Experiment
A (C57BL/6J x DBA/2J)F2 intercross was used to map QTLs involved in seizure susceptibility in response to electroshock stimulus. DBA/2J exhibits a lower maximal electroshock seizure threshold (MEST) than C57BL/6J. F1 and F2 animals exhibit intermediate MEST values. Seizure susceptibility also appears to be a sex-influenced trait. C57BL/6J and F2 female animals have significantly lower MEST values than males. A major QTL was mapped to Chromosome 1 (79 cM) with a LOD score of 12.6 near D1Mit150. This QTL mapped to the same position as Szs1, a QTL for PZT-induced seizure susceptibility. Congenic strain B6.D2-Mtv7a/Ty(Mtv7) verified the Szs1 locus on Chromosome 1. B6.D2-Mtv7a/Ty(Mtv7) carries a small portion of DBA/2J-like DNA on chromosome 1, including D1Mit150, on a C57BL/6J background. The congenic exhibits similar MEST values and susceptibility to PZT-induced seizures as DBA/2J. Other major loci mapped to Chromosome 2 (Szs7) with a LOD of 3.7 spanning 1 cM - 15.3 cM, Chromosome 5 (Szs11) with a LOD of 6.8 spanning 8 cM - 39 cM, and Chromosome 15 (Szv3, a previously mapped QTL for kainic acid-induced seizure susceptibility) with a LOD of 5.0 spanning 6.7 cM - 22.2 cM. Szs13 also mapped to Chromosome 15 with LOD = 5.0 spanning 46.9 cM - 52.2 cM. Suggestive loci were also identified: Szs8 (LOD = 2.9) on Chromosome 2 spanning 86 cM - 107 cM, Szs9 (LOD = 2.9) on Chromosome 10 spanning 27 cM - 40 cM, Szs10 (LOD = 3.2) on chromosome 11 spanning 20 cM - 34.25 cM, and Szs12 (LOD = 2.9) on Chromosome 13 spanning 45 cM - 59 cM.
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