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Age related changes in the effect of electroconvulsive shock on the blood brain barrier permeability in rats
Mechanisms of Ageing andDevelopment, 51 (1990) 149--155
149
Elsevier Scientific Publishers Ireland Ltd.
AGE R E L A T E D C H A N G E S IN T H E E F F E C T OF E L E C T R O C O N V U L S I V E SHOCK ON T H E B L O O D B R A I N B A R R I E R P E R M E A B I L I T Y IN RATS
B. t)ZTAS, M. KAYA and S. C A M U R C U Department of Physiology, lstanbul Faculty of Medicine, University of lstanbul, Capa, Istanbu134390
(Turkey) (Received February 24th, 1989) (Revision received May 1lth, 1989)
SUMMARY
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 o f 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 o f 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.
Key words: Evans-blue; Blood-brain barrier; Electroconvulsive shock INTRODUCTION
Normal neurological function requires the maintenance of an optimal neuronal microenvironment. The structural and functional integrity of the blood-brain barrier is of paramount importance in this regulatory function [1]. The blood-brain barrier is a dynamic interface between blood and brain that has both restrictive and permissive properties. Vascular disease is often accompanied by an increased cerebrovascular permeability due to damage of the blood-brain barrier at the 0047-6374/90/$03.50 Printed and Published in Ireland
© 1990 Elsevier Scientific Publishers Ireland Ltd.
150
endothelium that lines cerebral blood vessels [2]. Controversy exists concerning the contribution of vascular disease to cerebral changes that occur during senescence [3,41. Increased penetration of large molecules such as albumin into the central nervous system as a result of altered cerebrovascular permeability during electrically induced seizures has been reported by a number of investigators [5,6]. Electroconvulsive therapy is an effective treatment for patients suffering from serious m o o d disorders, usually depressive state [7,8]. Benbow showed that electroconvulsive therapy is effective treatment for elderly patients with severe depressive illness [8]. On the other hand, it is generally accepted that the blood-brain barrier in the newborns of some species is less restrictive than it is in the adult [9,10]. The first to study the blood-brain barrier in developing m a m m a l s was Behnsen who injected trypan blue into young mice at various times after their birth. At early ages the dye was more extensively distributed in the brain than in the adult mouse [1 1]. But some workers have failed to detect increased uptake of trypan blue into the brain after injection into the newborn rat [12]. Generally the blood brain barrier has been accepted to be immature in the fetus and new born [9,10,13]. The present study was performed for the purpose of elucidating the following two problems: (1) whether single electroconvulsive seizure and ten repeated electroconvulsive seizures alter cerebrovascular permeability in old animals; (2) and to compare the effect of single and ten repeated electroconvulsive seizures on the blood-brain barrier permeability in the young, adult and old rats. MATERIALS AND METHODS
Seventy-eight Wistar rats at different ages were used. The animals were grouped according to age: (1) 15-day-old rats; (2) 30-day-old rats; (3) young adult rats (4--5 months); and (4) old rats (24 months of age). They were housed in individual cages and allowed food and water ad libitum. We selected 24 months of age as " o l d " because this is the age most c o m m o n l y used by other workers to present " o l d " rats [141. The rats were anaesthetized with diethylether. The femoral artery was cannulated for recording of mean arterial blood pressure and a femoral vein was cannulated for i.v. injections. Evans blue, which binds in vivo to serum albumin was given for macroscopic identification of areas of blood brain barrier dysfunction. The dose of Evans blue was 4 m l / k g of a 2% solution in saline. At this dose, the dye almost completely binds to serum albumin [15]. Evans-blue staining is a qualitative measure of barrier integrity; However, R a p a p o r t et al. have shown that staining intensity is correlated with the elevation of P A ([14C]sucrose permeability x capillary surface area) [15]. PA was normal when staining was absent (grade 0), and rose in proportion to staining that was at and above a grade 1 + level [15]. Johansson has also shown that the correlation between visual estimation of Evans-blue albumin extra-
