The differential organization of medullary post-inspiratory activities.
Membrane potential trajectories of 68 bulbar respiratory neurones from the peri-solitary and peri-ambigual areas of the brain-stem were recorded in anaesthetized cats to explore the synaptic influences of post-inspiratory neurones upon the medullary inspiratory network. A declining wave of inhibitory postsynaptic potentials resembling the discharge of post-inspiratory neurones was seen in both bulbospinal and non-bulbospinal inspiratory neurones, including alpha- and beta-inspiratory, early-inspiratory, late-inspiratory and ramp-inspiratory neurones. Activation of laryngeal and high-threshold pulmonary receptor afferents excited bulbar post-inspiratory neurones, whilst in the case of inspiratory neurones such stimulation produced enhanced postsynaptic inhibition during the same period of the cycle. Activation of post-inspiratory neurones and enhanced post-inspiratory inhibition of inspiratory bulbospinal neurones was accompanied by suppression of the after-discharge of phrenic motoneurones. These results suggest that a population of post-inspiratory neurones exerts a widespread inhibitory function at the lower brain-stem level. Implications of such an inhibitory function for the organization of the respiratory network are discussed in relation to the generation of the respiratory rhythm.
Richter
D W
DW
I. Physiologisches Institut, Universität Heidelberg, Federal Republic of Germany.
Ballantyne
D
D
Remmers
J E
JE
D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D008526:Medulla Oblongata / Q000502:physiology*; D008564:Membrane Potentials; D009474:Neurons / Q000502:physiology*; D012018:Reflex / Q000502:physiology; D012119:Respiration