Aquatic contaminants alter genes involved in neurotransmitter synthesis and gonadotropin release in largemouth bass

• Published in: Aquatic toxicology 2009-10, Vol.95 (1), p.1-9
• Main Authors: Martyniuk, Christopher J., Sanchez, Brian C., Szabo, Nancy J., Denslow, Nancy D., Sepúlveda, Maria S.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Applied ecology; atrazine; bass; Bass - physiology; bioaccumulation; Biological and medical sciences; Brain; Brain - drug effects; Brain - metabolism; Cadmium; Ecotoxicology, biological effects of pollution; Female; Fish Proteins - genetics; Fish Proteins - metabolism; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation - drug effects; General aspects; genotoxicity; gonadotropin release; Gonadotropins - metabolism; Male; messenger RNA; Micropterus salmoides; Neurotransmitter Agents - genetics; neurotransmitters; PCB 126; Phenanthrene; pollutants; polychlorinated biphenyls; Salmonidae; Synecology; Toxaphene; transcription factors; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - toxicity; water pollution
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2009.06.009

Many aquatic contaminants potentially affect the central nervous system, however the underlying mechanisms of how toxicants alter normal brain function are not well understood. The objectives of this study were to compare the effects of emerging and prevalent environmental contaminants on the expression of brain transcripts with a role in neurotransmitter synthesis and reproduction. Adult male largemouth bass ( Micropterus salmoides) were injected once for a 96 h duration with control (water or oil) or with one of two doses of a single chemical to achieve the following body burdens (μg/g): atrazine (0.3 and 3.0), toxaphene (10 and 100), cadmium (CdCl 2) (0.000067 and 0.00067), polychlorinated biphenyl (PCB) 126 (0.25 and 2.5), and phenanthrene (5 and 50). Partial largemouth bass gene segments were cloned for enzymes involved in neurotransmitter (glutamic acid decarboxylase 65, GAD65; tyrosine hydroxylase) and estrogen (brain aromatase; CYP19b) synthesis for real-time PCR assays. In addition, neuropeptides regulating feeding (neuropeptide Y) and reproduction (chicken GnRH-II, cGnRH-II; salmon GnRH, sGnRH) were also investigated. Of the chemicals tested, only cadmium, PCB 126, and phenanthrene showed any significant effects on the genes tested, while atrazine and toxaphene did not. Cadmium (0.000067 μg/g) significantly increased cGnRH-II mRNA while PCB 126 (0.25 μg/g) decreased GAD65 mRNA. Phenanthrene decreased GAD65 and tyrosine hydroxylase mRNA levels at the highest dose (50 μg/g) but increased cGnRH-II mRNA at the lowest dose (5 μg/g). CYP19b, NPY, and sGnRH mRNA levels were unaffected by any of the treatments. A hierarchical clustering dendrogram grouped PCB 126 and phenanthrene more closely than other chemicals with respect to the genes tested. This study demonstrates that brain transcripts important for neurotransmitter synthesis neuroendocrine function are potential targets for emerging and prevalent aquatic contaminants.