The effect of minocycline on the masticatory movements following the inferior alveolar nerve transection in freely moving ratsReportar como inadecuado

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Molecular Pain

, 8:27

First Online: 20 April 2012Received: 17 January 2012Accepted: 20 April 2012


BackgroundTo determine the effects of inferior alveolar nerve transection IAN-X on masticatory movements in freely moving rats and to test if microglial cells in the trigeminal principal sensory nucleus prV or motor nucleus motV may be involved in modulation of mastication, the effects of microglial cell inhibitor minocycline MC on masticatory jaw movements, microglia Iba1 immunohistochemistry and the masticatory jaw movements and related masticatory muscle EMG activities were studied in IAN-X rats.

ResultsThe number of Iba1-immunoreactive IR cells both in prV and motV was significantly larger in IAN-X rats compared with sham rats on day 3 after IAN-X. The intraperitoneal i.p. administration of MC caused a significant reduction of the number of Iba1-IR cells both in prV and motV that was evident on day 14 after IAN-X. Furthermore, a significant reduction of the number of Iba1-IR cells could be observed in motV but not in prV after microinjection m.i. of MC into the motV of IAN-X rats. The rats also exhibited a significant decrease in the head-withdrawal threshold on the side ipsilateral to the IAN-X compared to the threshold before IAN-X and it lasted to day 14. In addition, IAN-X markedly affected the ability to rat to carry out mastication. The number of complete masticatory sequences was significantly decreased. Furthermore, the total masticatory sequence time and food preparatory PP period duration was significantly elongated in compared to sham rats. Although IAN-X significantly affected the total number of chewing cycles within the RC period of a masticatory sequence, it had no effect on the duration of the chewing cycles. On the other hand, systemic administration of MC both i.p. and m.i. in IAN-X rats significantly improved decreased head-withdrawal threshold and the impaired masticatory jaw movements.

ConclusionsThe present findings reveal that the strong modulation of masticatory jaw movements occurs following microglial cell activation after IAN-X, and the modulation recovers after inhibition of the microglial cell activation by MC, suggesting that microglial cell activation in the motV as well as in the prV has a pivotal role in modulating mastication following trigeminal nerve injury associated with orofacial neuropathic pain.

KeywordsMinocycline microglia trigeminal neuropathic pain trigeminal motor nucleus trigeminal principal sensory nucleus mastication modulation AbbreviationsIANinferior alveolar nerve

IAN-Xinferior alveolar nerve transection

prVtrigeminal principal sensory nucleus

motVtrigeminal motor nucleus

Vctrigeminal subnucleus caudalis



i.p.intraperitoneal injection


PBphosphate buffer

PBSphosphate-buffered saline


TGtrigeminal ganglion

PPpreparatory period

RCrhythmic-chewing period


CNScentral nervous system

CPGcentral pattern generator

Ververtical component of the jaw

Horhorizontal component of the jaw

Ant-postanterior-posterior component of the jaw

R-dig and L-digright and left digastric muscles

R-mass and L-massright and left masseter muscles

ANOVAanalysis of variance.

Electronic supplementary materialThe online version of this article doi:10.1186-1744-8069-8-27 contains supplementary material, which is available to authorized users.

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Autor: Rahman Md Mostafeezur - Hossain Md Zakir - Yoshiaki Yamada - Kensuke Yamamura - Koichi Iwata - Barry J Sessle - Junichi 


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