Radon inhalation decreases DNA damage induced by oxidative stress in mouse organs via the activation of antioxidative functions

Radon inhalation decreases the level of lipid peroxide (LPO); this is attributed to the activation of antioxidative functions. This activation contributes to the beneficial effects of radon therapy, but there are no studies on the risks of radon therapy, such as DNA damage. We evaluated the effect of radon inhalation on DNA damage caused by oxidative stress and explored the underlying mechanisms. Mice were exposed to radon inhalation at concentrations of 2 or 20 kBq/m3 (for one, three, or 10 days). The 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels decreased in the brains of mice that inhaled 20 kBq/m3 radon for three days and in the kidneys of mice that inhaled 2 or 20 kBq/m3 radon for one, three or 10 days. The 8-OHdG levels in the small intestine decreased by approximately 20-40% (2 kBq/m3 for three days or 20 kBq/m3 for one, three or 10 days), but there were no significant differences in the 8-OHdG levels between mice that inhaled a sham treatment and those that inhaled radon. There was no significant change in the levels of 8-oxoguanine DNA glycosylase, which plays an important role in DNA repair. However, the level of Mn-superoxide dismutase (SOD) increased by 15-60% and 15-45% in the small intestine and kidney, respectively, following radon inhalation. These results suggest that Mn-SOD probably plays an important role in the inhibition of oxidative DNA damage.

Neurobehavioral effects of acute low-dose whole-body irradiation

Radiation exposure has multiple effects on the brain, behavior and cognitive functions. It has been reported that high-dose (>20 Gy) radiation-induced behavior and cognitive aberration partly associated with severe tissue destruction. Low-dose (<3 Gy) exposure can occur in radiological disasters and cerebral endovascular treatment. However, only a few reports analyzed behavior and cognitive functions after low-dose irradiation. This study was undertaken to assess the relationship between brain neurochemistry and behavioral disruption in irradiated mice. The irradiated mice (0.5 Gy, 1 Gy and 3 Gy) were tested for alteration in their normal behavior over 10 days. A serotonin (5-HT), Dopamine, gamma-Aminobutyric acid (GABA) and cortisol analysis was carried out in blood, hippocampus, amygdala and whole brain tissue. There was a significant decline in the exploratory activity of mice exposed to 3 Gy and 1 Gy radiation in an open field test. We observed a significant short-term memory loss in 3 Gy and 1 Gy irradiated mice in Y-Maze. Mice exposed to 1 Gy and 3 Gy radiation exhibited increased anxiety in an elevated plus maze (EPM). The increased anxiety and memory loss patterns were also seen in 0.5 Gy irradiated mice, but the results were not statistically significant. In this study we observed that neurotransmitters are significantly altered after irradiation, but the neuronal cells in the hippocampus were not significantly affected. This study suggests that the low-dose radiation-induced cognitive impairment may be associated with the neurochemical in low-dose irradiation and unlike the high-dose scenario might not be directly related to the morphological changes in the brain.

Whole-brain irradiation differentially modifies neurotransmitters levels and receptors in the hypothalamus and the prefrontal cortex

BACKGROUND

Whole-brain radiotherapy is a primary treatment for brain tumors and brain metastasis, but it also induces long-term undesired effects. Since cognitive impairment can occur, research on the etiology of secondary effects has focused on the hippocampus. Often overlooked, the hypothalamus controls critical homeostatic functions, some of which are also susceptible after whole-brain radiotherapy. Therefore, using whole-brain irradiation (WBI) in a rat model, we measured neurotransmitters and receptors in the hypothalamus. The prefrontal cortex and brainstem were also analyzed since they are highly connected to the hypothalamus and its regulatory processes.

METHODS

Male Wistar rats were exposed to WBI with 11 Gy (Biologically Effective Dose = 72 Gy). After 1 month, we evaluated changes in gamma-aminobutyric acid (GABA), glycine, taurine, aspartate, glutamate, and glutamine in the hypothalamus, prefrontal cortex, and brainstem according to an HPLC method. Ratios of Glutamate/GABA and Glutamine/Glutamate were calculated. Through Western Blott analysis, we measured the expression of GABAa and GABAb receptors, and NR1 and NR2A subunits of NMDA receptors. Changes were analyzed comparing results with sham controls using the non-parametric Mann-Whitney U test (p < 0.05).

RESULTS

WBI with 11 Gy induced significantly lower levels of GABA, glycine, taurine, aspartate, and GABAa receptor in the hypothalamus. Also, in the hypothalamus, a higher Glutamate/GABA ratio was found after irradiation. In the prefrontal cortex, WBI induced significant increases of glutamine and glutamate, Glutamine/Glutamate ratio, and increased expression of both GABAa receptor and NMDA receptor NR1 subunit. The brainstem showed no statistically significant changes after irradiation.

CONCLUSION

Our findings confirm that WBI can affect rat brain regions differently and opens new avenues for study. After 1 month, WBI decreases inhibitory neurotransmitters and receptors in the hypothalamus and, conversely, increases excitatory neurotransmitters and receptors in the prefrontal cortex. Increments in Glutamate/GABA in the hypothalamus and Glutamine/Glutamate in the frontal cortex indicate a neurochemical imbalance. Found changes could be related to several reported radiotherapy secondary effects, suggesting new prospects for therapeutic targets.

Low dose γ radiation enhances antidepressant effect of resveratrol: Behavioral and neurochemical studies

The low dose of radiation (LDR) has received growing attention for its beneficial neuroprotective effect. This study was designed to investigate the enhancing effect of LDR on the antidepressant potential of resveratrol against diazepam-induced depression in mice. Female mice divided into five groups; control, diazepam (2 mg/kg), LDR (0.5Gy) + diazepam, resveratrol (20 mg/kg) + diazepam, LDR + resveratrol+diazepam. Mice received diazepam showed depressive symptoms as evidenced by decreased locomotor activity in the open field and increased immobility time in the forced swimming and tail suspension tests integrated with a marked decline in biogenic amines (serotonin, norepinephrine, and dopamine) in brain tissues. These effects were ameliorated by LDR or resveratrol administration demonstrating an antidepressant activity. Interestingly, LDR triggered the antidepressant effect of resveratrol as it restored the changes in behavioral tests, neurotransmitters, and neuro-histoarchitecture. In conclusion, these findings suggested that LDR could be considered as a novel adjuvant that augmented the resveratrol antidepressant effect and might serve as a potential therapeutic approach for depression.

A standardized Hippophae extract (SBL-1) counters neuronal tissue injuries and changes in neurotransmitters: implications in radiation protection

CONTEXT

Effects of a radioprotective, standardized leaf extract (code SBL-1) from traditional medicinal plant, sea buckthorn [Hippophae rhamnoides L. (Elaeagnaceae)], on neurotransmitters and brain injuries in rats showing radiation-induced conditioned taste aversion (CTA), are not known. Understanding CTA in rats is important because its process is considered parallel to nausea and vomiting in humans.

OBJECTIVE

This study investigated the levels of neurotransmitters, antioxidant defences and histological changes in rats showing radiation CTA, and their modification by SBL-1.

MATERIALS AND METHODS

The inbred male Sprague-Dawley rats (age 65 days, weighing 190 ± 10 g) were used. Saccharin-preferring rats were selected using standard procedure and divided into groups. Group I (untreated control) was administered sterile water, group II was 60Co-γ-irradiated (2 Gy), and group III was administered SBL-1 before irradiation. Observations were recorded up to day 5.

RESULTS

Irradiation (2 Gy) caused (i) non-recoverable CTA (≥ 64.7 ± 5.0%); (ii) degenerative changes in cerebral cortex, amygdala and hippocampus; (iii) increases in brain dopamine (DA, 63.4%), norepinephrine (NE, 157%), epinephrine (E, 233%), plasma NE (103%) and E (160%); and (iv) decreases in brain superoxide dismutase (67%), catalase (60%) and glutathione (51%). SBL-1 treatment (12 mg/kg body weight) 30 min before irradiation (i) countered brain injuries, (ii) reduced CTA (38.7 ± 3.0%, day 1) and (iii) normalized brain DA, NE, E, superoxide dismutase, catalase and CTA from day 3 onwards.

DISCUSSION AND CONCLUSION

Radiation CTA was coupled with brain injuries, disturbances in neurotransmitters and antioxidant defences. SBL-1 pretreatment countered these disturbances, indicating neuroprotective action.

