A decrease in the response of beta 1 adrenergic receptors to agonists (desensitization) is thought to play a major role in the pathogenesis of diseases such as congestive heart failure. However, currently, there is no in vivo model that will enable us to measure desensitization of the hemodynamic responses to beta 1 adrenergic receptors in vivo.

Our hypothesis is that constant 3 hours intravenous infusion of the selective beta1 adrenergic receptor agonist dobutamine will result in gradual decline in hemodynamic responses to dobutamine over time.

Inclusion Criteria:

• healthy subjects

Exclusion Criteria:

• consumption of any medications during the 2 weeks prior to the study
• history of chest pain or tachycardia