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Role of endogenous nitric oxide in the nucleus tratus solitarii on baroreflex control of heart rate in spontaneously hypertensive rats.
J Hypertens. 1998 Dec; 16(12 Pt 2):1993-9.JH

Abstract

OBJECTIVE

Toinvestigate the modulatory effect of endogenous nitric oxide (NO) in the nucleus tractus solitarii (NTS) on the baroreceptor reflex control of heart rate in conscious spontaneously hypertensive (SHR) and normotensive (WKY) rats.

DESIGN AND METHODS

Male age- and weight-matched SHR and WKY chronically instrumented with cannulas in the NTS, artery and vein were used. Basal pressure (AP), heart rate (HR) and reflex HR responses during loading/unloading of baroreceptors (phenylephrine/sodium nitroprusside, iv) were recorded during vehicle (3 nl/min) NG-monomethyl-L-arginine (L-NMMA) and L-arginine (L-Arg) infusions into the NTS. Constitutive NO synthase (NOS) activity was inferred by 3H-citrulline formation in the dorsal brain stem of other SHR and WKY groups.

RESULTS

In SHR a small dose of L-NMMA (30 ng/kg/min) restricted to the NTS did not change AP and HR (185+/-4 mmHg, 373+/-12 beats/min, respectively), but decreased the HR range (57+/-7 beats/min, a 34% reduction, P< 0.05) without changing further the impaired gain of baroreceptor reflex control of HR. In the WKY group similar results (significant 32% reduction in HR range, gain unchanged) were only attained with a dose 10 times higher (L-NMMA(NTS) = 300 ng/kg/min), no effect being observed with the small dose (HR range = 163+/-12 beats/min). In SHR, L-Arg(NTS) (900 ng/kg/min) did not improve baroreflex control of HR, but restored the depression of HR range when given after L-NMMA(NTS). Basal NOS activity in the dorsal brain stem was reduced in SHR (P < 0.05) when compared to WKY group.

CONCLUSIONS

NO modulates, at the NTS level, the baroreceptor reflex control of HR in both SHR and WKY not by altering the gain, but by increasing HR range during afferent stimulation. In SHR the depressed NO modulation is in accordance with the smaller NOS activity in the dorsal brain stem.

Authors+Show Affiliations

Department of Physiology and Biophysics, ICB, University of São Paulo, SP, Brazil.No 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

9886888

Citation

Pontieri, V, et al. "Role of Endogenous Nitric Oxide in the Nucleus Tratus Solitarii On Baroreflex Control of Heart Rate in Spontaneously Hypertensive Rats." Journal of Hypertension, vol. 16, no. 12 Pt 2, 1998, pp. 1993-9.
Pontieri V, Venezuela MK, Scavone C, et al. Role of endogenous nitric oxide in the nucleus tratus solitarii on baroreflex control of heart rate in spontaneously hypertensive rats. J Hypertens. 1998;16(12 Pt 2):1993-9.
Pontieri, V., Venezuela, M. K., Scavone, C., & Michelini, L. C. (1998). Role of endogenous nitric oxide in the nucleus tratus solitarii on baroreflex control of heart rate in spontaneously hypertensive rats. Journal of Hypertension, 16(12 Pt 2), 1993-9.
Pontieri V, et al. Role of Endogenous Nitric Oxide in the Nucleus Tratus Solitarii On Baroreflex Control of Heart Rate in Spontaneously Hypertensive Rats. J Hypertens. 1998;16(12 Pt 2):1993-9. PubMed PMID: 9886888.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Role of endogenous nitric oxide in the nucleus tratus solitarii on baroreflex control of heart rate in spontaneously hypertensive rats. AU - Pontieri,V, AU - Venezuela,M K, AU - Scavone,C, AU - Michelini,L C, PY - 1999/1/14/pubmed PY - 1999/1/14/medline PY - 1999/1/14/entrez SP - 1993 EP - 9 JF - Journal of hypertension JO - J. Hypertens. VL - 16 IS - 12 Pt 2 N2 - OBJECTIVE: Toinvestigate the modulatory effect of endogenous nitric oxide (NO) in the nucleus tractus solitarii (NTS) on the baroreceptor reflex control of heart rate in conscious spontaneously hypertensive (SHR) and normotensive (WKY) rats. DESIGN AND METHODS: Male age- and weight-matched SHR and WKY chronically instrumented with cannulas in the NTS, artery and vein were used. Basal pressure (AP), heart rate (HR) and reflex HR responses during loading/unloading of baroreceptors (phenylephrine/sodium nitroprusside, iv) were recorded during vehicle (3 nl/min) NG-monomethyl-L-arginine (L-NMMA) and L-arginine (L-Arg) infusions into the NTS. Constitutive NO synthase (NOS) activity was inferred by 3H-citrulline formation in the dorsal brain stem of other SHR and WKY groups. RESULTS: In SHR a small dose of L-NMMA (30 ng/kg/min) restricted to the NTS did not change AP and HR (185+/-4 mmHg, 373+/-12 beats/min, respectively), but decreased the HR range (57+/-7 beats/min, a 34% reduction, P< 0.05) without changing further the impaired gain of baroreceptor reflex control of HR. In the WKY group similar results (significant 32% reduction in HR range, gain unchanged) were only attained with a dose 10 times higher (L-NMMA(NTS) = 300 ng/kg/min), no effect being observed with the small dose (HR range = 163+/-12 beats/min). In SHR, L-Arg(NTS) (900 ng/kg/min) did not improve baroreflex control of HR, but restored the depression of HR range when given after L-NMMA(NTS). Basal NOS activity in the dorsal brain stem was reduced in SHR (P < 0.05) when compared to WKY group. CONCLUSIONS: NO modulates, at the NTS level, the baroreceptor reflex control of HR in both SHR and WKY not by altering the gain, but by increasing HR range during afferent stimulation. In SHR the depressed NO modulation is in accordance with the smaller NOS activity in the dorsal brain stem. SN - 0263-6352 UR - https://www.unboundmedicine.com/medline/citation/9886888/Role_of_endogenous_nitric_oxide_in_the_nucleus_tratus_solitarii_on_baroreflex_control_of_heart_rate_in_spontaneously_hypertensive_rats_ L2 - http://dx.doi.org/10.1097/00004872-199816121-00021 DB - PRIME DP - Unbound Medicine ER -