- Email: [email protected]
zif-268, in neonatal rat hippocampus
Developmental Brain Research 108 Ž1998. 303–306
Short communication
Electroconvulsive shock does not induce c-fos and junB, but TIS1 and TIS8 r zif-268, in neonatal rat hippocampus Hee Yeon Jung a , Ung Gu Kang a , Yeon Ho Joo a , Soo Churl Cho a , Song Hee Jeon b, Joo-Bae Park b, Yong Sik Kim a,) a b
Department of Psychiatry, Seoul National UniÕersity College of Medicine, Seoul 110-799, South Korea Department of Biochemistry, Seoul National UniÕersity College of Medicine, Seoul 110-799, South Korea Accepted 24 March 1998
Abstract The induction in the animal brain of immediate early genes ŽIEGs. is known to be age-dependent, and it was suggested that, during neonatal period, signaling pathways for the induction of IEGs are immature. In this study, we investigated the induction of various IEGs in neonatal rat hippocampus after electroconvulsive shock ŽECS.. ECS did not induce c-fos and junB in the hippocampus of 7-day-old rat, but these genes were weakly induced at postnatal 14 days and to an adult level at postnatal 21 days; two other IEGs, TIS1 Ž NGFI-B, nur77 . and TIS8 Ž zif-268, Egr-1, Krox-24, NGFI-A., were induced at postnatal 7 days, however. Our results suggested that during the neonatal period, signaling pathways for TIS1 and TIS8 induction in rat hippocampus after ECS are complete, while those for c-fos and junB are immature. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Electroconvulsive shock; c-fos; junB; TIS1; TIS8; Hippocampus; Development
Immediate early genes ŽIEGs. are a group of genes which are induced in cells by various stimuli without the synthesis of new proteins. These genes are induced in animal brains by various stimuli like seizures and light w4,13x. IEG induction in brain has been reported as age-dependent. Kainate-induced seizure-induced c-fos expression in adult but not in neonatal rat brain, which suggests that, in the latter, the signaling pathways for IEG induction activated by kainic acid-induced seizure are immature w10,15x. Electroconvulsive shock ŽECS. also induces IEGs in rat brain w8x. ECS induces brief tonic-convulsive seizures, while those induced by kainate are the limbic type, and much more prolonged. Observed differences in the phenomenology of seizures could result from differences in the signal transduction pathways that are activated after each stimulus w4x. In this paper, we examined the induction of IEGs after ECS in developing rat brain to determine whether the suggested immaturation of signal transduction pathways for IEG induction in neonatal brain after kainic )
Corresponding author. Department of Psychiatry, Seoul National University College of Medicine, 28 Yongondong, Chongnogu, Seoul 110-799, S outh K orea. F ax: q 82-2-744-7241; E -m ail: [email protected] 0165-3806r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. PII S 0 1 6 5 - 3 8 0 6 Ž 9 8 . 0 0 0 6 6 - 2
acid-induced seizure is generally applicable to other types of seizures. For the study, we selected four IEGs; c-fos, junB, TIS1 Ž NGF1-B, nur77 . and TIS8 Ž zif-268, Egr-1, Krox-24, NGF1-A.. These are known to be induced in rat brain by ECS w8x and their promoters are distinct. The c-fos promoter contains one each of CRE, SRE and AP-1 binding sites w12x; the promoter of TIS8 is similar, but has five SRE instead of one w2x. The junB promoter also contains one each of functional SRE and CRE, but, unlike in c-fos, these are in downstream of the gene w11x. TIS1 contains no obvious CRE but has four potential AP-1 binding sites w16,17x. The basal expression of c-fos and TIS8 was reported to be different in neonatal period; c-fos expression was very low in early neonatal period w9x, while TIS8 mRNA increased rapidly after birth w6x. Male Sprague–Dawley rats aged 7, 14 and 21 days were used in this study, and were treated in accordance with the NIH Guide for the Care and Use of Laboratory Animals. ECS Ž130 V, 0.5 s. was administered to the rats via ear-clip electrodes; sham rats were treated exactly the same as ECS-treated rats, but without the administration of the electric current. Rats were sacrificed by decapitation. Brain was dissected on ice and the hippocampi were
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H.Y. Jung et al.r DeÕelopmental Brain Research 108 (1998) 303–306
305
Fig. 2. Expression of TIS8 Ž Egr-1. at 0 and 60 min after ECS in developing rat hippocampus. After ECS Ž130 V, 0.5 s., rats were sacrificed at 0 and 60 min after ECS. Tissue lysates were fractionated in 10% SDS-polyacrylamide gel, and proteins were transferred to nitrocellulose membranes, which were immunoblotted with anti-Egr-1 antibody. The results are representative of four independent experiments. P: postnatal day.
