- This study describes the use of central and diffuse airway deposition patterns of isoproterenol and radiotracer aerosol alone, and in the presence of centrally deposited propranolol and radiotracer aerosol, to investigate the distribution of beta 2 adrenoreceptors in six asthmatic patients. The central deposition technique was only partially successful. No definite beta 2 receptor distribution pattern could be interpreted from the airway function responses. It was noted that 3-10 micrograms of isoproterenol in the airways was able to produce 50 percent of the maximum possible flow rate response. Centrally deposited propranolol was an effective antagonist of isoproterenol.