Cocaine is a major drug of abuse. Its primary mechanism of action is to block amine neurotransmitter uptake by neurons in the central nervous system. However, cocaine also has significant peripheral actions. The tissues which are exposed to the highest concentration of cocaine are those lining the respiratory tract. After inhalation of cocaine powder, reaches high concentrations on the nasal/airway, mucosa and remains there for extended periods of time (hours). Therefore, cocaine will have both acute and chronic actions on this tissue. The overall goal of this study is to understand the acute effects of cocaine on the respiratory mucosa and how chronic application alters the properties of the tissue. Cocaine has effects on the function of the mucosa, both basal and stimulated. At low concentrations cocaine increased the basal short circuit current developed by the tissue and released mucus. Higher concentrations (less than 1mM) inhibited both these processes. Neurotransmitter evoked responses were also inhibited. However, the cell types affected (e.g., mucus gland cells, ciliated epithelial cells) in the mucosa and the exact mechanisms (i.e., local anesthesia, receptor agonist, receptor antagonist, uptake blocker, et.c.) for these changes are not known. Therefore, we propose to study in detail the acute effects of cocaine on swine tracheal airway epithelial tissue and the acute and chronic effects on isolated identified surface epithelial and mucus gland cells. Short-circuit current will be measured in isolated tissue using the Ussing chamber technique. Mucus release from isolated gland cells will be measured with the cells mounted in a superfusion apparatus and quantitated using an enzyme-linked lectin assay (ELLA) very similar to the ELISA procedure. The chronic effects of cocaine will be examined on isolated homogeneous populations of surface epithelial and mucus gland cells. The cells will be grown in tissue culture inserts, under serum free conditions. The effects of chronic cocaine on the cultured cells will be determined by measuring actions on cell proliferation, neurotransmitter receptor properties, short circuit current and mucus release. The results from the proposed research will provide an understanding of which cell types are being affected after exposure to cocaine, the mechanisms by which cocaine is acting, and how cells are changed by chronic exposure to cocaine.
