The studies proposed in this grant seek to understand sensory nerve function in the mammalian cornea by relating the results obtained in experiments on the psychophysics, electrophysiology, and trophic aspects of the corneal innervation. Human studies of corneal sensation will use intensity matching of stimulus modality and cross adaptation to provide new information on the nature of corneal pain and receptor function in the human. Other work will examine the source of sensory changes associated with contact lens wear using the method of signal detection theory. Electrophysiological studies will use intracellular recording from trigeminal ganglion cells and intracellular tracers to correlate receptor physiology and anatomy. Experimentation on the receptor terminals has been made feasible by a method of producing oriented intraepithelial axons of long length. This work will investigate the precise relationship of the receptive field to the terminal and the electrogenic capabilities of the receptor membrane. Special staining techniques for use with transmission electron microscopy will determine the spatial order of substructures within the basal lamina and the effect of sensory denervation on this arrangement. Additional work will investigate the ability of the epithelium to make compensatory adjustments for the loss of sensory nerves using physiological and anatomical criteria. Various substances, including extracts of neural tissues, will be introduced into the deafferented cornea to determine if it is possible to mimic the trophic action of the sensory nerves. The effect of corneal wounds on the growth of nerve terminals will be investigated using neurohistological methods to determine the stimulus for growth.