Cells of origin, course, and termination patterns of the ventral, uncrossed component of the mature rat corticospinal tract

Brösamle, Christian; Schwab, Martin E.

doi:10.1002/(sici)1096-9861(19970922)386:2<293::aid-cne9>3.0.co;2-x

Cited by 175 publications

(123 citation statements)

References 37 publications

(53 reference statements)

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“…Approximately 5% of the corticospinal tract descends ipsilaterally in rats (Brosamle and Schwab, 1997) and it is possible that this pathway contributes to the maladaptive effects of training the intact forelimb in this present study. The ipsilateral corticospinal tract has not been found to be a significant contributor to skilled forelimb function in rats (Whishaw and Metz, 2002), but this does not rule out a potential role in the exaggeration of forelimb impairments seen after training the intact forelimb.…”

Section: Discussionmentioning

confidence: 72%

Maladaptive effects of learning with the less-affected forelimb after focal cortical infarcts in rats

Allred

Jones

2008

Experimental Neurology

109

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It is common following stroke to focus early rehabilitation efforts on developing compensatory use of the less-affected body side. Here we used a rat model of focal cortical infarct to examine how motor skill acquisition with the less-affected ("intact") forelimb influences sensorimotor function of the infarct-impaired forelimb and neural activity in peri-infarct cortex. Rats proficient in skilled reaching with one forelimb were given focal ischemic lesions in the contralateral sensorimotor cortex (SMC). Recovery in this forelimb was tested following a period of reach training focused on the intact forelimb or control procedures. Quantitative measures of the cumulatively expressed transcription factor, FosB/ΔFosB, were used to assay intact forelimb training effects on neuronal activity in remaining SMC of the infarcted hemisphere. Intact forelimb training worsened behavioral recovery in the impaired forelimb following unilateral focal ischemia. Furthermore, it decreased neuronal FosB/ΔFosB expression in layer II/III of peri-infarct SMC. These effects were not found in sham-operated rats trained sequentially with both forelimbs or in animals receiving bilateral forelimb training after unilateral infarcts. Thus, focused use of the intact forelimb has detrimental effects on recovery of impaired forelimb function following a focal ischemic injury and this is linked to reduced neuronal activation in remaining cortex. These results suggest that peri-infarct cortex becomes vulnerable to early post-stroke experience with the less-affected forelimb and that this experience may drive neural plasticity here in a direction that is maladaptive for functional outcome.

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Section: Discussionmentioning

confidence: 72%

Maladaptive effects of learning with the less-affected forelimb after focal cortical infarcts in rats

Allred

Jones

2008

Experimental Neurology

109

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“…WT and mutant mice were injected with various tracers at different postnatal ages (P0 -P45). DiI (Molecular Probes) and BDA (Molecular Probes) anterograde tracing was performed as described previously (31,32). Mice were injected blindly before determining genotype.…”

Section: Methodsmentioning

confidence: 99%

Plexin signaling selectively regulates the stereotyped pruning of corticospinal axons from visual cortex

Low

Liu

Faulkner

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Neurons in the developing CNS tend to send out long axon collaterals to multiple target areas. For these neurons to attain specific connections, some of their axon collaterals are subsequently pruned-a process called stereotyped axon pruning. One of the most striking examples of stereotyped pruning in the CNS is the pruning of corticospinal tract (CST) axons. The long CST collaterals from layer V neurons of the visual and motor cortices are differentially pruned during development. Here we demonstrate that select plexins and neuropilins, which serve as coreceptors for semaphorins, are expressed in visual cortical neurons at the time when CST axon collaterals are stereotypically pruned. By analyzing mutant mice, we find that the pruning of visual, but not motor, CST axon collaterals depends on plexin-A3, plexin-A4, and neuropilin-2. Expression pattern study suggests that Sema3F is a candidate local cue for the pruning of visual CST axons. Using electron microscopic analysis, we also show that visual CST axon collaterals form synaptic contacts in the spinal cord before pruning and that the unpruned collaterals in adult mutant mice are unmyelinated and maintain their synaptic contacts. Our results indicate that the stereotyped pruning of the visual and motor CST axon collaterals is differentially regulated and that this specificity arises from the differential expression of plexin receptors in the cortex.axon pruning ͉ corticospinal tract ͉ plexin A functional nervous system depends on the precise wiring of neuronal connections with appropriate targets. During early development, neurons tend to send out axons with excessive branches to multiple target areas. When the neuronal targets become mature, the unnecessary branches are specifically pruned. Stereotyped axon pruning, or pruning of long axon collaterals in a predictable manner, is a major phenomenon in the developing CNS. This type of pruning has been observed in species ranging from Drosophila to mouse and is thought to be essential for the normal development of the CNS (1-5).One classic example of stereotyped pruning in higher vertebrates is in the developing corticospinal tract (CST) (6-10). In developing rodents, CST axons originate from layer V cortical pyramidal neurons in all regions of the neocortex (9, 11). These axons are guided through the internal capsule, cerebral peduncle, and pyramidal tract and then turn dorsally to cross the midline at the pyramidal decussation before they reach the contralateral spinal cord (Fig. 1A). The targeting of primary CST axons to the spinal cord is followed by axon collateral branching to targets in the brainstem and spinal cord (Fig. 1B). This initial projection pattern of CST axons is later modified via stereotyped axon pruning as regions of the neocortex become specialized, and the rostral-caudal location of parent cells within the neocortex determines which axon collaterals are pruned (Fig. 1C). Thus, motor neurons in rostral cortex prune their axons from the superior and inferior colliculi, whereas visual neuron...

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“…Increased fiber density extends into the caudal spinal cord for at least 4 -8 mm. Because the efficiency of BDA labeling in the CST is ϳ1-2% (Brosamle and Schwab, 1997), the observation of 30 BDA-labeled CST fibers is likely to represent a total of 2000 CSTs innervating the caudal spinal cord under the influence of NgR(310)ecto-Fc. From ultrastructural studies, a value of 2000 lumbar CST fibers would comprise ϳ5% of the normal innervation density (Leenen et al, 1985).…”

Section: Ngr(310)ecto-stimulated Growth In Multiple Pathwaysmentioning

confidence: 99%

Blockade of Nogo-66, Myelin-Associated Glycoprotein, and Oligodendrocyte Myelin Glycoprotein by Soluble Nogo-66 Receptor Promotes Axonal Sprouting and Recovery after Spinal Injury

Li¹,

Liu²,

Budel³

et al. 2004

J. Neurosci.

285

242

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Cells of origin, course, and termination patterns of the ventral, uncrossed component of the mature rat corticospinal tract

Cited by 175 publications

References 37 publications

Maladaptive effects of learning with the less-affected forelimb after focal cortical infarcts in rats

Maladaptive effects of learning with the less-affected forelimb after focal cortical infarcts in rats

Plexin signaling selectively regulates the stereotyped pruning of corticospinal axons from visual cortex

Blockade of Nogo-66, Myelin-Associated Glycoprotein, and Oligodendrocyte Myelin Glycoprotein by Soluble Nogo-66 Receptor Promotes Axonal Sprouting and Recovery after Spinal Injury

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