Tonic activity of the crossed olivocochlear bundle in guinea pigs with idiopathic losses in auditory sensitivity.
In animals with pre-existing N1 threshold losses of unknown etiology, transection of the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle resulted in a marked improvement in thresholds in the region of the loss but not at adjacent frequencies with normal thresholds or increased threshold sensitivities. There was also an increase in N1 amplitudes. These effects were not obtained if, prior to COCB transection, the COCB were continuously stimulated for 1 min in these animals, nor were they obtained with COCB transection in animals with normal N1 thresholds and amplitudes. In the animals with idiopathic N1 threshold losses, there appeared to be a linear relationship between the amount of threshold sensitivity recovered after COCB transection and the amount of loss existing initially. Parallels between these results and the recently-demonstrated protective COCB effects on temporary threshold shifts in auditory sensitivity are discussed.
Rajan
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Department of Physiology, University of Western Australia.
D000818:Animals; D003051:Cochlea / Q000503:physiopathology*; D003714:Denervation; D006168:Guinea Pigs; D034381:Hearing Loss / Q000503:physiopathology*; D006315:Hearing Loss, Functional / Q000503:physiopathology*; D009847:Olivary Nucleus / Q000503:physiopathology*; D012684:Sensory Thresholds