Renal function, heart rate, and blood pressure during exercise and avoidance in dogs

Grignolo, Alberto; Koepke, J P; Obrist, P. A.

doi:10.1152/ajpregu.1982.242.5.r482

Cited by 12 publications

(11 citation statements)

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“…In the first study, 5 three of six conscious, saline-infused dogs decreased U Na V during SNS arousal, demonstrating individual differences in the response patterns as we found in our subjects. In a second study, 6 nine dogs increased and 21 dogs decreased U Na V during SNS arousal.…”

Section: Figure 2 Line Graphs Showing Patterns Of Plasma Renin Activsupporting

confidence: 71%

Patterns of sodium excretion during sympathetic nervous system arousal.

1991

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The purpose of this study was to examine Na + handling and regulation during 1 hour of behaviorally induced sympathetic nervous system (SNS) arousal followed by 2 hours of recovery. Two patterns of response were observed among experimental subjects, despite similar changes in blood pressure and heart rate. In one group (n=19), Na + excretion increased significantly during SNS arousal, which then decreased significantly during recovery (12-3 versus 16.0 versus 13.1 meq/hr, baseline, SNS arousal, recovery, respectively). Changes in Na + excretion were correlated with changes in creatinine clearance from baseline to SNS arousal (r=0.54) and SNS arousal to recovery (r=0.58), and were accompanied by significant increases in plasma renin activity (1.5 versus 2.0 ng/ml/hr) and aldosterone (8.5 versus 10J ng/ml/hr) from baseline to SNS arousal. Na + excretion decreased during SNS arousal in the other group of subjects (n=17) and remained below baseline levels during recovery (162 versus 12.7 versus 11.9 meq/hr). These changes were associated with significant decreases in creatinine clearance from baseline to recovery (138 versus 121 ml/min/1.73 m 2 ) and significant increases in plasma renin activity from baseline to SNS arousal (13 versus 2.2 ng/ml/hr) but not in aldosterone. Control subjects in =24) maintained baseline levels of each variable throughout the procedure. These results suggest that individuals differ in Na + handling and regulation during behavioral arousal. Decreases in Na + have been reported previously in humans and animals at risk for the development of hypertension. {Hypertension 1991;17:1156-1160) G uyton 1 has proposed that the renal-body fluid system is responsible for the long-term regulation of blood pressure (BP). Based on this model, increases in BP will cause the kidneys to increase the excretion of both salt (pressure natriuresis) and water (pressure diuresis), decreasing extracellular fluid volume and blood volume. This decreases cardiac output, which returns BP to previous levels. Conversely, decreases in BP increase Na + and water reabsorption, increasing cardiac output and returning BP to previous levels. The research of DiBona 2 and others 3 -9 is consistent with the hypothesis that the sympathetic nervous system (SNS) can influence the renal-body fluid system through direct actions on the renal tubules, changes in renal blood flow and glomerular filtration rate, and changes in plasma renin activity (PRA). PRA controls circulating levels of angiotensin II, which directly stimulates the renal tubules, and leads to the release of aldosterone, both of which promote Na + retention. The

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Section: Figure 2 Line Graphs Showing Patterns Of Plasma Renin Activsupporting

confidence: 71%

Patterns of sodium excretion during sympathetic nervous system arousal.

1991

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“…Previous studies of avoidance conditioning have reported acute decreases in renal blood flow, 22 decreases in renal excretion of sodium and water, 12 and increases in plasma renin activity." In the present experiments, avoidance sessions consumed only 90 minutes of the 24-hour day.…”

Section: Discussionmentioning

confidence: 98%

Progressive hypertension in dogs by avoidance conditioning and saline infusion.

