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Topographical gradient of R2D5-polypeptide expressed by granule cells of cat hippocampal dentate gyrus
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TOPOGRAPHICAL GRADIENT OF R 2 D 5 - P O L Y P E P T I D E E X P R E S S E D BY G R A N U L E CELLS OF CAT H I P P O C A M P A L D E N T A T E GYRUS. KENSAKU MORI r AKIKO TANI, JUN IKEDA t YUMIKO WATANABE, AND SHOGO OKAt Department of Neuroscience~ Osaka Bioscience Institute~ 6-2-4 F u r u e d a i ¢ S u i t a - s h i , O s a k a 565, J a p a n In cat hippocampus, m o n o c l o n a l a n t i b o d y (MAb) R2D5 specifically labeled granule cells of the d e n t a t e g y r u s a n d t h e i r axons, m o s s y fibers. The R2D5immunoreactivity of granule cells showed a pronounced gradient along the septotemporal a x i s o f the h i p p o c a m p a l d e n t a t e gyrus. In the temporal (ventral) parts, most o f the g r a n u l e c e l l s w e r e i n t e n s e l y l a b e l e d w i t h M A b R2D5, whereas g r a n u l e c e l l s l o c a t e d in p r o g r e s s i v e l y m o r e s e p t a l (dorsal) p a r t s s h o w e d g r a d u a l l y less i m m u n o r e a c t i v i t y to M A b R2D5. Immunoblot analysis after SDS-PAGE indicates t h a t the a n t i g e n m o l e c u l e is a s o l u b l e p r o t e i n w i t h mol. w e i g h t o f a b o u t 14 KDa. It has been generally assumed that molecules involved in establishing or maintaining the t o p o g r a p h i c a l o r g a n i z a t i o n o f n e u r o n a l s y s t e m s are expressed in spatial gradients. S i n c e the h i p p o c a m p a l d e n t a t e g y r u s has axonal connections which are o r g a n i z e d t o p o g r a p h i c a l l y , it c a n be a s s u m e d t h a t expression of the R2D5-antigen m o l e c u l e is c o r r e l a t e d w i t h the t o p o g r a p h i c a x o n a l c o n n e c t i o n s . In addition, the result t h a t the a n t i g e n m o l e c u l e is a soluble cytosol protein suggests that intrinsic functional properties of granule cells differs according to the c e l l p o s i t i o n a l o n g the s e p t o t e m p o r a l axis.
THE EFFECT OF Mg 2+ ON THE SYNAPTIC DEPRESSION OF CA1 PYRAMIDAL NEURONS INDUCED BY LOW FREQUENCY STIMULATION IN RAT HIPPOCAMPAL SLICES. YUK0 SEKIN0*, AND IKUK0 KOYAMA, Department 0_ffPhyslolo~y, Tokyo W0men's Medical College. 8-__!1Kawata-eh0, ShlnJuku-ku L Tokyo 162, Japan. The effects of a brief repetitive stimulation at various frequencies on the 0rth0dr0mle responses of CA1 pyramidal neurons of rat hlppocampal slices were compared in 1.3mM and 2.0 mM magnesium medium. In 1.3mM M ~ + medium, 0nly potentiation of synaptle responses was observed after 20, 50, and 100Hz conditioning stimulations. However, after 5 and 10Hz conditioning stimulations, a short la~tlng (30s-lmln) depression appeared that was followed by a small potentiation. In 2.0mM Mg z+ medium. 100Hz stimulation induced potentiation, but even SOHz stimulation induced synaptie depression in 3 of ii ( 27~ ) slices experimented. The incidence, degree, and duration of depression increased when the frequency of conditioning stimulation was decreased. The depresslgn induced by 5 or ]0Hz stimulation was stronger and lasted long~r ( 3 - 5 mln) in 2.0mM Mg z+ than in 1.3mM Mg z+. When APV (S0aM) was added to the 2.0mM Mg z+ medium to block NMDA receptors, the depression appeared mere strongly so that 50Hz stimulation caused depression in all slices experimented (n=5). These d a t a t h a t s y n a p t l c ~ e 2 r e s s l o n was c a u s e d by low f r e q u e n c y r e p e t i t i v e stimulation and o b s e r v e d c l e a r l y i n 2.0mM Mg~ medium s u g g e s t t h a t magnesium i o n s may p l a y an i m p o r t a n t r o l e not o n l y i n b l o c k i n g t h e I n d u c t i o n of p o t e n t i a t i o n , b u t a l s o i n e n h a n c i n g some i n h i b i t o r y mechanisms such as n e t w o r k s i n c l u d i n g l n t e r n e u r o n s In t h e h l p p o c a m p a l n e u r o n s .
