Correction: Dreismickenbecker et al. Electroencephalography-Based Effects of Acute Alcohol Intake on the Pain Matrix. Brain Sci. 2023, 13, 1659.

This paper [...].

Electroencephalography-Based Effects of Acute Alcohol Intake on the Pain Matrix.

The effects of acute and chronic intakes of high doses of alcohol on pain perception are well known, ranging from short-term analgesic effects to long-term sensitization and polyneuropathies. The short-term analgesic effects of ethanol consumption on subjective pain perception have been well studied in the literature. Recent advances in neuroimaging allow for an insight into pain-related structures in the brain, fostering the mechanistic understanding of the processing of nociceptive input and pain. We aimed to utilize EEG, combined with standardized noxious mechanical/thermal stimulation and subjective pain testing, to research the effects of acute alcohol intake on nociceptive processing and pain perception. We recruited 12 healthy subjects in an unblinded cross-over study design and aimed at achieving a blood alcohol level of 0.1%. Our data revealed a significant reduction in subjective pain ratings to noxious thermal and mechanical stimuli after alcohol ingestion. Our EEG data revealed suppressing effects on the cortical structures responsible for processing pain, the "pain matrix". We conclude that in addition to its analgesic effects, as expressed by the reduction in subjective pain, alcohol has a further impact on the "pain matrix" and directly affects the salience to a nociceptive stimulus.

Sensory testing and topical capsaicin can characterize patients with rheumatoid arthritis.

BACKGROUND AND OBJECTIVES: Our study aimed at examining the long-time inflammatory effects of rheumatoid arthritis (RA) as chronic immune-mediated disease on pain sensation and neuropathy development compared to healthy subjects (HS). METHODS: We used the quantitative sensory testing (QST) protocol of the German Research Network on Neuropathic Pain and Electroencephalography (EEG)-based contact heat evoked potentials (CHEPs) before and after topical capsaicin application. We recruited 16 RA patients in remission or low disease activity state (mean age: 59.38 years [± 10.18]) and 16 healthy subjects (mean age: 56.69 years [± 8.92]). RESULTS: The application of capsaicin cream on the thigh provoked a stronger effect in HS for both mechanical and heat pain thresholds (MPT and HPT, resp.), according to the area under the receiver operation characteristic (AUROC) (HS: HPT: 0.8965, MPT: 0.7402; RA: HPT: 0.7012, MPT: 0.6113). We observed contrary effects regarding changes in CHEPs (HS: g*max = - 0.65; RA patients: g*max = 0.72). CONCLUSION: As the overall effect of topical capsaicin application was higher in HS for QST, we suggest the existence of a sensitization of TRPV1 channels in RA patients caused by long-time chronical inflammation, despite a lack of clinical signs of inflammation due to adequate treatment. The effect in CHEPs probably uncovers neuropathic symptoms. The effect of topical capsaicin on HPTs and CHEPs can act as a marker for the extent of sensitization and the development of neuropathic symptoms. Further studies are needed to prove if our proposed method can act as a marker for the success of anti-inflammatory treatment. Key Points • The effect of topical capsaicin may represent the extent of TRPV1 sensitization in rheumatoid arthritis. • The effect of topical capsaicin on the amplitude level of CHEPs can unmask neuropathic symptoms. • The effect of topical capsaicin on CHEPs and HPTs can show the long-term consequences and the treatment success of RA patients in remission.

A self-made, low-cost infrared system for evaluating the sciatic functional index in mice.

The sciatic functional index (SFI) is a popular parameter for peripheral nerve evaluation that relies on footprints obtained with ink and paper. Drawbacks include smearing artefacts and a lack of dynamic information during measurement. Modern applications use digitized systems that can deliver results with less analytical effort and fewer mice. However, the systems are expensive (€40,000). This study aimed to evaluate the applicability and precision of a self-made, low-cost infrared system for evaluating SFI in mice. Mice were subjected to unilateral sciatic nerve crush injury (crush group; n = 7) and sham operation (sham group; n = 4). They were evaluated on the day before surgery, the 2(nd), 4(th) and 6(th) days after injury, and then every day up to the 23(rd) day after injury. We compared two SFI evaluation methods, i.e., conventional ink-and-paper SFI (C-SFI) and our infrared system (I-SFI). Our apparatus visualized footprints with totally internally reflected infrared light (950 nm) and a camera that can only detect this wavelength. Additionally we performed an analysis with the ladder beam walking test (LBWT) as a reference test. I-SFI assessment reduced the standard deviation by about 33 percent, from 11.6 to 7.8, and cut the variance around the baseline to 21 percent. The system thus requires fewer measurement repetitions and fewer animals, and cuts the cost of keeping the animals. The apparatus cost €321 to build. Our results show that the process of obtaining the SFI can be made more precise via digitization with a self-made, low-cost infrared system.