AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 1 32-R37, Copyright © 1990 by American Physiological Society
Cardiovascular effects of microinjection of ANF and brain natriuretic peptide into ventrolateral medulla
R. Ermirio, G. L. Avanzino, P. Ruggeri, M. Bergaglio and F. R. Calaresu
Istituto di Fisiologia Umana, Facolta di Medicina e Chirurgia, University of Genoa, Italy.
Cardiovascular effects of microinjection of atrial natriuretic factor (ANF)
into 77 sites of the ventrolateral medulla (VLM) were investigated in
urethan-anesthetized rats. Changes in mean arterial pressure (MAP) and
heart rate (HR) in response to injections of glutamate into these sites
were used to determine that they contained cardiovascular neurons. ANF (20
nl of 10(-7) M) decreased MAP [-8.9 +/- 1.5 (SE) mmHg] and HR [-9.0 +/- 2.8
(SE) beats/min] in 5 of 36 vasopressor sites identified by glutamate
located in the more rostral and lateral aspect of the rostral VLM (RVLM);
no effect was elicited in the other 31 RVLM sites. ANF decreased MAP (-10.4
+/- 2.4 mmHg) and HR (-9.8 +/- 3.0 beats/min) in 25 of 41 depressor sites
distributed throughout the caudal VLM (CVLM); no response was observed in
the other 16 CVLM sites. Brain natriuretic peptide (BNP) was microinjected
(20 nl of 10(-7) M) in 21 VLM sites, before or after microinjection of ANF.
BNP and ANF elicited similar results in 17 sites, a decline in MAP and HR
in 10 sites, and no effect in 7 sites. In the remaining four cases ANF
caused a decline in MAP and in HR, whereas BNP had minimal or no effect.
Cardiovascular responses to ANF microinjection into the RVLM and CVLM
support the hypothesis that ANF is involved in the transmission of
baroreceptor information from the nucleus tractus solitarii to these
medullary regions. The similarity of the results obtained with BNP and ANF
suggests that these peptides may serve similar roles in medullary pathways
involved in the control of the cardiovascular system.