151
vasation and the [125I]HSA ([125I]human serum albumin) content in the same brain is good [16]. Therefore, although a qualitative technique, Evans-blue staining is sufficient for the blood brain barrier experiments. Electroconvulsive shock was produced with the aid of a Ugo-Basil apparatus using special ear clips. The rats received one or ten repeated electroconvulsive shocks. Ten electroconvulsive shocks were applied providing a model o f status epilepticus. A 100-Hz square wave current (60 mA) of 100 V and with a pulse duration of 8 m was applied for 1.5 s [17]. These electroshock-stimuli were applied 5 min after the injection of Evans blue at intervals of approximately 25 s. In control rats, electroshock electrodes were placed on the ears o f rats but the current was not turned on. Approximately 15 min after last electroshock stimulus, the rats were killed by perfusion through the heart with saline followed by 10o70 formaldehyde to remove blood from the cerebral vessels. Brains were removed and after macroscopic inspection of the brain surface, 2--3 mm thick coronal blocks were cut by hand. Each coronal block was examined for the presence and distribution of Evans-blue albumin extravasation. Statistical analysis was performed using Student's t-test. RESULTS
The electrically-induced seizures typically consisted o f tonic flexion followed by a prolonged (8--10 s) period o f tonic forelimb and hindlimb extension and terminally, clonus. These electrically induced seizures lasted 20--25 s and this period decreased gradually to 5--8 s as the number o f the stimuli increased. The seizure pattern showed no marked alteration in rats 15 days to several months o f age. Mean arterial blood pressure increased immediately after each stimulus and fell to its initial level within a few seconds. The peak level o f mean arterial blood pressure decreased after each successive stimulus. Increase in mean arterial blood pressure due to seizures was 64 mmHg and 60 m m H g during one and ten repeated electroshock stimuli, respectively, in 30-day-old rats, and 64 m m H g and 56 mmHg in adult rats, and 60 mmHg and 55 m m H g in old rats. The increase in the arterial blood pressure was significant ( P < 0.001) compared with the initial values (Table I). The blood brain barrier competence or breakdown indicated by Evans-blue albumin extravasation in the 4 age groups is presented in Table I. In adult rats, in the control group and in the group given a single electroconvulsive shock, there was no coloration of the brain tissue except the pineal body (which has no blood brain barrier), whereas the group given ten repeated electroconvulsive seizures showed slight staining o f the thalamic nuclei, a n d / o r adjacent to the third ventricle, 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. Evans-blue albumin extravasation was a c o m m o n observation in hippocampus and, in some cases, a faint blueish color was also observed in the hypothalamus.
BETWEEN
11
10
11
1 ECS
10 E C S
10
10ECS
14
13
1 ECS
10ECS
8
1ECS
10ECS
121 ± 7
118 ± 9
114 ± 10
112 _+ 7
108 ± 6
176 ± 6*
178 ± 8*
--
168 ± 8*
172 ± 9*
--
163 ± 1 1 '
170 +_ 10"
--
55
60
--
56
64
--
60
64
--
--
--
--
--
---
4
6
5
8
14
10
7
8
6
3
3
4
*In c o m p a r i s o n with r e s p e c t i v e c o n t r o l value, P <
0.001 ( S t u d e n t ' s t-test).
I he visual e s t i m a t i o n o f E v a n s - b l u e e x t r a v i s i o n in the b r a i n s w a s g r a d e d on a scale f r o m 0 to 2 w h e r e 0 = n o n e , t = slight, 2 = m o d e r a t e .
5
6
Control
Old rats
10
Control
102 ± 9
103 ± 8
8
Adult rats
106 _+ I I
6
IECS
101 ± 9
--
--
--
1
.
--
5
--
--
3
--
--
8
7
7
1
.
.
. 3
N.
