Quantitative trait loci affecting the behavior of A/J and CBA/J intercrossmice in the elevated plus maze

How allelic diversity affects neural mechanisms to pro duce behavioral vari ation is largely unknown. The elevated plus maze, consisting of open and cl osed arms, has been used as a model of behavioral variation in rodent explo ration. Under dim illumination the nature of the sensory stimuli that influ ence arm choice is uncertain. Two inbred mouse strains, A/J (Tyr(c)/Tyr(c) the albino phenotype, mutation in tyrosinase) with a strong preference for closed arm entry, and CBA/J (Pdeb(rdl)/Pdeb(rdl) the retinal degeneration p henotype, mutation in the P-subunit of rod cGMP phosphodiesterase), with a weak preference for open arm entry, were studied under varying light. Becau se behavioral differences persist under red light, variation in light perce ption is not likely to fully account for variation in arm choice. To identi fy genetic factors influencing arm choice (100 x Open arm entries/Total arm entries) quantitative trait loci analyses (QTL) were performed on (A/J x C BA/J)F-2 mice. Two QTLs, one of which includes PDEB, were identified on Chr 5 (LOD > 10) and account for > 30% of the behavioral variation in arm pref erence. Tyr (Chr 7, 44 cM) was linked to closed arm entries but not arm pre ference, and is unlikely to be acting through a direct effect on light perc eption, because A/J arm entries were not affected by red light and there wa s no interaction with PDEB in the (A/J x CBA/J)F-2 mice. Whether the candid ate QTLs on Chr 5 affect arm choice through an effect on light perception i s unknown, but phenotypic differences between F-2 mice with retinal degener ation and CBA/J mice and F-2 mice with albinism and A/J mice suggest that f actors other than light sensitivity contribute to arm preference in these t wo strains.