| First Author | Muraguchi T | Year | 1995 |
| Journal | Mouse Genome | Volume | 93 |
| Issue | 4 | Pages | 1035-1037 |
| Mgi Jnum | J:30567 | Mgi Id | MGI:78684 |
| Citation | Muraguchi T, et al. (1995) Strain differences for tossing-up seizures and pentylenetetrazol-induced convulsions in CXB RI strains. Mouse Genome 93(4):1035-1037 |
| abstractText | Full text of Mouse Genome contribution: STRAIN DIFFERENCES FOR TOSSING-UP INDUCED SEIZURES AND PENTYLENETETRAZOL-INDUCED CONVULSIONS IN CXB RI STRAINS. Takehiko Muraguchi and Tadao Serikawa; Institute of Laboratory Animals, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-01 Japan. Introduction Pentylenetetrazol (PTZ) has been used as a reagent for testing the effects of anticonvulsant drugs in rodents, since the first report by Orloff et al. (1). Sugaya et al. (2) reported that the induction of convulsions by intravenous administration of PTZ is a simple and precise method as compared with the tossing-up procedure which has been used for induction of seizures in an epileptic mouse strain El (3, 4). We recently noticed that some aged CXBG mice (5) in our stock exhibit spontaneous tonic-clonic seizures. We therefore examined the seizure sensitivity on tossing-up procedure and PTZ-injection in the progenitor strains BALB/cBy and C57BL/6By and seven CXB RI strains (5). Materials and Methods Mice. BALB/cBy, C57BL/6By and seven CXB RI strains (CXBD, CXBE, CXBG, CXBH, CXBI, CXBJ and CXBK) were kindly supplied from Prof. K. Moriwaki (National Institute of Genetics, Mishima, Japan) and maintained in our institute. Fl hybrids between BALB/cBy and C57BL/6By were produced in our institute. Tossing-up procedure. The mouse was carefully removed from the home cage, placed on the metal mesh of the cage, and observed for 3 min. Then, it was tossed up 30 times in the air about 15 cm above the mesh. When the mouse displayed seizures with fewer tossing-up procedures than 30 times, the procedure was stopped immediately so as not to give excessive stimuli. The tossing-up procedure was applied once a week from 4 and 23 weeks of age (20 trials in total). Pentylenetetrazol injection. PTZ was dissolved in physiological saline diluent and injected into the tail vein. To determine the administration dose indicating a distinct strain difference on PTZ-induced convulsions, different doses of the reagent were administered to the two progenitor strains BALB/cBy and C57BL/6By. Then, the number of animals with induced convulsions was examined in the progenitor strains, their Fl hybrids and seven CXB RI strains with a fixed dose. Forty to sixty mice from each strain were used with approximately equal numbers of males and females. The raw percentage data obtained in the PTZ-experiment were arcsin-transformed, and used for statistical analysis (6). The minimum number of effective loci based on phenotypic groups for PTZ-induced convulsions was estimated by the equation of Dux et al. (7) Results and Discussion Spontaneous tonic-clonic seizures in CXBG mice. In our CXB RI stock, some CXBG mice, either female or male, exhibited tonic-clonic seizures from about 3 months of age without any stimuli. The other CXB RI strains and progenitor strains never showed seizures during their lifetime. Therefore, CXBG mice may contribute in epilepsy research as a genetically defined epileptic strain (8). Strain difference for Tossing-up-induced convulsions. The number of animals exhibiting seizures by tossing-up procedure gradually increased with repetition of the trial in many strains as shown in Fig. 1. However, the seizures were not induced constantly in each trial. In CXBK and CXBD strains, all mice tested exhibited seizures more than once. On the contrary, C57BL/6By and CXBI did not exhibit any seizures during the experiment. In summary, the strains tested were divided into 3 groups of sensitivity. 