Effect of chronic protein malnutrition on experimentally induced seizures in the rat

Impaired growth and neurological abnormalities in branched-chain alpha-keto acid dehydrogenase kinase-deficient mice

The BCKDH (branched-chain alpha-keto acid dehydrogenase complex) catalyses the rate-limiting step in the oxidation of BCAAs (branched-chain amino acids). Activity of the complex is regulated by a specific kinase, BDK (BCKDH kinase), which causes inactivation, and a phosphatase, BDP (BCKDH phosphatase), which causes activation. In the present study, the effect of the disruption of the BDK gene on growth and development of mice was investigated. BCKDH activity was much greater in most tissues of BDK-/- mice. This occurred in part because the E1 component of the complex cannot be phosphorylated due to the absence of BDK and also because greater than normal amounts of the E1 component were present in tissues of BDK-/- mice. Lack of control of BCKDH activity resulted in markedly lower blood and tissue levels of the BCAAs in BDK-/- mice. At 12 weeks of age, BDK-/- mice were 15% smaller than wild-type mice and their fur lacked normal lustre. Brain, muscle and adipose tissue weights were reduced, whereas weights of the liver and kidney were greater. Neurological abnormalities were apparent by hind limb flexion throughout life and epileptic seizures after 6-7 months of age. Inhibition of protein synthesis in the brain due to hyperphosphorylation of eIF2alpha (eukaryotic translation initiation factor 2alpha) might contribute to the neurological abnormalities seen in BDK-/- mice. BDK-/- mice show significant improvement in growth and appearance when fed a high protein diet, suggesting that higher amounts of dietary BCAA can partially compensate for increased oxidation in BDK-/- mice. Disruption of the BDK gene establishes that regulation of BCKDH by phosphorylation is critically important for the regulation of oxidative disposal of BCAAs. The phenotype of the BDK-/- mice demonstrates the importance of tight regulation of oxidative disposal of BCAAs for normal growth and neurological function.

Malnutrition and childhood epilepsy in developing countries

A high prevalence of epilepsy in children is frequently found in developing countries. Though high rates of acquired brain injury may contribute, the possibility that malnutrition may lower seizure threshold has rarely been examined. This review suggests potential biochemical mechanisms that could adversely affect seizure threshold, particularly the effect of malnutrition on inhibitory neurotransmitters and electrolytes. Supporting evidence from animal research and epidemiological findings in children are discussed.

Chronic malnutrition caused by a corn-based diet lowers the threshold for pentylenetetrazol-induced seizures in rats

The incidence of epilepsy is high in developing countries where malnutrition is prevalent. Although malnutrition is not a direct cause of seizures, chronic malnutrition may predispose the brain to seizures. In large undernourished human groups from Latin America, the most common sources of food are corn and corn derivatives. We used a rat model of chronic malnutrition, in which corn tortillas were the only solid food intake, to study the possible influence of malnutrition at late stages of brain development on the dynamics of experimental seizures induced by pentylenetetrazole (PTZ). The threshold and does of PTZ required to produce seizures were greatly reduced in malnourished rats. The model of malnutrition used in the study imitates a form of malnutrition common among large numbers of humans. Our results suggest that chronic malnutrition early in life induces changes that lower the seizure threshold and leave the brain more susceptible to seizures. Whether this observation relates to the high incidence of epilepsy in underdeveloped countries remains to be determined.

Hypoxic-ischemic encephalopathy sustained in early postnatal life may result in permanent epileptic activity and an altered cortical convulsive threshold in rat

The aim of this study was to investigate whether the rat cerebral cortex, damaged by hypoxia-ischemia in early postnatal life, would show an increased seizure susceptibility and/or spontaneous epileptic discharges in adulthood. To that end 12-13-day-old Wistar rat pups were unilaterally exposed to hypoxic-ischemic conditions. After a recovery period of about 2.5 months, recording and stimulation electrodes were permanently implanted over the left and right fronto-parietal neocortex. Long-term recording of baseline electrocortical activity showed that only those animals that had incurred severe brain damage, as was reflected by the presence of a cortical infarction, ran a high risk of developing permanent epileptic activity. With the aid of the stimulation electrodes the initial threshold for localized seizure activity was found to be the same for the experimental and non-treated groups. However, when the kindling-like decline of this threshold was assessed by repeated testing over a 2-week period, the infarcted animals tended to a more rapid decline but a higher stabilization level than the non-infarcted and control animals.

