Changes in rat brain monoamines, monoamine metabolites and histamine after a single administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Male Long-Evans rats were given 50 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) intraperitoneally and after 1, 4, 28 or 76 hr, noradrenaline, dopamine, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), tryptophan and histamine were measured in the brain (dissected into ten parts) as well as in the pituitary gland. Several slight but significant changes were observed, e.g. in the hypothalamus where HVA and 5-HIAA were decreased after 4 hr, noradrenaline was decreased after 76 hr and histamine increased after 28 hr. Several late changes were also found, conspicuously tryptophan was increased in most brain areas after 76 hr and in some cases earlier; these changes may be due to starvation after hypophagia rather than TCDD directly. The results demonstrate that TCDD causes changes in brain neurotransmitter systems, but the changes are minor and it is not likely that aminergic systems are the key mediators in TCDD-induced hypophagia.