1) Sensitive group, BALB/cBy; CXBD; CXBH; CXBK, 2) Intermediate group, CXBE; CXBG; CXBJ, and 3) Resistant group, C57BL/6By; CXBI. Three animals of the CXBG strain exhibited tonic-clonic seizures on the mesh before the tossing-up trial. However, no animals in other strains including the sensitive group showed the seizures at the observation stage. It was strange that 50% of CXBG mice did not exhibit seizures, but is conceivable if we consider that the mice may have experienced spontaneous seizures before the tossing-up trials. One explanation is that spontaneous seizures and tossing-up induced seizures may occur by independent mechanisms. Thus, the experimental data obtained by the tossing-up procedure was too complicated to perform further analysis. Fig. 1 (Legend). Seizures induced by tossing-up procedure given from 4 weeks of age. The percentage is calculated by cumulative number of animals with induced seizures. Fig. 2 (Legend). (A) Distribution of PTZ-induced convulsion threshold in BALB/cBy and C57BL/6By at 8 weeks of age with different doses of PTZ. (B) Rate of evoking convulsions by PTZ in CXB RI strains, the progeintor strains and the Fl hybrid mice at 8 weeks of age. Table 1. Susceptibility of CXB RI strains, the progenitor strains and their Fl hybrid to a 20 mg/kg dose of PTZ. Mice: BALB/cBy; No. of animals tested (N): 40; No. of animals induced (I): 38; I/N (%): 95.0; Phi=sin 1 (square root) I/N: 77.1. Mice: CXBK; No. of animals tested (N): 42; No. of animals induced (I): 39; I/N (%): 92.9; Phi=sin 1 (square root) I/N: 74.5. Mice: CXBD; No. of animals tested (N): 40; No. of animals induced (I): 31; I/N (%): 77.5; Phi=sin 1 (square root) I/N: 61.7. Mice: CXBH; No. of animals tested (N): 60; No. of animals induced (I): 40; I/N (%): 66.7; Phi=sin 1 (square root) I/N: 54.7. Mice: F1; No. of animals tested (N): 50; No. of animals induced (I): 21; I/N (%): 42.0; Phi=sin 1 (square root) I/N: 40.4. Mice: CXBG; No. of animals tested (N): 60; No. of animals induced (I): 19; I/N (%): 31.6; Phi=sin 1 (square root) I/N: 34.2. Mice: CXBE; No. of animals tested (N): 41; No. of animals induced (I): 9; I/N (%): 22.0; Phi=sin 1 (square root) I/N: 27.9. Mice: CXBJ; No. of animals tested (N): 43; No. of animals induced (I): 7; I/N (%): 16.3; Phi=sin 1 (square root) I/N: 23.8. Mice: C57BL/6By; No. of animals tested (N): 48; No. of animals induced (I): 7; I/N (%): 14.6; Phi=sin 1 (square root) I/N: 22.5. Mice: CXBI; No. of animals tested (N): 40; No. of animals induced (I): 2; I/N (%): 5.0; Phi=sin 1 (square root) I/N: 12.9. Strain differences in PTZ-induced seizure. BALB/cBy and C57BL/6By mice were injected with five different doses of PTZ (15, 18, 20, 22 and 25 mg/kg of body weight). When a 20 mg/kg dose of PTZ was given, 90% of BALB/cBy showed convulsions, but C57BL/6By mice showed no convulsions as shown in Fig. 2 (A). Thus, we decided to use 20 mg/kg of PTZ as the dose for analyzing mouse strain differences. The percentage of animals exhibiting convulsions was calculated in each CXB RI strain. As shown in Fig. 2 (B), the percentage for 6 inbred strains fall between the values of the progenitor strains (BALB/cBy, 95.0%; C57BL/6By, 14.6%) except for CXBI (5.0%), and the distributions showed significant differences (CXBJ, 16.3%; CXBE, 22.0%; CXBG, 31.6%; CXBH, 66.7%; CXBD, 77.5%; CXBK, 92.9%). The (CXB)Fl hybrid fell into the middle, 42.0%, between the progenitor levels. The percentage data were arcsin-transformed (see Table 1), and applied for a multiple range test. The minimum number of effective genes based on phenotypic groups was estimated as 2.0, which means that at least two genes are involved in the sensitivity of PTZ-induced convulsions. Although RI strains can be used for mapping of genes controlling not only qualitative traits but also quantitative traits, the number of CXB RI strains is too small for analysis (5). The genes controlling the strain differences found in the present study should be explored later with specially-constructed crosses and stocks. Acknowledgments. We would like to thank Dr. Wayne N. Frankel, The Jackson Laboratory, for helpful discussions and suggestions. This work was supported in part by research grants from the Japanese Ministry of Education, Science and Culture, and the Japanese Ministry of Health and Welfare. References 1. Orloff, M.J., et al. Pros. Soc. Exper. Biol. & Med. 1949; 70: 254-257. 2. Sugaya, E., et al. Epilepsia 1986; 27: 354-358. 3. Imaizumi, K., et al. Mouse News Let. 1964; 31: 57. 4. Rice, M.L., et al. Science 1991; 253: 669-673. 5. Baily, D.W. In The mouse in biomedical research Vol. I, Foster, H.L et al., Eds, 1981; pp. 223-239, Academic Press, Inc. 6. Mather, K. In Statistical Analysis in Biology. Fourth Edition, Methuen, London. 1965. 7. Dux, A., Muhlbock, O. and Baily, D.W. J. Natl. Cancer Inst. 1978; 61: 1125-1129. 8. Seyfried T.N. and Glaser G.H. Epilepsia 1985; 26: 143-150. |
