[Brain monoamine oxidase in highly aggressive C57BL and low aggressive CBA mice]

Highly aggressive C57BL mice were characterized by a higher MAO A activity in brain stem and hemispheres than low aggressive CBA mice at the age of 2 and 6 months. Emotional stress provoked by restraint resulted in a decrease of MAO A in the brain stem and hemispheres in 2-month-old C57BL mice which was prevented by actinomycin D. MAO A and MAO B in CBA mice did not react to stress. Aging of C57BL mice was accompanied by a decrease of MAO A activity in the hemispheres and of MAO B in the brain stem, while in CBA mice it was accompanied by a decrease of MAO B activity in the hemispheres. Actinomycin D increased MAO A activity in the brain stem of 6-month-old C57BL mice, but did not influence brain MAO in CBA mice. These date have demonstrated that the genotype of highly aggressive C57BL mice, as compared to low aggressive CBA mice, was expressed in a higher brain MAO A activity, which may have contributed to manifestation of aggressiveness in adult animals and of more reactive MAO A, which may be associated with peculiarities of regulation of its activity at the level of transcription but does not lead to disappearance of aggressiveness.