Ionizing radiation induces structural and functional damage on the molecules of rat brain homogenate membranes: a Fourier transform infrared (FT-IR) spectroscopic study

Humans can be exposed to ionizing radiation, due to various reasons, whose structural effects on biological membranes are not well defined. The current study aims to understand the ionizing radiation-induced structural and functional alterations in biomolecules of brain membranes using Fourier transform infrared (FT-IR) spectroscopy using rat animal models. For this purpose, 1000 cGy of ionizing radiation was specifically directed to the head of Sprague Dawley rats. The rats were decapitated after 24 h. The results revealed that the lipid-to-protein ratio decreased and that irradiation caused lipid peroxidation and increases in the amounts of olefinic =CH, carbonyl, and methylene groups of lipids. In addition, ionizing radiation induced a decrease in membrane fluidity, disordering of membrane lipids, strengthening of the hydrogen bonding of the phosphate groups of lipid head-groups, and weakening in the hydrogen bonding of the interfacial carbonyl groups of lipids. Radiation further caused significant decrements in the α-helix and turns, and significant increments in the β-sheet and random coil contents in the protein structure. Hierarchical cluster analyses, performed in the whole region (3030-1000 cm(-1)), lipid (3030-2800 cm(-1)), and protein (1700-1600 cm(-1)) regions separately, successfully differentiated the control and irradiated groups of rat brain membranes and showed that proteins in the membranes are affected more than lipids from the damages induced with ionizing radiation. As a result, the current study showed that FT-IR spectroscopy can be used successfully as a novel method to monitor radiation-induced alterations on biological membranes.

The effect of pulsed electromagnetic radiation from mobile phone on the levels of monoamine neurotransmitters in four different areas of rat brain

BACKGROUND

The use of mobile phones is rapidly increasing all over the world. Few studies deal with the effect of electromagnetic radiation (EMR) on monoamine neurotransmitters in the different brain areas of adult rat.

AIM

The aim of the present study was to investigate the effect of EMR on the concentrations of dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in the hippocampus, hypothalamus, midbrain and medulla oblongata of adult rats.

MATERIALS AND METHODS

Adult rats were exposed daily to EMR (frequency 1800 MHz, specific absorption rate 0.843 W/kg, power density 0.02 mW/cm2, modulated at 217 Hz) and sacrificed after 1, 2 and 4 months of daily EMR exposure as well as after stopping EMR for 1 month (after 4 months of daily EMR exposure). Monoamines were determined by high performance liquid chromatography coupled with fluorescence detection (HPLC-FD) using their native properties.

RESULTS

The exposure to EMR resulted in significant changes in DA, NE and 5-HT in the four selected areas of adult rat brain.

CONCLUSIONS

The exposure of adult rats to EMR may cause disturbances in monoamine neurotransmitters and this may underlie many of the adverse effects reported after EMR including memory, learning, and stress.

Exogenous melatonin modulates apoptosis in the mouse brain induced by high-LET carbon ion irradiation

The aim of this study was to investigate whether melatonin, a free radical scavenger and a general antioxidant, regulates the brain cell apoptosis caused by carbon ions in mice at the level of signal transduction pathway. Young Kun-Ming mice were divided into five groups: control group, irradiation group and three melatonin (1, 5, and 10 mg/kg daily for 5 days i.p.) plus irradiation-treated groups. An acute study was carried out to determine oxidative status, apoptotic cells, and mitochondrial membrane potential (ΔΨm) as well as pro- and anti-apoptotic protein levels in a mouse brain 12 hr after irradiation with a single dose of 4 Gy. In irradiated mice, a significant rise in oxidative stress and apoptosis (TUNEL positive) was accompanied by activated expression of Bax, cytochrome c, caspase-3, and decreased ΔΨm level. Melatonin supplementation was better able to reduce irradiation-induced oxidative damage marked by carbonyl or malondialdehyde content, and stimulate the antioxidant enzyme activities (superoxide dismutase and catalase) together with total antioxidant capacity. Moreover, administration with melatonin pronouncedly elevated the expression of Nrf2 which regulates redox balance and stress. Furthermore, melatonin treatment mitigated apoptotic rate, maintained ΔΨm, diminished cytochrome c release from mitochondria, down-regulated Bax/Bcl-2 ratio and caspase-3 levels, and consequently inhibited the important steps of irradiation-induced activation of mitochondrial pathway of apoptosis. Thus, we propose that the anti-apoptotic action with the alterations in apoptosis regulator provided by melatonin may be responsible at least in part for its antioxidant effect by the abolishing of carbon ion-induced oxidative stress along with increasing Nrf2 expression and antioxidant enzyme activity.

Pulsed high-intensity focused ultrasound enhances the relative permeability of the blood-tumor barrier in a glioma-bearing rat model

The use of pulsed high-intensity focused ultrasound (HIFU) with an ultrasound contrast agent (UCA) has been shown to disrupt the blood-brain barrier (BBB) noninvasively and reversibly in the targeted regions. This study evaluated the relative permeability of the blood-tumor barrier (BTB) after sonication by pulsed HIFU. Entry into the brain of chemotherapeutic agents is impeded by the BBB even though the permeability of this barrier may be partially reduced in the presence of a brain tumor. F98 glioma-bearing rats were injected intravenously with Evans blue (EB) with or without BTB disruption induced by pulsed HIFU. Sonication was applied at an ultrasound frequency of 1 MHz with a 5% duty cycle, and a repetition frequency of 1 Hz. The accumulation of EB in brain tumor and the tumor-to-contralateral brain ratio of EB were highest after pulsed HIFU exposure. Sonication followed by EB injection showed a tumor-to-contralateral brain ratio in the target tumors which was about 2 times that of the control tumors. This research demonstrates that pulsed HIFU enhances the relative permeability of the BTB in glioma- bearing rats. The results of this pilot study support the idea that further evaluation of other treatment strategies, such as HIFU exposure in addition to combined chemotherapy or repeated pulsed HIFU exposure to increase delivery of drugs into brain tumors, might be useful.

Transcranial optogenetic stimulation for functional mapping of the motor cortex

We developed a method that uses Channelrhodopsin-2 (ChR2) for transcranial optogenetic stimulation. This method is based on scanning a light beam over the brain, thereby photostimulating ChR2-expressing neurons in intact mice. As a proof of principle, we applied this technique to the motor cortex of transgenic mice expressing ChR2 in cortical pyramidal cells. Photostimulation induced limb movements that were time-locked with millisecond precision and could be induced at frequencies up to 20 Hz. By scanning this light beam, we could map the distribution of neurons associated with limb movement. With this approach we could simultaneously define motor maps controlling two limbs and could reproducibly generate such cortical motor maps over periods of weeks. This method allows non-invasive mapping of brain circuitry in living animals and could help define the connection between behavior and brain circuitry.

Interaction between cytotoxic effects of gamma-radiation and folate deficiency in relation to choline reserves

The search for non-toxic radio-protective drugs has yielded many potential agents but most of these compounds have certain amount of toxicity. Recent studies have indicated that bio-molecules such as folate and choline might be of radio-protective value as they are, within broad dose ranges, non-toxic to humans and experimental animals. The objective of the present study was to investigate choline dependent adaptive response to potential synergistic cytotoxic effect of folate deficiency and gamma-radiation. Male Swiss mice maintained on folate sufficient diet (FSD) and folate free diet (FFD) based on AIN-93M formula, were subjected to 1-4Gy total body gamma-irradiation. To investigate liver DNA damage, apurinic/apyrimidinic sites (AP sites) were quantified. A significant increase in liver DNA AP sites with concomitant depletion of liver choline reserves was observed when gamma-radiation was combined with folate deficiency. Further work in this direction suggested that cytotoxic interaction between folate deficiency and gamma radiation might induce utilization of choline and choline containing moieties by modifying levels of key regulatory enzymes dihydrofolate reductase (DHFR) and choline oxidase (ChoOx). Another major finding of these studies is that significant liver damage at higher doses of radiation (3-4Gy), might release considerable amounts of choline reserves to serum. In conclusion, a plausible interpretation of the present studies is that folate deprivation and gamma-radiation interact to mobilize additional choline reserves of hepatic tissue, for redistribution to other organs, which could not be utilized by folate deficiency alone. Present results clearly indicated a distinct choline pool in liver and kidney tissues that could be utilized by folate deficient animals only under radiation stress conditions.