immediately frozen on dry ice. At each time point, hippocampi from four rats were pooled and used for preparation of RNA and tissue lysate. Twenty micrograms of total RNA isolated by the acid guanidine thiocyanate–phenol–chloroform method w3x, were size fractionated in 1% denaturing agarose gel and then transferred to nylon membranes ŽAmersham.. RNA isolated from adult hippocampus 30 min after ECS was included as a positive control. The membranes were hybridized with 32 P-labelled cDNA probes of c-fos w5x, junB w14x, TIS1 and TIS8 Žkindly provided by Dr. Harvey R. Herschman.. After washing, the hybridized membranes were exposed to X-ray film with an intensifying screen for 1–3 days. The exposure time was determined by the density of the positive control. The membranes were reprobed after deprobing and, to control the amount of RNA, radiolabelled glyceraldehyde-3-phosphate dehydrogenase ŽGAPDH. c-DNA was also hybridized to the same membrane after deprobing. For Western blotting of TIS8, tissue lysates were fractionated in 10% SDS-polyacrylamide gel. After electrophoresis, proteins were transferred to nitrocellulose membranes, which were then immunoblotted with antiEgr-1 antibody ŽSanta Cruz Biotech.. After ECS, the expression of c-fos, junB, TIS1 and TIS8 in the hippocampus of postnatal 7- ŽP7., 14- ŽP14. and 21- ŽP21. day rats was examined. In neonatal hippocampus, the expression of c-fos, junB and TIS1 was not detected right after ECS, while TIS8 expression was observed. ECS did not induce c-fos and junB expression in P7 hippocampus ŽFig. 1A., but c-fos was induced by ECS at P14, with a peak at 45 min after ECS; the level of induced c-fos mRNA was however very low compared to that of adult rats. In P21 hippocampus, c-fos induction was observed at 15 min after ECS; it peaked at 30 min and then gradually decreased, before returning to its basal level at 120 min after ECS. The amount of c-fos mRNA at 30 min was almost the same as in the adult rat ŽFig. 1A.. The induction of junB in P7, P14 and P21 hippocampus after ECS was similar to that of c-fos ŽFig. 1B..
