Pain
-
Next-generation transcriptomics in combination with imaging-based approaches have emerged as powerful tools for the characterization of dorsal root ganglion (DRG) neuronal subpopulations. The mouse DRG has been well characterized by many independently conducted studies with convergent findings, but few studies have directly compared expression of population markers between mouse and human. This is important because of our increasing reliance on the mouse as a preclinical model for translational studies. ⋯ We found a large overlapping CGRP and P2X3R neuronal subpopulation in human, lumbar DRG that was not present in mouse. We also found differential expression in a variety of mRNAs for transient receptor potential channels, cholinergic receptors, potassium channels, sodium channels, and other markers/targets. These data offer insights into the spatial and functional organization of neuronal cell subpopulations in the rodent and human DRG and support the idea that sensory system organizational principles are likely different between both species.
-
Our goal was to examine the association between mental health disorders (MHD) and subsequent risk of opioid use among commercially insured youth and adults (aged 14-64 years) with comorbid chronic noncancer pain (CNCP) conditions. We conducted a retrospective cohort study using IQVIA Health Plan Claims database from January 1, 2006, to December 31, 2015. Chronic noncancer pain was defined as any diagnosis of back, head, neck, arthritis, or chronic pain (index date). ⋯ After adjusting for demographic and clinical factors, individuals with comorbid CNCP and MHD were significantly more likely to be prescribed opioids compared to those with only CNCP conditions. This effect varied by average daily dose and days supply: acute/low dose (1.08; 1.07-1.08); chronic/low dose (1.49; 1.49-1.50); acute/medium dose (1.07; 1.07-1.08); chronic/medium dose (1.61; 1.61-1.62); acute/high dose (1.03; 1.02-1.03); and chronic/high dose (1.53; 1.53-1.54). In individuals with CNCP, having a MHD was a strong predictor of prescription opioid use, particularly chronic use.
-
Diseases and disorders such as Parkinson disease, schizophrenia, and chronic pain are characterized by altered mesolimbic dopaminergic neurotransmission. Dopamine release in the nucleus accumbens influences behavior through both tonic and phasic signaling. Tonic dopamine levels are hypothesized to inversely regulate phasic signals through dopamine D2 receptor feedback inhibition. ⋯ These findings occurred independently of stimulus lateralization relative to the hemisphere of dopamine measurement. Our data show that (1) the mesolimbic dopamine circuit reliably encodes acute noxious stimuli; (2) ongoing pain produces decreases in dopaminergic tone; and (3) pain-induced decreases in tonic dopamine correspond to augmented evoked phasic dopamine release. Enhanced phasic dopamine neurotransmission resulting from salient stimuli may contribute to increased impulsivity and cognitive deficits often observed in conditions associated with decreased dopaminergic tone, including Parkinson disease and chronic pain.
-
We aimed to investigate whether small-fibre pathology, a common skin biopsy finding in patients with fibromyalgia, implies clinically important abnormalities of somatosensory system function and verify whether it is associated with voltage-gated sodium channel variants. In 57 consecutively enrolled patients with fibromyalgia, we used skin biopsy to distinguish patients with and without small-fibre pathology. In all patients, we assessed somatosensory system function using quantitative sensory testing (QST) and laser-evoked potentials and investigated voltage-gated sodium channel genotyping. ⋯ The SCN9A variant, found in a patient with small-fibre pathology, was an already profiled gain-of-function mutation, previously reported in small-fibre neuropathy. Our findings suggest that small-fibre pathology has a negligible impact on somatosensory system function in fibromyalgia. The genetic analysis suggests that patients with rare small-fibre neuropathy due to voltage-gated sodium channel variants may be misdiagnosed as patients with fibromyalgia.