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Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats.
J Hypertens. 2000 Dec; 18(12):1841-8.JH

Abstract

OBJECTIVES

In the present study, we evaluated the effect of angiotensin-(1-7) [Ang-(1-7)] and its selective antagonist, D-Ala7-Ang-(1-7) (A-779), at the nucleus tractus solitarii (nTS), in the modulation of the bradycardic component of the baroreceptor reflex.

METHODS

Mean arterial pressure (MAP) and heart rate were continuously recorded. Reflex changes in heart rate elicited by bolus injection of graded doses of phenylephrine were evaluated before and after bilateral microinjection (glass micropipette) of Ang-(1-7) (10 pmol or 25 pmol), A-779 (50 pmol) or saline (vehicle) into the nTS of urethane anesthetized male Wistar rats or spontaneously hypertensive rats (SHR). The averaged ratio between reflex changes in heart rate and changes in MAP was used as index of baroreflex sensitivity.

RESULTS

Microinjection of Ang-(1-7) into the nTS elicited significant decreases in MAP and heart rate in both Wistar and SHR. While the decrease in MAP was similar in both strains, the changes in heart rate were smaller in SHR. A-779 produced small changes in MAP and heart rate that were no different from those induced by saline. After microinjection of 10 pmol of Ang-(1-7) into the nTS of normotensive rats, there was a significant increase in baroreflex sensitivity. In SHR, only the microinjection of a higher dose (25 pmol) of Ang-(1-7) produced a significant increase in baroreflex sensitivity. A significant reduction inbaroreflex sensitivity was observed after microinjection of A-779 (50 pmol) in both strains.

CONCLUSIONS

These results indicate that Ang-(1-7) exerts a tonic modulatory effect on the baroreflex control of heart rate at the nTS, probably through a non-AT1 non-AT2 receptor subtype. In addition, our data showed a reduced sensitivity to Ang-(1-7) at the nTS of SHR, that could be accounting, at least in part, for the decreased baroreflex sensitivity present in this model of hypertension.

Authors+Show Affiliations

Departamento de Fisiologia e Biofisica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Brazil.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11132609

Citation

Chaves, G Z., et al. "Modulation of the Baroreflex Control of Heart Rate By Angiotensin-(1-7) at the Nucleus Tractus Solitarii of Normotensive and Spontaneously Hypertensive Rats." Journal of Hypertension, vol. 18, no. 12, 2000, pp. 1841-8.
Chaves GZ, Caligiorne SM, Santos RA, et al. Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats. J Hypertens. 2000;18(12):1841-8.
Chaves, G. Z., Caligiorne, S. M., Santos, R. A., Khosla, M. C., & Campagnole-Santos, M. J. (2000). Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats. Journal of Hypertension, 18(12), 1841-8.
Chaves GZ, et al. Modulation of the Baroreflex Control of Heart Rate By Angiotensin-(1-7) at the Nucleus Tractus Solitarii of Normotensive and Spontaneously Hypertensive Rats. J Hypertens. 2000;18(12):1841-8. PubMed PMID: 11132609.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats. AU - Chaves,G Z, AU - Caligiorne,S M, AU - Santos,R A, AU - Khosla,M C, AU - Campagnole-Santos,M J, PY - 2001/1/2/pubmed PY - 2001/4/3/medline PY - 2001/1/2/entrez SP - 1841 EP - 8 JF - Journal of hypertension JO - J. Hypertens. VL - 18 IS - 12 N2 - OBJECTIVES: In the present study, we evaluated the effect of angiotensin-(1-7) [Ang-(1-7)] and its selective antagonist, D-Ala7-Ang-(1-7) (A-779), at the nucleus tractus solitarii (nTS), in the modulation of the bradycardic component of the baroreceptor reflex. METHODS: Mean arterial pressure (MAP) and heart rate were continuously recorded. Reflex changes in heart rate elicited by bolus injection of graded doses of phenylephrine were evaluated before and after bilateral microinjection (glass micropipette) of Ang-(1-7) (10 pmol or 25 pmol), A-779 (50 pmol) or saline (vehicle) into the nTS of urethane anesthetized male Wistar rats or spontaneously hypertensive rats (SHR). The averaged ratio between reflex changes in heart rate and changes in MAP was used as index of baroreflex sensitivity. RESULTS: Microinjection of Ang-(1-7) into the nTS elicited significant decreases in MAP and heart rate in both Wistar and SHR. While the decrease in MAP was similar in both strains, the changes in heart rate were smaller in SHR. A-779 produced small changes in MAP and heart rate that were no different from those induced by saline. After microinjection of 10 pmol of Ang-(1-7) into the nTS of normotensive rats, there was a significant increase in baroreflex sensitivity. In SHR, only the microinjection of a higher dose (25 pmol) of Ang-(1-7) produced a significant increase in baroreflex sensitivity. A significant reduction inbaroreflex sensitivity was observed after microinjection of A-779 (50 pmol) in both strains. CONCLUSIONS: These results indicate that Ang-(1-7) exerts a tonic modulatory effect on the baroreflex control of heart rate at the nTS, probably through a non-AT1 non-AT2 receptor subtype. In addition, our data showed a reduced sensitivity to Ang-(1-7) at the nTS of SHR, that could be accounting, at least in part, for the decreased baroreflex sensitivity present in this model of hypertension. SN - 0263-6352 UR - https://www.unboundmedicine.com/medline/citation/11132609/Modulation_of_the_baroreflex_control_of_heart_rate_by_angiotensin__1_7__at_the_nucleus_tractus_solitarii_of_normotensive_and_spontaneously_hypertensive_rats_ L2 - http://dx.doi.org/10.1097/00004872-200018120-00019 DB - PRIME DP - Unbound Medicine ER -