[Effects of respiratory drugs on the cough reflex]

In order to understand the relationship between the cough and respiratory centers in the brain stem, we investigated the effects of respiratory stimulants, pentylenetetrazol (PTZ) and nikethamide (NK), and a respiratory depressant, pentobarbital (PB)on the cough reflex. Coughs were induced in lightly anesthetized dogs by intraarterially into the vertebral artery. The rate (RR), amplitude (RA), and volume (RV) of the respiration and the number (NC) and amplitude (AC) of the cough reflex induced were used as indices. PTZ and NK, even at subthreshold doses for respiratory stimulation, enhanced the cough reflex (NC; not AC). On the other hand, PB at subthreshold doses for a respiratory depression decreased both NC and AC. The above findings suggest that respiratory stimulants generally enhance the cough reflex, and respiratory depressants reduce the cough reflex. Additionally, the thresholds for the cough responses to respiratory drugs are lower than those for the respiratory responses.