Naringenin (5,7,4’-trihydroxyflavanone) is a natural bioflavonoid with numerous documented bioactivities in the central nervous system. The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc; medullary dorsal horn) is recognized as a pivotal site for integration and modulation of orofacial nociceptive inputs. However, the potential effects of naringenin on orofacial pain responses and the contributions of GABAA receptor modulation have not yet been examined. In this study, whole-cell patch-clamp technique was applied to evaluate the effects of naringenin on the GABAA receptor responses on SG neurons in the Vc, and to assess potential sex-related differences. The GABAA receptor agonist muscimol was applied alone or with naringenin on SG neurons in the Vc that were patch-clamped with high chloride pipette solution to augment GABAA potentials. Naringenin increased both the amplitude and the area under the curve of muscimol-mediated responses in the majority (64.7%) of neurons tested (n = 17), and these effects differed by sex, suggesting that naringenin may modulate orofacial pain in a sex-dependent manner by enhancing GABAA potentials on SG neurons in the Vc. Naringenin may thus be a promising prototype compound for developing therapeutic agents against orofacial pain.

Introduction
Materials and Methods
    1. Experimental animals and preparation of brainstemslices
    2. Reagents
    3. Diphenyl-1-picrylhydrazyl scavenging activity assay
    4. Electrophysiological patch clamp recording
    5. Data analysis and statistics
Results
    1. Antioxidant activity of naringenin
    2. Effect of naringenin on the muscimol-inducedcurrents
    3. Effects of naringenin on the muscimol-inducedmembrane excitability on the SG neurons
Discussion
Funding
Conflicts of Interest
References

• Seon Ah Park(Department of Oral Physiology, Institute of Oral Bioscience, School of Dentistry, Jeonbuk National University, Jeonju 54907, Republic of Korea)
• Seon Hui Jang(Department of Oral Physiology, Institute of Oral Bioscience, School of Dentistry, Jeonbuk National University, Jeonju 54907, Republic of Korea)
• Soo Joung Park(Department of Oral Physiology, Institute of Oral Bioscience, School of Dentistry, Jeonbuk National University, Jeonju 54907, Republic of Korea)
• Seong Kyu Han(Department of Oral Physiology, Institute of Oral Bioscience, School of Dentistry, Jeonbuk National University, Jeonju 54907, Republic of Korea) Corresponding author
• Dong Hyu Cho(Department of Obstetrics and Gynecology, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonbuk National University Medical School, Jeonju 54907, Republic of Korea) Corresponding author