Malnutrition and REM-sleep Deprivation Modulate in Rats the Impairment of Spreading Depression by a Single Sub-convulsing Dose of Pilocarpine

Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit

In the midst of concerns for potential neurodevelopmental effects after surgical anesthesia, there is a growing awareness that children who require sedation during critical illness are susceptible to neurologic dysfunctions collectively termed pediatric post-intensive care syndrome, or PICS-p. In contrast to healthy children undergoing elective surgery, critically ill children are subject to inordinate neurologic stress or injury and need to be considered separately. Despite recognition of PICS-p, inconsistency in techniques and timing of post-discharge assessments continues to be a significant barrier to understanding the specific role of sedation in later cognitive dysfunction. Nonetheless, available pediatric studies that account for analgesia and sedation consistently identify sedative and opioid analgesic exposures as risk factors for both in-hospital delirium and post-discharge neurologic sequelae. Clinical observations are supported by animal models showing neuroinflammation, increased neuronal death, dysmyelination, and altered synaptic plasticity and neurotransmission. Additionally, intensive care sedation also contributes to sleep disruption, an important and overlooked variable during acute illness and post-discharge recovery. Because analgesia and sedation are potentially modifiable, understanding the underlying mechanisms could transform sedation strategies to improve outcomes. To move the needle on this, prospective clinical studies would benefit from cohesion with regard to datasets and core outcome assessments, including sleep quality. Analyses should also account for the wide range of diagnoses, heterogeneity of this population, and the dynamic nature of neurodevelopment in age cohorts. Much of the related preclinical evidence has been studied in comparatively brief anesthetic exposures in healthy animals during infancy and is not generalizable to critically ill children. Thus, complementary animal models that more accurately "reverse translate" critical illness paradigms and the effect of analgesia and sedation on neuropathology and functional outcomes are needed. This review explores the interactive role of sedatives and the neurologic vulnerability of critically ill children as it pertains to survivorship and functional outcomes, which is the next frontier in pediatric intensive care.

Undernutrition - thirty years of the Regional Basic Diet: the legacy of Naíde Teodósio in different fields of knowledge

Undernutrition is characterized by an imbalance of essential nutrients with an insufficient nutritional intake, a disorder in which the clinical manifestations in most cases are the result of the economic and social context in which the individual lives. In 1990, the study by the medical and humanitarian Naíde Teodósio (1915-2005) and coworkers, which formulated the Regional Basic Diet (RBD) model for inducing undernutrition, was published. This diet model took its origin from the observation of the dietary habits of families that inhabited impoverished areas from the Pernambuco State. RBD mimics an undernutrition framework that extends not only to the Brazilian population, but to populations in different regions worldwide. The studies based on RBD-induced deficiencies provide a better understanding of the impact of undernutrition on the pathophysiological mechanisms underlying the most diverse prevalent diseases. Indexed papers that are analyzed in this review focus on the importance of using RBD in different areas of knowledge. These papers reflect a new paradigm in translational medicine: they show how the study of pathology using the RBD model in animals over the past 30 years has and still can help scientists today, shedding light on the mechanisms of prevalent diseases that affect impoverished populations.

Environmental enrichment reduces brain excitability in adult rats overnourished during lactation

OBJECTIVE

This study aimed to analyze whether exposure to environmental enrichment (EE) during the juvenile phase of life interferes with the electrical activity of the adult rat brain. In addition, the present research also investigated whether this putative effect on brain electrical activity could be affected by prior overnutrition during lactation. Electrophysiology was measured through cortical spreading depression (CSD), a phenomenon related to brain excitability.

METHODS

Wistar rats were suckled in litters of either nine or three pups, forming the nourished (N) or overnourished (ON) groups, respectively. At 36 days old, half of the animals from each nutritional condition were exposed to EE. The other half was kept in the standard environment (SE). At 90-120 days of life, each animal was anesthetized for CSD recordings.

RESULTS

Overnutrition during lactation caused increases (p < 0.05) in body and brain weights. The EE decelerated CSD propagation velocity regardless of nutritional state during lactation (p < 0.001). The CSD deceleration in the N-EE group was 23.8% and in the ON-EE group was 15% in comparison with the N-SE and ON-SE groups, respectively.

CONCLUSION

Our data demonstrated that EE exposure in the juvenile phase of the rat's life reduced brain excitability, and this effect was observed even if animals were overnourished during lactation. An EE could be considered an adjuvant therapeutic resource to modulate brain excitability.

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.