Simultaneous observation of glutamate, gamma-aminobutyric acid, and glutamine in human brain at 4.7 T using localized two-dimensional constant-time correlation spectroscopy

Localized two-dimensional constant-time correlation spectroscopy (CT-COSY) was used to resolve glutamate (Glu), gamma-aminobutyric acid (GABA), and glutamine (Gln) in the human brain at 4.7 T. In this method, three-dimensional localization was achieved using three radio frequency pulses of the CT-COSY module for slice selection. As this sequence could decouple JHH along the F1 direction, peak resolution of metabolites was improved even on a magnitude-mode display. In experiments on a phantom containing N-acetylaspartate, creatine, Glu, Gln, and GABA with a constant time delay (Tct) of 110 ms, cross peaks of Glu, Gln, and GABA were obtained on a spectrum processed with standard sine-bell windows, which emphasize sine-dependent signals along the t2 direction. In contrast, diagonal peaks of Glu C4H at 2.35 ppm, GABA C2H at 2.28 ppm, and Gln C4H at 2.44 ppm were resolved on a spectrum processed with Gaussian windows, which emphasize cosine-dependent signals along t2. Human brain spectra were obtained from a 27 mL voxel within the parieto-occipital region using a volume transverse electromagnetic (TEM) coil for both transmission and reception. Tct was 110 ms; the total scan time was 30 min. Diagonal peaks of Glu C4H, GABA C2H, and Gln C4H were also resolved on the spectrum processed with Gaussian windows. These results show that the localized two-dimensional CT-COSY method featuring 1H decoupling along the F1 direction could resolve Glu, GABA, and Gln signals in the human brain.

[Dependence of response reaction of root voles to low-intensity irradiation on the initial state of the tissue antioxidant system]

There has been studied the response of antioxidant (AO) reaction of the tissue system of the root voles Microtus oeconomus Pall. whose parents belonged to the populations long inhabiting the Republic Komi regions with different degrees of radioactive contamination on an additional radiation action at low doses. Differences have been revealed in the phospholipid content, activities of AO defense, intensities of processes of lipid peroxidation (LPO) in tissues of the vole offspring caught in the control and contaminated regions. It has been revealed that direction and degree of changes in the offspring tissues after the additional action are determined by the parameter value in the non-irradiated animal group. Intensity of the LPO processes in liver and brain was leveled after the long low-intensity irradiation. The obtained data and analysis of literature indicate that at predicting effects of chronic action of low doses of a damaging factor both in experiment and in the natural habitation, it is necessary to take into account initial characteristics of biological objects.

Modulation of radiation-induced biochemical changes in cerebrum of Swiss albino mice by Grewia Asiatica

The present study evaluates the possible radioprotective effect of Grewia asiatica fruit (rich in anthocyanin, carotenes, vitamin C, etc.) pulp extract (GAE) on cerebrum of Swiss albino mice exposed to 5 Gy gamma radiation. For this, healthy mice from an inbred colony were divided into four groups: (1) Control (vehicle treated) (2) GAE treated - mice in this group were orally supplemented with GAE (700 m/kg. b.w./day) once daily for fifteen consecutive days, (3) Vehicle treated irradiated mice, and (4) GAE + Irradiated - Mice in this group received distilled water orally equivalent to GAE (700 m/kg. b.w/day) for fifteen days consecutively. Mice were sacrificed at various intervals viz. 1-30 days. Radiation-induced augmentation in the levels of lipid peroxidation of mice cerebrum was significantly ameliorated by GAE pretreatment. Radiation-induced depletion in the level of glutathione and protein was prevented significantly by GAE administration.

Effects of 900-MHz electromagnetic field emitted from cellular phone on brain oxidative stress and some vitamin levels of guinea pigs

This study was designed to demonstrate the effects of 900-MHz electromagnetic field (EMF) emitted from cellular phone on brain tissue and also blood malondialdehyde (MDA), glutathione (GSH), retinol (vitamin A), vitamin D(3) and tocopherol (vitamin E) levels, and catalase (CAT) enzyme activity of guinea pigs. Fourteen male guinea pigs, weighing 500-800 g were randomly divided into one of two experimental groups: control and treatment (EMF-exposed), each containing seven animals. Animals in treatment group were exposed to 890- to 915-MHz EMF (217-Hz pulse rate, 2-W maximum peak power, SAR 0.95 w/kg) of a cellular phone for 12 h/day (11-h 45-min stand-by and 15-min spiking mode) for 30 days. Control guinea pigs were housed in a separate room without exposing EMF of a cellular phone. Blood samples were collected through a cardiac puncture and brains were removed after decapitation for the biochemical analysis at the end of the 30 days of experimental period. It was found that the MDA level increased (P<0.05), GSH level and CAT enzyme activity decreased (P<0.05), and vitamins A, E and D(3) levels did not change (P>0.05) in the brain tissues of EMF-exposed guinea pigs. In addition, MDA, vitamins A, D(3) and E levels, and CAT enzyme activity increased (P<0.05), and GSH level decreased (P<0.05) in the blood of EMF-exposed guinea pigs. It was concluded that electromagnetic field emitted from cellular phone might produce oxidative stress in brain tissue of guinea pigs. However, more studies are needed to demonstrate whether these effects are harmful or/and affect the neural functions.

[Influence of the chronic gamma-irradiation at the low doses during the near ontogenesis periods on the oxidative processes in rodent organs]

It is shown that the effect of the low intensity gamma-irradiation at the dose of 5.5 cGy during the 4 months including the antenatal period causes the most substantial changes of the peroxide content in the liver and in brain lipids and of TBA-reactive substances amount in organs and blood plasma of tundra vole F2 which are reproduced from parents during long-term inhabiting on the Ra-contaminated area in the Komi Republic. The consequences of the chronic gamma-irradiation at the doses of 4 cGy (the dose rate is 5 mR/h) and 31 cGy (the dose rate is 40 mR/h) are studied by the morphophysiological and by biochemical parameters in organs of mice CBA (males) within 3 months after exposure. The change of the scale of the interrelation between the liver and body masses and also between the sums of the more easily to the more poorly oxidizable fractions and the phosphatidyl choline to phosphatidyl ethanolamine ratio in the liver phospholipids in groups of the irradiated mice is found as compared with that in the control group. The absence of interrelation between the lipid peroxidation process intensity and the catalase activity in the murine liver and also between the disbalance of the biochemical functions and the dose rate and/or the dose of the gamma-irradiation is revealed. The analysis of the data obtained allow to conclude that the chronic gamma-radiation under low intensity has the systemic effect on the animal organism causing of its function on the other level.

Evidence for a role of Hsp70 in the neuroprotection induced by heat shock pre-treatment against 3,4-methylenedioxymethamphetamine toxicity in rat brain

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') produces acute hyperthermia which increases the severity of the selective serotoninergic neurotoxicity produced by the drug in rats. Heat shock protein 70 (Hsp70) is a major inducible cellular protein expressed in stress conditions and which is thought to exert protective functions. MDMA (12.5 mg/kg, i.p.), given to rats housed at 22 degrees C, produced an immediate hyperthermia and increased Hsp70 in frontal cortex between 3 h and 7 days after administration. MDMA, given to rats housed at low ambient temperature (4 degrees C) produced transient hypothermia followed by mild hyperthermia but no increase in Hsp70 expression, while rats treated at elevated room temperature (30 degrees C) showed enhanced hyperthermia and similar expression of Hsp70 to that seen in rats housed at 22 degrees C. Fluoxetine-induced inhibition of 5-HT release and hydroxyl radical formation did not modify MDMA-induced Hsp70 expression 3 h later. Four- or 8-day heat shock (elevation of basal rectal temperature by 1.5 degrees C for 1 h) or geldanamycin pre-treatment induced Hsp70 expression and protected against MDMA-induced serotoninergic neurotoxicity without affecting drug-induced hyperthermia. Thus, MDMA-induced Hsp70 expression depends on the drug-induced hyperthermic response and not on 5-HT release or hydroxyl radical formation and pre-induction of Hsp70 protects against the long-term serotoninergic damage produced by MDMA.

