Temperature effects on the auditory system: An amphibian case history

Abstract

The inner ear of anurans is unique in that it contains three organs specialized for sound reception. The amphibian papilla (AP), the basilar papilla (BP), and the saccule (S) are anatomically distinct, spatially separate organs each with its own complement of sensory hair cells and overlying tectorial structure. The BP and portions of the AP respond exclusively to airborne sounds, whereas other portions of the AP and the S exhibit sensitivity both to airborne sounds and to substrate-borne vibrations. Measurements from the auditory periphery of Rana pipiens pipiens suggest that in contrast to BP fibers, AP fiber tuning is highly temperature-dependent. Moreover, hair cells from the rostral AP and S exhibit a clear temperature dependence in their intracellular current step response, unlike caudally located AP and BP cells. Finally, spontaneous otoacoustic emissions, which presumably reflect hair cell motility, are highly temperature-dependent despite the fact that the upper portion of the emission frequency range (600–1600 Hz) corresponds to the domain of the BP. A model is presented that attempts to reconcile these disparate results. [Work supported by NIDCD Grant No. DC-00222.]