0736-5748192$5.00+0.00 PergamonPress Ltd. 0 1992 ISDN
Int. .I. Dev1. Neuroscience,Vol. 10, No. 4, pp. 301-311, 1992 Printedin Great Britain.
EFFECTS OF PENTYLENETETRAZOL-INDUCED SEIZURES ON DOPAMINE AND NOREPINEPHRINE LEVELS AND ON GLUCOSE UTILIZATION IN VARIOUS BRAIN REGIONS OF THE DEVELOPING RAT GHI?ZIEL EL HAMDI , * MARIE-JEANNE INSERM
U 272,
BOUTROY
and
ASTRID NEHLIG
Universite de Nancy I, 30, rue Lionnois, B.P. 3069, 54013 Nancy-CCdex, France
(Received 4 November 1991; in revised form 21 April 1992; accepted 24 April 1992)
Abstract-Levels of dopamine and norepinephrine were measured in seven brain areas after 60 min of sustained seizure activity induced by intraperitoneal repetitive timed administrations of pentylenetetrazol in rats at 10,14,17 and 21 days of postnatal life. The tissue levels of norepinephrine were markedly reduced in the majority of brain structures, except for striatum at 10 and 14 days. Conversely, dopamine concentrations increased in many areas and at various ages, except in cerebral cortex at 10 and 14 days and in midbrain between 14 and 21 days. PTZ seizures induced marked increases over control levels in the rates of glucose utilization, measured by the quantitative autoradiographic [‘4C]2-deoxyglucose method, in all dopamine- and norepinephrine-innervated areas studied at 10 and 14 days, except in cerebellar cortex at both ages and in frontal cortex and anteroventral thalamus at 14 days. At 17 and 21 days, glucose utilization remained increased over control levels in some areas, mainly in catecholaminergic cell groupings such as substantia nigra, ventral tegmental area and locus coeruleus, but was significantly reduced in cortex, caudate nucleus and thalamus, and similar to control rates in other regions. The present results suggest that pentylenetetrazol-induced seizures lead to a simultaneous increase in functional activity of norepinephrine neurons and an inhibition of dopaminergic-mediated neurons. They also confirm the maturation of connections, of metabolic activity and of neurotransmitter interaction within the brain, occurring mainly during the third week of postnatal life, paralleled by an increased selective vulnerability of some regions to this kind of insult. Key words: catecholamines, 2-deoxyglucose, brain, quantitative autoradiography.
seizures, pentylenetetrazol,
postnatal development,
rat
The involvement of various neurotransmitters in the cellular mechanisms of epilepsy has been extensively reported in several animal models.44*46,65Already in 1954, Chen et al. lo noticed that reserpine lowered the threshold for electroshock- and pentylenetetrazol (PTZ)-induced convulsions in mice. More recently, numerous data have reported the involvement of monoaminergic neurotransmitters in the susceptibility and severity of seizures. In the kindling model, cerebral norepinephrine (NE) and serotonin (5HT) depletion has been shown to facilitate the development of seizures in adult rats.2,3,‘3,55Similarly deficits in NE and 5HT have been described to occur prior to the induction of seizures in the genetically epilepsy-prone rat’5~29~30 and in the audiogenic mouse. 33,57Depletion of brain monoamines has also been described to facilitate electroshock4,19T36*67or drug-induced seizures in adult rodents.‘7,34 However, NA appears to be more important than dopamine (DA) in the modulation of seizure severity.31 Indeed, NE depletion facilitates seizures whereas DA deficits have no effect on convulsion threshold and severity. 13*45Changes in brain levels of NE, DA and 5HT have been studied in adult animals during the course of bicuculline-induced seizures. Whole brain levels of NE are reduced, whereas those of DA are first unaffected and increase thereafter. Cerebral 5HT levels transiently decrease to return to normal levels after 60 min of seizure activity.8 In the immature rat, motor expression of convulsive seizures and thresholds of electroshock stimulation change with age, according to the development of cerebral structure connections.47’48,62 The threshold to seizures is also decreased in 7-Sday-old rats after reduction of brain catecholamines (both DA and NE) and 5HT.39 However, at that stage, the change in *Author to whom all correspondence should be addressed at: INSERM U 272, “Pathologie et Biologie du Developpement Humain”, Universitd de Nancy I, 30, rue Lionnois, B.P. 3069,54013 Nancy-CCdex, France. Phone: (33)-83-37-3559, Fax: (33)~83-32-95-90. Abbreviations: CA, catecholamine; DA, dopamine, 2DG, 2-deoxyglucose; SHT, serotonin; NE, norepinephrine; P, postnatal day; PTZ, pentylenetetrazol; SE, status epilepticus.
