Previous research indicates that melatonin has a major role in pain transmission and has an ultra-sensitizing effect.
Dr. Fang Huang and colleagues from Sun Yat-sen University in China for the first time located the distribution of melatonin receptor 1 in the caudal spinal trigeminal nucleus. Their results, published in the Neural Regeneration Research (Vol. 8, No. 32, 2013), showed that when melatonin receptor 1 expression in the caudal spinal nucleus is significantly reduced, melatonin's regulatory effect on pain is attenuated.
Further study is required to determine whether the decreased melatonin receptor 1 expression in the central caudal trigeminal spinal nucleus can attenuate the analgesic effect of the melatonin/melatonin receptor/nitric oxide pathway.