Chemical activation of C(1)-C(2) spinal neurons modulates activity of thoracic respiratory interneurons in rats.
Discharge patterns of thoracic dorsal horn neurons are influenced by chemical activation of cell bodies in cervical spinal segments C(1)-C(2). The present aim was to examine whether such activation would specifically affect thoracic respiratory interneurons (TRINs) of the deep dorsal horn and intermediate zone in pentobarbital sodium-anesthetized, paralyzed, artificially ventilated rats. We also characterized discharge patterns and pathways of TRIN activation in rats. A total of 77 cells were classified as TRINs by location, continued burst activity related to phrenic discharge when the respirator was stopped, and lack of antidromic response from selected pathways. A variety of respiration-phased discharge patterns was documented whose pathways were interrupted by ipsilateral C(1) transection. Glutamate pledgets (1 M, 1 min) on the dorsal surface of the spinal cord inhibited 22/49, excited 15/49, or excited/inhibited 3/49 tested cells. Incidence of responses did not depend on whether the phase of TRIN discharge was inspiratory, expiratory, or biphasic. Phrenic nerve activity was unaffected by chemical activation of C(1)-C(2) in this preparation. Besides supraspinal input, TRIN activity may be influenced by upper cervical modulatory pathways.
Qin
C
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Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA. chao-qin@ouhsc.edu
Farber
J P
JP
Chandler
M J
MJ
Foreman
R D
RD
D000818:Animals; D002574:Cervical Vertebrae; D004558:Electric Stimulation; D004594:Electrophysiology; D018698:Glutamic Acid / Q000494:pharmacology; D007395:Interneurons / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012137:Respiratory System / Q000294:innervation*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013119:Spinal Cord Injuries; D013904:Thoracic Vertebrae
D018698:Glutamic Acid