Y-chromosomal effects on discrimination learning and hippocampal asymmetry in mice.

From a four-way cross between unrelated inbred strains of mice, a random-breeding line was developed that segregated at two coat-color loci and carried Y chromosomes from different sources. Adult males were used for measurements of black-white discrimination learning and 7-day response retention in a water maze, body weight, brain weight, and left- and right-side hippocampus weight. Clear evidence was obtained of Y-linked influences on response acquisition, body weight, right-side hippocampus weight, and hippocampal asymmetry, whereas direct effects of autosome 9 were indicated with regard to right-side hippocampus weight only. However, epistatic interactions of the Y chromosome with autosome 9 were found for response acquisition and body weight and with autosome 4 for hippocampal asymmetry.