Which of the following is the mechanism of action of salbutamol

  1. Activation of beta 1 receptors resulting in increased adenylyl cyclase activity, increasing cAMP
  2. Activation of beta 2 receptors resulting in increased adenylyl cyclase activity, increasing cAMP
  3. Activation of beta 2 receptors resulting in increased IP3 and DAG
  4. Binds to receptor tyrosine kinases resulting in dimerization