Effects of apomorphine and sodium Di-n-propylacetate on the aggressive behaviour of three strains of mice.

1. The effects of apomorphine and sodium Di-n-propylacetate (DPA, sodium valproate) on pain-induced aggressive behavior were investigated in three inbred strains of mice: BALB/c, C57B1/6 and DBA/2, which exhibited spontaneously low levels of aggression. 2. Apomorphine elicited aggressive behavior in the three strains, the range of effective doses being different for each strain of mice. 3. Di-n-propylacetate was effective in inhibiting apomorphine elicited aggression but the three strains exhibited a different sensitivity to this drug. 4. The effects of Di-n-propylacetate were not related to pain sensitivity, posture and locomotion. Only C57 strain exhibited a slight postural and locomotor impairment when injected with a higher dose of Di-n-propylacetate. 5. The results are discussed in terms of a genetic inference and of biological differences existing between these three strains.