Development of an experimental model of epilepsy in rats exposed to ozone

Non-invasive sensory neuromodulation in epilepsy: Updates and future perspectives

Epilepsy, one of the most common neurological disorders, often is not well controlled by current pharmacological and surgical treatments. Sensory neuromodulation, including multi-sensory stimulation, auditory stimulation, olfactory stimulation, is a kind of novel noninvasive mind-body intervention and receives continued attention as complementary safe treatment of epilepsy. In this review, we summarize the recent advances of sensory neuromodulation, including enriched environment therapy, music therapy, olfactory therapy, other mind-body interventions, for the treatment of epilepsy based on the evidence from both clinical and preclinical studies. We also discuss their possible anti-epileptic mechanisms on neural circuit level and propose perspectives on possible research directions for future studies.

The effects of weather on pediatric seizure: A single-center retrospective study (2005-2015)

BACKGROUND

Several studies have reported an association between seizure and the weather. However, reports are conflicting. Thus, we investigated whether emergency department visits due to seizure are affected by weather.

METHODS

We retrospectively analyzed 108,628 emergency department visits to Samsung Changwon Hospital by pediatric patients from January 2005 to December 2015. Among them, there were 3484 (3.2%) visits for any type of seizure. Seizures were categorized as febrile seizure, afebrile seizure, epilepsy, or status epilepticus. We used a distributed lag non-linear model with quasi-Poisson distribution to investigate the association between weather and pediatric seizure.

RESULTS

During this 11-year study period, over the half of total pediatric seizure patients were febrile seizure (53.5%) and the proportion for status epilepticus were the lowest (5.9%). Mean of mean temperature and diurnal temperature range were 14.7°C and 8.3°C. Mean humidity was 62.1%, mean of atmospheric pressure was 1015.5hPa and mean of sunshine was 6.3Hr. When considering the overall 0-15days lagged effect of weather, only mean temperature was significantly associated with emergency department visits. At lower temperatures, the number of emergency department visits increases and decreases at higher temperatures. All 4 types of seizure also showed similar patterns. In particular, only visits of febrile seizure were significantly associated with mean temperature.

CONCLUSION

We investigated the association weather and pediatric seizure by considering 0-15day lags. In particular, low mean temperature increase the emergency department visits for pediatric seizure and high mean temperature decrease the pediatric seizure. In addition, only febrile seizure of 4 seizure types was affected by mean average temperature.

Methylmercury: a potential environmental risk factor contributing to epileptogenesis

Epilepsy or seizure disorder is one of the most common neurological diseases in humans. Although genetic mutations in ion channels and receptors and some other risk factors such as brain injury are linked to epileptogenesis, the underlying cause for the majority of epilepsy cases remains unknown. Gene-environment interactions are thought to play a critical role in the etiology of epilepsy. Exposure to environmental chemicals is an important risk factor. Methylmercury (MeHg) is a prominent environmental neurotoxicant, which targets primarily the central nervous system (CNS). Patients or animals with acute or chronic MeHg poisoning often display epileptic seizures or show increased susceptibility to seizures, suggesting that MeHg exposure may be associated with epileptogenesis. This mini-review highlights the effects of MeHg exposure, especially developmental exposure, on the susceptibility of humans and animals to seizures, and discusses the potential role of low level MeHg exposure in epileptogenesis. This review also proposes that a preferential effect of MeHg on the inhibitory GABAergic system, leading to disinhibition of excitatory glutamatergic function, may be one of the potential mechanisms underlying MeHg-induced changes in seizure susceptibility.

Prenatal ozone exposure abolishes stress activation of Fos and tyrosine hydroxylase in the nucleus tractus solitarius of adult rat

Ozone (O3) is widely distributed in the environment, with high levels of air pollution. However, very few studies have documented the effects on postnatal development of O3 during pregnancy. The long-term effects of prenatal O3 exposure in rats (0.5 ppm 12 h/day from embryonic day E5 to E20) were evaluated in the adult nucleus tractus solitarius (NTS) regulating respiratory control. Neuronal response was assessed by Fos protein immunolabeling (Fos-IR), and catecholaminergic neuron involvement by tyrosine hydroxylase (TH) labeling (TH-IR). Adult offspring were analyzed at baseline and following immobilization stress (one hour, plus two hours' recovery); immunolabeling was observed by confocal microscopy. Prenatal O3 increased the baseline TH gray level per cell (p < 0.001). In contrast, the number of Fos-IR cells, Fos-IR/TH-IR colabeled cells and proportion of TH double-labeled with Fos remained unchanged. After stress, the TH gray level (p < 0.001), number of Fos-IR cells (p < 0.001) and of colabeled Fos-IR/TH-IR cells (p < 0.05) and percentage of colabeled Fos-IR/TH-IR neurons against TH-IR cells (p < 0.05) increased in the control group. In prenatal-O3 rats, immobilization stress abolished these increases and reduced the TH gray level (p < 0.05), indicating that prenatal O3 led to loss of adult NTS reactivity to stress. We conclude that long-lasting sequelae were detected in the offspring beyond the prenatal O3 exposure. Prenatal O3 left a print on the NTS, revealed by stress. Disruption of neuronal plasticity to new challenge might be suggested.

