The effect of ammonia infusion on brain monoamine metabolism in portacaval-shunted rats

The effect of ammonia infusion on monoamine metabolism was studied in the rat brain. Seven days after portocaval 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-hyd...

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Bibliographic Details
Published in:Research in experimental medicine 1989-01, Vol.189 (2), p.101-111
Main Authors: BUGGE, M, BENGTSSON, F, NOBIN, A, JEPPSSON, B, HULTBERG, B, JONUNG, T, HERLIN, P
Format: Article
Language:English
Subjects:
5-Hydroxytryptophan - analysis
Amino Acids - metabolism
Ammonia - poisoning
Animals
Biogenic Amines - metabolism
Biological and medical sciences
Brain - drug effects
Brain - metabolism
Catecholamines - metabolism
Hydroxyindoleacetic Acid - analysis
Liver, biliary tract, pancreas, portal circulation, spleen
Male
Medical sciences
Portacaval Shunt, Surgical
Rats
Rats, Inbred Strains
Serotonin - metabolism
Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases
Surgery of the digestive system
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Summary:The effect of ammonia infusion on monoamine metabolism was studied in the rat brain. Seven days after portocaval 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 6h. 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.
ISSN:0300-9130
1433-8580
DOI:10.1007/BF01851260