Neurotransmittor changes in the rat brain after portacaval anastomosis

Portacaval anastomosis in rats elevated the brain serotonin content by about 30%, the greatest increase being noted in the brain stem. A minor increase in norepinephrine content but no change in dopamine concentration was also noted. Low dose L-dopa treatment reversed the serotonin changes but did not affect catecholamine concentrations. Protein load tended to lower most transmittor concentrations without clinically affecting the animals. The formation of 5-HT from tryptophane in vitro in rat cortical slices was reduced by about 35% whereas the formation of 5-HIAA in the same slices was increased with about 60%. This in vitro study indicates a change in the activity of serotonin neurons caused by the protacaval shunt. The findings suggest that changes in brain serotonin metabolism and brain serotonin neurons may be an explanation of hepatic encephalopathy.