Baria Öztaş

Influence of antioxidants on the blood-brain barrier permeability during epileptic seizures

Pentylenetetrazol‐induced seizures in rats lead to the breakdown of the blood‐brain barrier. We compared the disruption of the blood‐brain barrier during epileptic seizure in untreated rats and in rats treated with vitamin E or selenium. The rats were supplemented with nontoxic doses of sodium selenite (4 pp) in drinking water for 3 months, or vitamin E (70 mg/kg) was given intraperitoneally for 30 min before the pentylenetetrazole injection. Evans‐blue was used as a blood‐brain barrier tracer and was given intravenously at a dose of 4 ml/kg of a 2% solution. The rats were divided into four experimental groups. Group I: control (n = 24); Group II: pentylenetetrazole‐induced seizure (n = 12); Group III: vitamin E injected + seizure (n = 12); Group IV: Selenium supplemented + seizure (n = 12). The rats subjected to epileptic seizures showed Evans‐blue albumin extravasations especially in the thalamic nuclei, brainstem, occipital, and frontal cortex. Mean values for Evans‐blue dye were found to be 0.28 ± 0.04 mg % brain tissue in control rats and 1.6 ± 0.2 mg % brain tissue after epileptic seizures (P < 0.01). The magnitude of distribution of the blood‐brain barrier during epileptic seizures was significantly less in rats treated with vitamin E or selenium. The mean value for Evans‐blue dye was found to be 1.2 ± 0.1 mg % brain tissue in selenium supplemented rats and 1.2 ± 0.1 mg % brain tissue in vitamin E injected rats after epileptic seizures. This difference between treated and untreated animals was found to be significant (P < 0.05). The findings of the present study suggest that free radicals contribute to disruption of the blood‐brain barrier during pentylenetetrazol‐induced seizures. J. Neurosci. Res. 66:674–678, 2001.

The effect of acute hypertension on blood-brain barrier permeability to albumin during experimentally induced epileptic seizures

The present study was to examine the effect on the blood-brain barrier function of a rapid blood pressure elevation and the duration of this pressure during bicuculline and pentylenetetrazol-induced seizures. The experiments were carried out on Wistar rats. Evans blue was used as a blood-brain barrier tracer. Our results showed that the presence of blood pressure increase does not always result in blood-brain barrier leakage during convulsions. Besides the rate of increase in the pressure, the duration of this increased pressure was the important factor in the disruption of blood-brain barrier during bicuculline or pentylenetetrazol-induced seizures.

Influence of Sex on the Blood Brain Barrier Permeability During Bicuculline-Induced Seizures

Sex related differences of the blood brain barrier permeability was investigated during bicuculline-induced seizures in Wistar rats. The rats were anesthetized with diethyl-ether. Evans-blue, which was used as a blood brain barrier tracer, was injected into femoral vein 5 minutes before administering bicuculline to induced grand mal seizures. Evans-blue albumin extravasation was determined as a macroscopical finding; and a quantitative estimation with spectrophotometer using homogenized brain to release the dye was also performed to evaluate the macroscopic findings. During convulsions the mean arterial blood pressure increased in both female and male rats, but the difference was in the extravasation of Evans-blue being more pronounced in the females. Blood brain barrier lesions were present in 85% of female rats and 61% of male rats. Mean value for Evans-blue dye in the whole brain was found to be 1.197 +/- .402 mg % in the group consisting of all the female rats, and .755 +/- .247 mg % in the group of all male rats during bicuculline-induced seizure. This difference between female and male rats was found to be statistically significant (p < .001). Severe protein leakage was seen in the thalamus, hypothalamus, hippocampus, globus pallidus, nucleus caudatus, periaqueductal gray and mesencephalon bilaterally in female rats. However, in male rats, Evans-blue leakage was similar to that of female rats except that the frequency and intensity of blood brain barrier breakdown was less after convulsions. Our results showed that the extravasation of Evans-blue albumin was most pronounced in the brains of female rats compared to male rats after bicuculline induced seizure.

Age related changes in the effect of electroconvulsive shock on the blood brain barrier permeability in rats.