In contrast to c-fos and junB, TIS1 and TIS8 were induced after ECS even in P7 hippocampus ŽFig. 1C and D.. Induced mRNA did not appear to vary according to age, but the peak of TIS1 induction tended to be earlier as age increased; at P7, it occurred 90 min after ECS; at P14, after 60 min; and at P21, after 45 min. In P21 hippocampus, the amount of TIS1 at the peak of its induction was also comparable to the amount found in adult rat. Unlike that of other IEGs, the temporal pattern of TIS8 induction was similar in P7, P14 and P21 hippocampus. The induction of TIS8 was apparent at 15 min, peaked at 45 min and started to decrease 90 min after ECS at all ages. The amounts of induced TIS8 in P7, P14 and P21 hippocampus at 30 min after ECS were almost the same as in adult rat ŽFig. 1D.. To confirm the induction of TIS8 in early neonatal hippocampus after ECS, we compared the amount of TIS8 protein at 0 and 60 min after ECS ŽFig. 2.. The level of TIS8 in hippocampus right after ECS was very low, but TIS8 expression was apparently increased at 60 min after ECS in P7 and P14 as well as P21 hippocampus. In this study, c-fos and junB were not induced in rat hippocampus after ECS at postnatal day 7, but were induced weakly at postnatal day 14. At postnatal day 21, the temporal pattern of c-fos induction and the amount of induced c-fos mRNA in rat hippocampus were almost the same as in adults. Our results indicate that c-fos and junB were not inducible in neonatal hippocampus after ECS, and are similar to those of previous reports, indicating that, in neonatal rat brain, c-fos was not induced by kainate-induced seizure w10,15x. Since c-fos was induced in embryonal rat hippocampus by reperfusion after hypoxiar ischemia w1x, the absence of c-fos induction in P7 hippocampus is probably not due to incompleteness of the transcription apparatus. It may instead be due to the immaturity of upstream signal transduction pathways involved in the induction of c-fos and junB w10,15x. Although c-fos and junB were not induced in P7 hippocampus after ECS, TIS1 and TIS8 were thus induced. We confirmed the increase of TIS8 protein after ECS by
Fig. 1. Induction of c-fos ŽA., junB ŽB., TIS1 ŽC., and TIS8 ŽD. after ECS in developing rat hippocampus. After ECS Ž130 V, 0.5 s. or sham treatment, rats were sacrificed at the indicated time points. Twenty micrograms of total RNA were size fractionated in 1% agarose gel containing formaldehyde, and transferred to nylon membranes. The membranes were hybridized with 32 P-labelled cDNA probes. Radioactivities were visualized by autoradiography. GAPDH was used to control the amount of RNA ŽE.. The results are representative of four independent experiments. P: postnatal day, Control: adult rat hippocampus at 30 min after ECS.
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immunoblotting. This suggest that the signaling pathways for the induction of TIS1 and TIS8 are distinct from those for the induction of c-fos and junB. TIS8 was not induced in neonatal hippocampus after kainic acid-induced seizure, which suggests that signaling pathways for TIS8 induction are immature during the neonatal period w10x. Our results indicate, however, that, in P7 hippocampus, signaling pathways for the induction of TIS8 after ECS-induced seizure are complete. It is therefore apparent that the signaling pathways for the induction of TIS8 after ECS- and kainic acid-induced seizures are different, and our results support previous observations that the induction of IEGs could be affected by age as well as by the phenotype of seizure w7x. Although TIS1 was induced after ECS in neonatal rat hippocampus, the induction peak tended to be earlier as age increased. This suggests that even though the signaling pathway for the induction of TIS1 after ECS is complete in neonatal hippocampus, there is some developmental changes in the components of that pathway. Our findings indicate that the induction of IEGs in neonatal rat brain depends on age and the type of seizure, and that, in neonatal rat brain, some signaling pathways for the induction of IEGs after seizure are defective, but others are complete. To clarify the mechanism of observed differences in the inducibility of IEGs in developing rat brains after various seizures, a better understanding of signaling pathways for the post-seizure induction of each IEG is needed.
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w6x
w7x
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Acknowledgements We thank Dr. H. Herschman for providing the TIS1 and TIS8 probes. This study was supported by a Genetic Engineering Research Grant from the Ministry of Education Ž1994. and a grant no. 2-95-156 from the Seoul National University Hospital Research Fund. Part of this study was performed at the Clinical Research Institute of the Seoul National University Hospital.
