Astrocytes in the rostral ventromedial medulla contribute to the maintenance of oro‐facial hyperalgesia induced by late removal of dental occlusal interference

Background Astrocytes in the rostral ventromedial medulla (RVM) contribute to descending pain modulation, but their role in oro‐facial pain induced by persistent experimental dental occlusal interference (PEOI) or following EOI removal (REOI) is unknown. Objective To explore the involvement of RVM a...

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Published in:Journal of oral rehabilitation 2022-02, Vol.49 (2), p.207-218
Main Authors: Mo, Si‐Yi, Bai, Shan‐Shan, Xu, Xiao‐Xiang, Liu, Yun, Fu, Kai‐Yuan, Sessle, Barry J., Cao, Ye, Xie, Qiu‐Fei
Format: Article
Language:English
Subjects:
Animals
astrocyte
Astrocytes
carbenoxolone
dental occlusal interference
Glial fibrillary acidic protein
Hyperalgesia
Male
Medulla Oblongata
Microinjection
oro‐facial pain
pain modulation
Pain perception
Rats
Rats, Sprague-Dawley
rostral ventromedial medulla
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Summary:Background Astrocytes in the rostral ventromedial medulla (RVM) contribute to descending pain modulation, but their role in oro‐facial pain induced by persistent experimental dental occlusal interference (PEOI) or following EOI removal (REOI) is unknown. Objective To explore the involvement of RVM astrocytes in PEOI‐induced oro‐facial hyperalgesia or its maintenance following REOI. Methods Male rats were randomly assigned into five groups: sham‐EOI, postoperative day 6 and 14 of PEOI (PEOI 6 d and PEOI 14 d), postoperative day 6 following REOI on day 3 (REOI 3 d) and postoperative day 14 following REOI on day 8 (REOI 8 d). The nociceptive head withdrawal threshold (HWT) and activities of RVM ON‐ or OFF‐cells were recorded before and after intra‐RVM astrocyte gap junction blocker carbenoxolone (CBX) microinjection. RVM astrocytes were labelled immunohistochemically with glial fibrillary acidic protein (GFAP) and analysed semi‐quantitatively. Results Persistent experimental dental occlusal interference‐induced oro‐facial hyperalgesia, as reflected in decreased HWTs, was partially inhibited by REOI at day 3 but not at day 8 after EOI placement. Increased GFAP‐staining area occurred only in REOI 8 d group in which CBX could inhibit the maintained hyperalgesia; CBX was ineffective in inhibiting hyperalgesia in PEOI 14 d group. OFF‐cell activities showed no change, but the spontaneous activity and responses of ON‐cells were significantly enhanced that could be suppressed by CBX in REOI 8 d group. Conclusion Rostral ventromedial medulla astrocytes may not participate in PEOI‐induced oro‐facial hyperalgesia or hyperalgesia inhibition by early REOI but are involved in the maintenance of oro‐facial hyperalgesia by late REOI.
ISSN:0305-182X
1365-2842
DOI:10.1111/joor.13211