Browsing by Author "Muir, Gillian D"

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Course of motor recovery following ventrolateral spinal cord injury in the rat
    (Elsevier, 2004-11) Webb, Aubrey A; Muir, Gillian D
    The purpose of this study was to determine the importance of the pathways running in the ventrolateral spinal funiculus for overground locomotion in adult, freely behaving rats. Left-sided ventrolateral cervical spinal cord injury was performed in adult female Long–Evans rats. The behavioural abilities of these animals were analyzed at 2 days, and weekly for up to 5.5 weeks following spinal cord injury. Behavioural testing consisted of Von Frey filament testing, ladder walking, a paw usage task, and the assessment of ground reaction forces during unrestrained trotting. Animals with injury to the left ventrolateral cervical spinal cord did not develop enhanced sensitivity to pedal mechanical stimulation. At 2 days following injury, animals had impaired skilled locomotion as indicated by increased number of footslips during ladder walking. At 2 days, these animals also used both limbs together more often for support while rearing, while using the forelimb ipsilateral to the injury less than did uninjured animals. Ground reaction force determination revealed that animals tend to bear less weight on the forelimb and hindlimb ipsilateral to the spinal cord injury 2 days after injury. All animals recovered normal or near normal sensorimotor abilities although subtle asymmetries in ground reaction forces were detectable at 5.5 weeks following spinal cord injury. These results suggest that axons in the ventrolateral spinal funiculi contribute to limb movements during exploration and locomotion but their roles can be served by other pathways after ventrolateral spinal injury.
  • Thumbnail Image
    ItemOpen Access
    Dorsolateral cervical spinal injury differentially affects forelimb and hindlimb action in rats
    (Blackwell, 2007-03) Muir, Gillian D; Webb, Aubrey A; Kanagal, Srikanth; Taylor, Laura
    In experimental spinal injury studies, damage to the dorsal half of the spinal cord is common but the behavioural effects of damage to specific pathways in the dorsal cord have been less well investigated. We performed bilateral transection of the dorsolateral spinal funiculus (DLF) on 12 Long–Evans rats at the third cervical spinal segment. We quantified overground locomotion by measuring ground reaction forces, step timing and step distances as animals moved unrestrained. We also assessed skilled locomotion by measuring footslip errors made while the animals crossed horizontal ladders, and examined paw usage in a cylinder exploration task and during a skilled reaching task. Ground reaction forces revealed that rats with bilateral DLF lesions moved with a symmetrical gait, characterized mainly by altered forces exerted by the hindlimbs, delayed onset of hindlimb stance, and understepping of the hindlimbs relative to the forelimbs. These alterations in overground locomotion were subtle but were nevertheless consistent between animals and persisted throughout the 6-week recovery period. During ladder crossing, rats with DLF lesions made more footslip errors with the hindlimbs after surgery than before. Spontaneous forelimb usage during exploration was not affected by DLF axotomy but lesioned animals were less successful during skilled reaching. This is the first study which describes preferentially altered hindlimb use during overground locomotion after cervical DLF transections. We discuss these findings in relation to previous work and to the possible contributions of different ascending and descending pathways in the DLF to locomotion and skilled movements in rats.
  • Thumbnail Image
    ItemOpen Access
    Fischer (F-344) rates have different morphology, sensorimotor and locomotor abilities compared to Lewis, Long-Evans, Sprague-Dawley and Wistar rats
    (Elsevier, 2003-09) Webb, Aubrey A; Gowribai, Krishnamoorthy; Muir, Gillian D
    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.
  • Thumbnail Image
    ItemOpen Access
    Mini-Review: Assessment of behavioural recovery following spinal cord injury in rats
    (Blackwell, 2000-09) Muir, Gillian D; Webb, Aubrey A
    Behavioural recovery is one of the primary goals of therapeutic intervention in animal models of disease. It is necessary, therefore, to have the means with which to quantify pertinent behavioural changes in experimental animals. Nevertheless, the number and diversity of behavioural measures which have been used to assess recovery after experimental interventions often makes it difficult to compare results between studies. The present review attempts to integrate and categorize the wide variety of behavioural assessments used to measure recovery in spinal-injured rats. These categories include endpoint measures, kinematic measures, kinetic measurements, and electrophysiological measurements. Within this categorization, we discuss the advantages and disadvantages of each type of measurement. Finally, we make some recommendations regarding the principles for a comprehensive behavioural analysis after experimental spinal cord injury in rats.
  • Thumbnail Image
    ItemOpen Access
    Sensorimotor behaviour following incomplete cervical spinal cord injury in the rat
    (Elsevier, 2005-12) Webb, Aubrey A; Muir, Gillian D
    Rats are one of the most commonly used species for spinal cord injury research. Since the advent of the Basso, Beattie, Bresnahan (BBB) locomotor rating scale, the majority of spinal cord injury research relies upon evaluating locomotor behaviour in thoracic spinal cord injury rat models. Slightly more than 50% of all traumatic spinal cord injuries in humans, however, occur at the level of the cervical spinal cord. Further, therapies aimed at thoracic spinal cord injuries may not be directly transferable to cervical spinal cord injuries. This could be due to (1) differences in distance between the cell bodies of injured axons and the injury site and (2) because some behaviours (e.g. stepping movements) used to evaluate the therapeutic potential of a given treatment are governed primarily by intraspinal neuronal circuitry while other behaviours (e.g. skilled reaching) require more sophisticated conscious integration of the sensorimotor system. Consequently, there is a need to develop and use experimental cervical spinal cord injury models and understand the behavioural characteristics of such models. The present review highlights the sensorimotor abilities of cervical spinal cord-injured rats, including both forelimb, hind limb, and whole body behaviours. We also provide insight into the neuroanatomic substrates important for performing a given behaviour, information which may prove essential in the development of site-directed therapeutic strategies.
  • Thumbnail Image
    ItemOpen Access
    Unilateral dorsal solumn and rubrospinal tract injuries affect overground locomotion in the unrestrained rat
    (Blackwell, 2003-07) Webb, Aubrey A; Muir, Gillian D
    The purpose of this study was to determine the importance of the rubrospinal pathway and the ascending components of the dorsal column for overground locomotion in adult, unrestrained rats. The dorsal column (excluding the corticospinal tract), the rubrospinal tract or both were damaged unilaterally in rats at the level of the upper cervical spinal cord. Behavioural analysis consisted of skilled locomotion (an evaluation of footslips during ladder walking), a paw usage task and the assessment of ground reaction forces during unrestrained locomotion. All lesioned animals used the forepaw ipsilateral to the lesions less while rearing. Animals with dorsal column injuries used the forelimb contralateral to the spinal injury significantly more while rearing compared with uninjured animals. All lesioned animals produced more footfalls while crossing the ladder compared with uninjured animals. All injuries, regardless of the pathway affected, resulted in significant alterations in body weight support and reduced braking forces from the forelimb ipsilateral to the injury during overground locomotion. Animals typically bore less weight on the hindlimb ipsilateral to the lesion compared with the hindlimb contralateral to the spinal injury. Taken together with previously published work, our data indicate that the rubrospinal and dorsal column pathways are important for forelimb support while rearing and for skilled locomotion. Additionally, the ascending dorsal column pathways and the rubrospinal tract play a role during flat surface overground locomotion and combined damage to these pathways does not alter the acquired gait.