Performance of a repetitive task by aged rats leads to median neuropathy and spinal cord inflammation with associated sensorimotor declines.
Summary of "Performance of a repetitive task by aged rats leads to median neuropathy and spinal cord inflammation with associated sensorimotor declines."
Epidemiological studies have demonstrated a relationship between advancing age and susceptibility to risk factors for median neuropathies and musculoskeletal disorders. In this study, we determined if performance of a voluntary reaching task by aged rats induced sensorimotor declines, median nerve dysfunction and increased inflammatory cytokines in peripheral nerves, muscle and spinal cord neurons. Aged (14 mon) rats were trained for 15 min/day for 4 weeks to learn a high repetition, low force (HRLF) task (19 reaches/min; 15% maximum pulling force). Aged task rats performed the task for 2 h/day, 3 days/wk, for 12 weeks (until they were 18 mon of age). No behavioral changes were detected in normal controls (NC) or food-restricted controls (FR C) as they aged. However, grip strength declined in HRLF rats in weeks 6-12 (P<0.01 each) and 12-week trained-only rats (TR; P<0.05), compared to NC. Mechanical hypersensitivity was present in weeks 9 and 12 HRLF reach limb forepaws (P<0.01 and P<0.05, respectively), and 12-week HRLF support limb forepaws (P<0.01) and hindpaws (P=0.03), compared to NC. By week 12, median nerve conduction velocity declined 23%, bilaterally, in HRLF (P<0.001 each), and 13% in TR (P<0.05), compared to NC. Tumor necrosis factor alpha (TNFα) increased in 12-week HRLF muscle (P=0.005), median nerve (P<0.01), and neurons in superficial lamina of HRLF cervical spinal cords (P<0.01), compared to NC. interleukin 1 beta (IL1β) also increased in superficial lamina neurons (P<0.01). Loss of grip strength was correlated with median nerve conduction slowing (r=0.70) as well as increased nerve and muscle TNFα (r=-0.38 and r=-0.41, respectively); decrease in forepaw withdrawal thresholds was correlated with median nerve conduction slowing (r=0.81), increased nerve TNFα (r=-0.59), and increased TNFα and IL1β in neurons in spinal cord dorsal horns (r=-0.52 and r=-0.47, respectively). Thus, aged rats performing a repetitive task exhibited sensorimotor declines that were associated with decreased median nerve conduction, and increased pro-inflammatory cytokines in the median nerve and cervical spinal cord neurons.
Department of Neurological Surgery, Thomas Jefferson University, 909 Walnut Street, Philadelphia, PA 19107, USA.
This article was published in the following journal.
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20673790
- DOI: http://dx.doi.org/10.1016/j.neuroscience.2010.07.041
Medical and Biotech [MESH] Definitions
Performance of an act one or more times, with a view to its fixation or improvement; any performance of an act or behavior that leads to learning.
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The detailed examination of observable activity or behavior associated with the execution or completion of a required function or unit of work.
Disease involving the median nerve, from its origin at the BRACHIAL PLEXUS to its termination in the hand. Clinical features include weakness of wrist and finger flexion, forearm pronation, thenar abduction, and loss of sensation over the lateral palm, first three fingers, and radial half of the ring finger. Common sites of injury include the elbow, where the nerve passes through the two heads of the pronator teres muscle (pronator syndrome) and in the carpal tunnel (CARPAL TUNNEL SYNDROME).
Carpal Tunnel Syndrome
Entrapment of the MEDIAN NERVE in the carpal tunnel, which is formed by the flexor retinaculum and the CARPAL BONES. This syndrome may be associated with repetitive occupational trauma (CUMULATIVE TRAUMA DISORDERS); wrist injuries; AMYLOID NEUROPATHIES; rheumatoid arthritis (see ARTHRITIS, RHEUMATOID); ACROMEGALY; PREGNANCY; and other conditions. Symptoms include burning pain and paresthesias involving the ventral surface of the hand and fingers which may radiate proximally. Impairment of sensation in the distribution of the median nerve and thenar muscle atrophy may occur. (Joynt, Clinical Neurology, 1995, Ch51, p45)
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