Impaired hippocampal LTP in inbred mouse strains can be rescued by β-adrenergic receptor activation

Long-term potentiation (LTP), an activity-dependent enhancement of synaptic strength, and memory can be influenced by neuromodulatory transmitters such as norepinephrine (NE) and also by genetic background. beta-Adrenergic receptor activation can facilitate the expression of hippocampal CA1 LTP induced by weak stimulus patterns, but its influence on LTP induced by stronger stimulus patterns is unclear. We examined neural NE and dopamine (DA) levels, beta-adrenergic receptor expression and hippocampal LTP in genetically diverse inbred mouse strains. Brain tissue levels of NE were significantly lower in strains 129S1/SvImJ (129), BALB/cByJ (BALB) and C3H/HeJ (C3H) than in C57BL/6NCrlBR (B6). Western blot analysis showed that hippocampal beta(1)-adrenergic receptor expression was similar in strains B6, 129 and C3H, but was increased in BALB. LTP was induced in area CA1 of hippocampal slices by four trains of high-frequency stimulation (HFS) of the Schaeffer collaterals in the four inbred strains. Two hours after induction, LTP was significantly reduced in strains 129, BALB and C3H compared to B6, correlating with neural NE levels. We rescued hippocampal LTP in strains 129, BALB and C3H to levels seen in B6 by bath application of 1 microm isoproterenol, a beta-adrenergic receptor agonist, during HFS. Propranolol, a beta-adrenergic receptor antagonist, blocked this rescue in 129, BALB and C3H but did not affect LTP in strain B6. Thus, although this form of multitrain LTP does not rely on beta-adrenergic receptor activation, our data show that pharmacological activation of beta-adrenergic receptors during multiple trains of HFS can rescue CA1 LTP in genetically diverse strains with impaired LTP.

Prolonged rewarding stimulation of the rat medial forebrain bundle: neurochemical and behavioral consequences

Extracellular dopamine levels were measured in the rat nucleus accumbens by means of in vivo microdialysis. Delivery of rewarding medial forebrain bundle stimulation at a low rate (5 trains/min) produced a sustained elevation of dopamine levels, regardless of whether train onset was predictable. When the rate of train delivery was increased to 40 trains/min, dopamine levels rose rapidly during the first 40 min but then declined toward the baseline range. The rewarding impact of the stimulation was reduced following prior delivery of stimulation at the high, but not the low, rate. These results support the idea that dopamine tone plays an enabling role in brain stimulation reward and is elevated similarly by predictable and unpredictable stimulation.

Sex differences in neurochemical effects of dopaminergic drugs in rat striatum

Previous data indicate that dopamine neurotransmission is differently regulated in male and female rats. The purpose of the present study was to investigate the dopamine transporter and autoreceptor as potential loci responsible for this sex difference. Fast cyclic voltammetry at carbon-fiber microelectrodes was used to monitor changes in electrically evoked levels of extracellular dopamine in the striata of anesthetized male and female rats before and after administration of an uptake inhibitor, a dopamine D2 antagonist, or a D3/D2 agonist. Administration of 40 mg/kg cocaine ip increased electrically-evoked extracellular dopamine concentrations in both sexes, but to a significantly greater extent in female striatum at the higher stimulation frequencies. The typical antipsychotic, haloperidol, increased dopamine efflux in both sexes but the effect was twice as large in the female striatum. The D3/D2 agonist quinpirole induced an unexpected, transient increase in dopamine efflux following high-frequency stimulation only in females, and evoked dopamine was higher in females across this entire time course. More detailed analysis of cocaine effects revealed no fundamental sex differences in the interaction of cocaine with DAT in vivo or in synaptosomes. These results indicate that nigrostriatal dopamine neurotransmission in the female rat is more tightly regulated by autoreceptor and transporter mechanisms, perhaps related by greater autoreceptor control of DAT activity. Thus, baseline sex differences in striatal dopamine regulation induce different pharmacologic responses. These results contribute to understanding sex differences in stimulant-induced locomotor activity in rats and may have broader implications for neurologic disorders and their pharmacotherapies in humans.

Impaired light masking in dopamine D2 receptor–null mice

Disruption of overt circadian rhythms can occur without influencing the endogenous pacemaker, the so-called 'masking' effect classically elicited by light. As the physiological pathways involved in light masking remain elusive, we analyzed mice lacking the dopamine D2 receptor. Although circadian rhythmicity was normal, D2R-null mice showed a markedly deficient light masking response, indicating that D2R-mediated signaling is an essential component of the neuronal pathways leading to light masking of circadian rhythms.

The brain 5HTergic response to an acute sound stress in rats with generalized (absence and audiogenic) epilepsy

The brain serotoninergic (5HTergic) system of epileptic subjects can influence their vulnerability to stress. We studied the putative dependency of 5HT neurotransmission parameters on emotional stress, and the presence, types and severity of seizures using rats with genetic generalized (absence and/or audiogenic) epilepsy, of WAG/Rij and Wistar strains. The animals were stressed by exposure to a short aversive noise or left without sound stimulation. Tissue concentrations of 5HT, tryptophan (TRT) and 5-hydroxyindolacetic acid (5HIAA) were assessed by HPLC. The stressor activated the 5HTergic system within thalamus (5HIAA elevated), frontal cortex (5HT, TRT elevated), hypothalamus (increased TRT) in all rats. However, the normal (non-epileptic) rats displayed the highest response in the frontal cortex and the lowest one in the thalamus, as compared to the epileptic rats. Absence-epileptic rats exhibited higher thalamic 5HIAA increase than their controls. Significant correlations existed between propensity of absence epilepsy and 5HTergic parameters measured in the cortex and hypothalamus of absence-epileptic rats. No major difference was found between groups with and without audiogenic epilepsy. The results imply that the stress response depends on the presence of epileptic pathology and the seizure type and severity. The brain 5HT may be involved in the control of the paroxysms and behaviour in absence-epileptic subjects.

Rotenone produces opposite effects upon mouse striatal dopamine function as a result of environmental temperature

Rotenone is a commonly used pesticide that can function as an environmental neurotoxin. Rotenone is a known mitochondrial complex I inhibitor which can lead to oxidative stress and results in dopaminergic cell death. Another environmental factor known to exacerbate oxidative stress and result in striatal dopaminergic cell death is elevated environmental temperature. In this study we evaluated the effects of a single injection of various doses of rotenone (0.65, 1.3 and 2.6 mg/kg) on striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations in CD-1 mice and compared this with a single injection of two doses of methamphetamine (MA - 10 or 20 mg/kg), a known striatal DA depleting agent, as administered to mice maintained at 21 degrees C (Experiment 1). These results were then compared to striatal DA and DOPAC concentrations of mice treated with rotenone (1.3 or 2.6 mg/kg) or MA (10 or 20 mg/kg) administered to mice maintained at 28 degrees C (Experiment 2). A single injection of rotenone to mice maintained at 21 degrees C resulted in a significant increase in DA and decrease in DOPAC concentrations for all doses tested compared to controls, whereas a single injection of MA at the same temperature resulted in a significant decrease in DA and no change in DOPAC concentrations. At a temperature of 28 degrees C, a single injection of rotenone resulted in a significant decrease in both DA and DOPAC concentrations similar to that seen with the MA-treated mice. Collectively, these results indicate that rotenone interacts with environmental temperature to produce opposite effects upon striatal DA concentrations -- significantly increasing striatal DA when administered at 21 degrees C and significantly decreasing striatal DA when administered at 28 degrees C, while producing similar decreases in striatal DOPAC under both temperatures.

Apoptotic cell death progression after photothrombotic focal cerebral ischaemia: effects of the lipophilic iron chelator 2,2'-dipyridyl

Two different forms of cell death have been distinguished morphologically following cerebral ischaemia: necrotic and apoptotic cell death. The aim of this study was to investigate the contribution of apoptosis to ischaemic damage by carefully depicting the temporal and spatial neuronal death following focal ischaemia. For this purpose, rats were subjected to chemical photothrombosis, and histological and biochemical analyses were performed over a period of 24 h after the onset of ischaemia. In addition, the effects of the lipophilic antioxidant iron chelator 2,2'-dipyridyl (DP) were evaluated 24 h after photothrombosis when the lesion volume was maximal. Our results showed two separate waves of neuronal death. In the first wave, shrunken dark neurons were massively present as early as 2 h after photothrombosis in the infarct core. From this initial neuronal abnormal population, progressive and time-dependent changes of both necrotic and apoptotic cell death were observed, leading to ghost neurons and apoptotic bodies after 24 h. The extension of the lesion coincided with a second wave of cell death. Massive and rapid neuronal loss occurred at the infarct border, which appeared as a sharply demarcated pale region. Procaspase and poly(ADP-ribose) polymerase-1 (PARP-1) cleavages were also detected in the infarct core and surrounding damaged tissue. DP treatment markedly blocked the enlargement of the lesion, the infarct border being rescued from infarction. Furthermore, a large decrease of apoptotic bodies was associated with a significant drop of caspase and PARP-1 cleavages, suggesting that the protective effect of DP closely correlates with limitation of apoptosis expansion.

