Two series of investigations will systematically explore what role(s), if any, melanin pigment may play in the structure and function of he mammalian inner ear. Melanocytes comprise one of at least three principal cell types in the stria vascularis of the cochlea and it is not known how these pigment cells interact with other strial components in the fluid and ion regulation of the endolymph. A broad goal of the proposed research is to better understand how the strial melanocytes function in the inner ear. The proposed studies would focus specifically on the melanocyte as a probe in normal and experimentally manipulated inner ears in both pigmented and albino animals. Albinos of a species have a normal distribution of melanocytes which completely lack melanin. Thus, they provide a means to study the stria vascularis containing non- relationship of inner ear pigmentation to peripheral auditory function. One series of studies will examine if the absence of melanin pigment is accompanied by other structural abnormalities in the albino inner ear. The aim of these studies is to determine which structures in the stria vascularis depend upon the presence of pigmented melanocytes for normal morphology. The nature of these pigment-dependent influences would be inferred through comparisons with striae from albino animals containing nonpigmented melanocytes. To date, there have been no systematic attempts to compare cochlear morphology between albino and pigmented animals quantitatively. A second group of experiments will study the influence of cochlear pigmentation on the response of the inner ear to acoustic over stimulation or aminoglycoside drug exposure. Both treatments are believed to influence the auditory system partially through their effect on cochlear pigmentation. The aim of these studies is to determine which structural components of the stria vascularis and inner ear depend upon the pigmented and albino guinea pigs following noise or aminoglycoside exposure. In addition to contributing to a better understanding of how pigmented cells may function in the inner ear, the proposed experiments will also address implications regarding the use of albinos as research models, particularly in studies of inner ear epithelia normally pigmented in most species including humans.