| Abstract: | The effects of 1-h exposure to hypercapnia (PaCO2, 90-110 MMHg) on cerebral indole amine metabolism were studied in rats by measurement of cerebral hemisphere contents of tryptophan, 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA), 5-HIAA content was increased after 1-h exposure to hypercapnia, whereas tryptophan, 5-HTP, and 5-HT remained unchanged from control. The accumulation of 5-HTP after decarboxylase inhibition with 3-hydroxybenzyl hydrazine was increased in hypercapnic rats and indicated an increased activity of tryptophan hydroxylase. During the 1-h exposure to hypercapnia there was increased accumulation of 5-HT after monoamine oxidase inhibition with pargyline and increased accumulation of 5-HIAA arter probenecid. The results indicate an increased synthesis and degradation of indole amines in acute hypercapnia. |
