[Study of neurological mechanism of lidocaine's suppression to tinnitus via microdialysis].
OBJECTIVE
To elucidate the neurological mechanism of lidocaine's suppression to tinnitus.


METHODS
Thirty-four Wistar rats weighing 300-350 grams were randomly divided into IC group (n = 17) and AC group (n = 17), according to microdialysis region. Each group was randomly subdivided into saline treatment group (n = 4), salicylate treatment group (n = 6), and salicylate + lidocaine treatment group (n = 7). Using in vivo microdialysis technique coupled with microbore HPLC-electrochemical detection, the present study first monitored the 5-HT release in IC and AC in salicylate-induced tinnitus animal models, and then, examined the effects of lidocaine on salicylate-induced 5-HT changes in IC and AC. The statistical analysis was performed using two-way ANOVA for repeated measures of raw data with time and treatment condition as main effects. Individual time-point values between no more than two groups were compared with the unpaired Student's t-test. The accepted level of significance was 0.05, two-tailed.


RESULTS
The 5-HT level increased to a maximum of 268% +/- 27% (mean +/- s) basal level in IC 2 h after salicylate application and of 277% +/- 24% basal level in AC around 3 h after application. And then, the 5-HT level gradually decreased to 157% +/- 16% of baseline in IC and 180% +/- 18% of baseline in AC by the end of the sixth hour. Saline did not alter the IC and AC dialysate 5-HT level in control rats. Two-way ANOVA with repeated measures indicated a significant effect of the condition factor [F (1, 8) = 413.949, P < 0.000001 in IC group; F(1,8) = 192.184, P < 0.000001 in AC group]. The increases of 5-HT levels in salicylate treatment groups were significantly reduced to 85% +/- 8% basal level in IC and 92% +/- 26% basal level in AC after local infusion of 1% lidocaine (P < 0.05). Compared with corresponding control value at that time (unpaired student t-test). Two-way ANOVA with repeated measures showed a significant difference between the salicylate group and salicylate + lidocaine group [P < 0.000001 with F(1, 11) = 329.267 for the condition factor in IC subgroup; P < 0.000001 with F(1, 11) = 133.844 for the condition factor in AC subgroup].


CONCLUSIONS
The suppression of lidocaine to tinnitus may be associated with the decrease of 5-HT level in IC and AC.
Liu
Jun-xiu
JX
Department of Otorhinolaryngology, Peking University Third Hospital, Beijing, 100083, China. liujunxiusanyuan@sina.com
Li
Xue-pei
XP
Dong
Yu
Y
Han
Hui-wan
HW
Liu
Guo-quan
GQ
D000818:Animals; D007031:Hypothalamus / Q000378:metabolism; D008012:Lidocaine / Q000494:pharmacology* / Q000627:therapeutic use; D017551:Microdialysis; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D020156:Salicylic Acid; D012701:Serotonin / Q000378:metabolism*; D013702:Temporal Lobe / Q000378:metabolism; D014012:Tinnitus / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism*
D012701:Serotonin; D008012:Lidocaine; D020156:Salicylic Acid