m
m
2
BARRIER
0
Maximum
Increase
BLOOD-BRAIN
Initial
SHOWING
Blood brain barrier breakdown"
SHOCKS (ECS)
(MABP) AND NUMBERS OF ANIMALS
ELECTROCONCULSIVE
BLOOD PRESSURE
Mean arterial blood pressure (mmHg)
Control
30-day
MEAN ARTERIAL
DURING SINGLE AND TEN REPEATED
Control
15-day
Experimental conditions
BREAKDOWN
THE RELATION
TABLE I
bO
153
In 15-day-old rats, the blood brain barrier breakdown to Evans-blue was found in the hippocampus, amygdala nuclei, the septum pellucidum, the hypothalamus, caudate putamen in all experimental groups. Blood-brain barrier disruption was the same after a single and ten electroshocks and the same in control and electroshocked rats. In old rats, the extravasation of Evans-blue albumin was most pronounced in the brain after ten repeated electroshocks. Evans-blue leakage was observed in the cerebral cortex, hypothalamus, corpus striatum, putamen, midbrain and thalamus in three out o f eight rats after ten repeated electroconvulsive seizures. DISCUSSION
Our results show that there was no change in the permeability of the blood-brain barrier to Evans-blue albumin associated with aging in the rats. The findings are consistent with the other experimental results. Rapoport et al. have found that cerebrovascular permeability to [~4C]sucrose does not increase with senescence in male Fischer 344 rats [4]. No differences were also observed in the brain distribution of horseradish peroxidase administered systemically in old and young mice [18]. However, when ten repeated electrical stimulations were given, a more pronounced increase in the permeability o f the blood-brain barrier was observed in the old rats as compared to adults. Sankar et al. have shown that the effect of amphetamine on the permeability o f the blood-brain barrier to albumin of the aged rats was significantly higher than the young rats [19]. During generalized seizures, the overall rate o f cerebral metabolism increases two- to five-fold depending on intensity and duration of the seizure [20]. Some age-related changes at the cerebral capillaries [21] and the increased energy consumption during seizures can provoke more blood-brain barrier disruption in old rats. However, although more blood-brain barrier breakdown was shown in three rats, no blood-brain barrier disruption was found in the other four rats during ten repeated electroconvulsive seizures. These results might suggest that they have some age-related histopathological changes in their vascular systems. In 15-day-old rats, blood-brain barrier leakage occurred that was similar in controls and all experimental groups. Thus, at 15 days there was accumulation of protein-dye complex in the cells of the hippocampus, amygdala nuclei, the caudate putamen, and the hypothalamus. Many investigators have noted that the bloodbrain barrier o f immature animals is more permeable than that of adults [1,9,22]. Stewart and Hayakaga showed that the high permeability in developing brain may be the result of leaky interendothelial junctions which are a consequence of vascular sprouting [9]. Vorbrodt et al. observed that the development of blood-brain barrier function is accompanied by the formation of enzymatic barrier in microblood vessels [22]. In 15 day-old rats, increased blood-brain barrier permeability in certain brain regions could not be provoked by electrically-induced seizures. In both 15-dayold and 30-day-old rats, the blood-brain barrier permeability was less disrupted by
154 e l e c t r o c o n v u l s i v e s e i z u r e s t h a n a d u l t r a t s . It is d i f f i c u l t t o e x p l a i n t h e s e p r o t e c t i v e mechanisms
of the blood-brain
barrier
young animals, since acute hypertension
during
electroconvulsive
causing blood-brain
s e i z u r e s in t h e
barrier breakdown
d u r i n g e l e c t r o c o n v u l s i v e s e i z u r e is s i m i l a r i n b o t h g r o u p s ( T a b l e I). B r a i n m y e l i n c o n t e n t i n c r e a s e s s i g n i f i c a n t l y d u r i n g t h e n e o n a t a l p e r i o d ; h e n c e it seems possible that blood-brain barrier permeability might be different in the neona t e t h a n i n t h e a d u l t [23]. K e t o n e b o d i e s a r e t h e m a j o r e n e r g y s o u r c e s in t h e s u c k l i n g b r a i n . I n t h e b r a i n o f t h e s u c k l i n g r a t , w h e r e e n e r g y is d e r i v e d p r i m a r i l y f r o m m o n o carboxylic acid metabolism
