Brain 5-hydroxytryptamine metabolism after portocaval anastomosis: relationship with ambulation

Chronic portocaval anastomosis (PCA) increased tryptophan and 5-hydroxyindoles in rat brain regions. PCA rats ambulated less than sham operated animals but showed positive correlations between ambulation and indices of brain 5-hydroxytryptamine (5-HT) metabolism, i.e., plasma free tryptophan, plasma non-esterified fatty acid, tryptophan in all brain regions, and 5-HT or 5-hydroxyindoleacetic acid in some regions. Results suggest a positive and non-causal association between motor activity and 5-HT metabolism in the PCA rats reflecting parallel responses of both variables to environmental stimulation. This may be superimposed on a normal inverse and causal relationship between motor activity and 5-HT metabolism.