Exposure of goldfish (Carassius auratus) to bluegills (Lepomis macrochirus) enhances expression of stress protein 70 mRNA in the brains and increasesplasma cortisol levels

The effect of psychological stress on HSP70 mRNA in the brains and plasma c ortisol levels in goldfish was examined. Stress was induced by exposure to a predator (bluegills). HSP70 mRNA and cortisol were determined by Northern blotting and ELISA, respectively. Goldfish exposed to four predators in th e same tank without a partition showed marked increases in HSP70 mRNA and c ortisol levels 6 hr and 12 hr after commencement of exposure. When goldfish were separated from bluegills with a net partition, HSP70 mRNA expression was enhanced after 6 hr, and returned to the control level after 12 hr. Pla sma cortisol levels increased after 2 hr, and returned to the control lever after 6 hr. When goldfish were placed in a transparent tank around which b luegills were swimming, HSP70 mRNA expression and cortisol levels increased after 6 hr and 12 hr. Goldfish exposed to water circulating through a tank with bluegills showed no sign of changes in HSP70 mRNA expression or corti sol levels. These results suggest that psychological stress enhanced HSP70 mRNA expression in the brains and increased plasma cortisol levels via visu al perception.