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Actions of glutamate antagonists on synaptic potentials in cat visual cortex in vitro
$135 IMMUNOCYTOCHEMICAL STUDY OF C O B A L T - I N D U C E D EPILEPTIC FOCUS. IKUKO KOYAMA "I t IKUKO NAGATSU 2, NOBUYUKI K A R A S A W A 2 , MINORU O N O Z U K A 3, YOKO K A T A Y A M A ~ KIKUKO *it ~ SHIGEY---U-K~DE-UR~ 3 ~ , ~ Department o~- P--~-siolog-~, Tokyo Women's M ~ College, Tokyo; 2 ) Department o f Anatomy, F u j i t a - G a k u e n Health University, Aichi; and 3 ) Department o f Anatomy, Gifu U n i v e r s i t y School of Medicine, Gifu, Japan. Topical a p p l i c a t i o n of cobalt on rat s o m a t o s e n s o r y cortex leads to epileptic activity at the focus. Since the Co-focus undergoes changes in tissue concentration of excitatory and inhibitory transmitters, such as glutamate (Glu) and GABA, we studied the d i s t r i b u t i o n of immunoreactive positive cells and synapses of these amino acids at the Co-focus and contralateral site. GABA i m m u n o - r e a c t i v e cells were fairly evenly d i s t r i b u t e d in all layers of the s o m a t o s e n s o r y cortex. However, Glu. positive cells were present p r e d o m i n a n t l y in pyramidal cell layers. There was a significant decrease in the number of GABA positive cells in the Cofocus compared to the c o n t r a l a t e r a l side or to the homologous area from untreated rats. The number of GABA positive terminals surrounded by GABA negative pyramidal cells was also decreased. There were also signs of a decrease in the number of G l u - p o s i t i v e cells in the Co-focus. In an EM study, in the Co-focus, GABA positive synapses symmetric with flat vesicles decreased, whereas G l u - s y n a p s e s asymmetric with pleomorphic vesicles increased. These changes and others, such as swelling of G l u - C e l l - b o d i e s and m i t o c h o n d r i a and an increase in dendritic tubules, may play an important role in eliciting discharges.
CHANGE OF FREE AMINO ACID LEVELS DURING DEVELOPMENT OF IRON-INDUCED EPILEPTOGENIC FOCUS OF RATS. MIDORI HIRAMATSU, ATSUSHI SHIOTA*, REI EDAMATSU *, AN__DDAKITANE MORI, Deparment o_~fNeurochemistry, Institute for Neurobiology, Okayama University Medical School, 2-5-1 Shikata-cho~ Okayama 700, Japan. Changes of excitatory and inhibitory amino acid neurotransmitter levels were examined in the cerebral cortex during development of iron-induced epilepsy in rat. Five microliters of 0.1M ferric chloride solution were injected into the left sensory motor cortex of rat. Free amino acid levels in the ipsilateral cortex were analyzed 3, 6, 9, 24, 48 hours and 4 weeks after the injection by high performance liquid chromatography. Excitatory and inhibitory amino acid levels changed significantly compared with control (saline injected) group during the development of ironinduced epileptogenic focus. Aspartate level decreased at 9 and 24 hours. Glutamine level decreased temporarily at 3 and 48 hours. GABA level decreased transiently at 6 hours. Taurine level increased temporarily at 3 hours, but decreased at 24 hours. Alanine level increased at one hour and 24 hours, and was still increased at 4 weeks. Temporary increase of glycine level was found at 24 hours. There was no change of glutamate level in this period. These results show that excitatory and inhibitory amino acid neurotransmitters in rat cerebral cortex change transiently during development of iron-induced epileptogenic focus. No significant change of these amino acid levels, except for alanine, was found after the formation of iron-induced epileptogenic focus.