Prenatal exposure to ozone disrupts cerebellar monoamine contents in newborn rats

Ozone (O3) is widely distributed in environments with high levels of air pollution. Since cerebellar morphologic disruptions have been reported with prenatal O3 exposure, O3 may have an effect on some neurotransmitter systems, such as monoamines. In order to test this hypothesis, we used 60 male rats taken from either, mothers exposed to 1 ppm of O3 during the entire pregnancy, or from mothers breathing filtered and clean air during pregnancy. The cerebellum was extracted at 0, 5, and 10 postnatal days. Tissues were processed in order to analyze by HPLC, dopamine (DA) levels, 3,4 dihydroxyphenilacetic acid (DOPAC) and homovanillic acid (HVA), norepinephrine (NA), serotonin, and 5-hydroxy-indole-acetic acid (5-HIAA) contents. Results showed a decrease of DA, NA, DOPAC and HVA mainly in 0 and 5 postnatal days. There were no changes in 5-HT levels, and 5-HIAA showed an increase after 10 postnatal days. DOPAC + HVA/DA ratio showed changes in 0 and 10 postnatal days, while 5-HIAA/5-HT ratio showed a slight decrease in 0 days. The data suggest that prenatal O3 exposure disrupts the cerebellar catecholamine system rather than the indole-amine system. Disruptions in cerebellar NA could lead to ataxic symptoms and also could limit recovery after cortical brain damage in adults. These finding are important given that recovery mechanisms observed in animals are also observed in humans.

Brain thiobarbituric acid-reactive substances in rats after short periods of ozone exposure

It has been proposed that molecules derived from reactions that occur between the ozone and the lung tissue mediate nonpulmonary effects caused by ozone exposure. Free radicals are among those proposed molecules that flow throughout the bloodstream to other organs producing lipid peroxidation. In order to elucidate on aspect of ozone toxicity mechanisms, we measured the thiobarbituric acid-reactive products (TBARS), as an index of lipid peroxidation, in a variety of brain regions in rats exposed to 1 ppm of ozone for 1, 3, 6, and 9h. Another group exposed to 9h of O(3) plus 3h of clean-air exposure was also included. The results showed an important increase in TBARS content in all the studied structures. Such effect seems to be transient. These findings indicates that acute ozone exposure can produce cerebral peroxidation as it has been found in rats exposed chronically, suggesting an involvement of free radicals in brain effects of ozone exposure.

Ozone exposure alters 5-hydroxy-indole-acetic acid contents in dialysates from dorsal raphe and medial preoptic area in freely moving rats. Relationships with simultaneous sleep disturbances

Ozone (O3) has been reported to affect sleep patterns and also striatal and mesencephalic contents of 5-hydroxy-indole-acetic acid (5-HIAA) in rats. The aim of this work was to elucidate the effects of O3 exposure in rats upon extracellular 5-HIAA levels in the dorsal raphe (DR) and the hypothalamic medial preoptic area (MPO), two structures involved in sleep-wake homeostasis. Exposure to O3 followed a bell-shaped diurnal pattern, similar to that observed in cities with high air pollution levels. The highest O3 concentration employed was 0.5 ppm. Simultaneous polygraphic records were performed to evaluate the concomitant effects of this exposure model on sleep patterns. Results showed that extracellular 5-HIAA levels increased by 28% in the DR (P=0.0213) while paradoxical sleep (PS) decreased by 56% (P=0.0000) during the light O3 exposure phase. A decrease of 32% in 5-HIAA levels in the MPO (P=0.0450), and of 22% in slow wave sleep (SWS) (P=0.0002) and an increase of 21% in wakefulness (P=0.0430) during the dark post-exposure (Dpost) phase were also observed. We propose that the decrease in PS is the behavioral expression of disruptions of serotonergic DR modulation and, that post-exposure effects observed in the MPO can be explained on the basis of the hypothalamic role in the sleep-wake cycle.

'Sensitivity syndromes' related to radiation exposures

The primary health effects of radiation are traditionally believed to result from cellular genetic damage. These effects are believed to result in a statistically detectable increase in the induction of cancer in exposed populations. A significant number of residents of areas affected by the Chernobyl disaster and workers involved in the clean-up ('liquidators') have reported debilitating physical illnesses that cannot be easily explained by a genetic effect. This paper presents results of a literature search that strongly suggests that a previously unrecognized neural pathway may be responsible for the induction of these debilities. In addition, a common link between radiation and chemical sensitivity syndromes may now be identified.