Mj. Kenney et al., Effects of midbrain and spinal cord transections on sympathetic nerve responses to heating, AM J P-REG, 278(5), 2000, pp. R1329-R1338
Citations number
34
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
In the present study, we investigated the contributions of forebrain, brain
stem, and spinal neural circuits to heating-induced sympathetic nerve disc
harge (SND) responses in chloralose-anesthetized rats. Frequency characteri
stics of renal and splenic SND bursts and the level of activity in these ne
rves were determined in midbrain-transected (superior colliculus), spinal c
ord-transected [first cervical vertebra (C1)], and sham-transected (midbrai
n and spinal cord) rats during progressive increases in colonic temperature
(T-c) from 38 to 41.6-41.7 degrees C. The following observations were made
. 1) Significant increases in renal and splenic SND were observed during hy
perthermia in midbrain-transected, sham midbrain-transected, C1-transected,
and sham C1-transected rats. 2) Heating changed the discharge pattern of r
enal and splenic SND bursts and was associated with prominent coupling betw
een renal-splenic discharge bursts in midbrain-transected, sham midbrain-tr
ansected, and sham C1-transected rats. 3) The pattern of renal and splenic
SND bursts remained unchanged from posttransection recovery levels during h
eating in C1-transected rats. We conclude that an intact forebrain is not r
equired for the full expression of SND responses to increased T-c and that
spinal neural systems, in the absence of supraspinal circuits, are unable t
o markedly alter the frequency characteristics of SND in response to acute
heat stress.