Nasal air puff stimulations and laryngeal, thoracic and abdominal muscle activities

In cats, we studied the activity of laryngeal, thoracic and abdominal muscles and the variations in oesophageal pressure in response to air puff stimulations of the nasal mucosa. Following single stimulations, inspiratory and laryngeal dilator muscles were transiently inhibited. During inspiratory inhibition, expiratory muscles and laryngeal constrictor were transiently activated. Repetitive air puff stimulations, which induced sneeze, evoked a similar pattern of transient activities during the inspiratory preparation of sneeze. This resulted in transient fluctuations of the oesophageal pressure, whose mean value became more negative as the preparatory inspiration enhanced. Our results suggest that the entire pool of respiratory neurons (bulbospinal, vagal and facial) works together in the sneeze reflex. Study of transient inspiratory inhibition demonstrates two periods during the preparatory inspiration phase of sneeze. In the first period transient effects are related to each shock of the stimulation. The second period is characterized by a diminution or a lack of transient effects associated with the stimulation. At the end of the expulsive phase, the diaphragm and the glottal dilator were further activated.