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Physiology of the Pain System
Published in Sahar Swidan, Matthew Bennett, Advanced Therapeutics in Pain Medicine, 2020
Nociceptive information enters Lissauer’s tract and then innervates the gray matter of the dorsal horn where primary afferents finally synapse in the dorsal horn of the spinal cord. In the dorsal horn of the spinal cord, neurotransmission occurs via two mechanisms. Glutamate released from the primary afferent and mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptor produces a robust but short-lasting depolarization of the second-order neuron.2 The second mechanism consists of peptides that produce a delayed and longer-lasting discharge as compared to the AMPA receptors. These peptidergic neurons contain peptide neurotransmitters such as CGRP, substance P, and growth factors such as brain-derived neurotropic factor. Peptides can enhance nociception, thus playing a role in central sensitization.2
Discussions (D)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
Heimer states that “Lissauer’s tract, which is a part of the propriospinal system, is sometimes referred to as the dorsolateral fasciculus, but it seems more appropriate to restrict the use of the term dorsolateral fasciculus to the collection of ascending sensory fibers in the dorsal part of the lateral funiculus.” (1983, p. 166)
The Somatosensory System
Published in Golara Honari, Rosa M. Andersen, Howard Maibach, Sensitive Skin Syndrome, 2017
As with the tactile system, pain, and thermal afferents, primary afferents synapse ipsilaterally and then the secondary afferents cross, but the crossings occur at different levels. Pain and temperature afferents enter the dorsal horn of the spinal cord and synapse within one or two segments, forming Lissauer’s tract as they do so. The dorsal horn is a radially laminar structure; the thin outermost layer is called the posterior marginalis layer, the second layer is the substantia gelatinosa, and the layer deeper to that is the nucleus proprius. The two types of pain fibers, C and A-δ, enter different layers of the dorsal horn. A-δ fibers enter the posterior marginalis and the nucleus proprius and synapse on a second set of neurons. These are the secondary afferents which will relay the signal to the thalamus. The secondary afferents from both layers cross to the opposite side of the spinal cord and ascend in the spinothalamic tract. The C fibers enter the substantia gelatinosa and synapse, but they do not synapse on secondary afferents. Instead, they synapse on interneurons—neurons which do not project out of the immediate area but relay the signal to the secondary afferents in either the posterior marginalis or the nucleus proprius. The spinothalamic tract ascends the entire length of the cord and the entire brainstem and, by the time that it reaches the midbrain, appears to be continuous with the medial lemniscus. These tracts enter the thalamus together.
Spinal cord involvement in Lewy body-related α-synucleinopathies
Published in The Journal of Spinal Cord Medicine, 2020
Raffaele Nardone, Yvonne Höller, Francesco Brigo, Viviana Versace, Luca Sebastianelli, Cristina Florea, Kerstin Schwenker, Stefan Golaszewski, Leopold Saltuari, Eugen Trinka
In a recent study, a prominent accumulation of α-synuclein pathology has been found in the sacral dorsal roots, Lissauer’s tract, and especially the lateral collateral region (LCR) in subjects with a primary diagnosis of PD and LBD. LCR is located lateral to the dorsal horn and is thought to be neurochemically distinct from other parts of the dorsal horn, which receives primary visceral sensory afferents from the bladder and distal colon via the pelvic nerve59 (Fig. 5).