Effects of African Trypanosomiasis on Brain Levels of Dopamine, Serotonin, 5‐Hydroxyindoleacetic Acid, and Homovanillic Acid in the Rabbit

: Serotonin (5‐HT) levels fell by 21% in the mid‐brain‐thalamus‐hypothalamus (MTH) region of the rabbit brain after chronic infection with the protozoan Trypanosoma brucei gambiense. 5‐HT did not decrease significantly in the caudate/putamen (CP) or the pons/medulla (PM) region. 5‐Hydroxyindoleacetic acid (5‐HIAA) levels were unchanged in the MTH and caudate/putamen (CP) but increased by 17% in the pons/medulla (PM) after infection. Dopamine (DA) levels rose by 19% and homovanillic acid (HVA) by 33% in the PM during infection. DA and HVA tended to be lower in the CP of infected rabbits, but the apparent decreases were not statistically significant. DA and HVA levels in the MTH were also unchanged by infection. These neurochemical changes may be involved in the behavioral symptoms that frequently accompany this disease in man and cattle.