title: Cannabinoid CB1 Receptor Agonists Do Not Decrease, but may Increase Acoustic Trauma-Induced Tinnitus in Rats.
abstract: Tinnitus has been suggested to arise from neuronal hyperactivity in auditory areas of the brain, and anti-epileptic drugs are sometimes used to provide relief from tinnitus. Recently, the anti-epileptic properties of the cannabinoid drugs have gained increasing interest; however, the use of cannabinoids as a form of treatment for tinnitus is controversial. In this study, we tested whether a combination of delta-9-tetrahydrocannabinol (delta-9-THC) and cannabidiol (CBD), delivered in a 1:1 ratio, could affect tinnitus perception in a rat model of acoustic trauma-induced tinnitus. Following sham treatment or acoustic trauma, the animals were divided into the following groups: (1) sham (i.e., no acoustic trauma) with vehicle treatment; (2) sham with drug treatment (i.e., delta-9-THC + CBD); (3) acoustic trauma-exposed exhibiting tinnitus, with drug treatment; and (4) acoustic trauma-exposed exhibiting no tinnitus, with drug treatment. The animals received either the vehicle or the cannabinoid drugs every day, 30 min before the tinnitus behavioral testing. Acoustic trauma caused a significant increase in the auditory brainstem response (ABR) thresholds in the exposed animals, indicating hearing loss; however, there was a partial recovery over 6 months. Acoustic trauma did not always result in tinnitus; however, among those that did exhibit tinnitus, some of them had tinnitus at multiple frequencies while others had it only at a single frequency. The cannabinoids significantly increased the number of tinnitus animals in the exposed-tinnitus group, but not in the sham group. The results suggest that cannabinoids may promote the development of tinnitus, especially when there is pre-existing hearing damage.
authors: Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago , Dunedin , New Zealand ; Brain Health Research Centre, School of Medical Sciences, University of Otago , Dunedin , New Zealand.
authors: Yiwen
authors: Y
authors: Zheng
authors: Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago , Dunedin , New Zealand ; Brain Health Research Centre, School of Medical Sciences, University of Otago , Dunedin , New Zealand.
authors: Peter
authors: P
authors: Reid
authors: Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago , Dunedin , New Zealand ; Brain Health Research Centre, School of Medical Sciences, University of Otago , Dunedin , New Zealand.
authors: Paul F
authors: PF
authors: Smith
keywords: acoustic trauma; cannabidiol; cannabinoids; delta-9-tetrahydrocannabinol; rat; tinnitus