EFFECTS OF SEROTONIN ON NUCLEUS ACCUMBENS NEURONS OF THE RAT BRAIN. NAOHISA UCHIMURA* 12r ALAN R. NORTH*3,SYOGORO NISHI2f and YOICHI NAKAZAWA* *t Departments of * Neuropsychiatry and z Physiology, Kurume University School of Medicine t Kurume r 830 Japan and ~Ore@on Health Sciences University, Oregon t 97201 U.S.A. The nucleus accumbens receives a moderately dense innervation from the raphe nuclei of the midbrain, and direct application of serotonin (5-HT) into the nucleus affects motor performance. Intracellular recordings were made from rat nucleus accumbens neurons in slices (300 ~M) superfused in vitro with a physiological saline solution. 5-HT (i-I00 ~M) depolarized 170 of 203 (84%) neurons. The depolarization was associated with an increase in the input resistance. Application of 5-HT to neurons voltage-clamped near their resting potential (typically about -80 mV) caused an inward current and a decrease in the slope conductance. The current caused by 5-HT reversed polarity at the potassium equilibrium potential. This reversal potential was linearly related to the logarithm of the extracellular potassium concentration. The depolarization caused by 5-HT persisted in tetrodotoxin (i ~M) and was not abolished by a solution that contained lower levels of calcium (0.24 mM), higher levels of magnesium (5 raM), and cobalt (2 mM). The action of 5-HT was occluded by barium (1-300 ~M). The 5-HT depolarization was competitively antagonized by the 5-HT 2 antagonists ketanserin and mianserin with dissociation equilibrium constants of 3 and 45 nM, respectively; spiperone (300 nM) also blocked the action of 5-HT. The depolarization was not mimicked or blocked by a number of other agonists and antagonists selective for the 5-HTI and 5-HT3 receptor types. These results show that neurons of the rat nucleus accumbens are depolarized by 5-HT acting at 5-HT 2 receptors to reduce conductance of the membrane to potassium ions.
TOPOGRAPHICAL GRADIENT OF R 2 D 5 - P O L Y P E P T I D E E X P R E S S E D BY G R A N U L E CELLS OF CAT H I P P O C A M P A L D E N T A T E GYRUS. KENSAKU MORI r AKIKO TANI, JUN IKEDA t YUMIKO WATANABE, AND SHOGO OKAt Department of Neuroscience~ Osaka Bioscience Institute~ 6-2-4 F u r u e d a i ¢ S u i t a - s h i , O s a k a 565, J a p a n In cat hippocampus, m o n o c l o n a l a n t i b o d y (MAb) R2D5 specifically labeled granule cells of the d e n t a t e g y r u s a n d t h e i r axons, m o s s y fibers. The R2D5immunoreactivity of granule cells showed a pronounced gradient along the septotemporal a x i s o f the h i p p o c a m p a l d e n t a t e gyrus. In the temporal (ventral) parts, most o f the g r a n u l e c e l l s w e r e i n t e n s e l y l a b e l e d w i t h M A b R2D5, whereas g r a n u l e c e l l s l o c a t e d in p r o g r e s s i v e l y m o r e s e p t a l (dorsal) p a r t s s h o w e d g r a d u a l l y less i m m u n o r e a c t i v i t y to M A b R2D5. Immunoblot analysis after SDS-PAGE indicates t h a t the a n t i g e n m o l e c u l e is a s o l u b l e p r o t e i n w i t h mol. w e i g h t o f a b o u t 14 KDa. It has been generally assumed that molecules involved in establishing or maintaining the t o p o g r a p h i c a l o r g a n i z a t i o n o f n e u r o n a l s y s t e m s are expressed in spatial gradients. S i n c e the h i p p o c a m p a l d e n t a t e g y r u s has axonal connections which are o r g a n i z e d t o p o g r a p h i c a l l y , it c a n be a s s u m e d t h a t expression of the R2D5-antigen m o l e c u l e is c o r r e l a t e d w i t h the t o p o g r a p h i c a x o n a l c o n n e c t i o n s . In addition, the result t h a t the a n t i g e n m o l e c u l e is a soluble cytosol protein suggests that intrinsic functional properties of granule cells differs according to the c e l l p o s i t i o n a l o n g the s e p t o t e m p o r a l axis.