Neurochemical effects of exercise and neuromuscular electrical stimulation on brain after stroke: a microdialysis study using rat model

Treadmill exercise and neuromuscular electrical stimulation are common clinical approaches for stroke rehabilitation. Both animal and clinical studies have shown the functional improvements after these interventions. However, the neurochemical effects on the ischemic brain had not been well studied. This study aimed at evaluating the effects of treadmill exercise and neuromuscular electrical stimulation (NMES), and studying their effects during a 2-week training, on the levels of common neurotransmitters (aspartate, glutamate, taurine and gamma-aminobutyric acid (GABA)) in the hippocampus following transient focal cerebral ischemia. Either treadmill exercise or neuromuscular electrical stimulation was prescribed to the rats 24 h after cerebral ischemia whereas Control group remained in cages for 2 weeks. Microdialysis technique was used to collect dialysates from ipsilesional hippocampus in vivo. It was found that the glutamate level was increased significantly during treadmill exercise and then returned to baseline level. Both interventions did not trigger significant effects on aspartate and glutamate basal levels during the 2 weeks. The relatively high taurine level in Control groups may suggest that the interventions might suppress the taurine release in hippocampus. GABA and aspartate levels did not showed significant changes over the 2 weeks in all groups. These results provide insights to explain the neurochemical effects on the ischemic injured brain during the course of rehabilitation.

Quantitative Neuropeptidomics of Microwave-irradiated Mouse Brain and Pituitary

In neuropeptidomics, the degradation of a small fraction of abundant proteins overwhelms the low signals from neuropeptides, and many neuropeptides cannot be detected by mass spectrometry without extensive purification. Protein degradation was prevented when mice were sacrificed with focused microwave irradiation, permitting the detection of hypothalamic neuropeptides by mass spectrometry. Here we report an alternative and very simple method utilizing an ordinary microwave oven to inhibit enzymatic degradation. We used this technique to identify brain and pituitary neuropeptides. Quantitative analysis using mass spectrometry in combination with stable isotopic labeling was performed to determine the effect of microwave irradiation on relative levels of neuropeptides and protein degradation fragments. Microwave irradiation greatly reduced the levels of degradation fragments of proteins. In contrast, neuropeptide levels were increased about 2-3 times in hypothalamus by the microwave irradiation but not increased in pituitary. In a second experiment, three brain regions (hypothalamus, hippocampus, and striatum) from microwave-irradiated mice were analyzed. Altogether 41 neuropeptides or fragments of secretory pathway proteins were identified after microwave treatment; some of these are novel. These peptides were derived from 15 proteins: proopiomelanocortin, proSAAS, proenkephalin, preprotachykinins A and B, provasopressin, prooxytocin, melanin-concentrating hormone, proneurotensin, chromogranins A and B, secretogranin II, prohormone convertases 1 and 2, and peptidyl amidating monooxygenase. Although some protein degradation fragments were still found after microwave irradiation, these appear to result from protein breakdown during the extraction and not to an enzymatic reaction during the postmortem period. Two of the protein fragments corresponded to novel protein forms: VAP-33 with a 7-residue N-terminal extension and beta tubulin with a glutathione on the Cys near the N terminus. In conclusion, microwave irradiation with an ordinary microwave oven effectively inhibits enzymatic postmortem protein degradation, increases the recovery of neuropeptides, and makes it possible to conduct neuropeptidomic studies with mouse brain tissues.

Purine level regulation during energy depletion associated with graded excitatory stimulation in brain

OBJECTIVES

The formation and release of adenosine following graded excitatory stimulation of the brain may serve important physiological functions such as sleep regulation, as well as an early resistance mechanism against excitotoxicity. However, adenosine at high levels may reflect merely the results of obstructed energy metabolism.

METHODS

We examined the extent to which levels of adenosine and adenylate energy charge are affected in vivo by graded excitatory stimulations of brain using unilateral intrastriatal injections of glutamatergic agents and head-focused high energy microwaving for accurate and precise measures of purines.

RESULTS

Our results confirmed that adenosine levels rise when adenylate energy charge decreases and showed that these increases occurred in three distinct phases with the rate of adenosine formation in each phase increasing as tissue adenylate energy charge was further depleted. In addition, we observed that, in most cases, the effects of focal excitatory stimulation on changes in tissue purine levels were restricted spatially within the immediate vicinity of the injection site; however, when strongly depolarizing stimuli were used, changes in purine levels could be observed in adjacent and, occasionally, even in contralateral brain regions.

DISCUSSION

These results provide new insight into purine regulation that occurs under physiologically relevant conditions, such as sleep and during the early stages of brain insults that induce excitotoxicity.

Aversive stimulation of the inferior colliculus changes dopamine and serotonin extracellular levels in the frontal cortex: modulation by the basolateral nucleus of amygdala

We have shown that stimulation of the neural substrates in the inferior colliculus (IC) causes a significant increase in the extracellular levels of dopamine (DA) in frontal cortex (FC). Also, it has been reported that the basolateral complex of the amygdala (BLA) serves as a filter for unconditioned and conditioned aversive information that ascend to higher structures from the brainstem. Linking these two kinds of information, this work examines whether inactivation of BLA interferes with the activation of cortical dopaminergic outputs produced by aversive stimulation of the IC. To this end, rats were implanted with an electrode in the IC for the determination of the threshold of escape responses. Each rat also bore a cannula implanted in the BLA for injections of lidocaine (10 microg/0.5 microL), muscimol (0.5 microg/0.5 microL), or its vehicle and a microdialysis probe in the FC for determination of the amount of DA and serotonin (5-HT). The data obtained show that IC electrical stimulation caused an increase in the DA release while it reduced the 5-HT release in the FC. BLA inactivation with both lidocaine or muscimol enhanced the aversiveness of the electrical stimulation of the IC and attenuated the increase in DA, while the reduction in 5-HT release in the FC remained unaffected. These findings suggest that ascending aversive information from IC on their way up to higher structures in the SNC courses with opposite modulation by DA/5-HT mechanisms in the FC. These processes are regulated by filters located in the BLA. It is proposed that the loss of these BLA regulatory mechanisms prevents the expression of these modulatory mechanisms in the FC that are adaptive responses in order to cope with unconditioned aversive stimulus triggered at the brainstem level.

Quantitative Measurements of Oxidative Stress in Mouse Skin Induced by X-Ray Irradiation

To find efficient methods to evaluate oxidative stress in mouse skin caused by X-ray irradiation, several markers and methodologies were examined. Hairless mice were irradiated with 50 Gy X-rays and skin homogenates or skin strips were prepared. Lipid peroxidation was measured using the skin homogenate as the level of thiobarbituric acid reactive substances. The level of lipid peroxidation increased with time after irradiation and was twice that of the control at 78 h. ESR spectra of skin strips showed a clear signal for the ascorbyl radical, which increased with time after irradiation in a manner similar to that of lipid peroxidation. To measure levels of glutathione (GSH) and its oxidized forms (GSSG) simultaneously, two HPLC methods, sample derivatization with 1-fluoro-2,4-dinitrobenzene and detection with a UV detector (method A) and no derivatization and detection with an electrochemical detector (method B), were compared and the latter was found to be better. No significant change was observed within 24 h after irradiation in the levels of GSH and GSSG measured by method B. The GSH/GSSG ratio may be a less sensitive parameter for the evaluation of acute oxidative stress caused by X-ray irradiation in the skin. Monitoring the ascorbyl radical seems to be a good way to evaluate oxidative stress in skin in vivo.

