Analysis of Electrophysiological Change in the Rat LC Nucleus after Salicylic Acid Treatment

Kim, Sang Chul; Kim, Seung Beom; Park, See Young; Jun, Byung Hoon

Abstract

BACKGROUND AND OBJECTIVES: The precise mechanism of salicylic acid induced tinnitus has not been clearly identified as yet in spite of wide range of studies undertaken. We looked for the electrophysiologic evidence that salicylic acid has effect on the Locus Coeruleus (LC) neurons in vitro. MATERIALS AND METHOD: In LC, we measured the neuronal firing rate and cell membrane property according to the concentration of salicylic acid with extracellular single unit recording and whole cell current clamp recording.
RESULTS
The basal firing activity was increased in 15 of the 20 LC nuclei, which were treated with 0.3 mM salicylic acid. Both 1mM and 2 mM salicylic acid increased the basal firing rate of all except for one LC neuron (n=20). These neurons also showed recovery after washing. However, 5 mM salicylic acid induced cell death after the bursting response in all of the LC neurons (n=10)(Fig. 2). There were no specific changes in the whole cell current-clamp recording of the LC neurons during the period of drug treatment (Fig. 3).
CONCLUSION
The dose dependent response pattern observed in the extracellular single unit recording and the fact that there were no specific changes in the whole-cell current-clamp recording following the salicylic acid treatment suggest that the salicylic acid induced intracellular change in the LC neuron is caused not by the direct ligand-receptor reaction but by the indirect 2nd messenger system.