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References w17x w1x Z. Binienda, A.C. Scallet, The effects of reduced perfusion and reperfusion on c-fos and HSP-72 protein immunohistochemistry in
gestational day 21 rat brains, Int. J. Dev. Neurosci. 12 Ž1994. 605–610. P.S. Changelian, P. Feng, T.C. King, J. Milbrandt, Structure of the NGFI-A gene and detection of upstream sequence responsible for its transcriptional induction by nerve growth factor, Proc. Natl. Acad. Sci. U.S.A. 86 Ž1989. 377–381. P. Chomczynski, N. Sacchi, Single-step method of RNA isolation by acid guanidinium thiocyanate–phenol–chloroform extraction, Anal. Biochem. 162 Ž1987. 156–159. A.J. Cole, S. Abu-Shakra, D.W. Saffen, J.M. Baraban, P.F. Worley, Rapid rise in transcription factor mRNAs in rat brain after electroshock-induced seizures, J. Neurochem. 55 Ž1990. 1920–1927. T. Curran, G. Peters, C. Van Beveren, N.M. Teich, I.M. Verma, FBJ murine osteosarcoma virus: identification and molecular cloning of biologically active proviral DNA, J. Virol. 44 Ž1982. 674–682. J. Herms, U. Zurmohle, R. Schlingensiepen, W. Brysch, K.H. Schlingensiepen, Developmental expression of the transcription factor zif268 in rat brain, Neurosci. Lett. 165 Ž1994. 171–174. F.E. Jensen, I.R. Firkusny, G.D. Mower, Differences in c-fos immunoreactivity due to age and mode of seizure induction, Mol. Brain Res. 17 Ž1993. 185–193. H.Y. Jung, U.G. Kang, Y.M. Ahn, Y.H. Joo, J.-B. Park, Y.S. Kim, Induction of tetradecanoyl phorbol acetate-inducible sequence ŽTIS . genes by electroconvulsive shock in rat brain, Biol. Psychiatry 40 Ž1996. 503–507. D.L. Parma, S.J. Benasayag, I. Szijan, Expression of c-myc and c-fos oncogenes in different rat brain regions during postnatal development, Int. J. Dev. Neurosci. 9 Ž1991. 613–619. K.R. Pennypacker, M.K. McMillian, J. Douglass, J.S. Hong, Ontogeny of kainate-induced gene expression in rat hippocampus, J. Neurochem. 62 Ž1994. 438–444. E.D. Perez-Albuerne, G. Schatteman, L.K. Sanders, D. Nathans, Transcriptional regulatory elements downstream of the junB gene, Proc. Natl. Acad. Sci. U.S.A. 90 Ž1993. 11960–11964. L.M. Robertson, T.K. Kerppola, M. Vendrell, D. Luk, R.J. Smeyne, C. Bocchiaro, J.I. Morgan, T. Curran, Regulation of c-fos expression in transgenic mice requires multiple interdependent transcription control elements, Neuron 14 Ž1995. 241–252. B. Rusak, H.A. Robertson, W. Wisden, S.P. Hunt, Light pulses that shift rhythms induce gene expression in the suprachiasmatic nucleus, Science 248 Ž1990. 1237–1240. K. Ryder, L.F. Lau, D. Nathans, A gene activated by growth factors is related to the oncogene v-jun, Proc. Natl. Acad. Sci. U.S.A. 85 Ž1988. 1487–1491. S.S. Schreiber, G. Tocco, I. Najm, C.E. Finch, S.A. Johnson, M. Baudry, Absence of c-fos induction in neonatal rat brain after seizures, Neurosci. Lett. 136 Ž1992. 31–35. M.A. Watson, J. Milbrandt, The NGFI-B gene, a transcriptionally inducible member of the steroid receptor gene superfamily: genomic structure and expression in rat brain after seizure induction, Mol. Cell. Biol. 9 Ž1989. 4213–4219. G.T. Williams, L.F. Lau, Activation of the inducible orphan receptor gene nur77 by serum growth factors: dissociation of immediate-early and delayed-early responses, Mol. Cell. Biol. 13 Ž1993. 6124–6136.
