Sneeze-evoking region within the brainstem.

The neuronal mechanisms of sneezing were examined in precollicular-postmammillary decerebrate cats. Mechanical stimulation (frequency 20 Hz, peak-to-peak displacement 0.5 mm) of the nasal membrane evoked a series of sneezes. In the same preparation, electrical stimulation (duration 0.2 ms, frequency 10 Hz, 5-50 microA) delivered to the lower brainstem also evoked sneezes. The changes in EMG activity and subglottic pressure during brainstem-induced sneeze were similar to those recorded nasal-induced sneeze. The sneeze-evoking region was located along the ventromedial part of the spinal trigeminal nucleus and the adjacent pontine-medullary lateral reticular formation, and extended rostrocaudally from P4.0 to P14.5 according to the Horsley-Clarke coordinates. These results suggest that the sneeze-evoking region is a distinct structure of the brainstem, having a homogeneous function. This region appears to control the epipharyngeal, intrinsic laryngeal and respiratory muscles. The integrated activity of these muscles underlies the generation of a sneeze.