V. Pontieri et al., Role of endogenous nitric oxide in the nucleus tratus solitarii on baroreflex control of heart rate in spontaneously hypertensive rats, J HYPERTENS, 16(12), 1998, pp. 1993-1999
Citations number
28
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Objective Toinvestigate the modulatory effect of endogenous nitric oxide (N
O) in the nucleus tractus solitarii (NTS) on the baroreceptor reflex contro
l of heart rate in conscious spontaneously hypertensive (SHR) and normotens
ive (WKY) rats.
Design and methods Male age- and weight-matched SHR and WKY chronically ins
trumented with cannulas in the NTS, artery and vein were used. nasal pressu
re (AP), heart rate (HR) and reflex HR responses during loading/unloading o
f baroreceptors (phenylephrine/ sodium nitroprusside, iv) were recorded dur
ing vehicle (3 nl/min) N-G-monomethyl-L-arginine (L-NMMA) and L-arginine (L
-Arg) infusions into the NTS. Constitutive NO synthase (NOS) activity was i
nferred by H-3-citrulline formation in the dorsal brain stem of other SHR a
nd 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, respectivel
y), but decreased the HR range (57 +/- 7 beats/min, a 34% reduction, P< 0.0
5) without changing further the impaired gain of baroreceptor reflex contro
l 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-NM
MA(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 i
mprove baroreflex control of HR, but restored the depression of HR range wh
en 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 r
ange during afferent stimulation In SHR the depressed NO modulation is in a
ccordance with the smaller NOS activity in the dorsal brain stem. J Hyperte
ns 1998, 16:1993-1999 (C) 1998 Lippincott Williams & Wilkins.