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 norepinephr ine (NE) contents in the discrete brain of male and female tilapia, Or eochromis mossambicus were investigated. Sexually mature males and fem ales were exposed to 26 degrees C, 29 degrees C, or 32 degrees C of wa ter temperature for 3 weeks. The hypothalamic 5-HT content in the 29 d egrees C and 32 degrees C acclimated male was lower than that in the 2 6 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 an d 29 degrees C groups. Similar results were found in the hypothalamic NE contents of males and females. In the optic lobe, the elevated temp erature acclimation (29 degrees C and 32 degrees C) resulted in a high er 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 temperatu re acclimation had no influence on the 5-HT content of males and femal es, but resulted in a lower NE content in both males and females. Thes e results demonstrate that the neurotransmitter activity of teleost is influenced by the thermal acclimation in a sex- and regional-dependen t pattern. The alterations of 5-HT and NE in the central nervous syste m might be involved in the physiological and biochemical responses tha t occur during thermal acclimation in fish. (C) 1997 Elsevier Science Ireland Ltd.