Pain and Anti-Pain Pathways

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Questions and Answers

Which neurotransmitter is NOT mentioned as blocking the transmission of pain signals at the 'pain gate'?

  • Serotonin
  • Opiates
  • Norepinephrine
  • Dopamine (correct)

Which of the following is used to reverse an overdose?

  • Pentazocine
  • Tramadol
  • Buprenorphine
  • Naloxone (correct)

Opioids can help influence cognitive and emotional processing.

True (A)

Fentanyl and its derivatives are less potent than morphine.

<p>False (B)</p> Signup and view all the answers

What is the function of endorphins?

<p>Analgesia, sleep regulation, and modulation of emotional responses.</p> Signup and view all the answers

What effect does naltrexone have on heroin?

<p>Renders heroin ineffective</p> Signup and view all the answers

Opium is derived from the juice of the ______ plant.

<p>poppy</p> Signup and view all the answers

Match the following opioid receptors with their respective endogenous ligands:

<p>MU = Endorphin KAPPA = Dynorphin DELTA = Enkephalin</p> Signup and view all the answers

_______ is a weak Mu antagonist combined with Kappa Agonists and serves as an analgesic.

<p>Pentazocine</p> Signup and view all the answers

What is the primary use of gabapentin and pregabalin?

<p>Decrease nociceptor excitation (D)</p> Signup and view all the answers

Match the following medications with their respective classifications:

<p>Buprenorphine = Partial Mu Agonist Naloxone = Mu Antagonist Tramadol = Mixed Agonist Pentazocine = Mixed Agonist - Antagonist</p> Signup and view all the answers

Which of the following statements about Suboxone is correct?

<p>It is a combination of buprenorphine and naloxone. (D)</p> Signup and view all the answers

Laudanum is a mixture of opioids and caffeine.

<p>False (B)</p> Signup and view all the answers

Partial Mu Agonists have a higher risk of respiratory depression compared to full agonists.

<p>False (B)</p> Signup and view all the answers

Name one effect of kappa receptors when activated.

<p>Analgesia or dysphoria.</p> Signup and view all the answers

Flashcards

Pain Pathway

The route pain signals travel from sensory nerve endings to brain regions processing pain and the feeling associated with pain.

Opioid Receptors

Specialized protein binding sites in the brain and body, including the spinal cord, that respond to endogenous (produced by the body) or exogenous (drug-derived) opioids.

Analgesia

The relief or lessening of pain.

Mu Opioid Receptor

A type of opioid receptor known for a strong influence on pain and pleasure pathways particularly when activated by exogenous opioids.

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Endogenous Opioid

Substances naturally produced within the body that bind to opioid receptors.

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Opiate

A class of drugs derived from opium poppy plant.

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Descending Antinociceptive Pathways

Brain pathways that can suppress pain signals traveling up the spinal cord.

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Opioid Agonist

A drug that activates opioid receptors.

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Morphine

An opioid pain reliever with high potency

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Naloxone (Narcan)

Drug used to reverse opioid overdoses

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Partial Mu Agonist

Medication that limits respiratory problems and drug abuse (less addiction)

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Buprenorphine (Subutex)

A partial mu agonist used to treat opioid addiction

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Suboxone

Combination of buprenorphine and naloxone

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Fentanyl

Powerful opioid, much stronger than morphine

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Naltrexone

Opioid blocker, taken to prevent opioid use

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Study Notes

Pain Pathways

  • Pain signals travel from free nerve endings to the spinal cord, then to the thalamus, and finally to the somatosensory cortex (location of pain).
  • Emotional and cognitive aspects of pain are processed through free nerve endings, spinal cord, thalamus, hippocampus, amygdala, and cingulate cortex.

Anti-Pain Pathways

  • Anti-pain pathways originate in the midbrain.
  • Serotonin and norepinephrine block pain signals at the "pain gate."
  • Opioids enhance the effect of serotonin and norepinephrine.

Decreasing Pain with Drugs

  • Reducing inflammation (aspirin, NSAIDs)
  • Inhibiting nociceptor excitation (gabapentin, pregabalin)
  • Decreasing neurotransmitter release (opioids)
  • Activating anti-pain pathways (antidepressants, opioids)
  • Influencing cognitive and emotional processing (opioids)

Terminology

  • Opium: Juice of the opium poppy.
  • Narcotic: Any drug inducing sleep.
  • Opiate: Drug extracted from opium (e.g., morphine, codeine).
  • Opioid: Endogenous ligand binding opioid receptors (e.g., endorphins, enkephalins, dynorphins); now used for both natural and synthetic drugs targeting opioid receptors.

Opium Source and History

  • Found in the Papaver somniferum plant.
  • Native to Eurasia.
  • Used for approximately 7000 years.
  • Combined with alcohol to make laudanum.
  • Hypodermic injection (1856) led to issues (e.g., "soldiers' disease").

Opioids (e.g., enkephalin)

  • Functions: Analgesia, sleep, antitussive, regulates intestinal motility.
  • Synthesis: Made from precursor polypeptides, cleaved by proteases.
  • Examples of precursor-product pairs: POMC → Endorphin, Proenkephalin → Enkephalin, Proendorphin → Endorphin, Dynorphin.
  • Receptors: Metabotropic (MU, KAPPA, DELTA).
  • Endogenous ligands: Endorphin, Dynorphin, Enkephalin.
  • Exogenous ligands: Morphine, Naloxone, Salvinorin A, Pentazocine (weak mu agonist), Kratom (partial mu agonist).

Opioid Drugs

  • Pure Agonists (mu): Morphine, codeine, heroin, methadone, meperidine (Demerol), Fentanyl (80-500x more potent than morphine).
  • Mu antagonists: Naloxone (Narcan; overdose reversal), Naltrexone (ReVia, Trexan; treatment to curb heroin effectiveness).
  • Partial Mu Agonists: Buprenorphine (Subutex), Tramadol (Ultram; blocks norepinephrine reuptake, releases serotonin, active metabolite extends effects).
  • Mixed Agonist-Antagonists: Pentazocine (Talwin; analgesic but dysphoria limits usefulness).
  • Suboxone: Buprenorphine + naloxone (orally inactive naloxone, active injected form).

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