Light-induced reduction of cytoplasmic free calcium in neurons proposed to be encephalic photoreceptors in chick brain

A population of cerebrospinal fluid-contacting neurons (CSFcn) in the lateral septal organ (LSO) may serve as encephalic photoreceptors (EPRs) functioning to signal the onset of seasonal reproductive development in birds. Previous studies on CSFcn in the LSO have focused on identification of retinal protein components in fixed brain tissue. In order to understand better the mechanisms underlying the light-induced photosexual response in birds, a physiological characterization is required. In this study, changes of intracellular free calcium concentration ([Ca2+]i) were monitored during light stimulation of CSFcn in the LSO in live brain slices from embryonic chicks. Using the fluorescent calcium indicator fluo-4, a reduced [Ca2+]i within CSFcn was recorded in response to photostimulation, which is consistent with what has been demonstrated in rods and cones following illumination. Results support the hypothesis that CSFcn in the LSO function as EPRs in the avian brain.

Levetiracetam influences human motor cortex excitability mainly by modulation of ion channel function—a TMS study

PURPOSE

Levetiracetam (LEV) is a new compound with anticonvulsive efficacy in focal and generalized epilepsies. Recent in vitro studies suggest LEV to act as a selective N-type-calcium-channel blocker.

METHODS

We used transcranial magnetic stimulation (TMS) in order to investigate if ion-channel blockade is relevant to the inhibitory CNS effects of LEV in vivo and if motor thresholds (MTs) are a valid TMS parameter to detect this mode of action. In a double blind, placebo-controlled, crossover study, the effects of single oral doses of 500 and 2000 mg LEV on motor thresholds, recruitment curves (REC), cortical induced silent period (CSP) and on intracortical inhibition (ICI) and facilitation (ICF) were studied in 10 healthy subjects.

RESULTS

A significant increase of motor thresholds was noticed after 2000 mg LEV as compared to placebo. The recruitment curve showed a trend towards motor evoked potential (MEP) amplitude reduction after LEV. LEV had no significant effect on CSP or on intracortical excitability as measured by inhibition and facilitation.

CONCLUSIONS

We conclude that the modulation of ion-channel function, reflected by motor threshold elevation and a trend towards recruitment curve suppression, is relevant to the inhibitory CNS effects of LEV in vivo, and therefore, may contribute to the anticonvulsive efficacy of LEV. GABAergic or glutamatergic mechanisms seem to be less important in vivo as measured by TMS.

Chronic rTMS induces subsensitivity of post-synaptic 5-HT1A receptors in rat hypothalamus

Chronic administration of several antidepressants, notably the selective serotonin re-uptake inhibitors (SSRIs) induces sub-sensitivity of post-synaptic 5-HT1A receptors in the hypothalamus. Chronic repetitive transcranial magnetic stimulation (rTMS) is a form of treatment for depression which is often compared to electroconvulsive shock therapy (ECT). rTMS was applied to rats either on a single occasion (acute) or daily for 8 d (chronic). Twenty-four hours after the last treatment, the rats were injected with saline or 8-OH-DPAT (50 microg/kg). The rats were killed 20 min later and trunk blood taken for measurement of corticosterone and ACTH levels. Chronic rTMS did not affect basal corticosterone or ACTH levels but significantly blunted the responses to 8-OH-DPAT, while acute rTMS had no effect on either basal or 8-OH-DPAT-stimulated responses. In common with several other antidepressant treatments, chronic rTMS reduces the sensitivity of post-synaptic 5-HT1A receptors in the hypothalamus. This effect may be significant in relation to the therapeutic mechanism of rTMS.

Electrical stimulation of the hippocampus disrupts prepulse inhibition in rats: frequency- and site-dependent effects

Prepulse inhibition (PPI) is a normal reduction in the startle response produced when a brief, low intensity stimulus is presented prior to a startle-evoking stimulus. PPI is often disrupted in humans diagnosed with schizophrenia. As similar stimuli elicit PPI in rodents and humans, interventions in rodents that disrupt PPI may reveal aspects of neuronal dysfunction relevant to schizophrenia. Stimulation of the ventral hippocampus (vHip) with NMDA significantly increases dopamine (DA) efflux in the nucleus accumbens (NAc) and disrupts PPI, whereas NMDA infusion into the dorsal hippocampus (dHip) fails to alter PPI. Our previous research shows that brief periods of 20 Hz electrical vHip stimulation also significantly increase NAc DA efflux. The present experiments assessed the effects of stimulating the vHip or dHip on PPI and NAc DA efflux. As predicted, 20 Hz stimulation (10 s, 300 microA) of the vHip, but not the dHip, reversibly disrupted PPI. In contrast, 2 Hz stimulation (100 s, 300 microA) of the vHip failed to affect PPI. Microdialysis experiments revealed that 20 Hz stimulation of the vHip increased NAc DA efflux only in the hemisphere ipsilateral to the stimulating electrode, whereas 20 Hz stimulation of the dHip failed to affect NAc DA efflux. These data demonstrate the regional specificity and frequency-dependent effects of hippocampal activity on PPI. Additionally, it is intriguing that both chemical and electrical stimulation of the vHip disrupt PPI and increase NAc DA efflux, however, the relevance of these changes in NAc DA efflux to the disruption of PPI remains to be determined.

Nitric oxide voltammetric measurements in the rat brain after gamma irradiation

The effects of a lethal gamma irradiation were investigated on cerebral NO-ergic system by using a voltammetric method in freely moving rats. It is reported that the cortical NO concentration increases right from the end of the radiation exposure (15 Gy) and reaches a maximal magnitude (+120%) 24 h later. A dose-effect relationship from 2 to 15 Gy for gamma-ray exposure has also been observed. The effects, obtained with either an NO synthase inhibitor nonselective for the different NO synthase isoforms or an NO synthase inhibitor selective for the constitutive isoform, suggest that the radiation-induced increase in NO is likely to be dependent on the inducible NO synthase isoform. Moreover, experiments performed under ex vivo conditions showed that the cortical mRNA level for Ca(++)-independent NO synthase, the brain NOS activity, and urinary nitrites/nitrates increased significantly 24 h after gamma-ray exposure. These results demonstrate that a supralethal whole-body irradiation alters the NO-ergic pathways. The increase in NO obtained under such conditions might constitute a good index of central nervous system radiosensitivity during the acute phase of the radiation syndrome.

Amelioration of radiation-induced oxidative stress and biochemical alteration by SOD model compounds in pre-treated γ-irradiated rats

INTRODUCTION

The role of metalloelements in tissue maintenance, function and response to injury offer a new approach to decreasing and/or treating radiation injury. We investigated the roles of CuL(2)SO(4), [MnL(2)O](2)Cl(4)(H(2)O)(2) and [(VL(2)O)(VL(2)H(2)O)]Cl(6) complexes (L=2-methylaminopyridine) of SOD-mimetic activities, in ameliorating the radiation-induced oxidative stress and alterations in some biochemical parameters in liver, kidney, spleen and brain in pretreated female rats exposed to gamma-irradiation.

METHODS

Both untreated-rats and rats treated with the above complexes were subjected to whole-body gamma-irradiation (6 Gy). 5'-Nucleotidase (5'-NT), acetylcholinesterase (AChE), adenosne triphosphatase (ATPase), superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GSSG-R) were assessed as well as liver DNA and RNA contents and total protein concentration were estimated in tissue homogenates of the above organs. The same parameters were assessed in non-irradiated treated rats and normal control rats. Results were compared to irradiated non-treated and normal control rats.

RESULTS

Pretreatment of gamma-irradiated rats with Mn(IV) or V(IV) complex produced a significant decrease in liver 5'-NT activity compared to the corresponding value of the untreated irradiated rats. In contrast, liver DNA and RNA contents and brain AChE and ATPase activities were significantly increased in irradiated rat group pre-treated with these metal complexes. Cu II, Mn IV or V IV complex inoculation prior to irradiation of normal rats exhibited a significant increase in SOD, CAT, GSSG-R activities and protein content of liver, kidney, spleen and brain homogenates compared with that of the untreated irradiated rats. The treatment of non-irradiated rats with these complexes produced a highly significant increase in mean activities of SOD and CAT, with no changes in other parameters vs. controls.

CONCLUSIONS

Cu(II), Mn(IV) and V(IV) 2-methylaminopyridine complexes offer a physiological approach to ameliorate the radiation-induced biochemical alterations. In addition, they provide sufficient protection against radiation injury of radiosensitive tissues.

