METHODS FOR INTEGRATING FLUOROMETRY IN THE STUDY OF HEARING ORGAN STRUCTURE AND FUNCTION

The measurement of function in the intact organ of Corti has up to now been achieved by three methods: electrophysiology, mechanical measure ment and biochemical analysis. The two former methods have supplied in formation at the level of single identified cells. We have used a four th method, optical fluorimetry, to measure hair cell function at the c ellular level in the intact organ of Corti. Here we describe the metho ds involved in fluorescence labelling and video-enhanced microscopy in combination with electrophysiological recording of cochlear microphon ic (CM) and summating potentials (SP). The guinea pig temporal bone co ntaining an intact ear drum, ossicular chain and cochlea can be mainta ined in the isolated state by perfusion of the scala tympani with oxyg enated tissue culture medium. Substances added to the perfusate readil y diffuse through the basilar membrane into the organ of Corti. In thi s way cells in the organ can be stained by a number of fluorescent pro bes which label different structures and functions. Here we have used two dyes which label mitochondria and fluoresce with an intensity prop ortional to metabolic activity. By simultaneous measurement of CM and SP the functional state of the organ can be monitored.