Assessment of functional recovery after spinal cord injury in rats by reticulospinal-mediated motor evoked responses.
Auditory startle reflexes (ASR) and cortico-myoelectric evoked potentials (CMyEP) were investigated as possible tests of descending motor function in a rat spinal cord injury model. ASR, which consist of stereotyped myoelectric responses recorded in limb and axial muscles to brief loud tones, were found to provide a simple, objective, and reliable measure of motor recovery after spinal cord injury (SCI). While ASR are easily recorded in awake rats, they are blocked by anesthetics, and thus cannot be recorded during the acute injury period. ASR were compared with CMyEP, which can be recorded while the animal is anesthetized. CMyEP were found to produce large myoelectric responses in the vastus lateralis and tibialis anterior hindlimb muscles of the rat similar to ASR except that latencies were approximately 3 msec earlier. Both ASR and CMyEP tended to be bilaterally symmetric regardless of the stimulus configuration, and threshold for responses were the same for both muscles in both hindlimbs. The results suggest that CMyEP may be related to ASR and thus mediated partly by reticulospinal pathways. Evidence supporting this hypothesis is reviewed.
Gruner
J A
JA
Dept. of Neurosurgery, New York University Medical Center, NY 10016.
Kersun
J M
JM
D000818:Animals; D001306:Auditory Pathways / Q000503:physiopathology; D002540:Cerebral Cortex / Q000503:physiopathology; D005073:Evoked Potentials, Somatosensory; D005260:Female; D009044:Motor Cortex / Q000503:physiopathology; D016065:Myoelectric Complex, Migrating; D009434:Neural Pathways / Q000503:physiopathology*; D011712:Pyramidal Tracts / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D013216:Reflex, Startle; D013119:Spinal Cord Injuries / Q000503:physiopathology*