Anderson¹,

Kearns²,

Better³

1983

Hypertension

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SUMMARY A group of dogs was trained on a free-operant avoidance-conditioning task that evoked acute increases in arterial pressure and heart rate during each of three daily 30-minute sessions. After 15 days of exposure to this procedure under conditions of normal sodium intake, 24-hour mean levels of arterial pressure remained unchanged. Another group of dogs received continuous intrarterial infusion of isotonlc saline at a constant rate of 185 mEq/24 hrs for 15 days, but no avoidance sessions. Again, 24-hour mean levels of arterial pressure did not change significantly. However, 24-hour mean levels of systolic (19.5 ± 6.2 mm Hg) and diastolic (13.7 ± 2.9 mm Hg) pressure rose progressively over a 15-day period in a third group of dogs exposed concurrently to the avoidance schedule and saline infusion procedure. The progressive hypertension was accompanied by no consistent changes in heart rate. These experiments indicate that behavioral stress can potentiate sodium hypertension and provide a new method for the study of physiological and behavioral factors in long-term blood pressure control. (Hypertension 5:286-291, 1983) KEY WORDS • arterial pressure * avoidance conditioning • dogs * heart rate • hypertension • sodium D EVELOPMENT of a model of chronic experimental hypertension in large animals with intact renal functions has remained a formidable experimental challenge. Attempts to produce a "neurogenic" hypertension in primates by exposure to avoidance conditioning over periods of months have been successful on occasion, 1 -2 but other studies 3 -4 have been unable to replicate these results and have concluded that long-term elevations in blood pressure do not result from intermittent evocation of cardiovascular "defense" reflexes alone. Similarly, long-term increases in salt intake can produce sustained hypertension in rodents, 5 but the preponderance of evidence indicates that hypertension is very difficult to produce in larger animals by salt loading procedures. 6Over the past several years, studies in our laboratory have led to the hypothesis that a combination of avoid- ance conditioning and saline infusion could generate a reliable model of chronic experimental hypertension. These studies and others 7 " 1 ' have shown that free-operant avoidance conditioning procedures are associated with characteristic cardiovascular changes in chronically-instrumented dogs during intervals of hours immediately preceding, as well as during avoidance-performance sessions. The pre-avoidance response consists of a progressive rise in arterial pressure mediated solely by increases in total peripheral resistance, while heart rate and cardiac output remain stable or decrease. This response appears to be a peripheral concomitant of attention to the environment, since it occurs only in well-trained dogs who have learned to quietly await the onset of the avoidance session, and then initiate avoidance behavior promptly following the onset of the stimulus. By contrast, the avoidance performance session is associated with a ...

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“…Abnormal retention of sodium may contribute to hypertension in other ways as well (3). Studies in the dog (4) and rat (5) show that psychological stress reduces renal excretion of sodium and fluid. This stress-induced retention is greater among young spontaneously hypertensive rats than among rats with no genetic predisposition for hypertension (5).…”

Section: Psychological Stress Induces Sodium and Fluid Retention In Mmentioning

confidence: 99%

“…Reports that stressful mental tasks increase plasma renin activity and decrease renal blood flow in certain individuals, particularly those with one or two hypertensive parents and those showing high heart rate responses to stress, suggest but do not demonstrate that excretion of sodium and fluid may be reduced (6)(7)(8). High heart rate response in humans reflects enhanced sympathetic nervous system activity during competitive and other mental tasks (7); in animals, stressinduced sodium retention is sympathetically mediated (4,5). The purpose of the present study was to determine whether exposing young men to competitive mental stress reduces their excretion of sodium and fluid, and whether any observed reductions are greater among those with known risk factors for hypertension [for example, parental or borderline hypertension (9, 10)] or those demonstrating high heart rate responses to stress.…”

Section: Psychological Stress Induces Sodium and Fluid Retention In Mmentioning

confidence: 99%

Psychological Stress Induces Sodium and Fluid Retention in Men at High Risk for Hypertension

Light

Koepke

Obrist

et al. 1983

Science

207

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Exposure to competitive mental tasks significantly reduced the urinary sodium and fluid excreted by young men with one or two hypertensive parents or with borderline hypertension. In this high-risk group, the degree of retention was directly related to the magnitude of heart rate increase during stress, suggesting common mediation by way of the sympathetic nervous system. Thus, psychological stress appears to induce changes in renal excretory functions that may play a critical role in long-term blood pressure regulation.

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Renal function, heart rate, and blood pressure during exercise and avoidance in dogs

Cited by 12 publications

References 0 publications

Patterns of sodium excretion during sympathetic nervous system arousal.

Patterns of sodium excretion during sympathetic nervous system arousal.

Progressive hypertension in dogs by avoidance conditioning and saline infusion.

Psychological Stress Induces Sodium and Fluid Retention in Men at High Risk for Hypertension

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