02272nas a2200253   4500008004100000022001400041245009400055210006900149260001200218300001600230490000700246520153000253653002401783653002601807653001501833653000801848653002301856100002101879700001301900700001301913700002301926700002101949856004801970       2006                        eng d  a0897-715100aCorticospinal tract transection permanently abolishes H-reflex down-conditioning in rats.0 aCorticospinal tract transection permanently abolishes Hreflex do  c11/2006  a1705–17120 v233 aPrevious studies have shown that corticospinal tract (CST) transection, but not transection of other major spinal cord tracts, prevents down-conditioning of the H-reflex, the electrical analog of the spinal stretch reflex. This study set out to determine whether the loss of the capacity for H-reflex down-conditioning caused by CST transection is permanent. Female Sprague-Dawley rats received CST, lateral column (LC), or dorsal column ascending tract (DA) transection at T8-9; 9-10 months later, they were exposed to the H-reflex down-conditioning protocol for 50 days. In the LC and DA rats, H-reflex size fell to 60 (+/- 9 SEM)% and 60 (+/- 19)%, respectively, of its initial size. This down-conditioning was comparable to that of normal rats. In contrast, H-reflex size in the CST rats rose to 170 (+/- 42)% of its initial size. A similar rise does not occur in rats exposed to down-conditioning shortly after CST transection. These results indicate that CST transection permanently eliminates the capacity for H-reflex down-conditioning and has gradual long-term effects on sensorimotor cortex function. They imply that H-reflex down-conditioning can be a reliable measure of CST function for long-term studies of the effects of spinal cord injury and/or for evaluations of the efficacy of experimental therapeutic procedures, such as those intended to promote CST regeneration. The results also suggest that the role of sensorimotor cortex in down-conditioning extends beyond generation of the essential CST activity.10acorticospinal tract10aH-reflex conditioning10aplasticity10arat10aspinal cord injury1 aChen, Xiang Yang1 aChen, Yi1 aChen, Lu1 aTennissen, Ann, M.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1711591501877nas a2200253   4500008004100000022001400041245007900055210006900134260001200203300001400215490000800229520115300237653002201390653002401412653001901436653001301455653000801468653002301476100002101499700001301520700002101533700002101554856004801575       2002                        eng d  a0006-899300aCorticospinal tract transection reduces H-reflex circadian rhythm in rats.0 aCorticospinal tract transection reduces Hreflex circadian rhythm  c06/2002  a101–1080 v9423 aIn freely moving rats and monkeys, H-reflex amplitude displays a marked circadian variation without change in background motoneuron tone. In rats, the H-reflex is largest around noon and smallest around midnight. The present study evaluated in rats the effects on this rhythm of calibrated contusions of mid-thoracic spinal cord and mid-thoracic transection of specific spinal cord pathways. In 33 control rats, rhythm amplitude averaged 29.0(+/-2.6 S.E.)% of H-reflex amplitude. Contusion injuries at T8-9 that destroyed 53-88% of the white matter significantly reduced the rhythm to 18.9(+/-2.4)% of H-reflex amplitude. Transection of the ipsilateral lateral column, which contains the rubrospinal, vestibulospinal, and reticulospinal tracts, or bilateral transection of the dorsal column ascending tract did not affect rhythm amplitude or phase. In contrast, bilateral transection of the main corticospinal tract significantly reduced the rhythm to 14.7(+/-6.6)%. These results indicate that the H-reflex circadian rhythm depends in part on descending influence from the brain and that this influence is conveyed by the main corticospinal tract.10acircadian rhythms10acorticospinal tract10adiurnal rhythm10aH-Reflex10arat10aspinal cord injury1 aChen, Xiang Yang1 aChen, Lu1 aWolpaw, Jonathan1 aJakeman, Lyn, B.  uhttp://www.ncbi.nlm.nih.gov/pubmed/1203185802808nas a2200277   4500008004100000022001400041245011500055210006900170260001200239300001400251490000700265520196900272653002402241653001802265653003402283653001902317653000802336653002002344653002302364100002102387700002202408700001302430700001802443700002102461856004802482       2001                        eng d  a0897-715100aShort-Term and medium-term effects of spinal cord tract transections on soleus H-reflex in freely moving rats.0 aShortTerm and mediumterm effects of spinal cord tract transectio  c03/2001  a313–3270 v183 aSpinal cord function is normally influenced by descending activity from supraspinal structures. When injury removes or distorts this influence, function changes and spasticity and other disabling problems eventually appear. Understanding how descending activity affects spinal cord function could lead to new means for inducing, guiding, and assessing recovery after injury. In this study, we investigated the short-term and medium-term effects of spinal cord bilateral dorsal column (DC), unilateral (ipsilateral) lateral column (LC), bilateral dorsal column ascending tract (DA), or bilateral dorsal column corticospinal tract (CST) transection at vertebral level T8-T9 on the soleus H-reflex in freely moving rats. Data were collected continuously for 10-20 days before and for 20-155 days after bilateral DC (13 rats), DA (10 rats), CST (eight rats), or ipsilateral LC (seven rats) transection. Histological examination showed that transections were 98(+/- 3 SD)% complete for DC rats, 80(+/- 20)% complete for LC rats, 91(+/- 13 SD)% complete for DA rats, and 95(+/-13)% complete for CST rats. LC, CST, and DA transections produced an immediate (i.e., first-day) increase in H-reflex amplitude. LC transection also produced a small decrease in background activity in the first few posttransection days. Other than this small decrease, none of the transections produced evidence for the phenomenon of spinal shock. For all transections, all measures returned to or neared pretransection values within 2 weeks. DA and LC transections were associated with modest increase in H-reflex amplitude 1-3 months after transection. These medium-term effects must be taken into account when assessing transection effects on operant conditioning of the H-reflex. At the same time, the results are consistent with other evidence that, while H-reflex rate dependence and H-reflex operant conditioning are sensitive measures of spinal cord injury, the H-reflex itself is not.10acorticospinal tract10adorsal column10adorsal column ascending tract10alateral column10arat10asoleus activity10aspinal cord injury1 aChen, Xiang Yang1 aFeng-Chen, K., C.1 aChen, Lu1 aStark, D., M.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/11284551