A 65-year-old woman is admitted to the intensive care unit (ICU) of the hos- pital with sepsis caused by a urinary tract infection. She is hypotensive, with a blood pressure of 80/40 mm Hg and has an elevated heart rate (tachycardia) and decreased urine output (oliguria). Along with the institution of appropri- ate antibiotic therapy and IV fluids, a decision is made to start her on an IV infusion of dopamine to attempt to raise her blood pressure.
1) What effects can be expected with low-dose dopamine?
2) Which receptors mediate these effects?
3) What effects occur with higher dose dopamine and which receptors mediate these?