 The splanchnic circulation contains a highly compliant venous bed which normally stores 25 of the blood volume, and receives up to 25 of the resting cardiac output. It is highly innervated by the sympathetic nervous system, and this neural regulation results in large volume shifts that modulate blood pressure BP. The splanchnic circulation may play a role in hypertension as suggested by studies showing that surgical splanchnic denervation effectively lowered BP in hypertensive subjects without affecting renal function. Recently, studies in animal models have shown that splanchnic sympathetic activation, particularly to capacitance vessels, was critical to the development of hypertension. The clinical translation of these findings to human hypertension has lagged behind because of limitations in previously available experimental approaches. The investigators propose to use splanchnic radionuclide plethysmography and sympathetic withdrawal with the ganglionic blocker trimethaphan to overcome these limitations. 