Radial maze performance, open-field and elevated plus-maze behaviors in Fyn-kinase deficient mice: Further evidence for increased fearfulness

Fyn-deficient mice produced by inserting the β-galactosidase gene (lacZ) into the fyn gene locus were tested in a radial maze, an open field and an elevated plus-maze. In the radial maze, the homozygous Fyn-deficient (fyn(z)/fyn(z)) mice showed no impairment in spatial learning, although they showed a stronger avoidance tendency for those arms located closer to the experimenter during pretraining (adaptation). In the open-field test, the fyn(z)/fyn(z) mice defecated more frequently in the bright condition than did the +/fyn(z) mice, and they were less active during the first 10-min test period than the +/fyn(z) mice. In addition, the temporal pattern of locomotor activity for fyn(z)/fyn(z) mice was altered by changing the illumination while the pattern for +/fyn(z) mice remained relatively unchanged. Scores reflecting the fear-response in the elevated plus-maze were higher in the fyn(z)/fyn(z) mice. These results indicate that Fyn deficiency increased fear-response, but did not impair spatial learning in the radial maze. It is suggested that we should take account of effects of emotional factors in the learning experiment using mutant mice.