EFFECTS OF INTRANASAL CHALLENGE WITH HISTAMINE, BRADYKININ AND PROSTAGLANDIN ON MIDDLE-EAR PRESSURE AND BLOOD-FLOW IN CYNOMOLGUS MONKEYS

Previous studies documented a significant increase in middle ear press ure following intranasal challenges with ascaris antigen or histamine in sensitized cynomolgus monkeys. To confirm that effects and investig ate the mechanism, 4 monkeys were intranasally challenged at separate sessions with histamine (10 mg), bradykinin (1, 10 mg) and prostagland in D2 (PgD2, 0.5, 1.0 mg) and followed for 90 min. Before and after ch allenge, middle ear pressure, mucosal blood flow, heart rate, blood pr essure, body temperature and the partial pressures of O-2 and CO2 in t he venous blood were measured. The results showed that while bradykini n challenge had no effect on these measures, PgD2 provoked increased m iddle ear pressure, and histamine resulted in a biphasic pattern of in creasing pressures followed by decreasing pressures. The pattern of ch ange in middle ear pressure after histamine challenge was explicable b y a mechanism involving transmucosal gas exchange, while that for PgD2 was related to increased mucosal inflammation. These results document the development of positive middle ear pressures during provoked nasa l inflammation and may have relevance to similar observations in the c linical setting.