Comparative study of acetylcholine synthesis in organs of freshwater teleosts.

The activity of acetylcholine (ACh) synthesizing enzyme, choline acetyltransferase (ChAT), and the content of ACh were determined in the brain, heart, red trunk muscle and midgut of 12 freshwater teleost species belonging to eight families: carp (Cyprinus carpio), tench (Tinca tinca), silver carp (Hypophthalmichtys molitrix), bighead (Hypophthalmichtys nobilis), wels (Silurus glanis), cat fish (Ictalurus nebulosus), eel (Anguilla anguilla), rainbow trout (Oncorhynchus mykiss), pike (Esox lucius), pike-perch (Stizosteidon lucioperca), ruffe (Acerina cernua) and pumpkinseed (Lepomis gibbosus). The rate of ACh degradation in the same tissues was characterized by measuring the activity of acetylcholinesterase (AChE). Comparisons by statistical evaluation of cholinergic parameters in the corresponding organs were made between the species or families. The highest ACh concentration was found in the brain (between 9.6 and 16.0 nmol/g), and the gut (4.6 to 17.4 nmol/g), followed by the heart (1.4 to 3.9 nmol/g) and trunk muscle (1.2 to 3.8 nmol/g). Good correlations were found between the ACh content and the ChAT activity in all the organs studied. The correlation coefficients were 0.92 and 0.72 for the brain and heart, respectively. The activity of ChAT and the amount of ACh found in the brain and trunk muscle varied considerably from one family to another, but was of comparable degree within one family. It was concluded that differences in the cholinergic parameters may reflect different feeding and swimming behavioral patterns.