Comprehensive Nursing Pharmacology Q 176
All narcotics, regardless of their origin, reduce pain by:
A. Stimulating opiate receptors.
B. Promoting the release of excitatory transmitters.
C. Releasing large quantities of endorphin.
D. Blocking the mu receptors.
Correct Answer: A. Stimulating opiate receptors.
It is the stimulation of cerebral opiate receptors that reduces pain. Also, some opioid agents can affect serotonin kinetics in the presence of other serotonergic agents. The proposed mechanism for this is through either weak serotonin reuptake inhibition and increased the release of intrasynaptic serotonin through inhibition of gamma-aminobutyric acidergic presynaptic inhibitory neuron on serotonin neurons.
Option B: Excitatory transmitters are not released during administration of morphine. Presynaptically, opioids block calcium channels on nociceptive afferent nerves to inhibit the release of neurotransmitters such as substance P and glutamate, which contribute to nociception.
Option C: Endorphin release is not associated with narcotic pain relief. Since endorphins act on the opiate receptors in our brains, they reduce pain and boost pleasure, resulting in a feeling of well-being. Endorphins are released in response to pain or stress, but they’re also released during other activities, like eating, exercise, or sex.
Option D: The mu receptors mediate analgesia and are not blocked during narcotic administration. Postsynaptically, opioids open potassium channels, which hyperpolarize cell membranes, increasing the required action potential to generate nociceptive transmission. The mu, kappa, and delta-opioid receptors mediate analgesia spinally and supraspinally.