ELECTROPHYSIOLOGY OF CILIARY BODY TRANSPORT PROCESSES

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Long-term objective of this proposal is the investigation of cellular mechanisms relating to the production of aqueous humor by the ciliary epithelium. Specific aims are the in vitro electrophysiologic study of transport processes on isolated preparations of the ciliary epithelium. These experiments will furnish information on normal physiological mechanisms and pharmacological-induced alterations involved in the active production of aqueous humor. Reduction of aqueous humor formation by medical therapy is a frequent treatment of the elevated intraocular pressure associated with glaucoma. Knowledge regarding cellular mechanisms responsible for aqueous humor production will provide insights into the normal rate of aqueous humor formation and possible pharmacologic mechanisms for the reduction in the rate of aqueous humor production. Isolated ciliary body preparations are mounted for measurement of transepithelial electrical parameters (potential difference, short-circuit current), net fluid transport, and unidirectional fluxes. These studies represent a consolidation of active transport and fluid flow in a tissue preparation maintaining the normal anatomic relationships between the double epithelial layers of the ciliary processes. Conventional micropipet impalement studies for measurement of membrane potential are performed in conjunction with the transepithelial measurements. These studies provide information on individual ciliary epithelial cells in relationship to ion movements and transport systems. In addition, intracellular iontophoretic injection of the fluorescent dye Lucifer Yellow is performed to study gap junctions which provide a pathway for intercellular communication (cell- cell coupling), thereby allowing cells to function as a syncytium. Electrophysiologic investigations are used to study the following classes of drugs: (i) halogenated anesthetic agents, (ii) adrenergic agonists and the interaction of neuropeptide Y with the adrenergic agonists, (iii) barbiturates, and (iv) sodium azide. These experiments will furnish information on mechanisms involved in the active production of aqueous humor and may result in new and unique antiglaucoma agents designed to inhibit the different sequential steps in aqueous humor production.