A METHOD FOR STUDYING EXPECTORANT ACTION IN ANIMALS BY DIRECT MEASUREMENT OF THE OUTPUT OF RESPIRATORY TRACT FLUIDS

¹ From the Department of Pharmacology, Queen's University, Kingston, Canada

A method is described for measuring the output of respiratory tract fluid (R.T.F.) in animals with data on cats and rabbits. The animals are anaesthetized with ethyl carbamate, a side arm cannula inserted into the trachea, the inspired air warmed to body temperature and saturated with water vapour. The R.T.F. is allowed to drain into a measuring tube and the exposed parts are insulated to prevent condensation of water vapour.

Under these conditions, rabbits and cats yield about 2 ml of R.T.F. per kilo body weight per 24 hours. The R.T.F. consists of a yellowish, opaque fluid containing mucus, chlorides, calcium, sodium, potassium, iodine compounds, leucocytes and epithelial cells.

Decreasing the temperature and humidity of the inspired air decreased the output of R.T.F. Smaller adult animals produced relatively more R.T.F. than larger adult animals and the output was decreased in the winter months. Sex did not influence the results nor did the respiratory rate.

Ammonium chloride, ammonium carbonate, powdered ipecac, glycerol guaiacolate (Resyl) and pilocarpine increase the rate of output of R.T.F. Ammonium chloride did not have this effect if given by mouth to animals with the gastric nerves severed.

Stimulation of the vagus nerve increased the output of R.T.F. in both rabbits and cats.

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