HIGH FREQUENCY OSCILLATIONS IN MEMBRANE POTENTIALS OF MEDULLARY INSPIRATORY
AND EXPIRATORY NEURONS (INCLUDING LARYNGEAL MOTONEURONS).
Huang, Wu-Xin, Morton I. Cohen, Qiping Yu, Wolf R. See, Qin He.
Department of Physiology and Biophysics, Albert Einstein College of
Medicine, Bronx, NY 10461.
APStracts 3:0087N, 1996.
SUMMARY AND CONCLUSIONS
1. In midcollicular decerebrate, unanesthetized, paralyzed cats, venti lated
with a cycle-triggered pump system, the properties of high-frequency
oscillations (HFO, 50-100 Hz) in membrane potentials (MP) of medullary inspir
atory (I) and expiratory (E) cells were studied. Simultaneous recordings were
taken from bilateral phrenic and recurrent laryngeal (RL) nerves and from
cells in the intermediate ventral respiratory group (intVRG, 0-1 mm rostral to
the obex) or the caudal ventral respiratory group (cVRG, 2-4 mm caudal to the
obex). 2. Spectral coherence analyses were used to detect the presence of HFOs
during I in cell MPs. Cross-correlation histograms (CCH) between the cell and
phrenic signals were used to ascertain cell-nerve HFO phase relations and to
identify cells as RL motoneurons. Of the 103 cells that had significant HFOs
(cell-phrenic coherences >/= 1.0), measurable HFO peak lags in the CCH were
seen in 53 cells: a) RL cells (9 I cells and 7 E cells); b) other types of
cell (8 intVRG I cells, 18 intVRG E cells, and 11 cVRG E cells). These cells
had high HFO correlations; the cell-phrenic coherence range was 0.35-0.94,
with mean HFO frequency of 58 Hz. 3. The cell-phrenic HFO lag (in ms) was
measured in the CCH as the lag of the primary peak (peak located nearest to
zero lag). The phase lag was defined as: (lag of primary peak in ms)/(HFO
period in ms). The phase lags differed markedly between two subsets of cells:
a) RL I cells had HFO depolarization peaks that lagged the phrenic HFO peaks
(average cell-phrenic phase lag = -0.18); b) the non-RL cells, regardless of
location (intVRG or cVRG) and type (I or E), had HFO depolarization peaks
leading (preceding) the phrenic HFO peaks (average cell-phrenic phase lag =
0.28). In addition, the cVRG E cells had significantly shorter cell-phrenic
phase lags than the intVRG E cells (0.23 vs. 0.31, respectively). 4. These
lags can be compared with the (I unit)-phrenic phase lags (aver age ca. 0.3)
found in earlier extracellular studies. a) There is a transmis sion delay of
ca. one-half HFO cycle from excitatory I cells to RL I cells. 2) Since a
depolarization peak in the MP of an E cell corresponds to the start of a
hyperpolarizing wave, the excitatory bulbospinal pathways from I cells have
transmission times comparable to those of the inhibitory intramedullary path
ways from I cells to E cells. 5. These results indicate that study of HFO
phase relations can furnish useful information on functional connectivity of
medullary respiratory neurons during the I phase.
Received 24 July 1995; accepted in final form 10 April 1996.
APS Manuscript Number J478-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 May 96