Acetylcholine turnover and aggression in related three strains of mice

Abstract

1. 1. This study compares brain levels of acetylcholine (ACh) and choline, and ACh brain turnover in 3 inbred strains of mice, CF-1, C57B1/6 By and Balb-c-By; these parameters were measured in control (aggregated) mice as well as following two paradigms, mild footshock and isolation, applied alone or in combination. 2. 2. Enzymic radioassay method was used to measure brain ACh and choline; ACh turnover was evaluated by two computation methods. 3. 3. Aggregated Balb-c-By mice exhibited low ACh and choline levels as compared to those of the mice of the two other strains. ACh levels of C57B1/6 By and CF-1 mice did not differ significantly; choline levels of CF-1 mice were almost twofold higher than those of C57B1/6 By mice. 4. 4. ACh turnover of aggregated CF-1 mice was about twice as high as that of C57B1/6 By and more than twice higher than that of Balb-c-By mice. 5. 5. The effects of shock, isolation, or shock combined with isolation on the brain levels of ACh and choline of mice of the 3 strains were inconsistent and, frequently absent. 6. 6. ACh turnover was significantly decreased in the brains of CF-1 by the two paradigms, whether employed alone or in combination; there was no additive effect when footshock was combined with isolation. 7. 7. ACh turnover did not change consistently after the two paradigms, employed alone or in combination, in the case of C57B1/6 By and Balb-c-By mice; in some cases, ACh turnover was increased. 8. 8. Footshock proved to be a mild inducer of aggression as compared to isolation in the 3 mice strains; footshock combined with isolation proved to synergize with respect to aggression in the 3 strains. Whether exposed to footshock and isolation alone or to the combination of these procedures, CF-1 mice were significantly more aggressive than Balb-c-By and C57B1/6 By mice. 9. 9. It is emphasized that consistent facilitatory effect of the two paradigms on aggression as well as additive effect on aggression resulting from combining footshock and isolation should be contrasted with the inconsistent effects of the two paradigms, applied alone or in isolation, on ACh turnover; altogether, the data did not indicate that aggression is related to increased brain ACh turnover.