Association between fighting behavior and catecholamine biosynthetic enzyme activity in two inbred mouse sublines.

Levels of three adrenal catecholamine synthesizing enzymes and isolation-induced fighting behavior were studied in two related sublines of the Balb/c inbred mouse strain. Enzyme levels were twice as high in the adrenals of Balb/cJ mice as in those of the Balb/cN mice; heterozygous progeny were intermediate between their parents in the levels of the three enzymes. These sublines also showed marked differences in their fighting behavior after a 2-week isolation period. Balb/cJ mice fought immediately after presentation of an intruder mouse, while Balb/cN mice did not fight at any time during the test. Heterozygous progeny behaved more like the Balb/cN (non-fighters). Analysis of F(2) mice suggested that the differences in fighting behavior were determined by a single gene, with fighting being recessive.