Vol. 93, Issue 1, 280-288, July 2002
Altered frequency responses of sympathetic nerve discharge
bursts after IL-1
and mild hypothermia
M. J.
Kenney,
F.
Blecha,
R. J.
Fels, and
D. A.
Morgan
Department of Anatomy and Physiology, Kansas State
University, Manhattan, Kansas 66506; and Department of Internal
Medicine, Cardiovascular Center, University of Iowa College of
Medicine, Iowa City, Iowa 52242
Although interleukin-1
(IL-1) administration produces nonuniform changes in the level of
sympathetic nerve discharge (SND), the effect of IL-1 on the
frequency-domain relationships between discharges in different
sympathetic nerves is not known. Autospectral and coherence analyses
were used to determine the effect of IL-1 and mild hypothermia (60 min after IL-1, colonic temperature from 38°C to 36°C)
on the relationships between renal-interscapular brown adipose tissue
(IBAT) and splenic-lumbar sympathetic nerve discharges in
chloralose-anesthetized rats. The following observations were made.
1) IL-1 did not alter renal-IBAT coherence values in the
0- to 2-Hz frequency band or at the cardiac frequency (CF). 2) Peak coherence values relating splenic-lumbar discharges
at the CF were significantly increased after IL-1 and during
hypothermia. 3) Hypothermia after IL-1 significantly
reduced the coupling (0-2 Hz and CF) between renal-IBAT but not
splenic-lumbar SND bursts. 4) Combining IL-1 and mild
hypothermia had a greater effect on renal-IBAT SND coherence values
than did mild hypothermia alone. These data demonstrate functional
plasticity in sympathetic neural circuits and suggest complex
relationships between immune products and SND regulation.
sympathetic nerve activity; autospectral analysis; coherence
analysis; chloralose; interleukin-1
