AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 2 370-R376, Copyright © 1989 by American Physiological Society
Catecholamine activity in paraventricular hypothalamus after hemorrhage in cats
K. V. Thrivikraman, D. A. Bereiter and D. S. Gann
Department of Surgery, Brown University, Rhode Island Hospital, Providence 02903.
Temporal changes in catecholamine activity within the paraventricular
nucleus (PVN) of the hypothalamus were assessed using in vivo voltammetry
after moderate hemorrhage in chloralose-anesthetized cats. Oxidation
current was measured with carbon microelectrodes, and the change at +250 mV
was used as an estimate of catecholamine activity. The magnitude and
directional change in catecholamine activity was assessed for each site
during the initial 3 min of blood loss. Of 62 recording sites, 45 sites
were located along the rostrocaudal extent of the medial PVN. Fifteen of
these 45 sites exhibited an increase, 15 others exhibited a decrease, and
the remaining 15 sites exhibited no change in catecholamine activity. The
magnitude of change in oxidation current was independent of the magnitude
of the decrease in arterial pressure after hemorrhage. Twelve of the 15
sites that exhibited increases in catecholamine activity were located in
the caudal PVN along its dorsomedial aspect, whereas the location of sites
that exhibited decreases in catecholamine activity were more widely
distributed throughout the nucleus. These data are consistent with the
hypothesis that an increase in the release of catecholamines within the
caudal PVN in response to hemorrhage is facilitatory for the release of
adrenocorticotropin and/or vasopressin.