303
threshold to convulsive phenomena IS prevented when catecholamine levels ;trc ~1aint~liIl~~i in rb_~ normal range, but is independent of changes in 5HT levels. I’)In the 15day-old rat. depiction (II’ both catecholamines and SHT seems necessary to reduce seizure threshold, whereas in the .30, day-old rat. only reduction of SHT is associated with II signiticant dcci-C~Li\c 111 seizure threshold.“’ It therefore appears from the two latter studies that there seems iZ) I-x ;i ~~evel~~prn~ntaf transiti(~n from catecholamincrgic to ser~~t~ninergic ~l~~?~iil~irlcc in reg~~lati(~ll tli seizure threshold during the first month of life in the rat.3s..t”.63 f-fowevcr 1IO our knowI&&.. thex are no data available on seizure-induced changes in brain amine content iu immature I;II> Therefore. in the present study. we investigated the consequences of severe status epilcpticu!, induced by repetitive timed injections of PT% on NE and DA levels in rcven different brain regions of immature rats at the ages of IO, I-t, 17 and 21 days of postnatal life, C~ltechl~l~~l~~ir~e levels in the different brain areas were related to changes in glucose utilization in d~pal~lin~rgic~ and noradrenergic-innervated regions. Cerebral SHT levels were not measured in the present study since this latter amine plays only a predominant role in the regulation of seizures in IO-dayold and adult rats. ” 40.h’
EXPERIMENTAL
PROCEDURES
Animals Adult Sprague-Dawley rats, 1 male and 2 females, were housed together in mating groups for 10 days and constantly maintained under standard laboratory conditions on a 12:12 light/dark cycle (light on at 0600 h). Food and water were available ad ljb~iu~. Pregnant rats, as determined by palpation, were put in individual cages 5 days after separation from the male. Each litter was reduced to 10 pups per mother at 1 day of age (the day of birth was taken as day 0). The experiments were performed in lo- (PIO), 14- (P14), 17- (P17) and 21- (P21) day-old rats. Ah animal experimentation was performed with the highest standards of animal care, according to the Guide for Care and Use of Laboratory Animals.
On the day of testing, PTZ dissolved in saline (10 mg/ml), was administered intraperitoneally to the rats. To reach long-lasting status epilepticus (SE), the animals received a first injection of 40 mg/kg and 10 min later an additional dose of 20 mglkg. Repetitive injections of 10 mg/kg each 10 min were then administered until SE was reached. The behavioral criteria characterizing SE have been described in detail at all ages studied.*” In PI0 and P14 animals, SE was usually reached at a dose of 60-70 mg of PTZ and was characterized by tonic-clonic seizures with flexions and extensions of forelimbs and usually only ffexions of hindlimbs. At PI7 and P21, SO-120 mg of PTZ were necessary to induce sustained seizures. At these ages, SE was characterized by tonic-clonic seizures with behavioral components more prominent, more violent and shorter than at an earlier age.23
For determination of brain content of DA and NE, animals were killed by decapitation at 60 min after the onset of SE. Control rats received the same number of saline injections as their paired PTZ-treated congeners and were killed 60 min after the last injection, corresponding to the one leading to SE in PTZ-exposed congener. This duration of SE was chosen to correspond to the end of the 2-deoxyglucose experiment. Prepffr~t~on of tissues. After decapitation, the brain was removed and dissected into the following regions: cerebral cortex, hippocampus, hypothalamus, striatum, midbrain, brainstem and cerebellum, according to Glowinski and Iversen.” Tissue pieces were homogenized in 20 volumes of chilled 0.2 M perchloric acid containing 7 mM MgClz and 2.6 mM EGTA. The homogenates were centrifuged at 20000 g for 15 min and the supernatant fluid was stored at -80°C until assay. For each d~terminatjon, according to the age and size of the structures. the areas of 3-6 animals were pooled. Cutechoiumine assay. DA and NE levels in the supernatant fluid of brain homogenates were assayed according to a radioenzymatic method,lh modified as described by Dennis and Scatton,‘” and Mitrovic.4y
Seizures, brain CA and glucose use
303
