OBJECTIVETo investigate the plasticity and the role of plasticity in the auditory cortex of rats which experienced tinnitus by screening the plasticity markers immediately early gene c-fos and the NMDA receptor's subtype NR2A.

METHODSThirty white Wistar rats were randomly distributed into 3 groups: sodium salicylate group (n = 12), physiological saline group (n = 12) and normal control group (n = 6). Tinnitus were induced by salicylate administration and tested by behavioral conditioning studies, and then immunohistochemical staining was used to observe the expression of c-fos and NR2A in the auditory cortex of each group.

RESULTSBehavioral evidence indicated that all of the twelve rats in the sodium salicylate group perceived tinnitus. Fos-positive neurons were observed in all rats, while they appeared as typical dark dots, corresponding to a labeling restricted to their nucleus. NR2A protein was mainly expressed in the cytoplast and membrane of the cortical pyramidal cells. The expression of c-fos and NR2A immunoreactive neurons in auditory cortexes of the sodium salicylate group was significantly higher than that of other two control groups.

CONCLUSIONSThe higher expression of c-fos and NR2A indicate that the neurotransmitters and receptors should be involved in the tinnitus, as well as suggest that neuronal plasticity occurs in the auditory cortex of rats experienced tinnitus, which may be played an important role in the mechanism of tinnitus.