Table 1 |.

The interactive effects of age and sex on sympathetic neurocirculatory control

	Young Men	Young Women	Older Men	Older Women
Integrated MSNA	Greater than young women	Lesser than young men	Greater than young men	Greater than young women
Sympathetic AP dischargea	Rate-coding and population-coding mechanisms exist to increase total MSNA during physiological stress		Greater resting sympathetic AP discharge plus impaired AP rate-coding and population-coding during physiological stress compared to young cohort
Relationship with integrated MSNA
Blood Pressure	No relationship	No relationshipb	Positive relationship	Positive relationship
Total Peripheral Resistance	Positive relationship	No relationshipb	Positive relationship	Positive relationship
Cardiac Output	Inverse relationship	No relationship	No relationship	No relationship
Autonomic (Sympathetic) Support of Blood Pressure	Greater than young women	Lesser than young men	Greater than young men	Greater than young women and similar to older men
Neurovascular Transduction	Greater than young women	Lesser than young men	Lesser than young men	Greater than young women
Alpha-adrenergic Vasoconstriction	Inverse relationship with MSNA	Lesser than young men c	Lesser than young men	Greater than young women
Beta-adrenergic Vasodilation	Does not buffer alpha-adrenergic vasoconstriction	Buffers alpha-adrenergic vasoconstriction	Does not buffer alpha-adrenergic vasoconstriction	Lesser than young women

AP, action potential; MSNA, muscle sympathetic nerve activity.

Footnotes:

^aSex differences in sympathetic AP discharge have not been investigated. As such, male and female groups are collapsed and only age comparisons are provided.

^bBeta-adrenergic blockade produces positive relationship

^cBeta-adrenergic blockade increases alpha-adrenergic constriction