Fischer (F-344) rats have different morphology, sensorimotor and locomotor abilities compared to Lewis, Long-Evans, Sprague-Dawley and Wistar rats.
Locomotor and/or sensory behaviour is commonly evaluated in laboratory rats in the field of neuroscience. Many strains of rats, however, have been propagated through intensive breeding programs. With any breeding program, traits are selected purposefully or inadvertently. We set out to investigate whether differences in morphology, sensory or motor behaviours exist using five age-matched strains of laboratory rats. Personal observations of morphological differences between different strains of rats led us to hypothesize that Fischer rats were dissimilar to the other strains in each of the parameters investigated. Evaluation of morphology involved measuring long-bone lengths and body weights of each strain. Motor skills were evaluated by measuring paw preferences while rearing, abduction of the distal portion of hindlimbs during locomotion, footfalls through a horizontal ladder during locomotion, and ground reaction forces generated during trotting. Sensory ability was assessed by von Frey testing. Fischer rats had shorter long-bone lengths, weighed less, and had significantly abducted distal portion of their hindlimbs during locomotion compared to the other strains. Lewis and Sprague-Dawley rats were less sensitive to mechanical pedal stimulation compared to Fischer rats. While rearing, all strains of rats tended to use individual forelimbs 25% of the time for each right and left limbs, and both forelimbs together 50% of the time. There were no significant differences in the number of footfalls during the ladder task. Ground reaction force determination revealed that Fischer and Sprague-Dawley rats bore more weight on their hindlimbs compared to forelimbs during locomotion, Long-Evans and Lewis rats bore more weight on their forelimbs compared to their hindlimbs, while Wistar rats distributed weight evenly between forelimbs and hindlimbs during trotting. We conclude that morphologic, sensory and motor differences exist between the five strains of laboratory rats examined and several of these differences are most pronounced in the Fischer strain.
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