Short communication
Electroconvulsive shock does not induce c-fos and junB, but TIS1 and TIS8 r zif-268, in neonatal rat hippocampus Hee Yeon Jung a , Ung Gu Kang a , Yeon Ho Joo a , Soo Churl Cho a , Song Hee Jeon b, Joo-Bae Park b, Yong Sik Kim a,) a b
Department of Psychiatry, Seoul National UniÕersity College of Medicine, Seoul 110-799, South Korea Department of Biochemistry, Seoul National UniÕersity College of Medicine, Seoul 110-799, South Korea Accepted 24 March 1998
Abstract The induction in the animal brain of immediate early genes ŽIEGs. is known to be age-dependent, and it was suggested that, during neonatal period, signaling pathways for the induction of IEGs are immature. In this study, we investigated the induction of various IEGs in neonatal rat hippocampus after electroconvulsive shock ŽECS.. ECS did not induce c-fos and junB in the hippocampus of 7-day-old rat, but these genes were weakly induced at postnatal 14 days and to an adult level at postnatal 21 days; two other IEGs, TIS1 Ž NGFI-B, nur77 . and TIS8 Ž zif-268, Egr-1, Krox-24, NGFI-A., were induced at postnatal 7 days, however. Our results suggested that during the neonatal period, signaling pathways for TIS1 and TIS8 induction in rat hippocampus after ECS are complete, while those for c-fos and junB are immature. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Electroconvulsive shock; c-fos; junB; TIS1; TIS8; Hippocampus; Development
Immediate early genes ŽIEGs. are a group of genes which are induced in cells by various stimuli without the synthesis of new proteins. These genes are induced in animal brains by various stimuli like seizures and light w4,13x. IEG induction in brain has been reported as age-dependent. Kainate-induced seizure-induced c-fos expression in adult but not in neonatal rat brain, which suggests that, in the latter, the signaling pathways for IEG induction activated by kainic acid-induced seizure are immature w10,15x. Electroconvulsive shock ŽECS. also induces IEGs in rat brain w8x. ECS induces brief tonic-convulsive seizures, while those induced by kainate are the limbic type, and much more prolonged. Observed differences in the phenomenology of seizures could result from differences in the signal transduction pathways that are activated after each stimulus w4x. In this paper, we examined the induction of IEGs after ECS in developing rat brain to determine whether the suggested immaturation of signal transduction pathways for IEG induction in neonatal brain after kainic )
Corresponding author. Department of Psychiatry, Seoul National University College of Medicine, 28 Yongondong, Chongnogu, Seoul 110-799, S outh K orea. F ax: q 82-2-744-7241; E -m ail: [email protected] 0165-3806r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. PII S 0 1 6 5 - 3 8 0 6 Ž 9 8 . 0 0 0 6 6 - 2
acid-induced seizure is generally applicable to other types of seizures. For the study, we selected four IEGs; c-fos, junB, TIS1 Ž NGF1-B, nur77 . and TIS8 Ž zif-268, Egr-1, Krox-24, NGF1-A.. These are known to be induced in rat brain by ECS w8x and their promoters are distinct. The c-fos promoter contains one each of CRE, SRE and AP-1 binding sites w12x; the promoter of TIS8 is similar, but has five SRE instead of one w2x. The junB promoter also contains one each of functional SRE and CRE, but, unlike in c-fos, these are in downstream of the gene w11x. TIS1 contains no obvious CRE but has four potential AP-1 binding sites w16,17x. The basal expression of c-fos and TIS8 was reported to be different in neonatal period; c-fos expression was very low in early neonatal period w9x, while TIS8 mRNA increased rapidly after birth w6x. Male Sprague–Dawley rats aged 7, 14 and 21 days were used in this study, and were treated in accordance with the NIH Guide for the Care and Use of Laboratory Animals. ECS Ž130 V, 0.5 s. was administered to the rats via ear-clip electrodes; sham rats were treated exactly the same as ECS-treated rats, but without the administration of the electric current. Rats were sacrificed by decapitation. Brain was dissected on ice and the hippocampi were
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H.Y. Jung et al.r DeÕelopmental Brain Research 108 (1998) 303–306
H.Y. Jung et al.r DeÕelopmental Brain Research 108 (1998) 303–306
305
Fig. 2. Expression of TIS8 Ž Egr-1. at 0 and 60 min after ECS in developing rat hippocampus. After ECS Ž130 V, 0.5 s., rats were sacrificed at 0 and 60 min after ECS. Tissue lysates were fractionated in 10% SDS-polyacrylamide gel, and proteins were transferred to nitrocellulose membranes, which were immunoblotted with anti-Egr-1 antibody. The results are representative of four independent experiments. P: postnatal day.
