This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the Committee on the Ethics of Animal Experiments of Boston University School of Medicine (Permit Number: AN-13926).
All rats utilized in this study were bred in-house. Inbred Dahl S/jrHsd and Dahl R/jrHsd rats were obtained from Harlan (Indianapolis, Indiana). We transferred two Dahl R chromosomal segments spanning Nav-5
onto the Dahl S genetic background. We implemented a “speed congenic” strategy 
to develop the two congenic lines. For this purpose we first produced a (Dahl S × Dahl R) F1 progeny followed by generation of an F1 × Dahl S backcross (BC1) population. We selected Nav-5
“carriers” from 300 BC1 subjects by genotyping the BC1 male progeny with flanking markers of the chromosomal segments planned to be transferred. For S.R17A; sr heterozygous at SNP2801868 and SNP2801895, and ss homozygous at nearby flanking markers, i.e. D17Rat24 and SNP2801949. For S.R17B; sr heterozygous at SNP2801895 and D17Rat36, and ss homozygous at nearby flanking markers, i.e. SNP2801879 and D17Rat44. We then produced 20 BC2 male subjects per congenic line and proceeded to screen subjects with 85 informative SNPs. One “best” S.R17A male breeder containing 97.6% Dahl S genetic background and one “best” S.R17B male breeder containing 95.2% Dahl S genetic background were chosen to continue with the inbreeding program. Back-crosses were performed up to BC6 at which level we established homozygous congenic lines for blood pressure measurements and Morris Water Maze performance. SR17A was >99.85% of Dahl S genetic background and S.R17B >99.70% of Dahl S genetic background.
We selected the following single nucleotide polymorphisms (SNPs) for congenic rat development from the rat genome data base (RGD): markers for S.R17A and S.R17B congenic fragments; D17Rat24, SNP2801868, SNP2801879, SNP2801895, SNP2801949, D17Rat36, D17Rat44. SNPs for implementation of “speed congenic” strategy, chr1: SNP2783361, SNP2783513, SNP2783573, SNP2783925, SNP2784073, SNP2784200, SNP2784723, SNP2784895, SNP2785046; chr2: SNP2785301, SNP2785499, SNP2785693, SNP2785860, SNP2786134, SNP2786276, SNP2786350, SNP2786619, SNP2786811, SNP2786979, SNP2787226; chr3: SNP2787599, SNP2787751, SNP2787947, SNP2788108, SNP2788217, SNP2788416; chr4: SNP2789191, SNP2789416, SNP2789717, SNP2789952, SNP2790223, chr5: SNP2790571, SNP2790733, SNP2790960, SNP2791234, SNP2791496, SNP2791711, SNP2791834; chr6: SNP2792065, SNP2792467, SNP2792754; chr7: SNP2793338, SNP2793565, SNP2793757, SNP2793904; chr8: SNP2794281, SNP2794450, SNP2794721, SNP2794865; chr9: SNP2795738, SNP2795947; chr10: SNP2796278, SNP2796474, SNP2796739, SNP2796966; chr11: SNP2797258, SNP2797443, SNP2797742; chr12: SNP2797924, SNP2798115; chr13: SNP2798475, SNP2798659, SNP2798785, SNP2798926; chr14: SNP2799254, SNP2799430, SNP2799825; chr15: SNP2800105, SNP2800195; chr16: SNP2800810, SNP2801108; chr17: SNP2801413, SNP2801584, SNP2801868, SNP2801948; chr18: SNP2802358, SNP2802507, SNP2802706; chr19: SNP2802997, SNP2803270; chr20: SNP2803540, SNP2803747; chrX: SNP2804065, SNP2804185, SNP2804233.
DNA was extracted from tail biopsies using the QIAamp Tissue Kit (Qiagen, Valencia, CA). SNP genotyping was carried out on an Applied Biosystems 7900 Real-Time PCR System. All SNP assays (TaqMan assays) were procured from Applied Biosystems and were validated in our laboratory. All SSLPs were detected by PCR genotyping followed by denaturing polyacrylamide gel electrophoresis.
Morris Water Maze Testing
The MWM task was performed as described 
using a 1.5 m diameter, circular water maze (filled with water at 25°C ±0.5), and a computer tracking system (Smart software program, Version 1.24, Panlab s.I., Barcelona, Spain). Distance was used to evaluate performance. Twelve swim trials were given per day (for 2 consecutive days). Animals were placed into the maze (at one of three randomized start positions located adjacent to the wall) and were allowed to traverse the maze in search of the escape platform. On each trial, a maximum swim time of 60 sec was imposed. Between trials, a 35 sec interval was imposed with the rat on the platform. At the end of the twenty-fourth trial, rats were removed to the home cage for 10 min, then the platform was removed (probe trial) and the rat was allowed to search for 1 minute. Sixteen Dahl S males, 16 S.R17A males and 16 S.R17B males were characterized in this MWM task for subsequent comparative analysis. Spatial accuracy was define as the ratio of % distance traveled in platform counter over the sum of % distance traveled over the four counters localized at analogous positions on corresponding quadrants (Spatial accuracy
% distance Tcounter/% distance Tcounter+% distance AL
counter+% distance AR
counter+% distance Ocounter).
We performed Two-Way ANOVA followed by Holm-Sidak test for acquisition performance comparisons and One-Way ANOVA followed by Holm-Sidak test for analysis of navigational performance on the probe trial.