1
|
McIlwrath SL, Montera MA, Gott KM, Yang Y, Wilson CM, Selwyn R, Westlund KN. Manganese-enhanced MRI reveals changes within brain anxiety and aversion circuitry in rats with chronic neuropathic pain- and anxiety-like behaviors. Neuroimage 2020; 223:117343. [PMID: 32898676 PMCID: PMC8858643 DOI: 10.1016/j.neuroimage.2020.117343] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 08/11/2020] [Accepted: 08/31/2020] [Indexed: 01/31/2023] Open
Abstract
Chronic pain often predicts the onset of psychological distress. Symptoms including anxiety and depression after pain chronification reportedly are caused by brain remodeling/recruitment of the limbic and reward/aversion circuitries. Pain is the primary precipitating factor that has caused opioid overprescribing and continued overuse of opioids leading to the current opioid epidemic. Yet experimental pain therapies often fail in clinical trials. Better understanding of underlying pathologies contributing to pain chronification is needed to address these chronic pain related issues. In the present study, a chronic neuropathic pain model persisting 10 weeks was studied. The model develops both anxiety- and pain-related behavioral measures to mimic clinical pain. The manganese-enhanced magnetic resonance imaging (MEMRI) utilized improved MRI signal contrast in brain regions with higher neuronal activity in the rodent chronic constriction trigeminal nerve injury (CCI-ION) model. T1-weighted MEMRI signal intensity was increased compared to controls in supraspinal regions of the anxiety and aversion circuitry, including anterior cingulate gyrus (ACC), amygdala, habenula, caudate, ventrolateral and dorsomedial periaqueductal gray (PAG). Despite continuing mechanical hypersensitivity, MEMRI T1 signal intensity as the neuronal activity measure, was not significantly different in thalamus and decreased in somatosensory cortex (S1BF) of CCI-ION rats compared to naïve controls. This is consistent with decreased fMRI BOLD signal intensity in thalamus and cortex of patients with longstanding trigeminal neuropathic pain reportedly associated with gray matter volume decrease in these regions. Significant increase in MEMRI T2 signal intensity in thalamus of CCI-ION animals was indication of tissue water content, cell dysfunction and/or reactive astrogliosis. Decreased T2 signal intensity in S1BF cortex of rats with CCI-ION was similar to findings of reduced T2 signals in clinical patients with chronic orofacial pain indicating prolonged astrocyte activation. These findings support use of MEMRI and chronic rodent models for preclinical studies and therapeutic trials to reveal brain sites activated only after neuropathic pain has persisted in timeframes relevant to clinical pain and to observe treatment effects not possible in short-term models which do not have evidence of anxiety-like behaviors. Potential improvement is predicted in the success rate of preclinical drug trials in future studies with this model.
Collapse
Affiliation(s)
| | - Marena A Montera
- University of New Mexico Health Sciences Center, Albuquerque, NM USA
| | - Katherine M Gott
- University of New Mexico Health Sciences Center, Albuquerque, NM USA
| | - Yirong Yang
- University of New Mexico Health Sciences Center, Albuquerque, NM USA
| | - Colin M Wilson
- University of New Mexico Health Sciences Center, Albuquerque, NM USA
| | - Reed Selwyn
- University of New Mexico Health Sciences Center, Albuquerque, NM USA
| | - Karin N Westlund
- Research Services New Mexico VA HealthCare System Albuquerque NM 87108 USA; University of New Mexico Health Sciences Center, Albuquerque, NM USA
| |
Collapse
|
2
|
Kaushal R, Taylor BK, Jamal AB, Zhang L, Ma F, Donahue R, Westlund KN. GABA-A receptor activity in the noradrenergic locus coeruleus drives trigeminal neuropathic pain in the rat; contribution of NAα1 receptors in the medial prefrontal cortex. Neuroscience 2016; 334:148-159. [PMID: 27520081 DOI: 10.1016/j.neuroscience.2016.08.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 07/20/2016] [Accepted: 08/03/2016] [Indexed: 12/24/2022]
Abstract
Trigeminal neuropathic pain is described as constant excruciating facial pain. The study goal was to investigate the role of nucleus locus coeruleus (LC) in a model of chronic orofacial neuropathic pain (CCI-ION). The study examines LC's relationship to both the medullary dorsal horn receiving trigeminal nerve sensory innervation and the medial prefrontal cortex (mPFC). LC is a major source of CNS noradrenaline (NA) and a primary nucleus involved in pain modulation. Although descending inhibition of acute pain by LC is well established, contribution of the LC to facilitation of chronic neuropathic pain is also reported. In the present study, a rat orofacial pain model of trigeminal neuropathy was induced by chronic constrictive injury of the infraorbital nerve (CCI-ION). Orofacial neuropathic pain was indicated by development of whisker pad mechanical hypersensitivity. Hypersensitivity was alleviated by selective elimination of NA neurons, including LC (A6 cell group), with the neurotoxin anti-dopamine-β-hydroxylase saporin (anti-DβH-saporin) microinjected either intracerebroventricularly (i.c.v.) or into trigeminal spinal nucleus caudalis (spVc). The GABAA receptor antagonist, bicuculline, administered directly into LC (week 8) inhibited hypersensitivity. This indicates a valence shift in which increased GABAA signaling ongoing in LC after trigeminal nerve injury paradoxically produces excitatory facilitation of the chronic pain state. Microinjection of NAα1 receptor antagonist, benoxathian, into mPFC attenuated whisker pad hypersensitivity, while NAα2 receptor antagonist, idazoxan, was ineffective. Thus, GABAA-mediated activation of NA neurons during CCI-ION can facilitate hypersensitivity through NAα1 receptors in the mPFC. These data indicate LC is a chronic pain generator.
Collapse
Affiliation(s)
- R Kaushal
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - B K Taylor
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - A B Jamal
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - L Zhang
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - F Ma
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - R Donahue
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - K N Westlund
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States.
| |
Collapse
|