WR-2721 (amifostine, ethyol) prevents motor and morphological changes induced by neonatal X-irradiation

Neonatal X-irradiation induces permanent abnormalities in cerebellar cortex cytoarchitecture and neurochemistry, as well as impairment in motor gait. The aim of the present work was to examine the potential protective properties of WR-2721 (Amifostine, Ethyol), a free radical scavenger, against the above mentioned alterations by using a previously described neuroprotection assessment protocol. Pre-irradiation treatment with amifostine was effective in partially preventing the cerebellar morphological damage and the motor gait impairment induced by ionizing radiation. No changes in cerebellar noradrenaline (NA) levels were detected in amifostine-treated irradiated animals. These results suggest that it is possible to counteract radiation-induced damage in the cerebella and motor gait of neonatal rats through oxygen free radical scavenger administration prior to irradiation. The presence of the agent before the injury occurs, favors the efficacy of amifostine neuroprotective activity. Clinical implications of this model are related to the daily exposure of many people to different sources of radiation (accidental, diagnostical or therapeutical).

Early neuroprotective effect of nitric oxide in developing rat brain irradiated in utero

Pregnant Wistar rats were exposed on day 17 of gestation to 1 Gy gamma irradiation from a Co(60) source. Even though it is established that gamma radiation-dependent damage is mainly due to free radical generation neither the ascorbyl radical/ascorbate ratio nor the lipid radical content in developing rat brain were affected by prenatal irradiation. A distinctive EPR signal for the adduct NO-Fe-MGD (g=2.03 and a(N)=12.5 G) was detected in brain homogenates prepared from irradiated rats. Nitric oxide (NO)-dependent EPR signal increased in a time-dependent manner up to 2h post-irradiation. NO concentration in unirradiated brains was 37+/-4 pmol/g brain and 45+/-2, 77+/-5 and 216+/-6 after 30, 60 and 120 min post-irradiation, respectively. Total nitric oxide synthase activity was increased by 77 and 51% after 30 and 60 min post-irradiation, respectively, and returned to control values after 120 min. Thus, increased NO steady-state concentration could be ascribed to an increase in NOS activity. Taken as a whole, these results suggest that NO might act to protect the developing brain from the cytotoxicity of reactive species.

Deep brain stimulation of the subthalamic nucleus versus levodopa challenge in Parkinson's disease: measuring the on- and off-conditions with FDG-PET

In order to compare the effects of high-frequency stimulation of the subthalamic nucleus (STN-DBS) and a levodopa-challenge on cerebral metabolic activity, we conducted PET scans with [(18)F]2-fluoro-2-deoxyglucose (FDG) in the drug- and stimulation- on- and off-condition in a single patient suffering from advanced PD. Our data revealed evidence for improved thalamocortical processing released from inhibition by overactive basal ganglia output nuclei in both on-conditions. While levodopa also led to a reduction of lentiform hyperactivity, effective STN stimulation seemed to interfere with distinct cerebellar and limbic circuits.

Blood-brain barrier permeability after gamma whole-body irradiation: an in vivo microdialysis study

The effects of total-body irradiation on the permeability of rat striatal blood-brain barrier (BBB) to [3H]alpha-aminoisobutyric acid (AIBA) and [14C]sucrose were investigated using the microdialysis technique. Seven days, 3 and 6 weeks, and 3, 5, and 8 months after gamma exposure at a dose of 4.5 Gy, no modification of the permeability to both [3H]AIBA and [14C]sucrose was observed. But, in the course of the initial syndrome, we observed a significant but transient increase in the BBB permeability to the two markers between 3 and 17 h after exposure. A secondary transient "opening" of the BBB to [14C]sucrose was noticed about 28 h following irradiation without the corresponding increase in BBB permeability to [3H]AIBA. On the contrary, the transport of [3H]AIBA through the BBB was decreased between 33 and 47 h postradiation. In conclusion, our experiments showed early modifications of BBB permeability after a moderate-dose whole-body exposure. Confirmation of these results with other tracers, in another experimental model or in humans, would have clinical applications for designing appropriate pharmacotherapy in radiotherapy and treatment of accidental overexposure.

Infrared-guided laser stimulation of neurons in brain slices

Infrared-guided laser stimulation is a new technique that allows precise and rapid stimulation of visualized neurons in brain slices. Infrared imaging of neurons with a new contrast system is combined with the photolytic release of caged neurotransmitters by an ultraviolet (UV) laser. Addition of caged neurotransmitters to the superfusion medium of neurons in brain slices allows local excitation in the micrometer range with a focused spot of UV light. In this way, the distribution of glutamate or gamma-aminobutyric acid (GABA) receptors on neuronal dendrites can be mapped. Furthermore, this technique can be used to map the connectivity of neuronal networks through the controlled stimulation of neighboring neurons. Because the laser stimulation can be performed much faster than can paired recording, it is also possible to search for synaptic connections between distant neurons that have a low probability of connectivity.

Tissue Raman spectroscopy for the study of radiation damage: brain irradiation of mice

Radiotherapy is routinely employed in the treatment of head and neck cancers. Acute cell death, radiation-activated chemical cascades, and the induction of genes coding for protective factors like cytokines are considered to be the major processes involved in radiation damage and repair. It should be possible to follow these processes by monitoring the biochemical interactions initiated by radiation. We have carried out Raman spectroscopy studies on tissue from mice subjected to brain irradiation to identify the biochemical changes occurring in tissue and brain as a result of radiation injury. These studies show that brain irradiation produces drastic spectral changes even in tissue far removed from the irradiation site. The changes are very similar to those produced by the stress of inoculation and restraint and the administration of an anesthetic drug. While the changes produced by stress or anesthetics last for only a short time (a few hours to 1 or 2 days), radiation-induced changes persist even after 1 week. The spectral changes can be interpreted in terms of the observation of new spectra that are dominated by bands due to proteins. The results thus support the hypothesis that various protective factors are released throughout the body when the central nervous system (CNS) is exposed to radiation.

[Endocrine disruptors and brain estrogen receptors: the current state of behavioral, neurochemical, and molecular biological studies]

Based on epidemiological studies and animal studies, endocrine disrupters have received considerable attention as exerting disrupting actions on the developing brain. On the other hand, there has been increasing evidence that sex hormones and thyroid hormones play important roles in the development of the brain, including sexual dimorphism during the perinatal stage. Thus it seems probable that perinatal exposure to endocrine disruptors, which may have an affect on biosynthesis, transport, action, and metabolism of the hormones, may disrupt brain development enough to impair the brain functions. In this review, we introduce the current state of studies on brain disrupting actions of endocrine disruptors, addressing their actions on the estrogen system, including our own findings. The outline of the findings thus far reported are as follows: (1) Perinatal exposure to relatively low concentrations of endocrine disrupters may cause an impairment of higher brain functions, such as sexual behavior and learning behavior, (2) There seems to be sexual difference about the impairment described above, (3) Endocrine disruptors may cause an increase in volume of some nuclei, such as the sexual dimorphic nucleus of the preoptic area and locus coeruleus of the brain, (4) The disruptor might change the level of some substances that are considered to be involved in synaptic functions. Much remained to be studied about how does each finding reported link the others, and about detailed mechanisms of the disrupting actions of endocrine disruptors on the developing brain.

Some neurotropic effects of low-intensity electromagnetic waves in rats with different typological characteristics of higher nervous activity

The effects of low-intensity electromagnetic waves (4200 MHz, modulated with quasichaotic signals at 20-20,000 Hz, energy density 15 microW/cm2; specific energy absorption not greater than 15 mJ/kg) on the neurochemical systems of the brain and on behavioral reactions were studied in experimental animals with different typological characteristics of higher nervous activity. These studies showed that electromagnetic waves produced marked changes in the state and activity of the monoaminergic mediator systems which were in general terms concordant with changes at the integrative level (mostly selective inhibitory effects). The nature of these processes depended to a significant extent on the typological characteristics of the animals.

