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

Abstract

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.

Effects of dilutional hyponatremia on brain organic osmolytes and water content in patients with cirrhosis

“…Raw data of those spectra acquired after February 2003 (when the LC model was acquired) were transferred to a separate Ultra 60 SUN‐WS (Sun Microsystems Inc., Santa Clara, CA) and postprocessed using the LC model version 620 to determine absolute metabolite concentrations. This is an automated, external reference method that uses a basis set of known metabolite concentrations for the different metabolites as a reference.…”