Bötzinger expiratory neurones inhibit propriobulbar decrementing inspiratory neurones

Although bulbospinal, expiratory neurones of the Bötzinger complex (BOT E-AUG) are known to have monosynaptic inhibitory connections to many bulbospinal respiratory neurones, their connections to propriobulbar respiratory neurones have not been so well characterized. We stimulated BOT E-AUG neurones with trains of pulses, and found an inhibition of medullary and phrenic respiratory activity with phase resetting. We also examined the response of propriobulbar, decrementing, inspiratory neurones (I-DEC) to the antidromic activation of BOT E-AUG neurones from the C3 segment of the spinal cord with single shocks and found evidence for a monosynaptic inhibition of the I-DEC neurones in the post-stimulus histograms of the extracellular firing. These results were obtained in 11 pentobarbital anaesthetized cats, and provide experimental support for a recent model of respiratory rhythmogenesis.