Regional acetylcholine turnover rates in the brains of three inbred strains of mice: correlation with some interstrain behavioural differences.
The hypothesis that the genetically determined behavioural differences which exist between the inbred mouse strains Balb/c, DBA/2 and C57Bl/6 may be related to differences in acetylcholine metabolism in certain regions of the brain has been tested. In vivo ACh turnover rates have been measured in three regions (hippocampus, caudate nucleus and frontal-parietal cortex) of the brains of each strain by following the rate of formation of labelled ACh, in these regions, after a pulse intravenous injection of a tracer dose of 3H labelled choline. Focused microwave procedures were used for the rapid fixation of brain tissue and Ch and ACh radioactivities were determined following their electrophoretic separation. Steady-state concentrations of Ch and ACh were measured by a sensitive radio-enzymatic method. Significant interstrain differences in ACh turnover rates are reported for each of the brain regions studied with the order of metabolic activity being Balb/c greater than DBA/2 greater than C57 Bl/6 in each case. These results are interpreted as being in agreement with previous reports on correlations between learning ability or locomotor activity and regional activities of choline acetyltransferase in the brains of these inbred strains. The correlations between the in vivo ACh turnover rates and (1) interstrain differences in behavioural measures and (2) regional choline acetyltransferase activities are discussed.