The opioid system consists of opioid receptors (which mediate the actions of
opium), their endogenous ligands (the enkephalins, endorphins, endomorphins,
dynorphin, and nociceptin), and the proteins involved in opioid production,
transport, and degradation. PET tracers for the various opioid receptor subtypes
are available, and changes in regional opioidergic activity have been assessed
during both sensory and affective processing in healthy individuals and in various disease conditions such as chronic pain, neurodegeneration, epilepsy, eating disorders, behavioral addiction, and substance abuse. It is not always clear whether observed changes of tracer binding reflect altered release of endogenous opioids or altered opioid receptor expression. This issue may be resolved by studies in experimental animals that combine in vivo PET imaging with ex vivo immunohistochemistry. Some radioligands for opioid receptors have suboptimal kinetics (i.e., slow dissociation from their target protein) or can induce undesired side effects even at low administered doses (sedation, respiratory arrest). Yet, PET offers the unique opportunity of quantifying opioid receptor-mediated signaling in the living human brain. PET imaging has provided evidence for a link between opioid neurotransmission and peripheral immune activation.
Original languageEnglish
Title of host publicationPET and SPECT of Neurobiological Systems
EditorsRudi Dierckx, Andreas Otte, Erik de Vries, Aren van Waarde, Adriaan Lammertsma
Place of PublicationCham
PublisherSpringer Nature
Number of pages59
ISBN (Electronic)978-3-030-53176-8
ISBN (Print)978-3-030-53175-1 , 978-3-030-53178-2
Publication statusPublished - 2021


  • Positron Emission Tomography (PET)
  • Human Brain
  • Radiopharmaceuticals
  • Pain
  • Personality Traits
  • Feeding Behavior
  • Affective responses
  • Physical Exercise
  • Receptor occupancy
  • Obesity
  • Substance abuse
  • Eating disorders
  • Epilepsy
  • Neurodegenerative diseases
  • Posttraumatic stress disorder
  • Borderline personality disorder
  • Major depressive disorder

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