title: Development of a duration threshold for modulating evoked neuronal responses after nerve root compression injury.
abstract: Cervical nerve roots are susceptible to compression injuries of various durations. The duration of an  applied compression has been shown to contribute to both the onset of persistent pain and also the degree of spinal cellular and  molecular responses related to nociception. This study investigated the relationship between peripherally-evoked activity in  spinal cord neurons during a root compression and the resulting development of axonal damage. Electrically-evoked spikes were  measured in the spinal cord as a function of time during and after (post-compression) a 15 minute compression of the C7 nerve  root. Compression to the root significantly (p=0.035) reduced the number of spikes that were evoked over time relative to sham.  The critical time for compression to maximally reduce evoked spikes was 6.6±3.0 minutes. A second study measured the post-  compression evoked neuronal activity following compression applied for a shorter, sub-threshold time (three minutes). Ten  minutes after compression was removed, the discharge rate remained significantly (p=0.018) less than baseline by 58±25%  relative to sham after the 15 minute compression, but returned to within 3±33% of baseline after the three minute compression.  Axonal damage was evident in the nerve root at day seven after nerve root compression only after a 15 minute compression.  These studies demonstrate that even a transient mechanical insult to the nerve root is sufficient to induce sustained neuronal  dysfunction and axonal pathology associated with pain, and results provide support that such minor neural tissue traumas can  actually induce long-lasting functional deficits.
authors.affiliation: Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104-6321, USA.
authors.forename: Kristen J
authors.initials: KJ
authors.lastname: Nicholson
authors.forename: Julia C
authors.initials: JC
authors.lastname: Quindlen
authors.forename: Beth A
authors.initials: BA
authors.lastname: Winkelstein
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000473:pathology*; D002574:Cervical Vertebrae / Q000503:physiopathology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D023421:Models, Animal; D009474:Neurons / Q000502:physiology*; D011843:Radiculopathy / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors