Although injury-induced afferent discharge declines significantly over time, experimental @entity9 persists unchanged for long periods. These observations suggest that processes that initiate experimental @entity9 may differ from those that maintain @entity158 . Here, the role of descending facilitation arising from developing plasticity in the rostral ventromedial medulla (RVM) in the initiation and maintenance of experimental @entity9 was explored. Tactile and thermal @entity56 were induced in @entity35 by spinal nerve ligation (SNL). RVM @entity3303 blocked SNL-induced @entity56 on post-SNL days 6-12 but not on post-SNL day 3. Lesion of RVM cells expressing mu-opioid receptors with @entity69236 did not prevent the onset of SNL-induced @entity56 , but these signs reversed to baseline levels beginning on post-SNL day 4. Similarly, lesions of the dorsolateral funiculus (DLF) did not prevent the onset of SNL-induced @entity56 , but these signs reversed to baseline levels beginning on post-SNL day 4. Lesions of the DLF also blocked the SNL-induced increase in spinal dynorphin content, which has been suggested to promote @entity9 . These data distinguish mechanisms that initiate the @entity1109 state as independent of descending supraspinal influences and additional mechanism(s) that require supraspinal facilitation to maintain @entity158 . In addition, the data indicate that these time-dependent descending influences can underlie some of the SNL-induced plasticity at the spinal level. Such time-dependent descending influences driving associated spinal changes, such as the upregulation of dynorphin, are key elements in the maintenance, but not initiation, of @entity1109 states.

Time-dependent descending facilitation from the rostral ventromedial medulla maintains, but does not initiate, XXXX .

@entity1109 :: ('MESH:D012678', 'Disease') :: ['neuropathic'] @entity69236 :: ('MESH:C431163', 'Chemical') :: ['dermorphin-saporin'] @entity3303 :: ('MESH:D008012', 'Chemical') :: ['lidocaine'] @entity56 :: ('MESH:D004342', 'Disease') :: ['hypersensitivity', 'tactile and thermal hypersensitivity'] @entity158 :: ('MESH:D010146', 'Disease') :: ['such pain'] @entity35 :: ('10116', 'Species') :: ['rats'] @entity9 :: ('MESH:D009437', 'Disease') :: ['neuropathic pain']
@entity9 :: (MESH:D009437,Disease) :: ['neuropathic pain']