immediately frozen on dry ice. At each time point, hippocampi from four rats were pooled and used for preparation of RNA and tissue lysate. Twenty micrograms of total RNA isolated by the acid guanidine thiocyanate–phenol–chloroform method w3x, were size fractionated in 1% denaturing agarose gel and then transferred to nylon membranes ŽAmersham.. RNA isolated from adult hippocampus 30 min after ECS was included as a positive control. The membranes were hybridized with 32 P-labelled cDNA probes of c-fos w5x, junB w14x, TIS1 and TIS8 Žkindly provided by Dr. Harvey R. Herschman.. After washing, the hybridized membranes were exposed to X-ray film with an intensifying screen for 1–3 days. The exposure time was determined by the density of the positive control. The membranes were reprobed after deprobing and, to control the amount of RNA, radiolabelled glyceraldehyde-3-phosphate dehydrogenase ŽGAPDH. c-DNA was also hybridized to the same membrane after deprobing. For Western blotting of TIS8, tissue lysates were fractionated in 10% SDS-polyacrylamide gel. After electrophoresis, proteins were transferred to nitrocellulose membranes, which were then immunoblotted with antiEgr-1 antibody ŽSanta Cruz Biotech.. After ECS, the expression of c-fos, junB, TIS1 and TIS8 in the hippocampus of postnatal 7- ŽP7., 14- ŽP14. and 21- ŽP21. day rats was examined. In neonatal hippocampus, the expression of c-fos, junB and TIS1 was not detected right after ECS, while TIS8 expression was observed. ECS did not induce c-fos and junB expression in P7 hippocampus ŽFig. 1A., but c-fos was induced by ECS at P14, with a peak at 45 min after ECS; the level of induced c-fos mRNA was however very low compared to that of adult rats. In P21 hippocampus, c-fos induction was observed at 15 min after ECS; it peaked at 30 min and then gradually decreased, before returning to its basal level at 120 min after ECS. The amount of c-fos mRNA at 30 min was almost the same as in the adult rat ŽFig. 1A.. The induction of junB in P7, P14 and P21 hippocampus after ECS was similar to that of c-fos ŽFig. 1B..