The assay is based on the 3-0-methylation of CA by the enzyme catechol-0-methyltransferase in the presence of S-adenosyl-[methyl-3H]methionine. Labelled 0-methylated products were transformed to less polar complexes by adding tetraphenylboron and thereafter extracted by diethylether. The reaction products were separated by thin-layer chromatography. Methoxywas eluted and the radioactivity measured. tyramine derived from DA 3-0-methylation, Normetanephrine derived from NE 3-0-methylation was oxidized further to vanillin and its radioactivity was counted after extraction. This procedure has been described in detail previously.22 Measurement
of local cerebral glucose utilization
Rates of local cerebral glucose utilization were measured by the quantitative autoradiographic [‘4C]2-deoxyglucose (2DG) method described by Sokoloff et al. ,59 adapted to the developing rat.‘” The [14C]2-deoxyglucose (4.625 MBq/kg; spec. act., 1.65-2.04 GBq/mmol; Commissariat a 1’Energie Atomique, Saclay, France) was injected as a pulse through a venous femoral catheter at 10 min after the onset of SE. Generalized seizures lasted for the whole duration of the 2DG experiment. Nine to 12 timed arterial blood samples were drawn from the femoral artery of freelymoving rats during the following 45 min for the measurement of plasma concentration of 2DG and glucose. At approximately 45 min after the pulse of 2DG, the animals were killed by decapitation. Brains were rapidly removed and frozen in isopentane chilled to -35°C and cut into 20 km coronal sections at -22°C in a cryostat. Sections were autoradiographed on Kodak SB5 film along with calibrated [‘4C]methylmethacrylate standards (Amersham, Arlington Heights, U.S.A.), using a special set of low r4C concentration standards for PlO and P14 animals. The autoradiographs were analyzed by quantitative densitometry with a computerized image processing system (Biocom 200, Les Ulis, France) or a manual microdensitometer (Macbeth, TD901, Kollmorgen Co., Newburgh, U.S.A.). Optical density measurements for each structure anatomically defined according to the developing rat brain atlas of Sherwood and Timiras58 were made bilaterally in a minimum of four brain sections without knowledge of the treatment of the animal. Rates of local cerebral glucose utilization were then calculated from the local tissue concentration of 14C, the time courses of the plasma 2DG and glucose concentrations, and the appropriate constants according to the operational equation of the method.59 Statistical analysis
The statistical methods used to analyze the data were a two-way analysis of variance and the two-tailed Student’s t-test to compare catecholamine levels and rates of glucose utilization between control and seizing animals and Bonferroni’s multiple comparison procedures to compare the levels in each group of animals with those in the immediate preceding stage. RESULTS Effect of PTZ on catecholamine levels
As shown in Tables 1 and 2, at all stages studied, SE induced an increase in DA amounts in all brain regions studied and a simultaneous decrease in NE concentrations, except in the striatum at PlO and P14, where NE content increased. In both controls and seizing animals, DA concentrations were lowest in cerebellum and reached very high levels in striatum. For NE, regional distribution was less heterogeneous than for DA. In both control and experimental rats, NE levels were lowest in cerebral cortex and cerebellum and highest in hypothalamus. Two-way analysis of variance
There was an effect of the nature of the treatment on both DA and NE brain concentrations. The nature of the treatment significantly affected DA concentrations in all brain areas studied with P values ranging from 10m4to 8 x 10e4. For NE amounts, this effect was significant in 6 of the 7 structures studied (P values ranging from low4 to 10m3), except in the striatum (P = 0.2724). Age effects were significant for both DA and NE in all areas (P values ranging from 10m4 to 3.39 X 10W2),except in cerebellum where no effect of age was recorded either for DA (P = 0.4341)
Table 2. Effects of seizures on norepinephrine levels m various brain regions of immature rats PI0 Cerebral
cortex
Hippocampus Hypothalamus Striatum Midbrain Brainstem Cerebellum
C‘ PTZ C’ PTZ (’ P-l‘% C PTZ C PT7 C‘ P-l‘%
PI 4 122t21 7 1 -t 22-I. I02 t 34 IbXi-59 533 1 135 32x i 83* ‘J3 ? 31 I42 i 1-l 216 + hl 18Oi37 45s 5 110 108 -t 50:; Ih7+ 1x 107 ~+12
1’7I 142 + 34 00 f lb*,* * XX L Y4 ll5_+SXi 118ot29X*’ 189 L lYS$ I75 4 55 171 ! hY 130 t 7x** 762 L! 70158.1 t 67 794 + xxnll I77 + 3x
1% + 74*
Values, expressed as ngig, are means t S.D. of S-6 determinations. *:P
Int. .I. Dev1. Neuroscience,Vol. 10, No. 4, pp. 301-311, 1992 Printedin Great Britain.
