CHOLINERGIC AND ADRENERGIC-STIMULATION OF MUCOCILIARY TRANSPORT IN THE RAT TRACHEA

Mucociliary transport in the rat trachea was monitored through a surgical window for approximately one hour. Rates were grouped according to 5-min intervals which were examined with analyses of variance. Rates were consistent within each rat, although inter-animal variability was pronounced. Unstimulated transport involved minimal amounts of mucus and averaged 4.5 +/- 1.4 mm/min. Pilocarpine, presumably a secretagogue, caused a sustained (55 +/- 10 min) increase to 5.7 +/- 1.6 mm/min. Isoproterenol, presumably a cilioexcitatory agent, caused a brief (14 +/- 6 min) peak in transport at 6.4 +/- 2.1 mm/min. There were slow and fast animals which remained relatively slow or fast during and after treatment, indicating that each rat had an individual base-line determined by factors other than those susceptible to stimulation. Transport ceased almost at once throughout the airway, as mucus became scanty although ciliary activity was widespread. It was concluded that both types of response revealed different mechanisms for the physiological modulation of mucociliary transport.