Effects of thermal acclimation on the neurotransmitters, serotonin and norepinephrine in the discrete brain of male and female tilapia, Oreochromis mossambicus.

Effects of thermal acclimation on the serotonin (5-HT) and norepinephrine (NE) contents in the discrete brain of male and female tilapia, Oreochromis mossambicus were investigated. Sexually mature males and females were exposed to 26 degrees C, 29 degrees C, or 32 degrees C of water temperature for 3 weeks. The hypothalamic 5-HT content in the 29 degrees C and 32 degrees C acclimated male was lower than that in the 26 degrees C group. In females, the hypothalamic 5-HT content in the 32 degrees C acclimated group was less than those in the 26 degrees C and 29 degrees C groups. Similar results were found in the hypothalamic NE contents of males and females. In the optic lobe, the elevated temperature acclimation (29 degrees C and 32 degrees C) resulted in a higher 5-HT content in both males and females; whereas, the NE content was increased by the elevated temperature acclimation in females but not altered in that of males. In the telencephalon, the elevated temperature acclimation had no influence on the 5-HT content of males and females, but resulted in a lower NE content in both males and females. These results demonstrate that the neurotransmitter activity of teleost is influenced by the thermal acclimation in a sex- and regional-dependent pattern. The alterations of 5-HT and NE in the central nervous system might be involved in the physiological and biochemical responses that occur during thermal acclimation in fish.