Neural Pathways Of Transmitting Signal Involved In Suppression Tinnitus From Yifeng Acupoint And Fengchi Acupoint To Inferior Colliculus

Tinnitus is an auditory phantom sensation of ringing in the ears that is experienced when no external sound is present, which can be divided into objective tinnitus with sound in vivo in patients and the subjective tinnitus without any sound source. Subjective tinnitus is more common, accounting for 90% of tinnitus patients in total. Subjective tinnitus arise because of the damage of the inner ear hair cells loud voice, noise exposure and application of drugs. The imbalance of excitement and inhibition inputs are transferred from the cochlea to auditory nucleus, and then the hyperactivity of neurons were induced in the acoustic nuclei, especially in IC. It has been discovered that the increase in firing rate of neurons in IC by reducing of GABA-release or down regulation of GABRA1 receptor induced tinnitus by animal models of tinnitus and patients with tinnitus. Clinical evidence shows that by microinjection of GABA receptor agonist into IC, we have made significant progress in the treatment of tinnitus patients. Therefore, the down function of GABAergic system in IC may be one of the main reason of tinnitus. According to available research data, tinnitus can be suppressed by acupuncture point electrical stimulation. The mechanism of this may be the more release of GABA in IC through the trigeminal nerve pathway to IC. But the detail of this pathway is still unclear.Acupoints stimulationin is a traditional Chinese treatment of tinnitus, which lasts a long history in China. Clinical experience shows that this method is very efficient, but the underlying mechanism is still unknown. Studies on meridians and acupoints show that the nervous system is one way of transferring acupuncture point signals. Whether Yifeng acupoint and Fengchi acupoint can active certain neural pathways, and transmit suppression signals to IC, is a question. According to previous studies of Shore and our lab, there may be two neural pathways from the acupoint stimulation site to IC. One is the acupuncture stimulation point→Sp5Ⅰ→IC, the other is the acupuncture stimulation point→Sp5Ⅰ→DNLL→IC pathway. Based on those, the following experiments were processed by using Fos immunohistochemistry and retrograde neural tracing technique in Saprague-Dawley rat. Those included three parts: First, by Yifeng acupoint and Fengchi acupoint stimulation active certain neurons in the central nervous system,marked by Fos protein.And then we observe if the positive Fos neurons were expressed in the auditory central nervous system. Second, by the injection of retrograde tracer FG into NLL and IC, observe the place of FG-labeled neurons. This provide us a morphological evidence.At last, we injecte FG to ECIC, the place which is closely related with tinnitus, stimulate the acupoint of Yifeng and observe the Fos and FG double-labeled neurons in NLL. This was an functional morphology evidence. The results of the experiment were as follows.1. Acupoint stimulationin of Yifeng and Fengchi can active neurons of Sp5, IC, NLL, CN and raphe nucleus in the central nervous system. The stimulation signal may have influence on the activition of neurons in the auditory central nervous system and raphe system. Acupoint stimulationin of Fengchi, we observed that the positive Fos neurons were located in the lateral parts of bilateral Sp5C. While acupoint stimulationin of Yifeng, the positive Fos neurons were located in the lateral and ventrolateral parts of contralateral Sp5Ⅰ. The afferent signals of the two acupionts in other places of Sp5 and IC, NLL, CN and raphe nucleus are almost the same. This maybe one of the interpretations that the acupiont of Fengchi and Yifeng are different.2. There exists direct projection from Sp5Ⅰto the NLL. FG-labeled neurons projecting to DNLL were located in theIand II layer of Sp5Ⅰ. FG-labeled neurons projecting to INLL were located in the third layer of the oral part of Sp5Ⅰ. These results show that signals from Sp5Ⅰto DNLL and INLL are different. In addition, we observed FG- labeled neurons in dorsal column nucleus. More neurons were also observed projecting from ECu to DNLL. These show us that NLL can receive deep and superficial sensation.3. There exists direct projection from Sp5Ⅰto IC. FG-labeled neurons projecting to IC were located in theIlayer of Sp5Ⅰ. There also exists direct projection from the dorsal column nucleus to IC. The Fos/FG double-labeled neurons were solely observed in DNLL after injecting FG into IC and stimulating Fengchi point. The result suggested that the sensory signal transmit from Fengchi point to IC can be relayed by DNLL.The results of the three parts show that the sensory signals of acupuncture Yifeng and Fengchi to IC is consistent with our previous hypothesis. One pathway is occupunture point→Sp5Ⅰ→IC, and the other is occupunture point→Sp5Ⅰ→DNLL→IC. It is shown below. The results of this study provid some basic information for further revealing of the neural mechanisms of suppression of tinnitus by acupoint stimulation.