Expiratory neurons in the region of the retrofacial nucleus: inhibitory effects of intercostal tendon organs.

Intercostal muscle tendon organs have an inhibitory effect on the medullary neurons driving all inspiratory muscles, and on a subpopulation of medullary bulbospinal expiratory neurons. Results from this study showed that the activity of expiratory related neurons in the region of the retrofacial nucleus (Botzinger complex) decreases during tendon organ afferent stimulation; the response is similar to that of caudal bulbospinal expiratory neurons. We conclude that these expiratory neurons do not mediate the tendon organ inhibition of medullary inspiratory neuronal activity.