Age-related changes in blood-brain barrier permeability to macromolecules were investigated during electrically induced seizures. Evans-blue was used as the barrier tracer. There was no change in the permeability of the blood brain barrier associated with aging in the rats. However, the extravasation of Evans-blue albumin was most pronounced in the brain after ten repeated electroshocks in old rats. In the adult group that was given a single electroconvulsive shock, there was no coloration of the brain tissue, whereas the group given ten repeated electroconvulsive seizures showed slight staining of the thalamic nuclei, hypothalamus, and midbrain in 5 out of 13 rats. In 30-day-old rats, Evans-blue leakage was similar to that of adults, except that the frequency and intensity of blood-brain barrier breakdown was less after ten repeated electroshocks. In 15-day-old rats, the blood-brain barrier breakdown to Evans-blue albumin was the same after a single and ten electroshocks and the same in control and electroshocked rats. According to our results ten repeated electroshocks have a more pronounced effect on the old animals and have less effect on the young animals in comparison to adult ones.

Influence of acute arterial hypertension on blood-brain barrier permeability in streptozocin-induced diabetic rats ☆

The effect of acute arterial hypertension on blood-brain barrier (BBB) permeability was studied in streptozocin-induced diabetic rats using Evans blue as a barrier tracer. Four groups of rats were studied: Group 1, normotensive normoglycemia; Group II, normotensive+diabetes mellitus; Group III, arterial hypertension+diabetes mellitus; Group IV, arterial-hypertension+normoglycemia. During adrenaline-induced acute arterial hypertension the mean arterial blood pressure increased in both non-diabetic and diabetic animals. Changes in BBB permeability were observed in 52% of the non-diabetic rats, and in 72% of the diabetic rats after adrenaline-induced acute arterial hypertension. Mean levels of Evans blue in the whole brain were found to be 0.63 +/- 0.1 mg% in non-diabetic and 0.90 +/- 0.2 mg% in diabetic rats. The difference between the non-diabetic and the diabetic rats was found to be statistically significant (P < 0.01). From these results it was suggested that the extravasation of Evans blue albumin is more pronounced in the brains of diabetic rats in comparison with non-diabetic rats after adrenaline-induced acute hypertension, which is indicative of changes in BBB permeability due to diabetes mellitus.

Effect of insulin-induced hypoglycemia on blood-brain barrier permeability

The effects of hypoglycemia on cerebrovascular permeability to the Evans blue-albumin complex were studied in rats injected with 50 IU/kg, i.v. crystalline zinc insulin. One group of hypoglycemic animals was warmed to keep their body temperatures close to 37 degrees C, and the rats in the other group were allowed to become hypothermic by hypoglycemia. The arterial blood pressures of the hypoglycemic rats were continuously monitored during the coma and a significant rise in pressure was observed in most animals at the end of the coma. When glucose was administered i.v. to five animals of each group, this elevated pressure returned to normal values within 0.5 min and the animals slowly recovered normal behavior. At termination of the coma, most brains in the hypothermic hypoglycemic group showed an intensive and extensive staining by Evans blue; whereas only two brains in the normothermic hypoglycemic group showed any noticeable extravasation of Evans blue-albumin. Arterial PO2, PCO2, and pH were determined and no significant difference was found between values from animals in hypoglycemic coma and the controls. Four animals were surface-cooled and were used to examine the effects of hypothermia on blood-brain barrier permeability. These brains did not show any macroscopically evident Evans blue-albumin extravasation. The results indicated that prolonged, severe hypoglycemia with hypothermia caused a profound blood-brain barrier dysfunction whereas normothermic hypoglycemia resulted in few cases of any noticeable increase in blood-brain barrier permeability.

Intracarotid hypothermic saline infusion: a new method for reversible blood-brain barrier disruption in anesthetized rats

An animal model for reversible blood-brain barrier disruption has been developed. Retrograde infusion of hypothermic saline solution (8 +/- 1 degree C) into the left external carotid artery of normothermic, Wistar rats reversibly increases cerebrovascular permeability to Evans blue albumin in the left cerebral hemisphere. Isotonic saline solutions at 37 degrees C for Group I and at 8 +/- 1 degree C for Group II were infused for 30 s at a constant rate of 0.12 ml/s into the left external carotid artery. Evans blue, the barrier tracer, was administered intravenously either prior to or at intervals 5, 30, 180, 360 min after the hypothermic saline infusion under pentobarbital anesthesia. All animals receiving hypothermic saline perfusion had disturbed blood-brain barrier permeability. Based on visual inspection, disruption grade in the left hemispheres of 10 of 16 animals was 3+. Mean values for Evans blue dye were found to be 0.32 +/- 0.08 mg% in left the hemisphere after normothermic saline infusion (Group 1), and 2.9 +/- 0.4 mg% in the same hemisphere after hypothermic saline infusion (Group II). The difference was found to be significant between Group I and Group II (P < 0.001). The increase in cerebrovascular permeability was temporary, however, although Evans blue albumin extravasion remained slightly elevated 3 h after infusion, it was normal 6 h after infusion.

