Dissociated effects of inhibition of catecholamine synthesis on motor activity, "emotionality," and aggression in mice.

The inhibitor of catecholamine synthesis at the tyrosine hydroxylase level, alpha-methyltyrosine, administered in daily doses of 250 mg/kg IP, altered motor activity and aggressive behavior of isolated male mice in ten-minute paired encounter tests conducted on nine successive days. Motor activity was determined by an electromagnetic activity meter which measures fine and coarse movements separately. Coarse motor activity correlated significantly with aggressive behavior. Nonaggressive fine motor activity was significantly increased, while all the parameters of aggressive behavior showed a significant decrease in aggression. Increased escape behavior, heterogrooming, squeaking, and two cases of stupor were observed, suggesting possible equivalents of anxiousness. The defecation rate did not differ from that of the control group, victors having had a higher rate than losers. Results are discussed in connection with the "construct of emotionality" and the hypothesis of there being several categories of aggression with corresponding biochemical correlations.