Recording of pulmonary afferent activities from receptors in the perfused lung preparation of bullfrog and effects of drugs on the afferent activities.

Afferent activities from receptors in the isolated lung of the bullfrog were recorded. Volley of afferent discharges synchronized with inflation of the lung and spontaneous discharges in the resting expiratory position were observed. When the solution of pH 9.5 was perfused in the pulmonary circulation, the rate of afferent discharges was slightly increased. When the pH was decreased to 5.5, the perfusion rate decreased and the rate of discharges was slightly increased initially, then markedly decreased. The amount of perfusion solution from the pulmonary vein per min and the firing frequency were almost restored to pretreatment level after the lung was perfused with normal Ringer's solution. When the temperature of the solution was from 20 degrees C to 10 degrees C, the rate of discharges was decreased. Epinephrine (1 x 10(-4) M) and 4-aminopyridine (1 x 10(-4) M and 1 x 10(-3) M) produced an increase in the rate of discharges in proportion to decrease in the perfusion rate. Histamine (1 x 10(-4) M) did not influence the firing frequency and the amount of perfusion solution from the vein per min. This method enables recording of the effect of drugs on the pulmonary afferent activities.