Journal of Applied Physiology, Vol 65, Issue 4 1572-1578, Copyright © 1988 by American Physiological Society
Respiratory resetting induced by spinal cord stimulation in the cat
D. F. Speck
Department of Physiology and Biophysics, University of Kentucky Medical Center, Lexington 40536-0084.
Electrical stimulation (50-150 microA, 0.5-ms duration, 3-300 Hz) was
performed within three different regions (lateral, ventrolateral, and
ventral) of the C2-C3 spinal cord of decerebrate, vagotomized, paralyzed,
and artificially ventilated cats. Spinal cord stimulation sites were
located by inserting monopolar or bipolar stimulating electrodes either at
the dorsolateral sulcus or at least 1 mm medial or lateral to the sulcus.
With stimulation at each site, alterations in respiratory rhythm,
orthodromic phrenic nerve responses, and antidromic activation of medullary
respiratory-modulated neurons were examined. Phrenic nerve responses to
cervical spinal cord stimulation consisted of an early excitation (2-4 ms)
and/or a late excitation (4-8 ms). Stimulation of the lateral region evoked
the greatest amplitude early response and stimulation of the ventrolateral
region produced the greatest late excitation. All three stimulus sites
elicited antidromic activation of some respiratory-modulated neurons in the
dorsal (DRG) and ventral respiratory groups (VRG). The lateral region was
the least effective resetting site, and it had the highest incidence of
antidromic activation of both DRG and VRG neurons. The ventrolateral region
of the cervical spinal cord was the most effective resetting site, but it
had the lowest incidence of antidromic activation of DRG
respiratory-modulated neurons. In addition, resetting responses were
observed with spinal cord stimulation at similar sites in the thoracic and
lumbar spinal cord regions thought to be devoid of inspiratory bulbospinal
axons.(ABSTRACT TRUNCATED AT 250 WORDS)