Prenatal malnutrition and development of the brain

In this review, we have summarized various aspects as to how prenatal protein malnutrition affects development of the brain and have attempted to integrate several broad principles, concepts, and trends in this field in relation to our findings and other studies of malnutrition insults. Nutrition is probably the single greatest environmental influence both on the fetus and neonate, and plays a necessary role in the maturation and functional development of the central nervous system. Prenatal protein malnutrition adversely affects the developing brain in numerous ways, depending largely on its timing in relation to various developmental events in the brain and, to a lesser extent, on the type and severity of the deprivation. Many of the effects of prenatal malnutrition are permanent, though some degree of amelioration may be produced by exposure to stimulating and enriched environments. Malnutrition exerts its effects during development, not only during the so-called brain growth spurt period, but also during early organizational processes such as neurogenesis, cell migration, and differentiation. Malnutrition results in a variety of minimal brain dysfunction-type syndromes and ultimately affects attentional processes and interactions of the organism with the environment, in particular producing functional isolation from the environment, often leading to various types of learning disabilities. In malnutrition insult, we are dealing with a distributed, not focal, brain pathology and various developmental failures. Quantitative assessments show distorted relations between neurons and glia, poor formation of neuronal circuits and alterations of normal regressive events, including cell death and axonal and dendritic pruning, resulting in modified patterns of brain organization. Malnutrition insult results in deviations in normal age-related sequences of brain maturation, particularly affecting coordinated development of various cell types and, ultimately, affecting the formation of neuronal circuits and the commencing of activity of neurotransmitter cell types and, ultimately, affecting the formation of neuronal circuits and the commencing of activity of neurotransmitter systems. It is obvious that such diffuse type "lesions" can be adequately assessed only by interdisciplinary studies across a broad range of approaches, including morphological, biochemical, neurophysiological, and behavioral analyses.

Effects of postnatal electroshock convulsions on epileptogenesis of the amygdala and hippocampus in adult rats

Adult rats which received repeated electroshock convulsions (ESCs) during postnatal development underwent electrical kindling of the amygdala (AM) and hippocampus (HIPP). Completion of kindling, especially AM kindling, was significantly faster in the groups with ESCs from the neonatal to late infantile age than in the control group. It is discussed that especially the late infantile age in the postnatal development was supposed to play an important role in the faster kindling brought about by postnatal convulsions and that the faster kindling was due in part to abbreviation of the partial seizure process. However, the neonatal ESC group showed significantly delayed completion of HIPP kindling.

Effects of prenatal protein malnutrition on perforant path kindling in the rat

Rats born to dams fed either a 6% (malnourished) or 25% (control) casein diet during gestation were all fostered to lactating dams on the 25% casein diet 24 h after birth and were maintained on this diet throughout life following weaning. At 90-120 days of age electrographic and behavioral responses to electrical kindling of the medial perforant pathway were investigated in animals from both the straight 25% diet (designated 25%/25% for the pre- and postnatal periods) and the dietary rehabilitated (designated 6%/25% casein diet for the pre- and postnatal periods) groups. Animals of the dietary rehabilitated group (6%/25%) were found to: (1) require a significantly lower stimulus intensity to evoke afterdischarge activity in the ipsilateral dentate gyrus; (2) progress through the various behavioral stages of kindling in a markedly different manner from the 25%/25% group, and; (3) require significantly more daily kindling stimulations to attain the full motor convulsive stage indicative of the kindled state. These results indicate that dietary protein rehabilitation at birth is incapable of reversing or significantly ameliorating the effects of gestational protein deficiency on susceptibility to seizure activity and acquisition of the kindled state. These findings indicate that gestational protein deficiency results in long-lasting, if not permanent, changes in neuronal systems in the hippocampal formation which are involved in both the electrographic and behavioral correlates of the kindling process.

Decreased susceptibility to local anesthetics-induced convulsions after paradoxical sleep deprivation

The effect of 50% convulsant (CD50) and 50% lethal (LD50) doses of lidocaine, bupivacaine and pentylenetetrazol were determined in mice stressed by paradoxical sleep deprivation (PSD). The results showed a reduced mortality after high doses of local anesthetics and decreased seizure susceptibility induced by bupivacaine after 48 h and 72 h of PSD. On the other hand this stressful manipulation increased the susceptibility to pentylenetetrazol-induced convulsions. These data may suggest a different mechanism of action for these drugs. Possible alterations in drug metabolism or on aminergic transmission after PSD may be involved in the protection to the toxic effect of the local anesthetics.