[23], t h e s e d i f f e r e n c e s b e t w e e n a d u l t a n d s u c k l i n g r a t
b r a i n a n d e n d o t h e l i a l cell m e t a b o l i s m m a y b e e f f e c t e d in t h e p r o t e c t i v e m e c h a n i s m of the blood-brain barrier during seizures. REFERENCES 1 2
3 4 5 6 7 8 9 l0 11 12 13
14
15 16
M. Bradbury, The Concept o f a Blood Brain Barrier. John Wiley and Sons, Chichester, New York, Bribonce Toronto, 1979. H.M. Wisniewski and P.B. Koslowski, Evidence for blood brain barrier changes in senile dementia of the Alzheimer Type (SDAT). In: F.N. Sinex and C.R. Merril (eds.), Annals o f the New York Academy o f Sciences, Vol. 396. Alzheimer" s Disease, Down's Syndrome, and Aging, The New York Academy of Sciences, New York, 1982, pp. 119--129. K. Nandy, Significance of brain-reactive antibodies in serum of aged mice. J. Gerontol., 30 (1975), 412--416. S.I. Rapoport, K. Ohno and K.D. Pettigrew, Blood brain barrier permeability in senescent rats. J. Geronto134 (1979) 162--169. B. t~ztas and U. Sandalci, Blood-brain barrier permeability after penetylenetetrazol and electronically induced seizure. IRCS Med. Sci., 12 (1984) 488--489. E. Westergaard, The blood brainbarrier to horseradish peroxidase under normal and experimental conditions. Acta NeuropathoL (Berl.), 39 (1977) 181--187. J.W. Thompson and J.D. Blaine, Use of ECT in the United States in 1979 and 1980. Am. J. Psychiatry, 144 (1987) 557--562. S.M. Benbow, The use of electroconvulsive therapy in old age psychiatry. Int. J. Geriatric Psychiatry, 2 (1987) 25--30. P.A. Stewart and E.M. Hayakawa, Inter endothelial junctional changes underlie the developmental tightening of the blood-brain barrier. Dev. Brain Res., 32 (1987) 271--28 I. N.R. Saunders and K.Mallgard, Development of the blood brain barrier. J. Dev. Physiol., 6 (1984) 45--57. G. Behnsen, Uber die Farbstoffspeicherung im Zentral nervensytem der weissen Maus in verschiedenen Alterzustanden. Z. Zellforsch., 4 (1927) 515--572. J.W. Millen and A. Hess, The blood brain barrier an experimental study with vital dyes. Brain, 81 (1958) 248--257. E.M. Cornford, W.M. Pardridge, C.D. Braun and W.H. Oldendorf, Increased blood-brain barrier transport of protein bound anticonvulsant drugs in the newborn. J. Cereb. Blood Flow Metab., 3 (1983) 280--286. M.C. McNamara, A.T. Miller, V.A. Beningnus and J.N. Davis, Age related changes in the effect of electroconvulsive shock(ECS) on the in vivo hydroxylation of tyrosic and tryptophan in rat brain. Brain Res., 131 1977)314--320. S.I. Rapoport, W.R. Fredericks, K. Ohno and K.D. Pettigrew, Quantitative aspects of reversible osmotic opening of the blood brain barrier. A rn. J. Physiol., 238 (1980) R421--R43 I. B. Johansson, The cerebrovascular permeability to protein after bicuculline and amphetamine administration in spontaneously hypertensive rats. Acta Neurol. Scand., 56 (1977) 397--404.
155 17
B. ()ztas and F. Dogu, The influence of electroshock on sodium and potassium ion content in different regions of rat brain. IRCS Med. Sci., 14 (1986) 1120--- 1121. 18 R.A. Rudick and S.J. Buell, Integrity of blood brain barrier to peroxidase in senescent mice. Neurobiol. Aging, 4 (1983) 283-- 287. 19 R. Sankar, E. Blossom, K. Clemons and P. Charles, Age-associated changes in the effects of amphetamine on the blood-brain barrier of rats. Neurobiol. Aging, 4 (1983) 65--68. 20 F. Plum and T.E. Duffy, The couple between cerebral metabolism and blood flow during seizures. "'Brain work"Alfred Benzon symposium VIII, Munksgaard (1975) pp.197--214. 21 E.M. Burns, T.W. Kruckeberg and P.K. Gaetano, Changes with ageing cerebral capillary morphology. NeurobioL Aging, 2 (1981) 285--291. 22 A.W. Vorbrodt, A.S. Lossinsky and H.M. Wisniewski, Localication of alkaline phosphatase activity in endothelial of developing and mature mouse blood-brain barrier. Dev. Neurosci., 8 (1986) 1-13. 23 E.M. Cornford and M.E. Cornford, Nutrient transport and the blood brain barrier in developing animals. Fed. Proc., 45 (1986) 2065--2072.
