AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 2 289-R295, Copyright © 1988 by American Physiological Society
Locus coeruleus monoaminergic activity and plasma corticotropin after hemorrhage in cats
K. V. Thrivikraman, D. E. Carlson and D. S. Gann
Department of Surgery, Brown University, Rhode Island Hospital, Providence 02902.
Temporal changes in monoaminergic activity in the locus coeruleus (LC) in
response to hemorrhage of 10 or 20% of blood volume were assessed using
normal pulse voltammetry in alpha-chloralose-urethan-anesthetized cats.
Oxidation current was measured with a carbon microelectrode, and changes at
230 and 450 mV were used as estimates of catecholaminergic and
indolaminergic activity, respectively. Plasma adrenocorticotropin (ACTH)
was measured by radioimmunoassay. Hemorrhage of 20% blood volume caused a
transient increase in the catecholaminergic activity in a compact area in
the ventral LC (vLC) that preceded increases in the plasma ACTH. The
increase in oxidation current at 450 mV was similar to that at 230 mV,
suggesting no significant contribution from indolamines. Dorsal rostral
pontine sites outside this area exhibited either sustained decreases in
oxidation current or no change in response to hemorrhage. The proportion of
sites that exhibited transient increases in oxidation current in the vLC
after the 10% blood loss was less than that after the 20% blood loss,
suggesting that this response was dependent on the magnitude of hemorrhage.
Since the LC was implicated previously in the control of ACTH release, we
suggest that hemodynamic signals traversing the LC activate
catecholaminergic mechanisms that, in turn, participate in the regulation
of ACTH release after hemorrhage.