Differences in antiepileptic drug efficacy in hippocampally kindled normal and microcephalic rats

The difference in antiepileptic drug efficacy was investigated in two groups of animals: 5 normal and 4 microcephalic rats. The latter were produced by a single i.p. injection of 30 mg/kg methylazoxymethanol acetate in the mother on the 15th day of gestation. Hippocampal kindling was performed to a seizure criterion in all animals followed by testing of the antiepileptic drugs vs placebo. Besides carbamazepine (CBZ), two new anticonvulsants were tested: (E)-2-[(alpha-amino)phenylmethylene]-benzo-[b]-thiophene-3(2H)-one (AF-CX 921) and its metabolite (E)-2-[alpha-amino)phenylmethylene]-benzo-[b]-thiophene-3(2H)-one- 1- oxide (AF-CX 1325). Frequency of occurrence and duration of afterdischarges and seizures were statistically examined. The duration of early afterdischarges (AD1) tended to be shorter in microcephalic than in normal animals in control and placebo periods. In contrast, during treatment with the antiepileptic drugs, AD1 durations were longer in microcephalic than in normal animals. This suggests that the drugs inhibited AD1 to a lesser extent in the microcephalics. Two other characteristics of EEG epileptic activity, focal spiking (FS) and late afterdischarges (AD2) also varied in the two groups. Both were significantly lower in occurrence in the microcephalic rats independent of treatment. Three types of behavioral manifestations were also examined: convulsive seizures (CS), epileptic behavior (EB) and quiet states (Q). The two groups of animals responded differently to the drugs with respect to Q and CS. In the microcephalics, AFCX 1325 and AFCX 921 were superior to CBZ, which in turn, was superior to placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of protein malnutrition on hippocampal kindling: electrographic and behavioral measures

Rats born to dams fed either a 6% (malnourished) or a 25% (control) casein diet during gestation and lactation and maintained on the diet of the dam after weaning were tested for electrographic and behavioral responses to electrically induced kindling of the CA1 field of the hippocampus beginning at 44 days of age. Animals in the 6% diet group had a significantly lower threshold to afterdischarge (AD), a significantly faster spread of AD activity to distal recording sites, significantly longer average duration of AD activity at all recording sites and a markedly altered behavioral progression toward seizure activity compared to control animals. These findings indicate that prenatal protein malnutrition results in hippocampal dysfunction as evidenced by both the electrographic and behavioral correlates of the kindling process. The data presented suggest that prenatal proteins malnutrition alters the response of hippocampal CA1 pyramids to electrical stimulation and that this alteration results in marked changes to both the electrographic and behavioral correlates of kindling.

Undernutrition induced by early pup separation delays the development of the thalamic reticular nucleus in rats

A Golgi-Cox study was conducted in neurons of the reticular and lateralis thalamic nuclei in normally and early undernourished Wistar rats at 12, 20, and 30 days of age. In a total of 630 neurons the cell body and the dendritic field areas, as well as the number of dendritic prolongations from camera lucida drawings were quantitated. A general and significant reduction in most reticular thalamic nucleus measurements of early-food-deprived rats was observed compared with control littermates. Additionally, reticular thalamic cells in both normal and neonatally underfed rats exhibited a progressive decline, particularly in cell body area with increasing age. In contrast, the lateral thalamic nucleus did not show significant differences between groups when similar neuronal measurements were carried out. The reticular thalamic nucleus is normally related to the control of sensory afferent transmission, and early food deprivation interferes with the growing process of this nucleus. Therefore the present data support the hypothesis that noxious perinatal environmental influences may result in a maturational deficiency of central nervous system modulatory mechanisms.

