Project Details


The purpose of this proposal is to investigate the interaction between
arterial baroreceptor reflexes and the actions of angiotensin (II) on the
central nervous system. Previous work by this applicant has indicated that
conscious sinoaortic baroreceptor denervated rats are 3.6 times more
sensitive to the pressor effects of intravenous bolus injection of
angiotensin than are baroreceptor intact rats. In comparison, the
baroreceptor denervated group was more than 1000 times more sensitive to
the pressor effects of central (intracerebroventricular) angiotensin
administration. The first specific objective of this study will be to more
rigorously define the extent of this very marked inhibitory influence of
the baroreflex on the central pressor actions of angiotensin. Experiments
are proposed to determine: (1) if the potentiation persists during
constant interacerebroventricular infusion of angiotensin, (2) the
contribution of cardiac output versus peripheral resistance to the
augmentation, (3) if the central actions of blood-borne angiotensin are
augmented with baroreceptor denervation, (4) if the potentiation occurs
with other centrally acting pressor agents, and (5) if a noncardiovascular
action of central angiotensin, such as drinking, is affected by
baroreceptor denervation. The second specific objective of this propsal
will be to examine the influence of angiotensin on baroreflex function.
This approach will examine the pressor sensitivity to continuous infusion
of angiotensin in baroreceptor intact versus denervated animals and will
include a comparison with baroreflex influences on pressor sensitivity to
phenylephrine and vasopressin. The possible influence of angiotensin on
baroreflex function will also be examined in anesthetized rats during
simulated baroreceptor activation by electrical stimulation of the aortic
depressor nerve while recording peripheral sympathetic nerve activity. As
further test of the contribution of the central action of angiotensin,
experiments will be repeated with a specific knife-cut in the anterior
hypothalamus which eliminates the central pressor effects of angiotensin.
These types of approaches will provide further understanding of neural
circulatory control specifically relating to baroreflex influences on the
central action of angiotensin and, conversely, the influence of angiotensin
on baroreflex control of arterial pressure.
Effective start/end date1/09/8531/08/86