| Abstract No.: | A-A1004 |
| Country: | Canada |
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| Title: | COMPARISON OF PUP DEVELOPMENT FROM BIRTH TO 24 DAYS OF AGE IN C3H/HESNJ (C3H) AND C3H/HESNJ-CM (COLOBOMA) MICE |
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| Authors/Affiliations: | 1 Kaitlyn Lee*; 1 Richard Brown;
1 Dalhousie University; Halifax, NS, Canada
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| Content: | Objectives: Coloboma (Cm) mice are heterozygous for a spontaneous mutation that causes a knockout of a 2-cM area on chromosome 2 (Jackson Laboratory, 2007. http://jaxmice.jax.org/strain/001547.html). This deletion results in abnormal posture, head bobbing, and circling behaviours that are not present in the background C3H strain. Cm mice show elevated locomotor activity and have been proposed as a model of ADHD due to their extremely hyperactive nature (Wilson, 2000. Neuroscience & Biobehavioral Reviews, 24:51-57). Because of their C3H background strain, these mice are homozygous for the retinal degeneration allele, and the absence of the Cm gene results in a spectrum of abnormal choroid development and microphthalmia (Theiler & Varnum, 1981. Anatomy & Embryology, 162:121-126).
Materials and methods: In order to examine the development of the Cm behavioural phenotype, this study compared physical, reflex and motor development of C3H and Cm pups from birth to 24 days of age. Pups were tested every two days starting at post-natal day two (PND 2), using a test battery consisting of the righting reflex (PND 2-10), negative geotaxis (PND 2-10), forelimb grip strength (PND 6- 16), automated open field (PND 10-24), homing test (PND 14), and weight gain (PND 2-24). In addition, days on which pups demonstrated the placing response, grasp reflex, rooting reflex, crossed-extensor reflex, and presented eye and pinnae detachment, were recorded.
Results: In the open field, Cm pups showed significantly higher horizontal activity and lower vertical activity than C3H pups. Differences in motor ability between strains were fist observed on PND 18 and increased until PND 24. Cm pups also demonstrated significantly earlier day of eye opening compared to C3H pups. Sex by strain interactions were found on the speed of the homing response, as female Cm mice returned to their home bedding faster than C3H females, but male Cm mice returned slower than C3H males. C3H males showed the grasp reflex earlier than C3H females, but there were no sex differences in Cm pups. Female Cm and male C3H mice showed a faster righting response than male Cm and female C3H mice. In all cases C3H females were slower than C3H males, and Cm females were faster than Cm males. Specifically, C3H females showed delayed development of the grasp reflex in comparison to other groups. There were no strain or sex differences in the age at which the placing reflex, rooting reflex, crossed extensor reflex, or pinnae detachment were shown, or on forelimb grip strength and rate of weight gain.
Conclusion: These results indicate that developmental differences between Cm and C3H pups begin at PND 18, and that these differences are shown primarily in motor and eye development. Sex differences and sex by strain interactions may be due to maternal strain and litter size effects.
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