Progress in brain research
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Most human spinal cord injuries involve contusions of the spinal cord. Many investigators have long used weight-drop contusion animal models to study the pathophysiology and genetic responses of spinal cord injury. ⋯ The MASCIS Impactor is a well-standardized rat spinal cord contusion model that produces very consistent graded spinal cord damage that linearly predicts 24-h lesion volumes, 6-week white matter sparing, and locomotor recovery in rats. All aspects of the model, including anesthesia for male and female rats, age rather than body weight criteria, and arterial blood gases were empirically selected to enhance the consistency of injury.
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Historical Article
Central control of information transmission through the intraspinal arborizations of sensory fibers examined 100 years after Ramón y Cajal.
About 100 years ago, Santiago Ramón y Cajal reported that sensory fibers entering the spinal cord have ascending and descending branches, and that each of them sends collaterals to the gray matter where they have profuse ramifications. To him this was a fundamental discovery and proposed that the intraspinal branches of the sensory fibers were "centripetal conductors by which sensory excitation is propagated to the various neurons in the gray matter". In addition, he assumed that "conduction of excitation within the intraspinal arborizations of the afferent fibers would be proportional to the diameters of the conductors", and that excitation would preferentially flow through the coarsest branches. ⋯ The PAD produced by single, or by small groups of GABAergic interneurons in group I muscle afferents, can remain confined to some sets of intraspinal arborizations of the afferent fibers and not spread to nearby collaterals. In muscle spindle afferents this local character of PAD allows cutaneous and descending inputs to differentially inhibit the PAD in segmental and ascending collaterals of individual fibers, which may be an effective way to decouple the information flow arising from common sensory inputs. This feature appears to play an important role in the selection of information flow in muscle spindles that occurs at the onset of voluntary contractions in humans.