Neuroscience letters
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Neuroscience letters · Oct 2012
Facilitation and habituation of the startle reflex over the tonically active biceps brachii muscle contralateral to electrical stimuli.
The aim of the present investigation was to explore the impact of muscle contraction on startle reflex responses after electrical stimuli (single or trains of 3) and to study startle reflex habituation. The electromyogram was recorded over the tonically active biceps brachii muscle in 19 healthy subjects contralateral to electrical stimuli (9-12mA) that were delivered at 1.0 and 0.4Hz over the superficial radial nerve. The muscle contraction level was varied by loading weight on the subject's bent arm (0.0, 1.0 or 1.5kg). ⋯ Startle reflex amplitudes decreased significantly by the influence of preceding stimuli (p<0.05). This study provides evidence that the startle reflex can be significantly influenced by weight load, i.e. by volitional influences. Startle reflex investigation over a contracted limb muscle results in a high probability of startle release and thereby improved detection of SR habituation following preceding stimuli.
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Neuroscience letters · Oct 2012
Nerve injury induces the expression of syndecan-1 heparan sulfate proteoglycan in peripheral motor neurons.
Heparan sulfate proteoglycans play important roles in embryogenesis, including the development of the central nervous system. However, their function in nerve regeneration is not yet understood. We previously reported that nerve injury induces the expression of heparan sulfate glycosaminoglycans and syndecan-1, a heparan sulfate proteoglycan, in injured hypoglossal motor neurons. ⋯ However, sciatic nerve axotomy induced very little syndecan-1 expression in injured spinal motor neurons. These results suggest that syndecan-1 may have a crucial role in the survival of injured motor neurons and in nerve regeneration after injury. Our observations also reveal the diversity of peripheral motor neurons.