THE EFFECT OF Mg 2+ ON THE SYNAPTIC DEPRESSION OF CA1 PYRAMIDAL NEURONS INDUCED BY LOW FREQUENCY STIMULATION IN RAT HIPPOCAMPAL SLICES. YUK0 SEKIN0*, AND IKUK0 KOYAMA, Department 0_ffPhyslolo~y, Tokyo W0men's Medical College. 8-__!1Kawata-eh0, ShlnJuku-ku L Tokyo 162, Japan. The effects of a brief repetitive stimulation at various frequencies on the 0rth0dr0mle responses of CA1 pyramidal neurons of rat hlppocampal slices were compared in 1.3mM and 2.0 mM magnesium medium. In 1.3mM M ~ + medium, 0nly potentiation of synaptle responses was observed after 20, 50, and 100Hz conditioning stimulations. However, after 5 and 10Hz conditioning stimulations, a short la~tlng (30s-lmln) depression appeared that was followed by a small potentiation. In 2.0mM Mg z+ medium. 100Hz stimulation induced potentiation, but even SOHz stimulation induced synaptie depression in 3 of ii ( 27~ ) slices experimented. The incidence, degree, and duration of depression increased when the frequency of conditioning stimulation was decreased. The depresslgn induced by 5 or ]0Hz stimulation was stronger and lasted long~r ( 3 - 5 mln) in 2.0mM Mg z+ than in 1.3mM Mg z+. When APV (S0aM) was added to the 2.0mM Mg z+ medium to block NMDA receptors, the depression appeared mere strongly so that 50Hz stimulation caused depression in all slices experimented (n=5). These d a t a t h a t s y n a p t l c ~ e 2 r e s s l o n was c a u s e d by low f r e q u e n c y r e p e t i t i v e stimulation and o b s e r v e d c l e a r l y i n 2.0mM Mg~ medium s u g g e s t t h a t magnesium i o n s may p l a y an i m p o r t a n t r o l e not o n l y i n b l o c k i n g t h e I n d u c t i o n of p o t e n t i a t i o n , b u t a l s o i n e n h a n c i n g some i n h i b i t o r y mechanisms such as n e t w o r k s i n c l u d i n g l n t e r n e u r o n s In t h e h l p p o c a m p a l n e u r o n s .
EFFECTS OF SEROTONIN ON NUCLEUS ACCUMBENS NEURONS OF THE RAT BRAIN. NAOHISA UCHIMURA* 12r ALAN R. NORTH*3,SYOGORO NISHI2f and YOICHI NAKAZAWA* *t Departments of * Neuropsychiatry and z Physiology, Kurume University School of Medicine t Kurume r 830 Japan and ~Ore@on Health Sciences University, Oregon t 97201 U.S.A. The nucleus accumbens receives a moderately dense innervation from the raphe nuclei of the midbrain, and direct application of serotonin (5-HT) into the nucleus affects motor performance. Intracellular recordings were made from rat nucleus accumbens neurons in slices (300 ~M) superfused in vitro with a physiological saline solution. 5-HT (i-I00 ~M) depolarized 170 of 203 (84%) neurons. The depolarization was associated with an increase in the input resistance. Application of 5-HT to neurons voltage-clamped near their resting potential (typically about -80 mV) caused an inward current and a decrease in the slope conductance. The current caused by 5-HT reversed polarity at the potassium equilibrium potential. This reversal potential was linearly related to the logarithm of the extracellular potassium concentration. The depolarization caused by 5-HT persisted in tetrodotoxin (i ~M) and was not abolished by a solution that contained lower levels of calcium (0.24 mM), higher levels of magnesium (5 raM), and cobalt (2 mM). The action of 5-HT was occluded by barium (1-300 ~M). The 5-HT depolarization was competitively antagonized by the 5-HT 2 antagonists ketanserin and mianserin with dissociation equilibrium constants of 3 and 45 nM, respectively; spiperone (300 nM) also blocked the action of 5-HT. The depolarization was not mimicked or blocked by a number of other agonists and antagonists selective for the 5-HTI and 5-HT3 receptor types. These results show that neurons of the rat nucleus accumbens are depolarized by 5-HT acting at 5-HT 2 receptors to reduce conductance of the membrane to potassium ions.