Opioids · Pharmacology

Which of the following is the primary mechanism of action for morphine at the cellular level?

  1. Activation of Gs-coupled receptors that raises intracellular cAMP levels
  2. Inhibition of adenylyl cyclase and opening of potassium channels
  3. Direct blockade of voltage-gated sodium channels
  4. Antagonism of NMDA glutamate receptors in the spinal cord
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Correct answer: Inhibition of adenylyl cyclase and opening of potassium channels

Opioids bind to G protein-coupled receptors (primarily Mu). This leads to the inhibition of adenylyl cyclase, decreased cAMP, the opening of postsynaptic potassium channels (hyperpolarization), and the closing of presynaptic calcium channels, effectively inhibiting neurotransmitter release.

Difficulty: Medium Question 1 of 20

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