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.
I. Physiologisches Institut, Universität Heidelberg, Federal Republic of Germany.
D W
DW
Richter
D
D
Ballantyne
J E
JE
Remmers
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