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  • 1
    Electronic Resource
    Electronic Resource
    Feedback control of Purkinje cell activity by the cerebello-olivary pathway (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 20 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The pathway from the deep cerebellar nuclei to the inferior olive, the source of the climbing fibre input to the cerebellum, inhibits olivary transmission. As climbing fibre activity can depress the background firing of the Purkinje cells, it was suggested that nucleo-olivary (N–O) inhibition is a negative feedback mechanism for regulating Purkinje cell excitability. This suggestion was investigated, in a set-up with decerebrate ferrets, both by blocking and by stimulating cerebellar output while recording Purkinje cell activity. Blocking the N–O pathway was followed by an increased climbing fibre activity and a dramatic reduction in simple spike firing. Stimulation of the N–O fibres depressed climbing fibre responses and caused an increase in simple spike firing. These results are taken as support for the feedback hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03789.x
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of blood ingestion on brain serotonin synthesis in portacaval-shunted rats (1987)
    Springer
    Research in experimental medicine 187 (1987), S. 353-358 
    Details
    ISSN: 1433-8580
    Keywords: Indoleamines ; Brain ; Rat ; Decarboxylase inhibition ; Portacaval shunt (PCS) ; Protein ingestion ; Encephalopathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rats with a portacaval shunt (PCS), the effect on the serotonin metabolism in the brain after oral administration of blood, a mixed amino acid solution (Vamin 14; KabiVitrum, Sweden) or a 10% glucose solution was studied. One week after PCS, the animals were fed with a gastric tube for 8 h and thereafter tested for behavioral abnormalities before decapitation at 12 h. The concentration of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were analyzed chromatographically (HPLC technique with electrochemical detection) in different regions of the brain. Estimation of synthetic rates of 5-hydroxyindoles was facilitated by aromatic aminoacid decarboxylase inhibition (m-hydroxybenzylhydrazine; NSD 1015). The brain concentrations of 5-HTP, 5-HT, and 5-HIAA were increased in all shunted rats as compared with sham-operated animals. Whether animals received blood, glucose, or aminoacid solution made no differences in the brain concentrations of 5-HTP and 5-HT. Concentrations of 5-HIAA were lower in those animals receiving blood as compared with the other shunted groups. No reproducible differences in the behavior of the animals were observed. These results suggest that massive blood administration 1 week after PCS in rats has no influence on the rate of brain indole synthesis. While alterations in serotonin metabolism may play a role in some forms of encephalopathy, this study implies that the behavioral and neurologic disorders which follow gastrointestinal tract hemorrhage in patients with liver failure may have other etiologies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01855661
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of ammonia infusion on brain monoamine metabolism in portacaval-shunted rats (1989)
    Springer
    Research in experimental medicine 189 (1989), S. 101-111 
    Details
    ISSN: 1433-8580
    Keywords: Monoamine metabolism ; Portacaval shunt (PCS) ; Encephalopathy ; Ammonia infusion ; Rat brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of ammonia infusion on monoamine metabolism was studied in the rat brain. Seven days after portacaval shunt (PCS) or sham operation animals were infused with ammonia or saline. Brain metabolism of serotonin and norepinephrine was studied after injection of a decarboxylase inhibitor (m-hydroxybenzylhydrazine, NSD 1015) which blocks the conversion of 5-hydroxytryptophan to serotonin and dihydroxyphenylalanine to dopamine. Neurologic testing was conducted before killing. Plasma and brain amino acids were measured. PCS animals infused with ammonia were in deep coma after 6 h infusion, whereas sham-operated animals were virtually unaffected. Brain amino acid analyses demonstrated increased concentrations of the aromatic amino acids and a tenfold increase in glutamine. Serotonin metabolism was diminished after 6 h. Dopamine synthesis was normal, but norepinephrine levels were low after 6 h. The study suggests that hyperammonemia in PCS rats results in a depression of the serotonin synthesis rate in accordance with two previous studies but in contrast to previous hypotheses on the regulation of serotonin metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01851260
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  • 4
    Electronic Resource
    Electronic Resource
    Brain serotonin metabolism and behavior in rats with carbon tetrachloride-induced liver cirrhosis (1987)
    Springer
    Research in experimental medicine 187 (1987), S. 429-438 
    Details
    ISSN: 1433-8580
