Effect of MAO A deficiency on different kinds of aggression and social investigation in mice.

Monoamine oxidase A (MAO A) degrades serotonin, dopamine and noradrenaline, factors critically involved in the regulation of aggression. Different kinds of aggression were investigated in Tg8, a transgenic mouse strain lacking a functional MAO A gene. MAO A-deficient mice differ from wild-type C3H/HeJ (C3H) in terms of showing higher territorial, predatory and isolation-induced aggression.

Altered behavior and alcohol tolerance in transgenic mice lacking MAO A: a comparison with effects of MAO A inhibitor clorgyline.

The influence of deficiency of monoamine oxidase A (MAO A) gene and the lack of enzyme MAO A on the behavior of transgenic mouse strain (Tg8) was studied. It was shown that MAO-A-lacking mice differed from mice of the wild-type strain C3H/HeJ (C3H) by an attenuated acoustic startle response, prepulse inhibition (PPI) was unchanged. In Tg 8 mice, the exploratory nose-poking in the holeboard test as well as exploratory line crossing in the "light-dark" test were decreased.

Dopaminergic brain system in the quaking mutant mouse.

Quaking mice (qk/qk), autosomal recessive mutants with central nervous system dysmyelinization, characterized behaviorally by abnormal locomotion and tremor, are found to have altered brain dopaminergic system parameters, in comparison with phenotypically normal heterozygous littermates. Dopamine metabolism is enhanced in structures of both nigrostriatal and mesolimbic systems, as revealed by increased metabolites content (that of homovanillic acid in striatum and concentration of 3,4-dihydroxy-phenylacetic acid in nucleus accumbens with tuberculum olfactorium) along with unchanged neurotransmitter levels in qk/qk mice. D1 and D2 receptor analysis via radioligand binding using [3H]-SCH 23390 and [3H]-spiperone, correspondingly, showed an increase of D2 receptor density with decreased affinity to D2 ligand in striatum of mutants: both Bmax and Kd were markedly higher.

Role of genotype in brain dopamine metabolism and dopamine-dependent behavior of mice.

In mice of eight inbred strains--BALB/c, AKR/J, DBA/2, CBA, C57B1/6, DD, CC57Br, and C3H/He--brain dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in striatum and nucleus accumbens with tuberculum olfactorium, the structures of two main dopaminergic systems--nigrostriatal and mesolimbic--were determined. In both dopaminergic regions, no strain effect on either dopamine or DOPAC levels was found, while for HVA content a highly significant hereditary determination was shown. Influences of selective D1 and D2 dopamine receptor agonists--SK&F 38393 and quinpirole, respectively--as well as that of a mixed D1/D2 agonist, apomorphine, on general locomotor activity and stereotypic climbing were studied.

Role of genotype and dopamine receptors in behaviour of inbred mice in a forced swimming test.

The role of genotype in the effects of selective D1 and D2 dopamine agonists and antagonists on behavioural despair (Porsolt's test) was studied. Mice of nine inbred strains showed significant interstrain differences in duration of immobility. The influence of dopaminergic drugs was assessed in six strains characterized by different levels of swimming activity.