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This laboratory recently reported that the blood pressure and muscle sympathetic nerve activity (MSNA) responses to cold pressor testing are greater in normotensive blacks than in age- and weight-matched normotensive whites. The present study was designed to determine the relationship between race, family history of hypertension, and sympathetic response to cold pressor testing. The study used microneurography to measure MSNA responses to cold pressor testing in normotensive blacks with (n = 8) and without (n = 8) and normotensive white subjects with (n = 8) and without (n = 10) a positive family history of hypertension. Resting blood pressure was lower in black subjects without a positive family history of hypertension but otherwise resting blood pressure, heart rate, and MSNA were similar in the four groups. Black subjects with a family history of hypertension manifested a greater increase in blood pressure and MSNA than both white groups. Blood pressure and sympathetic responses of black subjects with a negative family history of hypertension tended to be intermediate and were not statistically different from the other three groups. These results indicate that the greater sympathetic response to cold stress observed in normotensive African-Americans is true only of black subjects with a positive family history of hypertension.

Objective: To compare muscle sympathetic nerve activity (MSNA) in age- and weight-matched African-Americans and American Caucasians with primary hypertension., Design: Using microneurography, we compared MSNA at rest and in response to cold-pressor testing and handgrip exercise in 13 hypertensive African-Americans and 12 hypertensive American Caucasians., Methods: All subjects were withdrawn from antihypertensive medications for at least 2 weeks before the study. MSNA was recorded from the left peroneal nerve., Results: Resting MSNA was similar in the Blacks and the Caucasians. Increases in muscle efferent activity, mean arterial pressure and heart rate in response to the cold pressure and handgrip exercise were not significantly different in Black and in Caucasian subjects., Conclusion: MSNA, either at rest or in response to certain laboratory stressors, is not different in Black and in Caucasian hypertensive subjects with similar resting blood pressures.

The purpose of this study was to compare sympathetic nerve activity responses to the cold pressor test in black and white normotensive subjects. We recorded muscle sympathetic nerve activity (microneurography of the peroneal nerve), arterial blood pressure, and heart rate in 9 normotensive American blacks (24 +/- 2 years, mean +/- SEM) and 10 normotensive American whites (28 +/- 2 years) at rest and during hand immersion in ice water (cold pressor test). Body weight was not different in the two groups (72.4 +/- 3.7 versus 74.1 +/- 3.8 kg, black versus white subjects). During supine rest, mean arterial pressure (92 +/- 2 versus 93 +/- 3 mm Hg, black versus white), heart rate (66 +/- 4 versus 62 +/- 3 beats per minute, black versus white), and muscle sympathetic nerve burst frequency (12 +/- 2 versus 17 +/- 3 bursts per minute, black versus white) were not different in the two groups. During the cold pressor test, mean arterial pressure, heart rate, and muscle sympathetic nerve activity increased from supine rest in both groups. The magnitudes of increases in mean arterial pressure and total minute muscle sympathetic nerve activity were significantly greater in blacks than whites (33.5 +/- 3 versus 22.4 +/- 3 mm Hg and 416 +/- 24% versus 243 +/- 31% of control, respectively, black versus white, P < .05). The increases in heart rate were most significantly different for the two groups. These data suggest that the enhanced pressor response to cold stress observed in normotensive blacks is attributable to greater increases in peripheral sympathetic nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)