BRAIN MONOAMINE LEVELS AND ENERGY STATUS IN COMMON CARP (CYPRINUS-CARPIO) AFTER EXPOSURE TO SUBLETHAL LEVELS OF COPPER

Serotonin (5-hydroxytryptamine, 5-HT) and dopamine (DA) are two major monoamine neurotransmitters with a multitude of functions in the verte brate brain. In fish, the 5-HT system has been shown to be sensitive t o various forms of stress, but very few studies have examined the effe cts of toxic metals on these monoamine systems. Juvenile common carp w ere exposed to copper levels of 0.22, 0.34 and 0.84 mu M during 1 week . In telencephalon, dose-dependent falls in 5-HT and DA levels were ob served, with approximately 50% losses of these neurotransmitters at th e highest copper concentration. Although less dramatic, falls were als o seen in 5-HT and DA levels in hypothalamus and brain stem. No change s in 5-hydroxyindoleacetic acid (5-HIAA, the main 5-HT metabolite), AM P, ADP, ATP, adenylate energy charge or lactate levels were observed i n brain. However, lactate levels in blood plasma increased with copper concentration. A significant copper accumulation only occurred in the liver, while no changes in brain or muscle were seen. It is concluded that copper exposure of common carp causes decreased brain 5-HT and D A levels, two neurotransmitters involved in, for example, feeding beha viour and locomotor control in fish. In fact, in telencephalon a fall in 5-HT levels was seen already at a copper concentration below that w here food intake and movement were impaired.