EFFECTS OF DOPAMINE, DOBUTAMINE AND PHENTOLAMINE ON MIDDLE-EAR PRESSURE AND BLOOD-FLOW IN CYNOMOLGUS MONKEYS

To test the hypothesis that changes in mucosal perfusion could influen ce gas exchange and thus, middle ear pressure, the effects of systemic ally administered drugs showing alpha adrenergic effects on mucosal pe rfusion and middle ear pressure were evaluated in 4 cynomolgus monkeys . Two drugs with well characterized sympathomimetic effects, dopamine and dobutamine, were studied, and dopamine was combined with an antago nist, phentolamine. For each experiment, the monkeys were anesthetized with pentobarbital and followed for a 90 min baseline period. Then, t he drug was administered for 60 min with follow-up extending through t hat period and for an additional 60 min. Data consisted of repeated me asurements of rectal temperature, heart rate, blood pressure, left mid dle ear pressure and right mucosal blood velocity, volume and flow. Th e results documented an increase in middle ear pressure after intraven ous infusion of either dopamine or dobutamine and an attenuation of th e response by concurrent administration of phentolamine. Laser Doppler measurements documented a variable, non-directional change in blood v olume, velocity and flow. The changes in the middle ear pressure obser ved following systemic administration of autonomic drugs are consisten t with the rapid establishment of a transmucosal pressure gradient sec ondary to changes in the supply and/or metabolism of gases.