Ascending and Descending Pathways in the Spinal Cord

doi:10.1016/B978-0-12-374245-2.00008-5

The Rat Nervous System (Fourth Edition)

2015, Pages 115-130

https://doi.org/10.1016/B978-0-12-374245-2.00008-5 Get rights and content

Abstract

The white matter of the spinal cord is made up of the long ascending and descending spinal pathways to and from the brain and the spinal cord, and the spinal propriospinal pathways. Ascending pathways in the dorsal funiculus are the gracile and cuneate fasciculi, and the postsynaptic dorsal column pathway. The ventrolateral funiculus of the spinal cord contains the spinothalamic, spinocervico-thalamic, spinoreticular, spinomesencephalic (including spinotectal), spino-olivary, spinoparabrachial, spinohypothalamic, and spinocerebellar pathways. Nudo and Masterton identified 27 brain centers that give rise to descending tracts which reach the spinal cord. They showed that the largest tracts arose from the cerebral cortex (corticospinal), red nucleus (rubrospinal), vestibulospinal, and the hindbrain reticular formation. Smaller descending tracts arise from the hypothalamus (paraventricular nucleus), prethalamus (zona incerta), pretectum (nucleus of Darkschewitsch), midbrain (superior colliculus, periaqueductal gray, supraoculomotor nucleus, interstitial nucleus of Cajal, cuneiform nucleus), and hindbrain (parabigeminal nucleus, medial cerebellar nucleus, locus coeruleus, subcoeruleus nuclei, nucleus gigantocellularis, raphe nuclei, and the nucleus of the solitary tract).

References (0)

Cited by (15)

Adaptation of tape removal test for measurement of sensitivity in perineal area of rat
2020, Experimental Neurology
Citation Excerpt :
A standard experimental model of spinal cord injury in rodents is the dorsal column lesion. This lesion disrupts ascending sensory fibres from the dorsal root ganglia carrying tactile information, discriminatory touch, vibration and proprioception (Sengul and Watson, 2015). There are several behavioural tests for assessment of sensation in the limbs but none as yet for the perineal area.
Regeneration after spinal cord injury is a goal of many studies. Although the most obvious target is to recover motor function, restoration of sensation can also improve the quality of life after spinal cord injury. For many patients, recovery of sensation in the perineal and genital area is a high priority. Currently there is no experimental test in rodents for measuring changes in sensation in the perineal and genital area after spinal cord injury. The aim of our study was to develop a behavioural test for measuring the sensitivity of the perineal and genital area in rats. We have modified the tape removal test used routinely to test sensorimotor deficits after stroke and spinal cord injury to test the perineal area with several variations. A small piece of tape (approximately 1 cm²) was attached to the perineal area. Time to first contact and to the removal of the tape was measured. Each rat was trained for 5 consecutive days and then tested weekly. We compared different rat strains (Wistar, Sprague-Dawley, Long-Evans and Lewis), both genders, shaving and non-shaving and different types of tape. We found that the test was suitable for all tested strains, however, Lewis rats achieved the lowest contact times, but this difference was significant only for the first few days of learning the task. There were no significant differences between gender and different types of tape or shaving. After training the animals underwent dorsal column lesion at T10 and were tested at day 3, 8, 14 and 21. The test detected a sensory deficit, the average time across all animals to sense the stimulus increased from 1′32 up to 3′20. There was a strong relationship between lesion size and tape detection time, and only lesions that extended laterally to the dorsal root entry zone produced significant sensory deficits. Other standard behavioural tests (BBB, von Frey, ladder and Plantar test) were performed in the same animals. There was a correlation between lesion size and deficit for the ladder and BBB tests, but not for the von Frey and Plantar tests. We conclude that the tape removal test is suitable for testing perineal sensation in rats, can be used in different strains and is appropriate for monitoring changes in sensation after spinal cord injury.
Supraspinal respiratory plasticity following acute cervical spinal cord injury
2017, Experimental Neurology
Citation Excerpt :
The loss of ascending (spinobulbar) projections to the brainstem following C2Hx has not been well characterized. C2Hx will compromise afferent feedback from sensory receptors and spino-reticular pathways which modulate brainstem activity (Sengul and Watson, 2015; Watson et al., 2009). Overall, little is known about how these ascending pathways impact the activity of the respiratory neurons in the medulla in the uninjured spinal cord, let alone following injury.
Impaired breathing is a devastating result of high cervical spinal cord injuries (SCI) due to partial or full denervation of phrenic motoneurons, which innervate the diaphragm – a primary muscle of respiration. Consequently, people with cervical level injuries often become dependent on assisted ventilation and are susceptible to secondary complications. However, there is mounting evidence for limited spontaneous recovery of respiratory function following injury, demonstrating the neuroplastic potential of respiratory networks. Although many studies have shown such plasticity at the level of the spinal cord, much less is known about the changes occurring at supraspinal levels post-SCI. The goal of this study was to determine functional reorganization of respiratory neurons in the medulla acutely (> 4 h) following high cervical SCI. Experiments were conducted in decerebrate, unanesthetized, vagus intact and artificially ventilated rats. In this preparation, spontaneous recovery of ipsilateral phrenic nerve activity was observed within 4 to 6 h following an incomplete, C2 hemisection (C2Hx). Electrophysiological mapping of the ventrolateral medulla showed a reorganization of inspiratory and expiratory sites ipsilateral to injury. These changes included i) decreased respiratory activity within the caudal ventral respiratory group (cVRG; location of bulbospinal expiratory neurons); ii) increased proportion of expiratory phase activity within the rostral ventral respiratory group (rVRG; location of inspiratory bulbo-spinal neurons); iii) increased respiratory activity within ventral reticular nuclei, including lateral reticular (LRN) and paragigantocellular (LPGi) nuclei. We conclude that disruption of descending and ascending connections between the medulla and spinal cord leads to immediate functional reorganization within the supraspinal respiratory network, including neurons within the ventral respiratory column and adjacent reticular nuclei.
Functional Anatomy of the Spinal Tracts Based on Evolutionary Perspectives
2023, Korean Journal of Neurotrauma
The tracts, cytoarchitecture, and neurochemistry of the spinal cord
2023, Anatomical Record
Selection of preferred thermal environment and cold-avoidance responses in rats rely on signals transduced by the dorsal portion of the lateral funiculus of the spinal cord
2023, Temperature
The brain-body disconnect: A somatic sensory basis for trauma-related disorders
2022, Frontiers in Neuroscience

View all citing articles on Scopus

View full text

Chapter 8 - Ascending and Descending Pathways in the Spinal Cord

Abstract