Pilocarpine/ascorbic acid interaction in the immature brain: Electrophysiological and oxidative effects in well-nourished and malnourished rats

Ascorbic acid (AA) administration has been associated with neuroprotection against oxidative stress, although at high doses it can facilitate oxidation and acts like a proconvulsing drug. The pilocarpine-induced epilepsy model has been widely studied. However, less is known about the effects of sub-convulsive doses of pilocarpine on brain activity in immature animals under normal or deficient nutritional conditions. Herein, we investigated the effects of chronic pilocarpine administration in a sub-convulsive dose, with or without AA, on the excitability-related phenomenon denominated as cortical spreading depression (CSD) and levels of lipid peroxidation-induced malondialdehyde in well-nourished and malnourished rats. At postnatal days 7-28, rats received no gavage treatment (naïve group), saline (vehicle group), 45 mg/kg/d of pilocarpine and/or 120 mg/kg/d of AA. CSD propagation and malondialdehyde levels were analyzed at 34-40 days. The pilocarpine group presented with lower CSD velocities, while AA groups exhibited higher CSD velocities and augmented malondialdehyde levels compared with controls. The co-administration of AA partially antagonized the pilocarpine CSD effects, but did not revert it to control levels. Malnutrition increased CSD amplitude and velocity in comparison to the well-nourished condition. The electrocorticogram (ECoG) amplitude increased after CSD (ECoG potentiation) when compared with the baseline amplitude before CSD. However, no intergroup difference was observed in this CSD-related ECoG potentiation. The results support the hypothesis of a pilocarpine/ascorbic acid interaction in the immature rat brain and might help further the understanding of this interaction on neuronal electrical activity and oxidative stress.

Systematic review of the pharmacological agents that have been tested against spreading depolarizations

Spreading depolarization (SD) occurs alongside brain injuries and it can lead to neuronal damage. Therefore, pharmacological modulation of SD can constitute a therapeutic approach to reduce its detrimental effects and to improve the clinical outcome of patients. The major objective of this article was to produce a systematic review of all the drugs that have been tested against SD. Of the substances that have been examined, most have been shown to modulate certain SD characteristics. Only a few have succeeded in significantly inhibiting SD. We present a variety of strategies that have been proposed to overcome the notorious harmfulness and pharmacoresistance of SD. Information on clinically used anesthetic, sedative, hypnotic agents, anti-migraine drugs, anticonvulsants and various other substances have been compiled and reviewed with respect to the efficacy against SD, in order to answer the question of whether a drug at safe doses could be of therapeutic use against SD in humans.

Sexual differentiation of cortical spreading depression propagation after acute and kindled audiogenic seizures in the Wistar audiogenic rat (WAR)

SUMMARY

Brain excitability diseases like epilepsy constitute one factor that influences brain electrophysiological features. Cortical spreading depression (CSD) is a phenomenon that can be altered by changes in brain excitability. CSD propagation was presently characterized in adult male and female rats from a normal Wistar strain and from a genetically audiogenic seizure-prone strain, the Wistar audiogenic rat (WAR), both previously submitted (RAS(+)), or not (RAS(-)), to repetitive acoustic stimulation, to provoke audiogenic kindling in the WAR-strain. A gender-specific change in CSD-propagation was found. Compared to seizure-resistant animals, in the RAS(-) condition, male and female WARs, respectively, presented CSD-propagation impairment and facilitation, characterized, respectively, by lower and higher propagation velocities (P<0.05). In contraposition, in the RAS(+) condition, male and female WARs displayed, respectively, higher and lower CSD-propagation rates, as compared to the corresponding controls. In some Wistar and WAR females, we determined estrous cycle status on the day of the CSD-recording as being either estrous or diestrous; no cycle-phase-related differences in CSD-propagation velocities were detected. In contrast to other epilepsy models, such as Status Epilepticus induced by pilocarpine, despite the CSD-velocity reduction, in no case was CSD propagation blocked in WARs. The results suggest a gender-related, estrous cycle-phase-independent modification in the CSD-susceptibility of WAR rats, both in the RAS(+) and RAS(-) situation.

