Aim: Observe the effects of er-long-zuo-ci-wan (EIZCW, a compound of Chinese Traditional Medicine) on the spontaneous discharge of external cortex of inferior colliculus (ICx) and secondary auditory cortex (AII) of chronic tinnitus model rats induced by salicylate acid, to explore the neural mechanisms underlying ELZCW preventing tinnitus.
Methods: 30 adult SD rats were involved and divided into three groups, normal control group, chronic tinnitus model group and ELZCW prevention group. Extracellular recording techniques and stereotaxic method were used. The spontaneous spikes were recorded and analyzed from ICx and all in different group rats. The average rate of spontaneous discharge and the interspike interval histogram of spontaneous activities were used as indexes.
Results: (1) Compared with normal control group, the average rate of spontaneous discharge recorded from the ICx in the chronic tinnitus model group increased significantly (4.57 +/- 0.54 Hz vs. 3.14 +/- 0.40 Hz, P < 0.05). Furthermore analysis showed that the discharge rate of short spike interval from the ICx in the chronic tinnitus model group increased than that of the normal group (0-40 ms: 58% vs. 40%; 0-4 ms: 9% vs. 5%). And there was an increasing tendency of the average rate of spontaneous discharge recorded from the AII in the chronic tinnitus model group compared with that in the normal group. (2) Compared with the chronic tinnitus model group, the average rate of spontaneous discharge recorded from the ICx and AII in the ELZCW prevention group significantly decreased than that in the chronic tinnitus model group (ICx: 2.41 +/- 0.21 Hz vs. 4.57 +/- 0.54 Hz, P < 0.01. AII: 2.24 +/- 0.24 Hz vs. 4.57 +/- 0.54 Hz , P < 0.01). And the discharge rate of short spike interval from the ICx and AII in the chronic tinnitus model group decreased than that in the normal control group (ICx: 0-40 ms 50% vs. 58%, 0-4 ms 4% vs. 9%. All: 0-22 ms: 24% vs. 31%, 0-8 ms 19% vs. 16%).
Conclusion: If the increasing of the spontaneous activities of ICx and AII in chronic tinnitus rats means tinnitus, the use of ELZCW could decrease this kind of changes.