    Keywords: Liver cirrhosis ; Carbon tetrachloride ; Rats ; Brain 5-hydroxyindole metabolism ; Decarboxylase inhibition ; Open-field behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Increased brain serotonin metabolism has been suggested as an etiologic factor in the development of portal-systemic encephalopathy (PSE) in connection with liver disease. We therefore investigated brain serotonin metabolism and open-field behavior (spontaneous activity and exploration) in rats with carbon tetrachloride (CCl4)-induced liver cirrhosis. Brain serotomin metabolism was evaluated in rats pretreated with an amino acid decarboxylase inhibitor. The 5-hydroxyindoles were analyzed by high-performance liquid chromatography (HPLC) with electrochemical detection. The results revealed an increased serotonin synthesis rate in all investigated brain regions in rats with histologically verified diffuse micronodular cirrhosis of the liver. Slightly impaired open-field behavior (i.e., decreased spontaneous activity) in the cirrhotic rats could not be excluded. However, the elevated brain serotonin synthesis rate could not be correlated to any abnormalities in open-field behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01852181
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of liver ischaemia on brain monoamine synthesis in the rat (1987)
    Springer
    Research in experimental medicine 187 (1987), S. 119-130 
    Details
    ISSN: 1433-8580
    Keywords: Indoleamines ; Catecholamines ; Brain ; Rat ; Encephalopathy ; Dearterialisation ; Liver ischaemia ; Decarboxylase inhibition ; Porta caval shunt (PCS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Subtotal or total liver ischaemia was induced in the rat by dividing the hepatic artery (Expt. I) or by total dearterialisation of the liver (Expt. II) 2 days after porta-caval shunt (PCS). The animals received i.v. a 10% glucose infusion for 5 h after the last operation and were killed by decapitation. At the end of the experiment all animals with liver ischaemia were in Grade III coma. In different regions of the CNS 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), were analysed by HPLC-technique with electrochemical detection, while dihydroxyphenylalanine (DOPA), dopamine (DA) and norepinephrine (NE) were analysed with a radio enzymatic method after blocking the decarboxylation of 5-HTP to 5-HT and DOPA to DA by inhibition of the aromatic amino acid decarboxylase enzyme with m-hydroxybenzylhydrazine (NSD 1015) in order to estimate the synthesis rate of 5-hydroxyindoles and catecholamines. In Expt. I concentrations of 5-HTP in animals with PCS were increased as compared to sham operation. In animals with liver ischaemia, 5-HTP concentrations were increased as compared to sham operation but similar to those in animals with PCS alone. These results suggest that ligation of the hepatic artery for 5 h in PCS animals does not further accelerate the rate of brain indole synthesis. In Expt. II, the 5-HTP concentrations were increased in PCS animals as compared to sham operation. Animals with total liver dearterialisation exhibited decreased 5-HTP levels as compared to PCS, suggesting a decreased brain indole synthesis after severe liver ischaemia. In Expt. II, CNS concentrations of DOPA following PCS were unaltered as compared with sham-operated animals. In animals with total liver dearterialisation, DOPA levels were increased, suggesting an augmented catecholamine synthesis. The NE levels were lower than in PCS and in shamoperated animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01851973
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  • 6
    Electronic Resource
    Electronic Resource
    Brain 5-HT1 and 5-HT2 binding sites following portacaval shunt in the rat (1989)
    Springer
    Research in experimental medicine 189 (1989), S. 249-256 
    Details
    ISSN: 1433-8580
    Keywords: Brain ; 5-HT1 and 5-HT2 binding sites ; (3H)serotonin ; (3H)ketanserin ; Open field behavior ; Portacaval shunt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Brain serotonin 5-HT1 and 5-HT2 binding properties were investigated in experimental chronic portal-systemic encephalopathy (PSE). Endto-side portacaval shunted (PCS) rats were subjected to open field behavioral testing (spontaneous activity and exploration) 3 weeks after the shunt procedure. Each individual animal was then assayed for 5-HT1 and 5-HT2 binding properties (Bmax and KD) in the cortex + hippocampus by the use of radioligand binding and rapid filtration technique. (3H)serotonin was used to label 5-HT1 binding sites and (3H)ketanserin to label 5-HT2 binding sites. Results revealed that the PCS rats exhibited significant behavioral changes with decreased spontaneous activity and exploratory behavior as compared with sham-operated controls (sham). The affinity for, and the number of, 5-HT1 and 5-HT2 binding sites, respectively, were not different between PCS and sham rats. The brain 5-HT1 and 5-HT2 binding porperties were within the range of Bmax and KD previously reported for normal rats when similar techniques are used. This first report in PCS rats on the subject of brain 5-HT1 and 5-HT2 binding properties demonstrates that no major alterations are likely to occur. This contrasts the knowledge of a markedly increased brain serotonin synthesis rate in the PCS rat, suggesting minor functional relevance of the perturbed brain serotonin metabolism associated with chronic PSE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01852256
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