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Relation between septo-hippocampal cholinergic system and the discrimination learning in rats: A microdialysis study
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RELATION BETWEEN SEPTO-HIPPOCAMPAL CHOLINERGIC SYSTEM AND THE DISZRIMINATION LEARNING IN RATS: A MICRODIALYSIS STUDY. YUTAKA YAMAMUROl, KOJI HORI’, HITOSHI IWANQ?,_OHUN GONI,_JUNICHI TANAKA3 and MASAHIKO NOMURAl, Iti@. of Phvsiol. and IPsychiatry. &l&ma WSch.. Moroyama. hum-pun. Saitama 350-04, JAPAN. 1Dept. of Human Develop.. Naruto Univ. of Fdusab.n, Naruto. Tokushima 772. JAPAN. To investigate the regulation of septo-hippocampal cholinergic system by dopaminergic inputs to the septum under a discrimination or non-discrimination learning task, an in viva microdialysis method with dual probe approach was used. Rats were trained to discriminate between lamp-on and lamp-off states under an operant-type learning procedure. Dialysis probes were inserted into the hippocampus and the medial septum of each rat. A dialysis experiment was then conducted in which extracellular levels of acetylcholine (ACh) in the hippocampus and dopamine (DA) in the medial septum were measured ACh level was significantly enhanced during learning session and rapidly before, during and after the learning session. The level of DA rapidly increased within 20 min, and then decreased. returned to their basal value after the session. However, rats in the non-discrimination group showed no significant changes in DA, and the increase in ACh tended to be delayed. These results suggest that DAergic inputs to the septum may be involved in the control of septo-hippocampal cholinergic system which is of importance for the discriminative learning behavior.
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ENHANCEMENT OF THE RAT HIPPOCAMPUS MONOAMINE TURNOVER DURING ONGOING BEHAVIOR IN A RADIAL MAZE TASK. AKIHIKO USHIGOMEl, JUNICHI TANAKAI. UTAKA YAMAMURO*. KOJI HORP AND MASAHIKO NOMURAZ, 1Dept. of Human Development, Nsruto Univ. of Fdu&jon. Naruto, Tokushima, 772, *Dept. of Phvsiol., Saitama Med. Sch., Iruma-gun, Saitama, 350-04, Janan. In an attempt to clarify the role of monoaminergic neural inputs to the hippocampus in the spatial learning processes, the present study measured extracellular levels of serotonin (5-HT), dopamine (DA) and their metabolites in the hippocampus of rats while and after they performed a radial maze task with the in viva microdialysis method. In a group of rats (n = 5), the dialysis experiment was carried out at the first trial of the maze task. The concentrations of Shydroxyindoleacetic acid (5HIAA) and 3,4dihydroxyphenylacetic acid (DOPAC) significantly increased during the learning session as compared to their basal levels. In another group of rats (n = 6), which were trained under the maze task more than 20 trials and demonstrated the stable correct response, the content of S-HIAA in the hippocampus significantly increased during learning the task as compared to the pre-learning basal level. These results show that the monoaminergic systems in the hippocampus are activated during ongoing behavior in the radial maze task. (Supported by Grant 5780602 from the Ministry of Education, Science and Culture, Japan, to J.T.)
DIFFERENTIAL DISTRIBUTION OF CALBINDIN D, PARVALBUMIN, CARLETININ, SOMATOSTATIN, AND SUBSTANCE I’ IN AMMON’S HORN, PROSLJBICULUM, AND SUBICULUM IN MACAQUE MONKEYS. ., Sch . of Med... 173 1~ AKIKO YAM-K0 S&Q. AND TOMIO -NI. Dept. of -Univ Lorente de N6 (1934) differentiated the prosubiculum from the subiculum in monkeys with the GoIgi method; the prosubiculum was composed of modified pyramidal cells that were continuous with pyramidal cells in the pyr&dal layer of ?A1 subfield of Ammon’s horn, but the subiculum was not. In this study, in order to get more information about the prosubiculum, immunocytochemical properties of cells of the hippocampal formation in Japanese macaques were examined. ABC-immunohistochemistory was performed using antibodies to calbindin D (CD), parvalbumin (PA), carletinin (CR), somatostatin (SS), and substance P (SE’). Animals were deeply anesthetized with ketamine and Nembutal followed by perfusion through the heart. CD immunoreactivity was present in pyramidal cells of Ammon’s horn and modified pyramidal cells of the prosubiculum. Some CDir, multipolar cells were also distributed in the lacunomoleculare and oriens layers of Ammon’s horn, in the pyramidal and oriens layers of the prosubiculum, and in a11 layers of the subiculum. PA immunoreactivity was exclusively present in nonpyramidal cells in the hippocampl formation; PA-ir cells were located in the oriens and pyramidal layers. CR immuoreactivity was localized in nonpyramidal cells in the hippocampal formation; most of CR-ir cells were distributed in the molecular layer with some in the pyramidal and oriens layers, although in the prosubiculum CR-ir cells were frequently seen in the region containning modified pyramidal cells. SS and SP immunoreactivities were localized in nonpyramidal cells in the hippocampal formation. In Ammon’s horn, most of SS-ir cells were present in the stratum oriens with some in the pyramidal layer. In the prosubiculum, SS-ir cells were distributed in the pyramidal and oriens layers, while in the subiculum, a few SS-ir cells were found only in the stratum oriens. Distribution of SF’-ir cells in the hippocampal formation was similar to that of SS-ir cells. Our results indicated that the prosubicuum and the subiculum were completely different in terms of immunocytochemistory, and that pyramidal cells in Ammon’s horn and modified pyramidal cells in the prosubiculum shared some characteristics in common.