In contrast to c-fos and junB, TIS1 and TIS8 were induced after ECS even in P7 hippocampus ŽFig. 1C and D.. Induced mRNA did not appear to vary according to age, but the peak of TIS1 induction tended to be earlier as age increased; at P7, it occurred 90 min after ECS; at P14, after 60 min; and at P21, after 45 min. In P21 hippocampus, the amount of TIS1 at the peak of its induction was also comparable to the amount found in adult rat. Unlike that of other IEGs, the temporal pattern of TIS8 induction was similar in P7, P14 and P21 hippocampus. The induction of TIS8 was apparent at 15 min, peaked at 45 min and started to decrease 90 min after ECS at all ages. The amounts of induced TIS8 in P7, P14 and P21 hippocampus at 30 min after ECS were almost the same as in adult rat ŽFig. 1D.. To confirm the induction of TIS8 in early neonatal hippocampus after ECS, we compared the amount of TIS8 protein at 0 and 60 min after ECS ŽFig. 2.. The level of TIS8 in hippocampus right after ECS was very low, but TIS8 expression was apparently increased at 60 min after ECS in P7 and P14 as well as P21 hippocampus. In this study, c-fos and junB were not induced in rat hippocampus after ECS at postnatal day 7, but were induced weakly at postnatal day 14. At postnatal day 21, the temporal pattern of c-fos induction and the amount of induced c-fos mRNA in rat hippocampus were almost the same as in adults. Our results indicate that c-fos and junB were not inducible in neonatal hippocampus after ECS, and are similar to those of previous reports, indicating that, in neonatal rat brain, c-fos was not induced by kainate-induced seizure w10,15x. Since c-fos was induced in embryonal rat hippocampus by reperfusion after hypoxiar ischemia w1x, the absence of c-fos induction in P7 hippocampus is probably not due to incompleteness of the transcription apparatus. It may instead be due to the immaturity of upstream signal transduction pathways involved in the induction of c-fos and junB w10,15x. Although c-fos and junB were not induced in P7 hippocampus after ECS, TIS1 and TIS8 were thus induced. We confirmed the increase of TIS8 protein after ECS by
Fig. 1. Induction of c-fos ŽA., junB ŽB., TIS1 ŽC., and TIS8 ŽD. after ECS in developing rat hippocampus. After ECS Ž130 V, 0.5 s. or sham treatment, rats were sacrificed at the indicated time points. Twenty micrograms of total RNA were size fractionated in 1% agarose gel containing formaldehyde, and transferred to nylon membranes. The membranes were hybridized with 32 P-labelled cDNA probes. Radioactivities were visualized by autoradiography. GAPDH was used to control the amount of RNA ŽE.. The results are representative of four independent experiments. P: postnatal day, Control: adult rat hippocampus at 30 min after ECS.
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H.Y. Jung et al.r DeÕelopmental Brain Research 108 (1998) 303–306
immunoblotting. This suggest that the signaling pathways for the induction of TIS1 and TIS8 are distinct from those for the induction of c-fos and junB. TIS8 was not induced in neonatal hippocampus after kainic acid-induced seizure, which suggests that signaling pathways for TIS8 induction are immature during the neonatal period w10x. Our results indicate, however, that, in P7 hippocampus, signaling pathways for the induction of TIS8 after ECS-induced seizure are complete. It is therefore apparent that the signaling pathways for the induction of TIS8 after ECS- and kainic acid-induced seizures are different, and our results support previous observations that the induction of IEGs could be affected by age as well as by the phenotype of seizure w7x. Although TIS1 was induced after ECS in neonatal rat hippocampus, the induction peak tended to be earlier as age increased. This suggests that even though the signaling pathway for the induction of TIS1 after ECS is complete in neonatal hippocampus, there is some developmental changes in the components of that pathway. Our findings indicate that the induction of IEGs in neonatal rat brain depends on age and the type of seizure, and that, in neonatal rat brain, some signaling pathways for the induction of IEGs after seizure are defective, but others are complete. To clarify the mechanism of observed differences in the inducibility of IEGs in developing rat brains after various seizures, a better understanding of signaling pathways for the post-seizure induction of each IEG is needed.
w2x
w3x
w4x
w5x
w6x
w7x
w8x
w9x
w10x
w11x
w12x
Acknowledgements We thank Dr. H. Herschman for providing the TIS1 and TIS8 probes. This study was supported by a Genetic Engineering Research Grant from the Ministry of Education Ž1994. and a grant no. 2-95-156 from the Seoul National University Hospital Research Fund. Part of this study was performed at the Clinical Research Institute of the Seoul National University Hospital.
w13x
w14x
w15x
w16x
References w17x w1x Z. Binienda, A.C. Scallet, The effects of reduced perfusion and reperfusion on c-fos and HSP-72 protein immunohistochemistry in
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