Action of Citral on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Juvenile Mice

Thao Thi Phuong Nguyen ； Seon Hui Jang ； Soo Joung Park ； Dong Hyu Cho ； Seong Kyu Han

《The Chinese Journal of Physiology》 62卷5期 (2019/10) Pp. 175-181

https://doi.org/10.4103/CJP.CJP_32_19

摘要

The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) is admitted as a pivotal site of integrating and regulating orofacial nociceptive inputs. Although citral (3,7-dimethyl-2,6-octadienal) is involved in antinociception, the action mechanism of citral on the SG neurons of the Vc has not been fully clarified yet. In this study, we examined the direct membrane effects of citral and how citral mediates responses on the SG neurons of the Vc in juvenile mice using a whole-cell patch-clamp technique. Under high chloride pipette solution, citral showed repeatable inward currents that persisted in the presence of tetrodotoxin, a voltage-gated Na^+ channel blocker, and 6-cyano-7-nitro-quinoxaline-2,3-dione, a non-N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, D-2-amino-5-phosphonopentanoic acid, an NMDA receptor antagonist. However, the citral-induced inward currents were partially blocked by picrotoxin, a gamma-aminobutyric acid (GABA_A)-receptor antagonist, or by strychnine, a glycine receptor antagonist. Further, the citral-induced responses were almost blocked by picrotoxin with strychnine. We also found that citral exhibited additive effect with GABA-induced inward currents and glycine-induced inward currents were potentiated by citral. In addition, citral suppressed the firing activities by positive current injection on the SG neurons of the Vc. Taken together, these results demonstrate that citral has glycine- and/ or GABA-mimetic actions and suggest that citral might be a potential target for orofacial pain modulation by the activation of inhibitory neurotransmission in the SG area of the Vc.

關鍵字

Citral ； gamma-aminobutyric acid_A receptor ； glycine receptor ； patch clamp ； substantia gelatinosa neuron

參考文獻

Light AR, Perl ER. Spinal termination of functionally identified primary afferent neurons with slowly conducting myelinated fibers. J Comp Neurol 1979;186:133-50.

Cervero F. The substantia gelatinosa of the spinal cord. Pain 1982;12:185-6.

Bereiter DA, Hirata H, Hu JW. Trigeminal subnucleus caudalis: Beyond homologies with the spinal dorsal horn. Pain 2000;88:221-4.

Ren K, Dubner R. The role of trigeminal interpolaris-caudalis transition zone in persistent orofacial pain. Int Rev Neurobiol 2011;97:207-25.

Sessle BJ. Acute and chronic craniofacial pain: Brainstem mechanisms of nociceptive transmission and neuroplasticity, and their clinical correlates. Crit Rev Oral Biol Med 2000;11:57-91.