The effect of minocycline on the masticatory movements following the inferior alveolar nerve transection in freely moving rats
Background: To 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...
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| Format: | Article |
| Language: | English |
| Published: |
2012
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| Online Access: | http://eprints.um.edu.my/8517/1/The_effect_of_minocycline_on_the_masticatory_movements_following_the_inferior_alveolar_nerve_transection_in_freely_moving_rats.pdf http://eprints.um.edu.my/8517/ |
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| Institution: | Universiti Malaya |
| Language: | English |
| Summary: | Background: To 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.
Results: The 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 headwithdrawal
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.
Conclusions: The 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.
Keywords: Minocycline, microglia, trigeminal neuropathic pain, trigeminal motor nucleus, trigeminal principal
sensory nucleus, mastication, modulation |
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