A New Study
The authors of the study are Nelson Ruiz-Opazo, of the Section of Molecular Medicine, Boston University School of Medicine, Boston, MA, and John Tonkiss, from the Center for Behavioral Development and Mental Retardation, Boston University School of Medicine, Boston, MA. Their study, entitled "X-Linked Loci Influence Spatial Navigation Performance in Dahl Rats," now appears in the Articles in Press section of Physiological Genomics, one of one of 14 scientific journals published monthly by the American Physiological Society (APS) (www.the-aps.org).
Dahl S/hsd (n=12) and Dahl R/hsd (n=12) male rats were obtained. Reciprocal mating of the parental strains (Dahl R female x Dahl S male and Dahl S female x Dahl R male) produced two types of F1 male hybrids: F1[RXS] (n=12) and F1[SXR] (n=11), respectively. A cohort was derived from brother-to-sister mating of F1 (R female x S male) hybrids to produce and F2 male segregation population (n=178). Behavioral testing was performed on parental, F1 and F2 cohorts at 12 weeks of age.
The Morris water maze (MWM) task was performed using a circular water maze and a computer tracking system. A circular platform was placed at the center of one of four imaginary quadrants and the water rendered opaque. Swim distance was used to evaluate performance.
Genotyping (the "blueprint" or set of instructions for building and maintaining a live creature) was done with six chromosome X markers. Quantitative trait locus (QTL; the combined influences of numerous genes) analysis was performed using the cumulative distance traveled over the 24 trials as the index of acquisition performance (ACQTD). The percent of distance traveled on the probe trial was used as the index of spatial accuracy (SpA). Linkage map, marker regression and interval mapping analyses were done to generate a likelihood ratio statistic as a measure of the significance of a possible QTL. A backcross analytic design was used to perform both the permutation test as well as the QTL analysis. Genetic distances were calculated with a Kosambi mapping function, and critical significance values for interval mapping were determined by a permutation test.
Two-Way Repeated Measures ANOVA, one-way ANOVA or t-tests (when indicated) were used to analyze behavioral data. All statistical tests were two-tailed and differences were considered significant at the P<0.05 level.
The researchers found that:
These results provide evidence for the existence of independent genetic determinants for of different aspects of spatial learning and memory performance. Clearly, new insights into the genetic mechanisms underlying the cognitive function can be gleaned from such analysis and the Dahl rat appears to provide a powerful model to accomplish those goals.
Source: Articles in Press section of the journal Physiological Genomics. The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.