ACTIONS OF GLUTAMATE ANTAGONISTS ON SYNAPTIC POTENTIALS IN CAT VISUAL CORTEX IN VITRO. AYAHIK0 NISHIGORI* TETSUYA SHIROKAWA TADAHARU TSUMOT0 AND FUMITAKA KIMURA*, Department o_ff Neurophysiology, Biochemical Research Center, Osaka University Medical School, Kita-ku, Osaka 530, Japan. Glutamate (Glu) may be an excitatory transmitter in cat visual cortex. Glu receptors can be classified into three types according to their affinity for agonists: N-methyl-D-aspartate (NMDA), quisqualate and kainate receptors. Using slice preparations of cat visual cortex, we determined which types of receptor mediate excitatory responses of layer IV and II/III cells to electrical stimulation of the underlying white matter. We used 2-amino-5-phosphonovalerate (APV) as a selective antagonist for NMDA receptors and kynurenate (KYNA) as a broad-spectrum antagonist. In most layer IV cells, application of 0.5-1.0 mM KYNA with the perfusion medium suppressed spike discharges recorded extracellularly, but application of APV (50 uM) did not. In layer II/III cells, KYNA a n t a g o n i z e d excitatory postsynaptic potentials ( E P S P s ) recorded I n t r a c e l l u l a r l y so t h a t s l o p e s of t h e i r r i s i n g phase and peak a m p l i t u d e s were d r a m a t i c a l l y reduced. By c o n t r a s t , APV s u p p r e s s e d the EPSP s l o p e s i n some of the c e l l s but not i n o t h e r s . A P V - s e n s i t i v e EPSPs tended t o be induced w i t h l o n g e r l a t e n c i e s than A P V - i n s e n s i t l v e EPSPs i n l a y e r I I / I I I of the c o r t e x .
CHANGE OF FREE AMINO ACID LEVELS DURING DEVELOPMENT OF IRON-INDUCED EPILEPTOGENIC FOCUS OF RATS. MIDORI HIRAMATSU, ATSUSHI SHIOTA*, REI EDAMATSU *, AN__DDAKITANE MORI, Deparment o_~fNeurochemistry, Institute for Neurobiology, Okayama University Medical School, 2-5-1 Shikata-cho~ Okayama 700, Japan. Changes of excitatory and inhibitory amino acid neurotransmitter levels were examined in the cerebral cortex during development of iron-induced epilepsy in rat. Five microliters of 0.1M ferric chloride solution were injected into the left sensory motor cortex of rat. Free amino acid levels in the ipsilateral cortex were analyzed 3, 6, 9, 24, 48 hours and 4 weeks after the injection by high performance liquid chromatography. Excitatory and inhibitory amino acid levels changed significantly compared with control (saline injected) group during the development of ironinduced epileptogenic focus. Aspartate level decreased at 9 and 24 hours. Glutamine level decreased temporarily at 3 and 48 hours. GABA level decreased transiently at 6 hours. Taurine level increased temporarily at 3 hours, but decreased at 24 hours. Alanine level increased at one hour and 24 hours, and was still increased at 4 weeks. Temporary increase of glycine level was found at 24 hours. There was no change of glutamate level in this period. These results show that excitatory and inhibitory amino acid neurotransmitters in rat cerebral cortex change transiently during development of iron-induced epileptogenic focus. No significant change of these amino acid levels, except for alanine, was found after the formation of iron-induced epileptogenic focus.
ACTIONS OF GLUTAMATE ANTAGONISTS ON SYNAPTIC POTENTIALS IN CAT VISUAL CORTEX IN VITRO. AYAHIK0 NISHIGORI* TETSUYA SHIROKAWA TADAHARU TSUMOT0 AND FUMITAKA KIMURA*, Department o_ff Neurophysiology, Biochemical Research Center, Osaka University Medical School, Kita-ku, Osaka 530, Japan. Glutamate (Glu) may be an excitatory transmitter in cat visual cortex. Glu receptors can be classified into three types according to their affinity for agonists: N-methyl-D-aspartate (NMDA), quisqualate and kainate receptors. Using slice preparations of cat visual cortex, we determined which types of receptor mediate excitatory responses of layer IV and II/III cells to electrical stimulation of the underlying white matter. We used 2-amino-5-phosphonovalerate (APV) as a selective antagonist for NMDA receptors and kynurenate (KYNA) as a broad-spectrum antagonist. In most layer IV cells, application of 0.5-1.0 mM KYNA with the perfusion medium suppressed spike discharges recorded extracellularly, but application of APV (50 uM) did not. In layer II/III cells, KYNA a n t a g o n i z e d excitatory postsynaptic potentials ( E P S P s ) recorded I n t r a c e l l u l a r l y so t h a t s l o p e s of t h e i r r i s i n g phase and peak a m p l i t u d e s were d r a m a t i c a l l y reduced. By c o n t r a s t , APV s u p p r e s s e d the EPSP s l o p e s i n some of the c e l l s but not i n o t h e r s . A P V - s e n s i t i v e EPSPs tended t o be induced w i t h l o n g e r l a t e n c i e s than A P V - i n s e n s i t l v e EPSPs i n l a y e r I I / I I I of the c o r t e x .