Adrenergic Agonists Practice Test

Alpha-1 adrenergic receptors are linked to Gq proteins. When activated, they stimulate phospholipase C, which cleaves PIP2 into IP3 and DAG. IP3 releases calcium from the endoplasmic reticulum, increasing intracellular calcium, while DAG helps activate protein kinase C in concert with Ca2+. This rise in Ca2+ drives responses like smooth muscle contraction. Other adrenergic pathways use different second messengers (cAMP via Gs or Gi, or cGMP), which is why those options don’t fit the α1 mechanism.