T. Nakata et al., CARDIOVASCULAR CHANGE AND HYPOTHALAMIC NOREPINEPHRINE RELEASE IN RESPONSE TO ENVIRONMENTAL-STRESS, The American journal of physiology, 264(4), 1993, pp. 784-789
The major objective of this study was to compare the magnitude and dur
ation of cardiovascular (CV) responses to acute environmental stresses
with the associated patterns of noradrenergic activity in the paraven
tricular nucleus (PVN) and posterior nucleus (PH) of the hypothalamus.
Simultaneous microdialysis samples of extracellular norepinephrine (N
E) were collected at 5-min intervals from PVN and PH and the CV respon
ses were recorded before, during, and for 15 min after acute shaker (c
age oscillation) stress or inhalation of ether vapor in freely moving
rats. Five minutes of shaker stress, 60 and 150 cycles/min, elicited p
ressor responses coupled with increases in dialysate NE from both PVN
and PH in a frequency-dependent manner. Tachycardia occurred at 150 bu
t not 60 cycles/min. Ten minutes after 60 cycles/min and 15 min after
150 cycles/min, NE efflux in PH was still increased, whereas in PVN it
returned to control as had arterial pressure and heart rate. Ether va
por elicited a transient CV response but a continuing efflux of NE in
PH and PVN. Urethan anesthesia raised baseline values of dialysate NE
in PH and PVN but significantly attenuated cardiovascular and dialysat
e NE responses to shaker stress. We conclude that acute environmental
stress simultaneously elicits CV responses and the efflux of NE from P
VN and PH but, during or after stress, CV values may return to control
levels while NE efflux remains elevated in PVN and/or PH.