Novel trigeminal slice preparation method for studying mechanisms of nociception transmission

https://doi.org/10.1016/j.jneumeth.2017.05.019Get rights and content
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Highlights

  • A trigeminal slice including the subnucleus caudalis and root entry was prepared.

  • Optical fluorescence intensity measurement was used for calcium imaging.

  • Stimulation of the root entry evoked a fluorescence intensity in the Vc.

  • An intracellular calcium increase was mediated by glutamate receptor transmission.

  • This new method of slice preparation is a good model for trigeminal nociception.

Abstract

Background

The trigeminal subnucleus caudalis (Vc) plays a critical role in transmission and modulation of nociceptive afferent inputs, and exhibits a similar layer construction to the spinal dorsal horn. However, afferent inputs enter the brainstem and project to a separately located nucleus. It has previously been difficult to record responses of the Vc to afferent fiber activation in a brainstem slice preparation. The aim of the present study was to establish a novel brainstem slice preparation method to study trigeminal nociceptive transmission mechanisms.

New method

Thirty adult 6–7-week-old C57/BL6J male mice were included in the study. Obliquely sliced brainstem sections at a thickness of 600 μm, which included the Vc and the root entry zone to the brainstem, were prepared. The Vc response to electrical stimulation of afferent fibers was observed as a change in intracellular calcium concentration by fluorescence intensity response.

Results

Electrical stimulation of afferent inputs to the trigeminal nerve increased fluorescent intensity in the Vc, which was completely diminished by tetrodotoxin and significantly suppressed by the AMPA/kainate antagonist CNQX (paired t-test, P < 0.001), although the non-competitive NMDA antagonist (+)-MK801 maleate resulted in no changes. These results suggested a glutamate receptor-mediated response.

Comparison with existing methods/conclusion

This brainstem slice preparation will be useful for investigating nociceptive transmission mechanisms of the trigeminal nerve.

Keywords

Trigeminal spinal nucleus
Caudalis
Slice
Calcium imaging
Root entry

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