Comparison of the Activities of Na+,K+-ATPase in Brains of Rats at Different Ages

Background: Na+,K+-ATPase is known to be responsible for the ionic homeostasis in excitable tissues. The energy cost of Na+,K+-ATPase activity is increased in the active brain, so it would be important to ascertain whether defects in brain metabolism in aging are associated with changes in the properties of Na+,K+-ATPase. Objective: The aim of this study was to investigate the influence of age on the Na+,K+-ATPase activity in developing rat brains from the age of 1 day to 24–28 months. Methods: Crude microsomal preparations were obtained from the brains of newborn (n = 8), 18-day-old (n = 8), 4- to 5-month-old (n = 12), and 24- to 28-month-old (n = 14) rats. Then the ATPase activity was measured and expressed as micromoles of inorganic phosphorus released per milligram of protein per hour. Results: The increased tendency in brain Na+,K+-ATPase activity from newborn to 18 days of age suggested that the Na pump is mature soon after birth. No significant differences could be detected in the enzyme activity between newborn and adult rats. In contrast, the Na+,K+-ATPase activity in aged rat brains was found to be significantly lower than in the other age groups of rats tested (p < 0.001). Conclusion: Our results suggest that aging-induced inhibitions in the brain Na+,K+-ATPase activity may be implicated in the depression of neuronal excitability and in the age-related impairments of cognitive functions.

Asymmetrical changes in blood–brain barrier permeability during pentylenetetrazol-induced seizures and in acute hypertension

The asymmetrical breakdown of the blood-brain barrier to Evans-blue was studied in male and female rats during epileptiform seizures and in acute hypertension. The animals were divided into six groups. Group I: control female; Group II: control male; Group III: female + acute hypertension; Group IV: male + acute hypertension; Group V: female + seizure; Group VI: male + seizure. Asymmetric breakdown of the blood-brain barrier had been seen in female rats treated with pentylenetetrazol. Pentylenetetrazol-induced seizure produces less disruption of the blood-brain barrier in right cerebral hemisphere than in left cerebral hemisphere in female rats. There were no asymmetrical changes of blood-brain barrier permeability between the left and right hemispheres in acute hypertension in both sexes, and male rats treated with pentylenetetrazol.

Influence of profound hypothermia on the blood-brain barrier permeability during acute arterial hypertension

In hypothermic rats with acute hypertension induced by intravenous injection of adrenalin, regional changes in blood-brain barrier permeability to macromolecules were investigated using Evans blue as indication. Evans blue albumin extravasation was determined as a macroscopic finding and a quantitative estimation with a spectrophotometer using homogenized brain to release the dye was also performed to evaluate the macroscopic findings. Five groups of rats were studied: Group I: normothermia + acute hypertension; Group II: hypothermia + acute hypertension; Group III: control hypothermia; Group IV: normothermia + hypotension; Group V: control normothermia. The rats were anaesthetized with diethyl-ether. Body temperature was lowered by submerging anaesthetized animals in an ice water bath. The colonic temperature was reduced to 20 +/- 1 degrees C. During adrenaline-induced acute hypertension the mean arterial blood pressure increased in both normothermic and hypothermic animals. Blood-brain barrier lesions were present in 40% of normothermic rats, and 60% of hypothermic rats after adrenaline-induced hypertension. Mean value for Evans blue dye in the whole brain was found to be 0.530 +/- 0.202 mg% in the normothermic rats and 0.752 +/- 0.256 mg% in the hypothermic rats during adrenaline-induced hypertension. This difference between normothermic and hypothermic rats was found to be statistically significant (P less than 0.01). Our results showed that the extravasation of Evans blue albumin was most pronounced in the brains of hypothermic rats compared to normothermic rats after adrenaline-induced acute hypertension.