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RELATION BETWEEN SEPTO-HIPPOCAMPAL CHOLINERGIC SYSTEM AND THE DISZRIMINATION LEARNING IN RATS: A MICRODIALYSIS STUDY. YUTAKA YAMAMUROl, KOJI HORI’, HITOSHI IWANQ?,_OHUN GONI,_JUNICHI TANAKA3 and MASAHIKO NOMURAl, Iti@. of Phvsiol. and IPsychiatry. &l&ma WSch.. Moroyama. hum-pun. Saitama 350-04, JAPAN. 1Dept. of Human Develop.. Naruto Univ. of Fdusab.n, Naruto. Tokushima 772. JAPAN. To investigate the regulation of septo-hippocampal cholinergic system by dopaminergic inputs to the septum under a discrimination or non-discrimination learning task, an in viva microdialysis method with dual probe approach was used. Rats were trained to discriminate between lamp-on and lamp-off states under an operant-type learning procedure. Dialysis probes were inserted into the hippocampus and the medial septum of each rat. A dialysis experiment was then conducted in which extracellular levels of acetylcholine (ACh) in the hippocampus and dopamine (DA) in the medial septum were measured ACh level was significantly enhanced during learning session and rapidly before, during and after the learning session. The level of DA rapidly increased within 20 min, and then decreased. returned to their basal value after the session. However, rats in the non-discrimination group showed no significant changes in DA, and the increase in ACh tended to be delayed. These results suggest that DAergic inputs to the septum may be involved in the control of septo-hippocampal cholinergic system which is of importance for the discriminative learning behavior.
2328
ENHANCEMENT OF THE RAT HIPPOCAMPUS MONOAMINE TURNOVER DURING ONGOING BEHAVIOR IN A RADIAL MAZE TASK. AKIHIKO USHIGOMEl, JUNICHI TANAKAI. UTAKA YAMAMURO*. KOJI HORP AND MASAHIKO NOMURAZ, 1Dept. of Human Development, Nsruto Univ. of Fdu&jon. Naruto, Tokushima, 772, *Dept. of Phvsiol., Saitama Med. Sch., Iruma-gun, Saitama, 350-04, Janan. In an attempt to clarify the role of monoaminergic neural inputs to the hippocampus in the spatial learning processes, the present study measured extracellular levels of serotonin (5-HT), dopamine (DA) and their metabolites in the hippocampus of rats while and after they performed a radial maze task with the in viva microdialysis method. In a group of rats (n = 5), the dialysis experiment was carried out at the first trial of the maze task. The concentrations of Shydroxyindoleacetic acid (5HIAA) and 3,4dihydroxyphenylacetic acid (DOPAC) significantly increased during the learning session as compared to their basal levels. In another group of rats (n = 6), which were trained under the maze task more than 20 trials and demonstrated the stable correct response, the content of S-HIAA in the hippocampus significantly increased during learning the task as compared to the pre-learning basal level. These results show that the monoaminergic systems in the hippocampus are activated during ongoing behavior in the radial maze task. (Supported by Grant 5780602 from the Ministry of Education, Science and Culture, Japan, to J.T.)
DIFFERENTIAL DISTRIBUTION OF CALBINDIN D, PARVALBUMIN, CARLETININ, SOMATOSTATIN, AND SUBSTANCE I’ IN AMMON’S HORN, PROSLJBICULUM, AND SUBICULUM IN MACAQUE MONKEYS. ., Sch . of Med... 173 1~ AKIKO YAM-K0 S&Q. AND TOMIO -NI. Dept. of -Univ Lorente de N6 (1934) differentiated the prosubiculum from the subiculum in monkeys with the GoIgi method; the prosubiculum was composed of modified pyramidal cells that were continuous with pyramidal cells in the pyr&dal layer of ?A1 subfield of Ammon’s horn, but the subiculum was not. In this study, in order to get more information about the prosubiculum, immunocytochemical properties of cells of the hippocampal formation in Japanese macaques were examined. ABC-immunohistochemistory was performed using antibodies to calbindin D (CD), parvalbumin (PA), carletinin (CR), somatostatin (SS), and substance P (SE’). Animals were deeply anesthetized with ketamine and Nembutal followed by perfusion through the heart. CD immunoreactivity was present in pyramidal cells of Ammon’s horn and modified pyramidal cells of the prosubiculum. Some CDir, multipolar cells were also distributed in the lacunomoleculare and oriens layers of Ammon’s horn, in the pyramidal and oriens layers of the prosubiculum, and in a11 layers of the subiculum. PA immunoreactivity was exclusively present in nonpyramidal cells in the hippocampl formation; PA-ir cells were located in the oriens and pyramidal layers. CR immuoreactivity was localized in nonpyramidal cells in the hippocampal formation; most of CR-ir cells were distributed in the molecular layer with some in the pyramidal and oriens layers, although in the prosubiculum CR-ir cells were frequently seen in the region containning modified pyramidal cells. SS and SP immunoreactivities were localized in nonpyramidal cells in the hippocampal formation. In Ammon’s horn, most of SS-ir cells were present in the stratum oriens with some in the pyramidal layer. In the prosubiculum, SS-ir cells were distributed in the pyramidal and oriens layers, while in the subiculum, a few SS-ir cells were found only in the stratum oriens. Distribution of SF’-ir cells in the hippocampal formation was similar to that of SS-ir cells. Our results indicated that the prosubicuum and the subiculum were completely different in terms of immunocytochemistory, and that pyramidal cells in Ammon’s horn and modified pyramidal cells in the prosubiculum shared some characteristics in common.
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