Malnutrition-induced changes of responses evoked in the rat prefrontal cortex as revealed by sensitivity to strychnine

Susceptibility to strychnine of somatosensory responses evoked in the prefrontal cortex was studied in normal and protein-malnourished rats in three groups. (a) The normal group was from mothers fed a 21% casein diet. (b) The prenatally malnourished group was from mothers fed a 6% casein diet during 5 weeks prior to mating and throughout gestation. (c) The postnatally malnourished group born from dams fed a 6% casein diet throughout the nursing period. At 45 days of age, sensitivity of the responses to 0.5% strychnine sulfate solution was tested by measuring changes in peak-to-peak amplitude. The results showed that cortical neurons of the postnatally protein-restricted group had decreased susceptibility to strychnine, indicating functional disturbances of glycinergic synapses.

Long-term effect of postnatal hypoxia on the seizure susceptibility in rats

The effects of postnatal hypoxia at ten days of age on the pentylenetetrazol (PTZ)-induced seizure and amygdaloid kindling were investigated in male adult rats. The rats with postnatal hypoxia were significantly more susceptible to PTZ and had a significantly more easily induced amygdaloid kindling with a rapid propagation of afterdischarges to the contralateral amygdala than the control group. Light microscopic examination in one adult rat brain with postnatal hypoxia revealed no abnormal histopathological changes. The present study suggests that the consequences of postnatal hypoxia in rats remain for a long time as enhancement in seizure susceptibility.

A single neonatal pentylenetetrazol or hyperthermia convulsion increases kindling susceptibility in the adult rat

Convulsions were induced in young rats (1-21 days) with pentylenetetrazol or hyperthermia. As adults, these animals were kindled electrically in the basolateral or cortical amygdala, the hippocampus, or the pyriform cortex. Fewer amygdala stimulations were required to evoke major motor seizures in subjects treated at 1, but not at 10 or 21 days of age. No further facilitation in kindling rate was observed in subjects receiving 3 convulsions on days 1, 3 and 5 or 1, 5 and 9. This facilitation of electrical kindling was limited to the amygdaloid sites. The results could not be attributed to gross brain damage or differential convulsion histories. This age-limited, structure-specific effect suggests that the amygdala may represent a unique seizure-generating system in the brain that is sensitive to neural alteration at particular times during development.

Facilitation of kindling in adult rats following neonatal exposure to lindane

Neonatal male rats were exposed to lindane or corn oil directly by gavage or indirectly by maternal exposure. All surviving offspring were implanted with amygdaloid electrodes 90 days after weaning. Amygdaloid kindling began 10 days later using standard procedures. Neonatal lindane-exposed rats kindled significantly faster (9.9 +/- 0.5 days) than control groups (11.2 +/- 0.5 days). Lindane-exposed rats tended to have longer and more severe seizures than did non-exposed rats on each trial during kindling acquisition. These findings demonstrate that high exposures of lindane during development can lead to enduring changes in the nervous system that facilitate adult kindling.

The effect of postnatal undernourishment on epileptiform kindling of dorsal hippocampus

Rats were undernourished postnatally from birth through 20 days of age. They were subsequently tested for susceptibility to motor seizures kindled in hippocampus in adulthood. Compared to littermate control animals the postnatally undernourished rats were more susceptible to the kindling treatment. We conclude that early postnatal undernourishment has a permanent effect on susceptibility of the hippocampus to electrically-induced seizures.

Developmental protein malnutrition: influences on the central nervous system of the rat

Our group has been carrying out interdisciplinary studies on the effects of prenatal and postnatal protein malnutrition on the developing rat brain. Anatomical, physiological, biochemical and behavioral approaches using the same animal model have revealed that protein malnutrition affects the brain at various levels, i.e., (1) anatomical, as revealed by Golgi findings of deranged dendritic trees on analysis of cortical and subcortical areas; (2) physiological, as revealed by delayed sleep pattern maturation, disturbances in seizure thresholds, slowing of sensory cortico-cortical and thalamocortical evoked potentials, and changed power in hippocampal theta activity; (3) biochemical, as revealed by marked increases in biogenic amines dating from birth, as well as modifications in tryptophan metabolism; and (4) behavioral, as revealed by various changes in responses to different kinds of aversive stimulation. Reversal studies have revealed that many changes are permanent and not amenable to nutritional rehabilitation even at birth, which is before the brain growth spurt in the rat. Our paradigm closely mimicks the human condition of low level, chronic protein undernutrition and thus reveals the underlying disturbances due to malnutrition. The dietary reversal studies are attempts at pin-pointing critical brain growth periods, beyond which recovery of functions is not possible.