Primary Afferent Projections to the Spinal Cord

Şengül, Gülgün

doi:10.1016/b978-0-12-374245-2.00005-x

Cited by 2 publications

(2 citation statements)

References 94 publications

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“…The SDH receives glutamatergic inputs from C fibers and Aδ fibers of the dorsal root ganglia, spinal cord glutamatergic interneurons [43], and brain stem reticular formation [30], and a D2R agonist inhibits these inputs [30,44]. Similar to these studies, we observed that D2R agonists significantly inhibited the sEPSC frequency in the SDH neurons, and the effect was much stronger in the 6-OHDA-lesioned mice than in the saline control mice.…”

Section: Discussionsupporting

confidence: 85%

D2 receptor activation relieves pain hypersensitivity by inhibiting superficial dorsal horn neurons in parkinsonian mice

et al. 2020

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Chronic pain is a common and undertreated nonmotor symptom in Parkinson's disease (PD). Although chronic pain is improved by L-dopa in some PD patients, the underlying mechanisms remain unclear. In this study, we established PD mice by unilateral microinjection of 6-OHDA in the medial forebrain bundle to investigate the contribution of spinal cord dopamine receptors to parkinsonian pain hypersensitivity. The von Frey filament tests and thermal pain tests revealed that these PD mice displayed decreased nociceptive thresholds in both hindpaws; intrathecal injection of L-dopa or apomorphine significantly increased the mechanical and thermal nociceptive thresholds, and the analgesic effect was mimicked by ropinirole (a D2 receptor agonist), but not SKF38393 (a D1/D5 receptor agonist), and blocked by sulpiride (a D2 receptor antagonist), but not SKF83566 (a D1/D5 receptor antagonist). Whole-cell recordings in lumber spinal cord slices showed that superficial dorsal horn (SDH) neurons in PD mice exhibited hyperexcitability, including more depolarized resting membrane potentials and more action potentials evoked by depolarizing current steps, which were mitigated by ropinirole. Furthermore, ropinirole inhibited the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) in SDH neurons more strongly in PD mice than in control mice. However, sulpiride caused less disinhibition of sEPSCs in PD mice than in control mice. Taken together, our data reveal that pain hypersensitivity in PD mice is associated with hyperexcitability of SDH neurons, and both events are reversed by activation of spinal D2 receptors. Therefore, spinal D2 receptors can be promising therapeutic targets for the treatment of PD pain.

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Section: Discussionsupporting

confidence: 85%

D2 receptor activation relieves pain hypersensitivity by inhibiting superficial dorsal horn neurons in parkinsonian mice

et al. 2020

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“…Large diameter, Type I or Type II afferents could also have been excited. 29 Considering that muscle contractions were completely abolished after administration of pancuronium, it is quite unlikely that direct depolarization of the muscle fibers contributed in any significant degree to contractions induced by electrical stimuli used in the present study. Blocking the contraction, in the presence of electrical stimulation, significantly reduced the neuronal response to electrical stimulation, suggesting that direct stimulation of primary afferents was not the major contributor to the increased DHN response during contractions.…”

Section: Dhn Responses To Muscle Contractionmentioning

confidence: 68%

Deep Tissue Incision Enhances Spinal Dorsal Horn Neuron Activity During Static Isometric Muscle Contraction in Rats

He¹,

Sugiyama²,

Kang³

et al. 2019

The Journal of Pain

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Translational correlates to pain with activities after deep tissue injury have not been studied to a great extent. We hypothesized that deep tissue incision causes greater activation of nociceptiontransmitting neurons evoked by muscle contraction. In vivo neuronal activity was recorded in 203 dorsal horn neurons (DHNs) from 97 rats after sham, skin-only, or skin + deep muscle incision. We evaluated DHN responses to static, isometric muscle contractions induced by direct electrical stimulation of the muscle. The effect of pancuronium on DHN response to contractions was also examined. Approximately 50% of DHNs with receptive fields in the hindpaw was excited during muscle contraction. One-second, 0.5-and 1.0-gram muscle contractions produced greater DHN activity after skin + deep muscle incision [median (interquartile range): 32 (5-39); p = 0.021 and 36 (26-46) impulses; p = 0.006, respectively] than after sham [6 (0-21) and 15 (8-32) impulses, respectively]. Neuromuscular blockade with pancuronium inhibited the muscle contractions and DHN activation during electrical stimulation, demonstrating contraction-induced activation. The greater response of spinal DHNs to static muscle contraction after skin + deep muscle incision may model and inform mechanisms of dynamic pain after surgery. Perspective: Completing various activities are important milestones for recovery and hospital discharge after surgery. Skin + deep muscle incision caused greater activation of nociceptiontransmitting dorsal horn neurons evoked by muscle contraction compared to skin-only incision. This result suggests an important contribution of deep muscle injury to activity-evoked hyperalgesia after surgery.

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Primary Afferent Projections to the Spinal Cord

Cited by 2 publications

References 94 publications

D2 receptor activation relieves pain hypersensitivity by inhibiting superficial dorsal horn neurons in parkinsonian mice

D2 receptor activation relieves pain hypersensitivity by inhibiting superficial dorsal horn neurons in parkinsonian mice

Deep Tissue Incision Enhances Spinal Dorsal Horn Neuron Activity During Static Isometric Muscle Contraction in Rats

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