Summary

Alpha-1 adrenergic receptors are G-protein coupled receptors that make up the sympathetic response in the autonomic nervous system. When a ligand binds to the Alpha-1 receptor, it’s corresponding Gq protein will trigger a cascade of downstream messengers, including phospholipase C, IP3, and DAG. Since alpha-1 receptors are found on smooth muscle, activation of these receptors will lead to muscle contraction, such as vasoconstriction, pupil dilation, and bladder sphincter constriction. 

Key Points

• Alpha-1 Receptors
  • Signaling
    • Use the Gq signaling pathway
  • Outcomes
    • Vasoconstriction
    • Mydriasis (pupil dilation)
    • Urinary sphincter contraction (less urine)