AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 2 296-R301, Copyright © 1988 by American Physiological Society
Noradrenergic turnover increases in locus coeruleus after hemorrhage in cats
K. V. Thrivikraman, D. E. Carlson and D. S. Gann
Department of Surgery, Brown University, Rhode Island Hospital, Providence 02902.
Push-pull perfusion was used to determine monoaminergic activity in the
locus coeruleus (LC) of alpha-chloralose-urethan-anesthetized cats after
20% hemorrhage. Blood was withdrawn from 0 to 3 min and reinfused from 10
to 13 min. Continuous 5-min interval samples of perfusate were collected
from -5 to 15 min. Concentrations of the monoamines were determined using
high-performance liquid chromatography with electrochemical detection. The
perfusion sites (n = 21) were identified histologically. In a group of
eight contiguous sites in the ventral LC (vLC),
4-hydroxy-3-methoxy-phenyl(ethylene)glycol (MHPG) increased significantly
from 0.50 +/- 0.22 (control) to 1.19 +/- 0.42 pmol/5 min during the first 5
min after hemorrhage (P less than 0.05). This response differed
significantly from that obtained at the remaining 13 sites. Other
metabolites were not often detectable for many sites either within or
outside vLC, and their responses to hemorrhage were not significant. The
response of MHPG in the vLC indicates that norepinephrine (NE) turnover
increases in this area selectively and implicates NE in the increase in the
catecholamine oxidation current reported previously using in vivo
voltammetry. Since the vLC was shown previously to facilitate
adrenocorticotropin (ACTH) release, the increase in NE turnover after
hemorrhage could induce ACTH release. This increase may also act locally to
modulate the ascending hemodynamic signal.
