Changes in phrenic, hypoglossal and recurrent laryngeal nerve activities after intravenous infusions of aminophylline in cats.

Aminophylline is known to have respiratory stimulant properties, and it has been suggested that it may also be effective in sleep apnoea. However, its role in this disorder remains uncertain. Theoretically, increasing upper airway motoneural activity in order to maintain airway patency might alleviate obstructive sleep apnoea. On the other hand, increasing the respiratory drive may also prove beneficial in treating central sleep apnoea. In these studies, we attempted to determine the effect of aminophylline on neural activities of the upper airway and diaphragm. We administered intravenously either a low dose (4 mg.kg-1) or a high dose (16 mg.kg-1) of aminophylline to decerebrated, vagotomized and paralysed cats, and continuously recorded the phrenic hypoglossal and recurrent laryngeal nerve activities for 3 h. Results showed that a high dose of aminophylline induced a marked increase in phrenic nerve activity, but not hypoglossal or recurrent laryngeal nerve activity. In a group treated with a low dosage of aminophylline, a significant increase of activity was found in all three nerves. Furthermore, phrenic nerve activity increased more with a high dose than with a low dose. We confirmed that aminophylline has dose-dependent and selective effects on respiratory neural activity. A low dose acts on the upper airway and diaphragm, but a high dose induces a marked increase in central respiratory drive. According to our results, low dose aminophylline might be beneficial in obstructive sleep apnoea, whereas, a high or low dose might improve some cases of central sleep apnoea.