Marked Impairment in Baroreflex Control of Heart Rate in Spontaneously Hypertensive Rats with Chronic Myocardial Infarction

We examined the effect of α2-adrenoreceptor blockade in the nucleus of the solitary tract (NTS) on baroreflex responses elicited by electrical stimulation of the left aortic depressor nerve (ADN) in urethane-anesthetized spontaneously hypertensive rats (SHR, n = 11) and normotensive Wistar-Kyoto rats (WKY, n = 11). ADN stimulation produced a frequency-dependent decrease in mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). In SHR, unilateral microinjection of idazoxan into the NTS markedly reduced baroreflex control of MAP, RSNA, and HR and had a disproportionately greater influence on baroreflex control of MAP than of RSNA. In WKY, idazoxan microinjections did not significantly alter baroreflex function relative to control vehicle injections. These results suggest that baroreflex regulation of arterial pressure in SHR is highly dependent on NTS adrenergic mechanisms. The reflex regulation of sympathetic outflow to the kidney is less influenced by the altered α2-adrenoreceptor mechanisms in SHR.

Download Full-text

Regression of myocardial hypertrophy and influence of adrenergic system

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1983.244.1.h97 ◽

1983 ◽

Vol 244 (1) ◽

pp. H97-H101 ◽

Cited By ~ 4

Author(s):

S. Sen ◽

R. C. Tarazi

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Regression Analysis ◽

Arterial Pressure ◽

Spontaneously Hypertensive Rats ◽

Myocardial Hypertrophy ◽

Cardiac Response ◽

Adrenergic System ◽

Hypertensive Rats ◽

Spontaneously Hypertensive

Studies of regression of myocardial hypertrophy in spontaneously hypertensive rats (SHR) suggest that the adrenergic system may play an important role in the reversal of hypertrophy. The effect of propranolol on reversal of hypertrophy, however, is still controversial. This study describes the effect of propranolol, given alone or in combination with hydralazine in different ratios for 4 wk, on blood pressure (BP), ventricular weight, and myocardial catecholamine (MC) concentrations. The data show that a certain ratio of propranolol to hydralazine (750:30) leads to moderate BP control (196-156 mmHg) without increased MC (634 vs. 552 ng/g) and moderately reduced hypertrophy. Reduction of BP alone with increased MC (hydralazine alone) or reduction of MC without BP control (propranolol alone) failed to reduce hypertrophy. A significant correlation between both ventricular weight and heart rate with MC (r = 0.6) was obtained by multiple regression analysis. This study suggests that adrenergic factors seem to play an important role in modulating structural cardiac response to variations in arterial pressure.

Download Full-text

Long-term administration of L-arginine did not influence blood pressure, heart rate, cardiac hypertrophy or arterial wall thickness of spontaneously hypertensive rats

Experimental Physiology ◽

10.1113/expphysiol.1998.sp004141 ◽

1998 ◽

Vol 83 (5) ◽

pp. 595-603 ◽

Cited By ~ 14

Author(s):

F Kristek

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Cardiac Hypertrophy ◽

Wall Thickness ◽

Spontaneously Hypertensive Rats ◽

Arterial Wall ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Term Administration

Download Full-text

Central and baroreflex control of heart period during the wake-sleep cycle in spontaneously hypertensive rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00086.2007 ◽

2007 ◽

Vol 293 (1) ◽

pp. R293-R298 ◽

Cited By ~ 14

Author(s):

Chiara Berteotti ◽

Valentina Asti ◽

Vera Ferrari ◽

Carlo Franzini ◽

Pierluigi Lenzi ◽

...

Keyword(s):

Eye Movement ◽

Negative Correlation ◽

Spontaneously Hypertensive Rats ◽

Heart Period ◽

Hypertensive Rats ◽

Baroreflex Control ◽

Spontaneously Hypertensive ◽

Relative Contribution ◽

Central Commands ◽

Peak Value

We investigated whether the relative contribution of the baroreflex and central commands to the control of heart period differs between spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) during physiological behavior. Rats were instrumented with an arterial catheter and with electrodes for discriminating wakefulness, nonrapid eye movement sleep (NREMS), and rapid eye movement sleep (REMS). The cross-correlation function (CCF) between spontaneous fluctuations of heart period and mean arterial pressure was computed at frequencies <0.2 Hz. The baroreflex determines a positive correlation between heart period and previous pressure values. This pattern was observed in the CCF during quiet wakefulness (QW) and NREMS, and in QW, it was accompanied by a pronounced negative correlation between heart period and subsequent pressure values. The relative baroreflex contribution to the control of heart period, estimated from the positive peak value of the CCF, was lower in SHR than in WKY during QW but not during NREMS. During REMS, the CCF showed a negative correlation between heart period and both previous and subsequent pressure values, reflecting the prevalence of central autonomic commands. The relative contribution of central commands to the control of heart period, estimated from the negative peak value of the CCF, was lower in SHR than in WKY during REMS. These results suggest that during QW and REMS, the control of heart period exerted by the baroreflex and central commands, respectively, is less effective in SHR than in WKY. This difference is not apparent in a behavioral state of autonomic stability such as NREMS.

Download Full-text