Risks associated with oral atenolol use: Therapeutic dose of atenolol ranges from 50 mg to 200 mg per day. Common side effects of chronic atenolol therapy include tiredness (26%), dizziness (13%), depression (12%), cold, tingling, or numbness in the hands or feet (12%), and shortness of breath (6%). Other common adverse effects of atenolol include slow heart rate (bradycardia), a decrease in blood pressure when going from a lying-down or sitting position to standing, a spinning sensation (vertigo), lightheadedness, diarrhea, and nausea. We will use a low dose of atenolol (25 mg) in this study to minimize the risk of occurrence of these adverse effects. Rare (< 1%) side effects of therapeutic doses of atenolol include an increase in liver enzymes, allergic reactions, headache, impotence (also known as erectile dysfunction), Peyronie's disease, worsening of psoriasis, reversible hair loss, vision problems, dry mouth, Raynaud's phenomenon, unexplained rash, and dry eyes. These adverse effects are not anticipated with a single low dose of atenolol that will be administered to our volunteers.