Timing of medullary late-inspiratory neuron discharges: vagal afferent effects indicate possible off-switch function.
1. In decerebrate paralyzed cats, we observed the responses of ventral and dorsal medullary inspiratory (I) neurons to two types of vagal afferent input that shorten neural I: lung inflation and vagal electrical stimulation. 2. A study population of 15 I neurons whose firing patterns suggested involvement in the inspiratory OFF-switch (IOS) was selected on the basis of two criteria: late onset of firing and excitation by vagal inputs. 3. Firing in relation to the end of I showed two types of response to vagal inputs. The pre-expiratory onset time (time from initial spike to end of I) was either unchanged (type 1 response in 5/15 neurons) or significantly changed (type 2 response in 10/15 neurons). 4. It is suggested that type 1 neurons, whose firing patterns remain closely locked to the end of I despite considerable changes of I duration, are involved in promoting the IOS, whereas type 2 neurons are either not involved (e.g., late-onset premotor neurons) or are involved at an earlier temporal processing stage.
Department of Physiology, Albert Einstein College of Medicine, Bronx, New York 10461.
M I
MI
Cohen
W X
WX
Huang
R
R
Barnhardt
W R
WR
See
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D002415:Cats; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D001239:Inhalation / Q000502:physiology*; D008168:Lung / Q000294:innervation*; D008526:Medulla Oblongata / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D012125:Respiratory Center / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*