EFFECTS OF PENTYLENETETRAZOL-INDUCED SEIZURES ON DOPAMINE AND NOREPINEPHRINE LEVELS AND ON GLUCOSE UTILIZATION IN VARIOUS BRAIN REGIONS OF THE DEVELOPING RAT GHI?ZIEL EL HAMDI , * MARIE-JEANNE INSERM
U 272,
BOUTROY
and
ASTRID NEHLIG
Universite de Nancy I, 30, rue Lionnois, B.P. 3069, 54013 Nancy-CCdex, France
(Received 4 November 1991; in revised form 21 April 1992; accepted 24 April 1992)
Abstract-Levels of dopamine and norepinephrine were measured in seven brain areas after 60 min of sustained seizure activity induced by intraperitoneal repetitive timed administrations of pentylenetetrazol in rats at 10,14,17 and 21 days of postnatal life. The tissue levels of norepinephrine were markedly reduced in the majority of brain structures, except for striatum at 10 and 14 days. Conversely, dopamine concentrations increased in many areas and at various ages, except in cerebral cortex at 10 and 14 days and in midbrain between 14 and 21 days. PTZ seizures induced marked increases over control levels in the rates of glucose utilization, measured by the quantitative autoradiographic [‘4C]2-deoxyglucose method, in all dopamine- and norepinephrine-innervated areas studied at 10 and 14 days, except in cerebellar cortex at both ages and in frontal cortex and anteroventral thalamus at 14 days. At 17 and 21 days, glucose utilization remained increased over control levels in some areas, mainly in catecholaminergic cell groupings such as substantia nigra, ventral tegmental area and locus coeruleus, but was significantly reduced in cortex, caudate nucleus and thalamus, and similar to control rates in other regions. The present results suggest that pentylenetetrazol-induced seizures lead to a simultaneous increase in functional activity of norepinephrine neurons and an inhibition of dopaminergic-mediated neurons. They also confirm the maturation of connections, of metabolic activity and of neurotransmitter interaction within the brain, occurring mainly during the third week of postnatal life, paralleled by an increased selective vulnerability of some regions to this kind of insult. Key words: catecholamines, 2-deoxyglucose, brain, quantitative autoradiography.
seizures, pentylenetetrazol,
postnatal development,
rat
The involvement of various neurotransmitters in the cellular mechanisms of epilepsy has been extensively reported in several animal models.44*46,65Already in 1954, Chen et al. lo noticed that reserpine lowered the threshold for electroshock- and pentylenetetrazol (PTZ)-induced convulsions in mice. More recently, numerous data have reported the involvement of monoaminergic neurotransmitters in the susceptibility and severity of seizures. In the kindling model, cerebral norepinephrine (NE) and serotonin (5HT) depletion has been shown to facilitate the development of seizures in adult rats.2,3,‘3,55Similarly deficits in NE and 5HT have been described to occur prior to the induction of seizures in the genetically epilepsy-prone rat’5~29~30 and in the audiogenic mouse. 33,57Depletion of brain monoamines has also been described to facilitate electroshock4,19T36*67or drug-induced seizures in adult rodents.‘7,34 However, NA appears to be more important than dopamine (DA) in the modulation of seizure severity.31 Indeed, NE depletion facilitates seizures whereas DA deficits have no effect on convulsion threshold and severity. 13*45Changes in brain levels of NE, DA and 5HT have been studied in adult animals during the course of bicuculline-induced seizures. Whole brain levels of NE are reduced, whereas those of DA are first unaffected and increase thereafter. Cerebral 5HT levels transiently decrease to return to normal levels after 60 min of seizure activity.8 In the immature rat, motor expression of convulsive seizures and thresholds of electroshock stimulation change with age, according to the development of cerebral structure connections.47’48,62 The threshold to seizures is also decreased in 7-Sday-old rats after reduction of brain catecholamines (both DA and NE) and 5HT.39 However, at that stage, the change in *Author to whom all correspondence should be addressed at: INSERM U 272, “Pathologie et Biologie du Developpement Humain”, Universitd de Nancy I, 30, rue Lionnois, B.P. 3069,54013 Nancy-CCdex, France. Phone: (33)-83-37-3559, Fax: (33)~83-32-95-90. Abbreviations: CA, catecholamine; DA, dopamine, 2DG, 2-deoxyglucose; SHT, serotonin; NE, norepinephrine; P, postnatal day; PTZ, pentylenetetrazol; SE, status epilepticus.
