In this study, the effects of the Polycyclic Aromatic Hydrocarbon (PAH) Benzo (α) pyrene (BαP) exposure on the levels of serotonin (5-HT) and dopamine (DA) in the pituitary and hypothalamus of Yellowfin seabream, (Acanthopagrus latus) were examined. To assess the acute stress responses, vegetable oil (2 µl g-1) containing BαP (50 mg kg-1) was injected into the treatment group of fish (the vegetable oil alone was the control), and brain samples from different groups were collected 3 hr after injection. Base line group was not injected. To study the long-term stress, brains were collected from both injected groups after 72 hr. The amounts of serotonin, dopamine, and amine metabolites in the hypothalamus and pituitary were measured. Results showed that BαP influenced the serotonergic system more than the dopaminergic system for both acute and prolonged stress in both the hypothalamus and pituitary. Acute exposure to BαP induced significant decreases in DA and increases in DOPAC (3, 4-dihydroxyphenylacetic acid) in the pituitary (P<0.05). Major changes induced by both acute and prolonged exposure to BαP included significant decreases in 5-HT, increases in 5-HIAA (5-hydroxy-3- indoleacetic acid) and increases in the 5-HIAA/5-HT ratio (P<0.05). These exposures might affect the synthesis, storage, uptake/release, and degradation of the neurotransmitters in the hypothalamus and pituitary of sea bream, especially the pituitary gland.
