ABSTRACT
Subjective tinnitus is a chronic neurological disorder in which phantom sounds are perceived. Drugs that increase GABAergic neurotransmission in the CNS are sometimes used as a treatment. One such drug is the GABA(B) receptor agonist L-baclofen. The aim of this study was to investigate the effects of L-baclofen on the psychophysical attributes of tinnitus in rats.The effects of 1, 3 or 5 mg/kg L-baclofen (s.c.) on the psychophysical attributes of tinnitus were investigated using a conditioned lick suppression model, following acoustic trauma (a 16 kHz, 110 dB pure tone presented unilaterally for 1 h) in rats. In pre-drug testing, acoustic trauma resulted in a significant increase in the auditory brainstem-evoked response (ABR) threshold in the affected ear (P < 0.008) and a significant decrease in the suppression ratio (SR) compared to sham controls in response to the 20 kHz tones, but not the broadband noise or the 10 kHz tones (P < 0.002). The 3 and 5 mg/kg doses of L-baclofen significantly reversed the frequency-specific decrease in the SR in the acoustic trauma group, indicating that the drug reduced tinnitus. Following washout from the 3 mg/kg dose, but not the 5 mg/kg dose, the significant decrease in the SR for the acoustic trauma group returned, suggesting a return of the tinnitus. These results suggest that L-baclofen should be reconsidered as a drug treatment for tinnitus. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.
Subject(s)
Baclofen/therapeutic use , Evoked Potentials, Auditory, Brain Stem/drug effects , GABA-B Receptor Agonists/therapeutic use , Hearing Loss, Noise-Induced/complications , Tinnitus/drug therapy , Animals , Baclofen/administration & dosage , Behavior, Animal/drug effects , Dose-Response Relationship, Drug , GABA-B Receptor Agonists/administration & dosage , Male , Rats , Rats, Wistar , Tinnitus/etiologyABSTRACT
AIM OF THE STUDY: Traditional Chinese medicine (TCM) has been reported to successfully alleviate tinnitus, although well-controlled studies have not been conducted. In this study, we attempted to test a TCM, Er Ming Fang (EMF01) containing Rehmannia glutinosa, Cornus officinalis, Salvia mittiorrhiza, Pueraria, Schisandra chinensis, Poria cocos and Platycodon grandiflorum, on salicylate-induced tinnitus in rats, using a conditioned lick suppression paradigm. MATERIALS AND METHODS: A pilot study examined the effect of 8.75 g/kg and 17.5 g/kg EMF01 (delivered by oral gavage for 20 days) and showed a slight decrease in the suppression ratio (SR) in the 8.75 g/kg group. In order to confirm the possible effect of EMF01 on tinnitus at 8.75 g/kg, a further study was carried out with a larger sample size. RESULTS: While there were statistically significant differences between the treatment groups, post hoc tests revealed that EMF01 did not have any significant effect on salicylate-induced tinnitus. CONCLUSIONS: While this study does not support the efficacy of EMF01 in the treatment of salicylate-induced tinnitus, further studies should be conducted to determine if it alleviates tinnitus associated with acoustic trauma.