Respiratory tract ciliated cells, obtained from the rabbit trachea and maintained In culture, were sensitive to mechanical stimulation. The mechanical deformation of the cell surface In· duced a rapid, but transient, Increase in ciliary beat frequency. In addition, the beat frequency of these ciliated ceUs was also Increased in 8 dose-. dependent manner by the~ adrenerglcdrug Isoproterenol (10-1 to 10-0 M) and by the calcium lonophore A23187 (10-6 and 10-5 M). To determine If drug and mechanosensltlve activation of ciliary beat frequency arise from a common or different cellular mechanism. we Investigated the effect of mechanical stimulation on beat frequency In the presence of Isoproterenol or A231B7. In Isoproterenol (10-8 to 10-0 M), none of the parameters used to describe the ciliary beat frequency response to mechanical stimulation was altered. In A23187 (10-8 M or above), the magnitUde of the beat frequency response was significantly reduced or almost abol·