The hair cell of the inner ear transduces mechanical stimuli into electrical signals that post-synaptically convey auditory and vestibular information to the central nervous system of the organism. This research will use the inner ear from the anuran species, Rana pipiens, for comparative cellular studies of vestibular and auditory hair cells. Intrinsic membrane properties of hair cells will be examined with electrophysiological and anatomical techniques. Experimental procedures used in this research will include (1) intracellular recording with current- and voltage-clamp techniques using patch electrodes, (2) bath application of pharmacological compounds, and (3) thin sectioning. The experiments will characterize the nature and extent of diversity in hair cell membrane properties and will examine the relationship between hair cell function (electrophysiology) and structure (morphology). Experiments will be conducted on hair cells from a vestibular organ, the sacculus, and from an auditory organ, the basilar papilla. Electrophysiological studies of dissociated hair cells will focus on pharmacological separation of ionic currents under voltage clamp, and measurement of cell resonance under current clamp. Anatomical studies will bc conducted on dissociated hair cells and on hair cells in thin sections. The microscope will be used to examine morphological properties such as hair cell bundle shape and cell body dimensions. A comparative analysis of electrophysiological and anatomical data will permit (1) assessment of diversity in hair cell properties within each organ (2) assessment of diversity in hair cell properties between organs. The data also will bc used to test the hypothesis that a correlation exists between hair cell morphology and hair cell electrical properties. Understanding of normal vestibulo-auditory function as well as dysfunction will require extensive knowledge of mechanisms underlying signal transduction by hair cells. This research is intended to advance that understanding by providing insight into differences between auditory and vestibular hair cells related to their specialized function in sensing stimulus modalities of different origin and frequency. The broad objective of the research proposed here is to increase understanding of the cellular mechanisms underlying stimulus reception and information processing in the internal ear. This small grant project is intended to lay the foundation for long-term studies of hair cell development and differentiation.
