by the restricted application of a 2% KCl solution over the left premotor cortex. Electrophysiological events were recorded using a pair of Ag/AgCl agar-Ringer electrodes for 2 or 6 h. An optical fractionator was applied to count the Egr-1 positive cells. We found that CSD increased Egr-1 expression in a time- and event-dependent manner in the ipsilateral/left hemisphere. Although CSD did not cross the midline, multiple CSD inductions were associated with an increased number of Egr-1 positive cells in the contralateral/right hemisphere. Thus, repeated CSD waves may have far reaching effects that are more global than previously considered possible. The mechanism of contralateral expression is unknown, but we speculate that callosal projections from the depolarized hemisphere may be related to this phenomenon.

Long lasting behavioral and electrophysiological action of early administration of guanosine: Analysis in the adult rat brain.

Guanosine (GUO) is a guanine-based purine that has been extensively described in the literature as an endogenous nucleoside with participation in brain cell signalling pathways. Here, we evaluated whether chronic treatment with exogenous guanosine during brain development altered behavioral and electrophysiological parameters in adulthood. Rat pups received a daily intraperitoneal injection of 10, 50 or 100 mg/ kg/day GUO, or saline solution or no treatment (naive group) from postnatal (P) day 7 to P27. At P 60-65 the animals were behaviorally tested in the Elevated Plus-Maze (EPM). On P90-100, the electrophysiological phenomenon known as cortical spreading depression (CSD) was recorded on the right cortical surface for 4 h. With the EPM task, GUO treatment was associated with a significant increase in rearing behavior and a non-significant trend towards anxiogenic behavior. In a dose-dependent manner, GUO significantly (p < 0.01) increased weight gain on P90, and reduced the CSD propagation velocity from 3.42 ±â€¯0.10 and 3.43 ±â€¯0.10 mm/min in the Naive and Vehicle controls, respectively, to 3.05 ±â€¯0.12 mm/min, 2.87 ±â€¯0.07 mm/min and 2.25 ±â€¯0.25 mm/min in the groups treated with 10, 50 and 100 mg/kg/d GUO, respectively. The results confirmed the hypothesis that the chronic treatment with GUO early in life modulates CSD and body weight. Data on CSD propagation suggest that, besides its suppressing action on glutamatergic transmission (via enhancement of astrocytic glutamate uptake), GUO might act as an antioxidant in the brain, a hypothesis that deserves further exploration.

Brain Aging and Electrophysiological Signaling: Revisiting the Spreading Depression Model.

As a consequence of worldwide improvement in health care, the aging portion of the human population has increased, now representing a higher proportion of the total population. This fact raises great concern regarding how to age while maintaining good brain function. Very often, alterations in brain electrophysiological signaling are associated with age-dependent functional disorders of the brain. Therefore, animal models suitable for the study of age-related changes in electrical activity of the brain can be very useful. Herein, we review changes in brain electrophysiological features as a function of age by analyzing studies in the rat brain on the phenomenon known as cortical spreading depression (CSD). Alterations in the brain's capability to generate and propagate CSD may be related to differences in the propensity to develop certain neurological diseases, such as epilepsy, stroke, and migraine, which can biunivocally interact with the aging process. In this review, we revisit ours and others' previous studies on electrophysiological features of the CSD phenomenon, such as its velocity of propagation and amplitude and duration of its slow negative DC shift, as a function of the animal age, as well as the interaction between age and other factors, such as ethanol consumption, physical exercise, and nutritional status. In addition, we discuss one relatively new feature through which CSD modulates brain signaling: the ability to potentiate the brain's spontaneous electrical activity. We conclude that the CSD model might importantly contribute to a better understanding of the aging/brain signaling relationship.

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.

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.

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.

Sub-Convulsing Dose Administration of Pilocarpine Reduces Glycemia, Increases Anxiety-Like Behavior and Decelerates Cortical Spreading Depression in Rats Suckled on Various Litter Sizes.

Epilepsy and malnutrition constitute two worldwide health problems affecting behavior and brain function. The cholinergic agonist pilocarpine (300-380 mg/kg; single administration) reproduces the human type of temporal lobe epilepsy in rats. Pilocarpine-induced epilepsy in rodents has been associated with glycemia, learning and memory and anxiety disturbances. Cortical spreading depression (CSD) is a neural response that has been linked to brain excitability disorders and its diseases, and has been shown to be antagonized by acute pilocarpine. This study aimed to further investigate the effect of chronic pilocarpine at a sub-convulsing dose on weight gain, blood glucose levels, anxiety-like behavior and CSD. In addition, we tested whether unfavorable lactation-induced malnutrition could modulate the pilocarpine effects. Wistar rats were suckled under normal size and large size litters (litters with 9 and 15 pups; groups L9 and L15, respectively). From postnatal days (PND) 35-55, these young animals received a daily intraperitoneal injection of pilocarpine (45 mg/kg/day), or vehicle (saline), or no treatment (naïve). On PND58, the animals were behaviorally tested in an open field apparatus. This was immediately followed by 6 h fasting and blood glucose measurement. At PND60-65, CSD was recorded, and its parameters (velocity of propagation, amplitude, and duration) were calculated. Compared to the control groups, pilocarpine-treated animals presented with reduced weight gain and lower glycemia, increased anxiety-like behavior and decelerated CSD propagation. CSD velocity was higher (p < 0.001) in the L15 groups in comparison to the corresponding groups in the L9 condition. The results demonstrate an influence of chronic (21-day) administration of a sub-convulsing, very low dose (45 mg/kg) of pilocarpine on CSD propagation, anxiety-like behavior, glycemia and body weight. Furthermore, data reinforce the hypothesis of a relationship between CSD and brain excitability. The lactation condition seems to differentially modulate these effects.

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.

Evidence of an inverse correlation between serotonergic activity and spreading depression propagation in the rat cortex.

Various neurological and psychiatric diseases lead to alterations in cortical serotonergic activity as one of their underlying processes. However, the electrophysiological implication of changes in serotonergic activity remains a matter of investigation. In this study, we investigated whether brain serotonergic activity influences the excitability-related phenomenon known as cortical spreading depression (CSD). CSD parameters (propagation velocity, and amplitude and duration of the DC-shift) was evaluated in rats that received two treatments that increased cortical serotonergic activity, electrical stimulation of the raphe nuclei and subcutaneous injection of a selective serotonin reuptake inhibitor, sumatriptan. A third group of rats was tested on a low-tryptophan diet rat model of serotonin depletion. Control rats for these three groups received, respectively, sham raphe stimulation, saline injection, and a tryptophan-supplemented diet. Compared to controls, electrical stimulation of the raphe nuclei and sumatriptan administration decelerated CSD and increased the duration of the negative DC-shift of CSD, whereas the low-tryptophan diet was associated with significantly accelerated CSD propagation and shortened DC-shift of CSD (p<0.05). We concluded that serotonergic neurons are very important for stabilizing the delicate equilibrium between excitatory and inhibitory neuronal influences that determines cortical excitability and CSD propagation. Our pharmacological, electrophysiological and dietary data suggest that cortical serotonergic activity negatively modulates CSD propagation in the rat cortex. Reduced central serotonergic activity, as can be observed in several neurological and psychiatric diseases, may constitute a pathological factor for increased sensitivity to CSD.