A [14C]iodoantipyrine study of inter-regional correlations of neural substrates following central post-stroke pain in rats.

Hsiang-Chin Lu,Bai Chuang Shyu,Wei-Jen Chang,Yung-Hui Kuan,Andrew Chih-Wei Huang

doi:10.1186/s12990-015-0006-5

Hsiang-Chin Lu, Bai Chuang Shyu + Show 3 more

Open Access

https://doi.org/10.1186/s12990-015-0006-5

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Abstract

BackgroundCentral pain syndrome is characterized by a combination of abnormal pain sensations, and pain medications often provide little or no relief. Accumulating animal and clinical studies have shown that impairments of the spinothalamic tract (STT) and thalamocingulate pathway causes somatosensory dysfunction in central post-stroke pain (CPSP), but the involvement of other neuronal circuitries in CPSP has not yet been systematically examined. The aim of the present study was to evaluate changes in brain activity and neuronal circuitry using [14C]iodoantipyrine (IAP) in an animal model of CPSP.ResultsRats were subjected to lateral thalamic hemorrhage to investigate the characteristics of CPSP. Thermal and mechanical hyperalgesia developed in rats that were subjected to thalamic hemorrhagic lesion. The medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), striatum, thalamus, hypothalamus, and amygdala were more active in the CPSP group compared with rats that were not subjected to lateral thalamic hemorrhage. The inter-regional correlation analysis showed that regional cerebral blood flow in the mPFC was highly correlated with the amygdala in the right brain, and the right brain showed complex connections among subregions of the ACC. Rats with CPSP exhibited strong activation of the thalamocingulate and mPFC-amygdala pathways.ConclusionsThese results corroborate previous findings that the STT and thalamocingulate pathway are involved in the pathophysiological mechanisms of CPSP symptoms. The mPFC, amygdala, and periaqueductal gray emerged as having important correlations in pain processing in CPSP. The present data provide a basis for a neural correlation hypothesis of CPSP, with implications for CPSP treatment.

Highlights

Central pain syndrome is characterized by a combination of abnormal pain sensations, and pain medications often provide little or no relief
The ROI analysis indicated that the infralimbic cortex (IL), Cingulate cortex area 1 (Cg1), Secondary motor cortex (M2), Agranular insular dorsal cortex (AID), Agranular insular ventral cortex (AIV), Hippo-3, and periaqueductal gray (PAG) of the left hemisphere and IL, prelimbic cortex (PrL), Cg11, M2, and amygdala of the right hemisphere were activated
The comparison of the left and right hemispheres in the central post-stroke pain (CPSP) and sham groups showed that the neural subregions of the medial prefrontal cortex (mPFC)-amygdala pathway, spinothalamic tract (STT), and medial thalamus (MT)-anterior cingulate cortex (ACC) pathway were significantly correlated in the right hemisphere compared with the left hemisphere in the CPSP group (p < 0.05)

Summary

Introduction

Central pain syndrome is characterized by a combination of abnormal pain sensations, and pain medications often provide little or no relief. Accumulating animal and clinical studies have shown that impairments of the spinothalamic tract (STT) and thalamocingulate pathway causes somatosensory dysfunction in central post-stroke pain (CPSP), but the involvement of other neuronal circuitries in CPSP has not yet been systematically examined. The aim of the present study was to evaluate changes in brain activity and neuronal circuitry using [14C]iodoantipyrine (IAP) in an animal model of CPSP. Many clinical symptoms are manifested after stroke, including motor deficits, cognitive dysfunction, language problems, emotional disturbances, social maladjustment, somatosensory dysfunction, and central pain [1,2]. A recent study showed that the expression of interleukin-1β in the hippocampus, prefrontal cortex, and brainstem may be correlated with chronic neuropathic painlike behavior [9]. A review article reported that the descending pain modulation system, including the dorsolateral prefrontal cortex, rostral anterior cingulate cortex (ACC), amygdala, hippocampus, periaqueductal gray (PAG), and

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