303
threshold to convulsive phenomena IS prevented when catecholamine levels ;trc ~1aint~liIl~~i in rb_~ normal range, but is independent of changes in 5HT levels. I’)In the 15day-old rat. depiction (II’ both catecholamines and SHT seems necessary to reduce seizure threshold, whereas in the .30, day-old rat. only reduction of SHT is associated with II signiticant dcci-C~Li\c 111 seizure threshold.“’ It therefore appears from the two latter studies that there seems iZ) I-x ;i ~~evel~~prn~ntaf transiti(~n from catecholamincrgic to ser~~t~ninergic ~l~~?~iil~irlcc in reg~~lati(~ll tli seizure threshold during the first month of life in the rat.3s..t”.63 f-fowevcr 1IO our knowI&&.. thex are no data available on seizure-induced changes in brain amine content iu immature I;II> Therefore. in the present study. we investigated the consequences of severe status epilcpticu!, induced by repetitive timed injections of PT% on NE and DA levels in rcven different brain regions of immature rats at the ages of IO, I-t, 17 and 21 days of postnatal life, C~ltechl~l~~l~~ir~e levels in the different brain areas were related to changes in glucose utilization in d~pal~lin~rgic~ and noradrenergic-innervated regions. Cerebral SHT levels were not measured in the present study since this latter amine plays only a predominant role in the regulation of seizures in IO-dayold and adult rats. ” 40.h’
EXPERIMENTAL
PROCEDURES
Animals Adult Sprague-Dawley rats, 1 male and 2 females, were housed together in mating groups for 10 days and constantly maintained under standard laboratory conditions on a 12:12 light/dark cycle (light on at 0600 h). Food and water were available ad ljb~iu~. Pregnant rats, as determined by palpation, were put in individual cages 5 days after separation from the male. Each litter was reduced to 10 pups per mother at 1 day of age (the day of birth was taken as day 0). The experiments were performed in lo- (PIO), 14- (P14), 17- (P17) and 21- (P21) day-old rats. Ah animal experimentation was performed with the highest standards of animal care, according to the Guide for Care and Use of Laboratory Animals.
On the day of testing, PTZ dissolved in saline (10 mg/ml), was administered intraperitoneally to the rats. To reach long-lasting status epilepticus (SE), the animals received a first injection of 40 mg/kg and 10 min later an additional dose of 20 mglkg. Repetitive injections of 10 mg/kg each 10 min were then administered until SE was reached. The behavioral criteria characterizing SE have been described in detail at all ages studied.*” In PI0 and P14 animals, SE was usually reached at a dose of 60-70 mg of PTZ and was characterized by tonic-clonic seizures with flexions and extensions of forelimbs and usually only ffexions of hindlimbs. At PI7 and P21, SO-120 mg of PTZ were necessary to induce sustained seizures. At these ages, SE was characterized by tonic-clonic seizures with behavioral components more prominent, more violent and shorter than at an earlier age.23
For determination of brain content of DA and NE, animals were killed by decapitation at 60 min after the onset of SE. Control rats received the same number of saline injections as their paired PTZ-treated congeners and were killed 60 min after the last injection, corresponding to the one leading to SE in PTZ-exposed congener. This duration of SE was chosen to correspond to the end of the 2-deoxyglucose experiment. Prepffr~t~on of tissues. After decapitation, the brain was removed and dissected into the following regions: cerebral cortex, hippocampus, hypothalamus, striatum, midbrain, brainstem and cerebellum, according to Glowinski and Iversen.” Tissue pieces were homogenized in 20 volumes of chilled 0.2 M perchloric acid containing 7 mM MgClz and 2.6 mM EGTA. The homogenates were centrifuged at 20000 g for 15 min and the supernatant fluid was stored at -80°C until assay. For each d~terminatjon, according to the age and size of the structures. the areas of 3-6 animals were pooled. Cutechoiumine assay. DA and NE levels in the supernatant fluid of brain homogenates were assayed according to a radioenzymatic method,lh modified as described by Dennis and Scatton,‘” and Mitrovic.4y
Seizures, brain CA and glucose use
303