The influences of extremely low frequency magnetic fields on clonidine-induced sleep in 2-day-old chicks

1. It has been shown that magnetic fields (MFs) affect a variety of biological effects in animal brains. There have been few experiments on the effects of MFs on sleep. Therefore, we investigated whether extremely low frequency (ELF) MFs affect the sleep induced by clonidine, a central alpha(2)-adrenoceptor agonist. Clonidine produced dose-related increase of the sleeping time and dose-related decrease of the onset time in 2-day-old chicks. 2. Exposure of chicks to MFs (5, 10, 20 G; for 3, 6, 9, 12 h) significantly increased the clonidine-induced sleep time as a direct function of intensity and duration of MF application. Clonidine reduced noradrenaline or tyrosine in the brain, an effect which was not further changed in animals exposed to MF. 3. To determine whether the gamma amino butyric acid A (GABA(A))/benzodiazepine (BZD) receptor system is involved in the decrease in clonidine-induced sleep caused by activation of central alpha(2)-adrenergic systems, we examined exposure of chicks to the effects of the BZD receptor antagonist flumazenil (0.5 mg kg(-1), i.p.) and GABA(A) antagonist bicuculline (0.1 mg kg-1, i.p.) on clonidine-induced sleep. Bicuculline and flumazenil inhibited the increase of clonidine-induced sleep time by MFs. Clonidine or MFs did not change GABA levels in the brain. 4. These results suggest that MFs can increase clonidine-induced sleep via a change of GABA(A) and BZD receptor system irrespective of the concentration of GABA or noradrenaline in the brain of 2-day-old chicks.

[The neurotropic effects of low-intensity electromagnetic waves in rats with different typological characteristics of higher nervous activity]

The effects of the ultralow-intensity electromagnetic fields (EMF, frequency of 4200 and 970 MHz, modulated by a quasistochastic signal in the range of 20-20,000 Hz, power density 15 microW/cm2, specific body absorption rate up to 4.5 mJ/kg) on the reactions of the central nervous system (CNS) of rats with different types of behavior were studied. Some neurochemical and behavioral mechanisms of rats' reactions were investigated. It was shown that the EMF produce pronounced changes in the state and activity of monoaminergic brain systems. These changes, on the whole, correspond to the alterations at the integrative level (predominantly, of the inhibitory character).

[The effect of electromagnetic radiation on the monoamine oxidase A activity in the rat brain]

The effect of the ultralow power pulse-modulated electromagnetic radiation (EMR, power density 10 microW/cm2; carrying frequency 915 MHz; modulating pulses with frequency 2, 4, 6, 8, 12, 16 and 20 Hz) on activity of monoamine oxidase (MAO-A), enzyme involved in the oxidative deamination of monoamines, was investigated. It was established that the increase of activity MAO in hypothalamus reached the maximal meaning at modulation frequency of 6 Hz that corresponded 160% (p < 0.01) of the control level; and at modulation frequency of 20 Hz the decrease of enzyme activity up to 74% (p < 0.01) was found. Mainly the action of ultralow power pulse-modulated EMR on activity of MAO in hippocamp was activating; and the maximal increase of enzyme activity up to 174% (p < 0.01) was registered at modulation frequency of 4 Hz.

Radiation exposure does not alter metallothionein III isoform expression in mouse brain

The level of metallothionein III mRNA and protein, a brain-specific isoform of metallothionein (MT), was investigated in the brain of MT-I and -II gene knockout (MT-null) mice exposed to 20 Gy whole-body gamma-irradiation. Because MT-null mice did not express MT-I or MT-II isoforms, the total brain MT content in these mice represented the isoform MT-III only. MT-III protein content was determined by a cadmium-binding assay, and the MT mRNA level was measured by reverse transcription followed by polymerase chain reaction (RT-PCR). Both MT-III protein content and mRNA expression in the brains of MT-null mice were not affected by exposure to whole-body irradiation. These results indicate that mouse brain MT-III expression is not induced by ionizing radiation.

IRIDIUM exposure increases c-fos expression in the mouse brain only at levels which likely result in tissue heating

With the rapid development of wireless communication technology over the last 20 years, there has been some public concern over possible health effects of long-term, low-level radiofrequency exposure from cellular telephones. As an initial step in compiling a database for risk analysis by government agencies, the effects of 1-h exposure of mice to a 1.6-GHz radiofrequency signal, given as either a continuous wave or pulse modulated at 11 Hz with a duty cycle of 4:1 and a pulse duration of 9.2 ms IRIDIUM), on c-fos gene expression in the brain was investigated. The IRIDIUM signal is the operating frequency for a ground-to-satellite-to-ground cellular communications web which has recently become fully operational, and was named as such due to the original designed employment of the same number of low orbiting satellites as there are electrons orbiting the nucleus of an iridium atom. The expression of c-fos was not significantly elevated in the brains of mice until exposure levels exceeded six times the peak dose and 30 times the whole body average dose as maximal cellular telephone exposure limits in humans. Higher level exposure using either continuous wave (analog) or IRIDIUM signals elevated c-fos to a similar extent, suggesting no obvious pulsed modulation-specific effects. The pattern of c-fos elevation in limbic cortex and subcortex areas at higher exposure levels is most consistent with a stress response due to thermal perception coupled with restraint and/or neuron activity near thermoregulatory regions, and not consistent with any direct interaction of IRIDIUM energy with brain tissue.

PCR assay of DNA damage and repair at the gene level in brain and spleen of gamma-irradiated young and old rats

The PCR amplification of fragments of transcribed (beta-actin, p53) and nontranscribed (IgE, heavy chain) genes in brain and spleen DNA from gamma-irradiated and unirradiated 2- and 28-month-old rats was studied. The amplification levels of fragments of these genes in DNA from old rats were substantially lower than those from young rats, which suggested that these gene fragments in old-rat DNA contained lesions blocking thermostable polymerase in PCR. The beta-actin and IgE gene fragments of spleen DNA from old rats exhibited a significantly higher level of lesions inhibiting Tth polymerase compared to analogous fragments of brain DNA from the same animals. DNA from the tissues of gamma-irradiated rats showed the amount of damage inhibiting amplification to be dependent on animal age and the postirradiation time before DNA isolation. As judged from the changes in the amplification level of gene fragments, there was no preferential fast repair of lesions in the actively transcribed gene beta-actin compared to the nontranscribed gene IgE (heavy chain) in the brain and spleen of gamma-irradiated young and old rats. The amplification results suggest that equal amounts of DNA lesions were repaired in the brain of both old and young rats during the first 0.5 h of the postirradiation time (fast-repair phase), whereas in the subsequent postirradiation period over 5 h (slow-repair phase), the efficiency of damage elimination in the brain DNA of old rats was markedly lower. As for the spleen tissue, the elimination of lesions blocking Tth polymerase was much lower in old gamma-irradiated animals for both of the repair phases.

Localization of glutathione and induction of glutathione synthesis-related proteins in mouse brain by low doses of gamma-rays

First, we determined the cerebral localization of reduced glutathione (GSH) in normal mice by means of autoradiography using 99mTc-meso-hexamethyl propylene oxime. A highly specific localization of GSH in the cerebellum and hippocampus was observed. Secondly, we measured the elevation of GSH level in the brain after low-dose gamma-irradiation. The cerebral GSH levels increased soon after irradiation with 50 cGy of gamma-rays, reaching a maximum at 3 h post-treatment, then remaining significantly higher than that of the non-irradiated control until 12 h and returning to the control level by 24 h. Thirdly, we examined the induction of the activities and the mRNAs of proteins involved in the synthesis and regeneration of GSH in the brain of mice subjected to low-dose gamma-ray irradiation. The level of mRNA for gamma-glutamylcysteine synthetase was significantly increased at 0.5 h, and remained high until 2 h post-irradiation (50 cGy). The level was transiently lowered to the non-irradiated control level at 3 h and slightly increased again after 6 h post-irradiation. gamma-Glutamylcysteine synthetase activity was significantly increased 3 h after irradiation, and remained high up to 24 h post-irradiation. As for glutathione reductase, the mRNA level was increased at 0.5 h, and peaked strongly at 2 h, while the enzyme activity was significantly increased at 6 h after irradiation, and continued to increase up to 24 h. The level of mRNA for thioredoxin, which contributes to GSH biosynthesis by supplying cysteine to the de novo pathway, peaked between 0.5 h and 2 h post-irradiation, and rapidly declined thereafter. The content of thioredoxin showed a transient decrease immediately after irradiation, but was then remarkably elevated, reaching a maximum at 3 h, and thereafter declining sharply. These results indicate that the increase in endogenous GSH in mouse brain soon after low-dose gamma-ray irradiation is a consequence of the induction of GSH synthesis-related proteins and occurs via both the de novo synthesis and the regeneration pathways.