Regional concentrations of serotonin, tryptophan, 5-hydroxyindoleacetic acid, dopamine, and norepinephrine in the ovine brain.

Regional concentrations of tryptophan, serotonin (5HT), 5-hydroxyindoleacetic acid (5HIAA), norepinephrine, and dopamine were determined in the ovine brain. Tryptophan concentrations varied between 18.6 nmoles/g of tissue (hypothalamus, midbrain) and 26.9 nmoles/g (cerebellum). The 5HT concentrations varied 0.34 nmoles/g (cerebellum) and 3.75 nmoles/g (midbrain). The concentration of 5HIAA varied between 1.78 nmoles/g (cerebellum) and 5.02 nmoles/g (hypothalamus). Large concentrations of norepinephrine were found in the hypothalamus (4.37 nmoles/g) and midbrain (2.08 nmoles/g), while the frontal cortex, thalamaus, hippocampus, and cerebellum were all relatively low in norepinephrine (0.65 to 0.95 nmoles/g). The concentration of dopamine was between 0.32 nmoles/g (hippocampus) and 39.8 nmoles/g (caudate nucleus). Generally, the distribution of these compounds in the ovine brain is similar to their regional distribution in other mammalian species. It was observed, however, that the ratio of 5HT/5HIAA appears to be relatively lower in sheep than in other species, suggesting that interspecies differences in the metabolism of 5HT or elimination of 5HIAA (or both) may exist.