Differential effects of chronic partial sleep deprivation and stress on serotonin-1A and muscarinic acetylcholine receptor sensitivity

Disrupted sleep and stress are often linked to each other, and considered as predisposing factors for psychopathologies such as depression. The depressed brain is associated with reduced serotonergic and enhanced cholinergic neurotransmission. In an earlier study, we showed that chronic sleep restriction by forced locomotion caused a gradual decrease in postsynaptic serotonin-1A receptor sensitivity, whilst chronic forced activity alone, with sufficient sleep time, did not affect receptor sensitivity. The first aim of the present study was to examine whether the sleep loss-induced change in receptor sensitivity is mediated by adrenal stress hormones. The results show that the serotonin-1A receptor desensitization is independent of adrenal hormones as it still occurs in adrenalectomized rats. The second aim of the study was to establish the effects of sleep restriction on cholinergic muscarinic receptor sensitivity. While sleep restriction affected muscarinic receptor sensitivity only slightly, forced activity significantly hypersensitized the muscarinic receptors. This hypersensitization is because of the stressful nature of the forced activity protocol as it did not occur in adrenalectomized rats. Taken together, these data confirm that sleep restriction may desensitize the serotonin-1A receptor system. This is not a generalized effect as sleep restriction did not affect the sensitivity of the muscarinic cholinergic receptor system, but the latter was hypersensitized by stress. Thus, chronic stress and sleep loss may, partly via different pathways, change the brain into a direction as it is seen in mood disorders.

Serotonin and 5-hydroxy-indole-acetic acid contents in dorsal raphe and suprachiasmatic nuclei in normal, malnourished and rehabilitated rats under 24 h of sleep deprivation

It has been discussed that serotonin (5-HT) could be involved in the effects of sleep deprivation (SD) and/or malnutrition (M) on the sleep-wake cycle. The aim of this work was to study the effects of the M, SD and its interaction on 5-HT and 5-hydroxy-indole-acetic acid (5-HIAA) contents in the dorsal raphe (DR) and the suprachiasmatic nuclei (SCN), two sleep-wake cycle regulators. Forty-eight puppets rats were obtained from mothers fed with low or normal casein diet. They were allocated in 3 groups (n=16 each): prenatal/postnatal casein malnutrition (6/6%), prenatal casein malnutrition/nutritional casein rehabilitation (6/25%) and prenatal/postnatal casein well-nourished state (25/25%). When rats were 60 days old, 24 animals were exposed to sleep deprivation by means of forced locomotion during 24 h. The remaining 24 were kept under normal conditions of sleep-wake cycle. Then, all animals were sacrificed by decapitation. DR and SCN were dissected and processed to determine the 5-HT and 5-HIAA contents by means of HPLC. It was observed that 6/6% rats showed a 5-HT increase (DR p<0.011; SCN p<0.019) as well as in SD (DR p<0.0008; SCN p<0.0009) with respect to 25/25% rats. No differences were found in 6/25% rats. Therefore, 5-HIAA decreased significantly in both nuclei in all the groups, notably in M+SD animals (DR p<0.001; SCN p<0.001). We conclude that the sleep-wake cycle disruptions produced by chronic M and SD are mediated in part by a synergistic effect on 5-HT in the DR-SCN pathway, perhaps due to a delay in the development of such brain structures.

Fluoxetine inhibits cortical spreading depression in weaned and adult rats suckled under favorable and unfavorable lactation conditions

Wistar rats (n = 58) were injected subcutaneously during the lactation period with fluoxetine (5, 10, 20 or 40 mg/kg/day) and cortical spreading depression (SD) was recorded immediately after weaning (25-30 days of life). An additional group (10 mg/kg; n = 8) was SD-recorded at 60-70 days. As compared to the saline-injected (n = 24) or "ingenuous" (n = 16) controls, fluoxetine dose-dependently reduced (P < 0.05) SD-velocities in the young rats by 4, 6, 16 and 15%, respectively, and in adult rats by 13%. In another experiment (26 adult rats), topical cortical application of fluoxetine (5 and 10 mg/ml solutions over the intact dura-mater for 10 min; n = 12 and 14, respectively) dose-dependently reduced SD-velocity (7.6% and 43.3% maximal reductions; P < 0.05). SD-propagation was blocked in 4 out of the 14 W-rats topically treated with the highest fluoxetine concentration (10 mg/ml). This topical fluoxetine effect was reverted after flushing the treated region with saline. In additional, 58 early-malnourished rats, fluoxetine applied during the suckling period (10 mg/kg/day, s.c.) and topically (10 mg/ml) also reduced (P < 0.05) SD-velocities by 18 and 22% for the systemic treatment (young and adult animals, respectively) and by 22.4% for the topical one. The present fluoxetine action supports the hypothesis of an antagonistic serotoninergic influence on SD, as previously suggested in experiments using other serotoninergic drugs. Data also suggest that early malnutrition does not greatly affect fluoxetine effects on SD.