Fig. 3. Effects of transmitters on pre-oral ciliary beating. (A) Under control conditions, cilia beat at approximately 8-9 Hz and all three phases are evident. (B) Perfusions of 10^-6 mol l^-1 serotonin caused a threefold increase in ciliary beat frequency (CBF). Different phases are no longer evident in this recording (but see Fig. 5). (C) Perfusion of 10^-7 mol l^-1 dopamine slowed the ciliary beat frequency. All three phases of activity are apparent, but additional, irregular peaks (arrows) were also observed. (D) Perfusion of 10^-7 mol l^-1 Leu-enkephalin did not alter ciliary beat frequency but change the waveform of the beat cycle, with the normal three-phase form no longer evident. Scale bar, 150 ms.