Reduced Basal Ganglia μ-Opioid Receptor Availability in Trigeminal Neuropathic Pain: A Pilot Study

Abstract

BackgroundAlthough neuroimaging techniques have provided insights into the function of brain regions involved in Trigeminal Neuropathic Pain (TNP) in humans, there is little understanding of the molecular mechanisms affected during the course of this disorder. Understanding these processes is crucial to determine the systems involved in the development and persistence of TNP.FindingsIn this study, we examined the regional μ-opioid receptor (μOR) availability in vivo (non-displaceable binding potential BPND) of TNP patients with positron emission tomography (PET) using the μOR selective radioligand [11C]carfentanil. Four TNP patients and eight gender and age-matched healthy controls were examined with PET. Patients with TNP showed reduced μOR BPND in the left nucleus accumbens (NAc), an area known to be involved in pain modulation and reward/aversive behaviors. In addition, the μOR BPND in the NAc was negatively correlated with the McGill sensory and total pain ratings in the TNP patients.ConclusionsOur findings give preliminary evidence that the clinical pain in TNP patients can be related to alterations in the endogenous μ-opioid system, rather than only to the peripheral pathology. The decreased availability of μORs found in TNP patients, and its inverse relationship to clinical pain levels, provide insights into the central mechanisms related to this condition. The results also expand our understanding about the impact of chronic pain on the limbic system.

Buprenorphine maintenance and mu-opioid receptor availability in the treatment of opioid use disorder: Implications for clinical use and policy

“…Selection of relatively healthy, opioid-dependent individuals does not represent BUP patients in clinical practice, and limits generalizability of research findings. Interestingly, patients with chronic pain who are not taking opioids exhibit lower μOR availability in pain-related brain regions than controls (Harris et al, 2007; DosSantos et al, 2012), which may reflect excess endogenous opioid release during persistent nociceptive signaling. It would be informative to ascertain whether chronic pain-related variations in endogenous opioid tone alter BUP-induced changes in μOR availability and/or clinical outcomes for opioid use or pain.…”

An updated synthesis of [11C]carfentanil for positron emission tomography (PET) imaging of the μ‐opioid receptor

“…1,2 Reliable methods for quantification of [ 11 C]CFN binding are available, 3 and recent work suggests that the radiotracer binds preferentially to μ-opioid receptor subtype 1, compared 4 to subtype 2. Our physician colleagues have used [ 11 C]CFN to investigate the role of the μ-opioid system in tobacco smoking, 5 obesity and weight loss, 6 pain regulation as well as sex and genetic influences on these mechanisms, [7][8][9][10][11] social distress and reward, 12 drug addiction, 13,14 and migraine 15 and to understand emotion regulation and the pathophysiology and treatment responses in major depression. [16][17][18] We have also recently used [ 11 C]CFN to compare the effects of intranasal and intravenous administration of opioids in rhesus monkeys.…”

μ ‐Opioid activation in the prefrontal cortex in migraine attacks – brief report I

“…Recent advances in positron emission tomography (PET) with [11C]carfentanil (CFN), a selective radiotracer for lORs, have demonstrated that there is a faulty lOR availability (nondisplaceable binding potential, BPND) in chronic trigeminal pain patients in vivo, 5 but information is still lacking regarding migraine. In this ª 2014 The Authors.…”