149
Elsevier Scientific Publishers Ireland Ltd.
AGE R E L A T E D C H A N G E S IN T H E E F F E C T OF E L E C T R O C O N V U L S I V E SHOCK ON T H E B L O O D B R A I N B A R R I E R P E R M E A B I L I T Y IN RATS
B. t)ZTAS, M. KAYA and S. C A M U R C U Department of Physiology, lstanbul Faculty of Medicine, University of lstanbul, Capa, Istanbu134390
(Turkey) (Received February 24th, 1989) (Revision received May 1lth, 1989)
SUMMARY
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 o f 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 o f 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.
Key words: Evans-blue; Blood-brain barrier; Electroconvulsive shock INTRODUCTION
Normal neurological function requires the maintenance of an optimal neuronal microenvironment. The structural and functional integrity of the blood-brain barrier is of paramount importance in this regulatory function [1]. The blood-brain barrier is a dynamic interface between blood and brain that has both restrictive and permissive properties. Vascular disease is often accompanied by an increased cerebrovascular permeability due to damage of the blood-brain barrier at the 0047-6374/90/$03.50 Printed and Published in Ireland
© 1990 Elsevier Scientific Publishers Ireland Ltd.
150
endothelium that lines cerebral blood vessels [2]. Controversy exists concerning the contribution of vascular disease to cerebral changes that occur during senescence [3,41. Increased penetration of large molecules such as albumin into the central nervous system as a result of altered cerebrovascular permeability during electrically induced seizures has been reported by a number of investigators [5,6]. Electroconvulsive therapy is an effective treatment for patients suffering from serious m o o d disorders, usually depressive state [7,8]. Benbow showed that electroconvulsive therapy is effective treatment for elderly patients with severe depressive illness [8]. On the other hand, it is generally accepted that the blood-brain barrier in the newborns of some species is less restrictive than it is in the adult [9,10]. The first to study the blood-brain barrier in developing m a m m a l s was Behnsen who injected trypan blue into young mice at various times after their birth. At early ages the dye was more extensively distributed in the brain than in the adult mouse [1 1]. But some workers have failed to detect increased uptake of trypan blue into the brain after injection into the newborn rat [12]. Generally the blood brain barrier has been accepted to be immature in the fetus and new born [9,10,13]. The present study was performed for the purpose of elucidating the following two problems: (1) whether single electroconvulsive seizure and ten repeated electroconvulsive seizures alter cerebrovascular permeability in old animals; (2) and to compare the effect of single and ten repeated electroconvulsive seizures on the blood-brain barrier permeability in the young, adult and old rats. MATERIALS AND METHODS
Seventy-eight Wistar rats at different ages were used. The animals were grouped according to age: (1) 15-day-old rats; (2) 30-day-old rats; (3) young adult rats (4--5 months); and (4) old rats (24 months of age). They were housed in individual cages and allowed food and water ad libitum. We selected 24 months of age as " o l d " because this is the age most c o m m o n l y used by other workers to present " o l d " rats [141. The rats were anaesthetized with diethylether. The femoral artery was cannulated for recording of mean arterial blood pressure and a femoral vein was cannulated for i.v. injections. Evans blue, which binds in vivo to serum albumin was given for macroscopic identification of areas of blood brain barrier dysfunction. The dose of Evans blue was 4 m l / k g of a 2% solution in saline. At this dose, the dye almost completely binds to serum albumin [15]. Evans-blue staining is a qualitative measure of barrier integrity; However, R a p a p o r t et al. have shown that staining intensity is correlated with the elevation of P A ([14C]sucrose permeability x capillary surface area) [15]. PA was normal when staining was absent (grade 0), and rose in proportion to staining that was at and above a grade 1 + level [15]. Johansson has also shown that the correlation between visual estimation of Evans-blue albumin extra-