The assay is based on the 3-0-methylation of CA by the enzyme catechol-0-methyltransferase in the presence of S-adenosyl-[methyl-3H]methionine. Labelled 0-methylated products were transformed to less polar complexes by adding tetraphenylboron and thereafter extracted by diethylether. The reaction products were separated by thin-layer chromatography. Methoxywas eluted and the radioactivity measured. tyramine derived from DA 3-0-methylation, Normetanephrine derived from NE 3-0-methylation was oxidized further to vanillin and its radioactivity was counted after extraction. This procedure has been described in detail previously.22 Measurement
of local cerebral glucose utilization
Rates of local cerebral glucose utilization were measured by the quantitative autoradiographic [‘4C]2-deoxyglucose (2DG) method described by Sokoloff et al. ,59 adapted to the developing rat.‘” The [14C]2-deoxyglucose (4.625 MBq/kg; spec. act., 1.65-2.04 GBq/mmol; Commissariat a 1’Energie Atomique, Saclay, France) was injected as a pulse through a venous femoral catheter at 10 min after the onset of SE. Generalized seizures lasted for the whole duration of the 2DG experiment. Nine to 12 timed arterial blood samples were drawn from the femoral artery of freelymoving rats during the following 45 min for the measurement of plasma concentration of 2DG and glucose. At approximately 45 min after the pulse of 2DG, the animals were killed by decapitation. Brains were rapidly removed and frozen in isopentane chilled to -35°C and cut into 20 km coronal sections at -22°C in a cryostat. Sections were autoradiographed on Kodak SB5 film along with calibrated [‘4C]methylmethacrylate standards (Amersham, Arlington Heights, U.S.A.), using a special set of low r4C concentration standards for PlO and P14 animals. The autoradiographs were analyzed by quantitative densitometry with a computerized image processing system (Biocom 200, Les Ulis, France) or a manual microdensitometer (Macbeth, TD901, Kollmorgen Co., Newburgh, U.S.A.). Optical density measurements for each structure anatomically defined according to the developing rat brain atlas of Sherwood and Timiras58 were made bilaterally in a minimum of four brain sections without knowledge of the treatment of the animal. Rates of local cerebral glucose utilization were then calculated from the local tissue concentration of 14C, the time courses of the plasma 2DG and glucose concentrations, and the appropriate constants according to the operational equation of the method.59 Statistical analysis
The statistical methods used to analyze the data were a two-way analysis of variance and the two-tailed Student’s t-test to compare catecholamine levels and rates of glucose utilization between control and seizing animals and Bonferroni’s multiple comparison procedures to compare the levels in each group of animals with those in the immediate preceding stage. RESULTS Effect of PTZ on catecholamine levels
As shown in Tables 1 and 2, at all stages studied, SE induced an increase in DA amounts in all brain regions studied and a simultaneous decrease in NE concentrations, except in the striatum at PlO and P14, where NE content increased. In both controls and seizing animals, DA concentrations were lowest in cerebellum and reached very high levels in striatum. For NE, regional distribution was less heterogeneous than for DA. In both control and experimental rats, NE levels were lowest in cerebral cortex and cerebellum and highest in hypothalamus. Two-way analysis of variance
There was an effect of the nature of the treatment on both DA and NE brain concentrations. The nature of the treatment significantly affected DA concentrations in all brain areas studied with P values ranging from 10m4to 8 x 10e4. For NE amounts, this effect was significant in 6 of the 7 structures studied (P values ranging from low4 to 10m3), except in the striatum (P = 0.2724). Age effects were significant for both DA and NE in all areas (P values ranging from 10m4 to 3.39 X 10W2),except in cerebellum where no effect of age was recorded either for DA (P = 0.4341)
Table 2. Effects of seizures on norepinephrine levels m various brain regions of immature rats PI0 Cerebral
cortex
Hippocampus Hypothalamus Striatum Midbrain Brainstem Cerebellum
C‘ PTZ C’ PTZ (’ P-l‘% C PTZ C PT7 C‘ P-l‘%
PI 4 122t21 7 1 -t 22-I. I02 t 34 IbXi-59 533 1 135 32x i 83* ‘J3 ? 31 I42 i 1-l 216 + hl 18Oi37 45s 5 110 108 -t 50:; Ih7+ 1x 107 ~+12
1’7I 142 + 34 00 f lb*,* * XX L Y4 ll5_+SXi 118ot29X*’ 189 L lYS$ I75 4 55 171 ! hY 130 t 7x** 762 L! 70158.1 t 67 794 + xxnll I77 + 3x
1% + 74*
Values, expressed as ngig, are means t S.D. of S-6 determinations. *:P
