Hypertension, Vol 6, 482-488, Copyright © 1984 by American Heart Association
KL Barnes and CM Ferrario
Electrical stimulation of the dog's area postrema (AP) induces a response
that mimics the pressor response produced by intravertebral infusion of
low-dose angiotensin II, which causes an increase in mean arterial pressure
associated with transient tachycardia and increased peripheral resistance.
The present study investigated in morphine- chloralose anesthetized dogs
whether: 1) the characteristics of the AP pressor response are influenced
by the presence of carotid sinus afferents; 2) structures rostral to the
medulla influence the AP pressor response; and 3) the pressor pathway is
initiated by neurons within the AP. Since bilateral cervical sinovagal
denervation, which potentiated the phenylephrine pressor response, did not
affect the pressor response to AP stimulation, the data provide evidence
for an inhibitory influence exerted upon the central baroreflex mechanism
by the AP pressor mechanism. The unaltered AP pressor response after
midcollicular transection suggests that the efferent pathway is contained
within the brain stem caudal to the pons. Finally, the elimination of the
pressor response following kainic acid microinjection into the AP provides
evidence that the AP pressor mechanism is initiated by neurons within the
AP, rather than by fibers of passage from other pressor centers. These
results suggest that the AP produces its facilitation of central
sympathetic vasomotor outflow via a pathway contained within the medulla.
ARTICLES
Location of the area postrema pressor pathway in the dog brain stem
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