151
vasation and the [125I]HSA ([125I]human serum albumin) content in the same brain is good [16]. Therefore, although a qualitative technique, Evans-blue staining is sufficient for the blood brain barrier experiments. Electroconvulsive shock was produced with the aid of a Ugo-Basil apparatus using special ear clips. The rats received one or ten repeated electroconvulsive shocks. Ten electroconvulsive shocks were applied providing a model o f status epilepticus. A 100-Hz square wave current (60 mA) of 100 V and with a pulse duration of 8 m was applied for 1.5 s [17]. These electroshock-stimuli were applied 5 min after the injection of Evans blue at intervals of approximately 25 s. In control rats, electroshock electrodes were placed on the ears o f rats but the current was not turned on. Approximately 15 min after last electroshock stimulus, the rats were killed by perfusion through the heart with saline followed by 10o70 formaldehyde to remove blood from the cerebral vessels. Brains were removed and after macroscopic inspection of the brain surface, 2--3 mm thick coronal blocks were cut by hand. Each coronal block was examined for the presence and distribution of Evans-blue albumin extravasation. Statistical analysis was performed using Student's t-test. RESULTS
The electrically-induced seizures typically consisted o f tonic flexion followed by a prolonged (8--10 s) period o f tonic forelimb and hindlimb extension and terminally, clonus. These electrically induced seizures lasted 20--25 s and this period decreased gradually to 5--8 s as the number o f the stimuli increased. The seizure pattern showed no marked alteration in rats 15 days to several months o f age. Mean arterial blood pressure increased immediately after each stimulus and fell to its initial level within a few seconds. The peak level o f mean arterial blood pressure decreased after each successive stimulus. Increase in mean arterial blood pressure due to seizures was 64 mmHg and 60 m m H g during one and ten repeated electroshock stimuli, respectively, in 30-day-old rats, and 64 m m H g and 56 mmHg in adult rats, and 60 mmHg and 55 m m H g in old rats. The increase in the arterial blood pressure was significant ( P < 0.001) compared with the initial values (Table I). The blood brain barrier competence or breakdown indicated by Evans-blue albumin extravasation in the 4 age groups is presented in Table I. In adult rats, in the control group and in the group given a single electroconvulsive shock, there was no coloration of the brain tissue except the pineal body (which has no blood brain barrier), whereas the group given ten repeated electroconvulsive seizures showed slight staining o f the thalamic nuclei, a n d / o r adjacent to the third ventricle, 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. Evans-blue albumin extravasation was a c o m m o n observation in hippocampus and, in some cases, a faint blueish color was also observed in the hypothalamus.
BETWEEN
11
10
11
1 ECS
10 E C S
10
10ECS
14
13
1 ECS
10ECS
8
1ECS
10ECS
121 ± 7
118 ± 9
114 ± 10
112 _+ 7
108 ± 6
176 ± 6*
178 ± 8*
--
168 ± 8*
172 ± 9*
--
163 ± 1 1 '
170 +_ 10"
--
55
60
--
56
64
--
60
64
--
--
--
--
--
---
4
6
5
8
14
10
7
8
6
3
3
4
*In c o m p a r i s o n with r e s p e c t i v e c o n t r o l value, P <
0.001 ( S t u d e n t ' s t-test).
I he visual e s t i m a t i o n o f E v a n s - b l u e e x t r a v i s i o n in the b r a i n s w a s g r a d e d on a scale f r o m 0 to 2 w h e r e 0 = n o n e , t = slight, 2 = m o d e r a t e .
5
6
Control
Old rats
10
Control
102 ± 9
103 ± 8
8
Adult rats
106 _+ I I
6
IECS
101 ± 9
--
--
--
1
.
--
5
--
--
3
--
--
8
7
7
1
.
.
. 3
N.
m
m
2
BARRIER
0
Maximum
Increase
BLOOD-BRAIN
Initial
SHOWING
Blood brain barrier breakdown"
SHOCKS (ECS)
(MABP) AND NUMBERS OF ANIMALS
ELECTROCONCULSIVE
BLOOD PRESSURE
Mean arterial blood pressure (mmHg)
Control
30-day
MEAN ARTERIAL
DURING SINGLE AND TEN REPEATED
Control
15-day
Experimental conditions
BREAKDOWN
THE RELATION
TABLE I
bO
153
In 15-day-old rats, the blood brain barrier breakdown to Evans-blue was found in the hippocampus, amygdala nuclei, the septum pellucidum, the hypothalamus, caudate putamen in all experimental groups. Blood-brain barrier disruption was the same after a single and ten electroshocks and the same in control and electroshocked rats. In old rats, the extravasation of Evans-blue albumin was most pronounced in the brain after ten repeated electroshocks. Evans-blue leakage was observed in the cerebral cortex, hypothalamus, corpus striatum, putamen, midbrain and thalamus in three out o f eight rats after ten repeated electroconvulsive seizures. DISCUSSION
Our results show that there was no change in the permeability of the blood-brain barrier to Evans-blue albumin associated with aging in the rats. The findings are consistent with the other experimental results. Rapoport et al. have found that cerebrovascular permeability to [~4C]sucrose does not increase with senescence in male Fischer 344 rats [4]. No differences were also observed in the brain distribution of horseradish peroxidase administered systemically in old and young mice [18]. However, when ten repeated electrical stimulations were given, a more pronounced increase in the permeability o f the blood-brain barrier was observed in the old rats as compared to adults. Sankar et al. have shown that the effect of amphetamine on the permeability o f the blood-brain barrier to albumin of the aged rats was significantly higher than the young rats [19]. During generalized seizures, the overall rate o f cerebral metabolism increases two- to five-fold depending on intensity and duration of the seizure [20]. Some age-related changes at the cerebral capillaries [21] and the increased energy consumption during seizures can provoke more blood-brain barrier disruption in old rats. However, although more blood-brain barrier breakdown was shown in three rats, no blood-brain barrier disruption was found in the other four rats during ten repeated electroconvulsive seizures. These results might suggest that they have some age-related histopathological changes in their vascular systems. In 15-day-old rats, blood-brain barrier leakage occurred that was similar in controls and all experimental groups. Thus, at 15 days there was accumulation of protein-dye complex in the cells of the hippocampus, amygdala nuclei, the caudate putamen, and the hypothalamus. Many investigators have noted that the bloodbrain barrier o f immature animals is more permeable than that of adults [1,9,22]. Stewart and Hayakaga showed that the high permeability in developing brain may be the result of leaky interendothelial junctions which are a consequence of vascular sprouting [9]. Vorbrodt et al. observed that the development of blood-brain barrier function is accompanied by the formation of enzymatic barrier in microblood vessels [22]. In 15 day-old rats, increased blood-brain barrier permeability in certain brain regions could not be provoked by electrically-induced seizures. In both 15-dayold and 30-day-old rats, the blood-brain barrier permeability was less disrupted by
154 e l e c t r o c o n v u l s i v e s e i z u r e s t h a n a d u l t r a t s . It is d i f f i c u l t t o e x p l a i n t h e s e p r o t e c t i v e mechanisms
of the blood-brain
barrier
young animals, since acute hypertension
during
electroconvulsive
causing blood-brain
s e i z u r e s in t h e
barrier breakdown
d u r i n g e l e c t r o c o n v u l s i v e s e i z u r e is s i m i l a r i n b o t h g r o u p s ( T a b l e I). B r a i n m y e l i n c o n t e n t i n c r e a s e s s i g n i f i c a n t l y d u r i n g t h e n e o n a t a l p e r i o d ; h e n c e it seems possible that blood-brain barrier permeability might be different in the neona t e t h a n i n t h e a d u l t [23]. K e t o n e b o d i e s a r e t h e m a j o r e n e r g y s o u r c e s in t h e s u c k l i n g b r a i n . I n t h e b r a i n o f t h e s u c k l i n g r a t , w h e r e e n e r g y is d e r i v e d p r i m a r i l y f r o m m o n o carboxylic acid metabolism
[23], t h e s e d i f f e r e n c e s b e t w e e n a d u l t a n d s u c k l i n g r a t
b r a i n a n d e n d o t h e l i a l cell m e t a b o l i s m m a y b e e f f e c t e d in t h e p r o t e c t i v e m e c h a n i s m of the blood-brain barrier during seizures. REFERENCES 1 2
3 4 5 6 7 8 9 l0 11 12 13
14
15 16
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