Altered Dopamine Responses to Monetary Rewards in Female Fibromyalgia Patients with and without Depression: A [11C]Raclopride Bolus-plus-Infusion PET Study

Replication of neural responses to monetary incentives and exploration of reward-influenced network connectivity in fibromyalgia

Neuroimaging research has begun to implicate alterations of brain reward systems in chronic pain. Previously, using functional magnetic resonance imaging (fMRI) and a monetary incentive delay (MID) task, Martucci et al. (2018) showed that neural responses to reward anticipation and outcome are altered in fibromyalgia. In the present study, we aimed to test the replicability of these altered neural responses to reward in a separate fibromyalgia cohort. In addition, the present study was conducted at a distinct U.S. location but involved a similar study design. For the present study, 20 patients with fibromyalgia and 20 healthy controls participated in MID task fMRI scan procedures and completed clinical/psychological questionnaires. fMRI analyses comparing patient and control groups revealed a consistent trend of main results which were largely similar to the prior reported results. Specifically, in the replication fibromyalgia cohort, medial prefrontal cortex (MPFC) response was reduced during gain anticipation and was increased during no-loss (non-punishment) outcome compared to controls. Also consistent with previous findings, the nucleus accumbens response to gain anticipation did not differ in patients vs. controls. Further, results from similarly-designed behavioral, correlational, and exploratory analyses were complementary to previous findings. Finally, a novel network-based functional connectivity analysis of the MID task fMRI data across patients vs. controls implied enhanced connectivity within the default mode network in participants with fibromyalgia. Together, based on replicating prior univariate results and new network-based functional connectivity analyses of MID task fMRI data, we provide further evidence of altered brain reward responses, particularly in the MPFC response to reward outcomes, in patients with fibromyalgia.

Relationship between behavioral and mood responses to monetary rewards in a sample of Indian students with and without reported pain

Physical pain has become a major health problem with many university students affected by it worldwide each year. Several studies have examined the prevalence of pain-related impairments in reward processing in Western, Educated, Industrialized, Rich, and Democratic (WEIRD) countries but none of the studies have replicated these findings in a non-western cultural setting. Here, we aimed to investigate the prevalence of physical pain symptoms in a sample of university students in India and replicate our previous study conducted on university students in Switzerland, which showed reduced mood and behavioral responses to reward in students with significant pain symptoms. We grouped students into a sub-clinical (N = 40) and a control group (N = 48) to test the association between pain symptoms and reward processes. We used the Fribourg reward task and the pain sub-scale of the Symptom Checklist (SCL-27-plus) to assess physical symptoms of pain. We found that 45% of the students reported high levels of physical symptoms of pain and interestingly, our ANOVA results did not show any significant interaction between reward and the groups either for mood scores or for outcomes related to performance. These results might yield the first insights that pain-related impairment is not a universal phenomenon and can vary across cultures.

Understanding and restoring dopaminergic function in fibromyalgia patients using a mindfulness-based psychological intervention: a [18F]-DOPA PET study. Study protocol for the FIBRODOPA study—a randomized controlled trial

Background

Fibromyalgia (FM) is a very prevalent and debilitating chronic pain disorder that is difficult to treat. Mindfulness-based techniques are regarded as a very promising approach for the treatment of chronic pain and in particular FM. The Mindfulness-Oriented Recovery Enhancement (MORE) intervention, a mindfulness-based group intervention, has shown beneficial effects in opioid-treated chronic pain patients, including reduced pain severity, functional interference, and opioid dosing, by restoring neurophysiological and behavioral responses to reward. The first evidence for a hypodopaminergic state and impaired reward processing in FM has been reported. However, little is known about its impact on dopamine (DA) function and in particular with regard to DA responses to monetary reward in FM. The aim of the present study protocol is to evaluate if MORE is able to restore the DA function in FM patients, in particular with regard to the DA responses to reward, and to reduce pain and mood complaints in FM.

Methods

The present study is a multi-center interventional RCT with 3 time points: before the intervention, after completion of the intervention, and 3 months after completion of the intervention. Sixty-four FM patients will be randomly assigned to either the MORE intervention (N = 32) or a non-intervention control group (N = 32). Additionally, a comparison group of healthy women (N = 20) for PET measures will be enrolled and another group of healthy women (N = 15) will do the ambulatory assessments only. The MORE intervention consists of eight 2-h-long group sessions administered weekly over a period of 8 weeks. Before and after the intervention, FM participants will undergo [18F] DOPA positron emission tomography (PET) and functional MR imaging while performing a reward task. The primary outcome will be endogeneous DA changes measured with [18F] DOPA PET at baseline, after the intervention (after 8 weeks for the non-intervention control group), and at 3 months’ follow-up. Secondary outcomes will be (1) clinical pain measures and FM symptoms using standardized clinical scales; (2) functional brain changes; (3) measures of negative and positive affect, stress, and reward experience in daily life using the ambulatory assessment method (AA); and (4) biological measures of stress including cortisol and alpha-amylase.

Discussion

If the findings of this study confirm the effectiveness of MORE in restoring DA function, reducing pain, and improving mood symptoms, MORE can be judged to be a promising means to improve the quality of life in FM patients. The findings of this trial may inform health care providers about the potential use of the MORE intervention as a possible non-pharmacological intervention for FM.

Trial registration

ClinicalTrials.govNCT 04451564. Registered on 3 July 2020. The trial was prospectively registered.

The role of dentate gyrus dopaminergic receptors in the lateral hypothalamic-induced antinociception during persistent inflammatory pain in male rats

The lateral hypothalamus (LH) is one of the key brain areas involved in pain modulation. Also, the dentate gyrus (DG) of the hippocampus expresses various receptors, including dopaminergic receptors. Dopaminergic receptors play a key role in pain transmission and modulation within the brain. The present study aimed to investigate the involvement of DG dopaminergic receptors in the LH-induced antinociception during the presence of inflammatory pain. Male Wistar rats were used in this study. Cannulae were unilaterally implanted in their skull for microinjections into the LH and DG. The LH was chemically stimulated by carbachol injection (250 nM/0.5 μl saline). In separate groups, different doses (0.25, 1, and 4 μg/0.5 μl vehicle) of the D1- and D2-like dopamine receptor antagonists (SCH23390 and Sulpiride, respectively) were microinjected into the DG, 5 min prior to intra-LH injection of carbachol. Five min after the second injection, formalin test as a persistent inflammatory pain model in animals was done in all rats. The results revealed that carbachol could induce antinociception following formalin injection into rat's hind paw. The 4 μg dose of both antagonists significantly reduced the LH stimulation-induced antinociception in both phases of formalin pain responses. Although the 1 μg dose of sulpiride significantly reduced antinociception during both phases, 1 μg SCH23390 could only reduce this antinociception during the late phase. These findings demonstrate the involvement of DG dopaminergic receptors in the LH-induced antinociception. The results also suggest that the effectiveness of DG dopaminergic receptors is more pronounced during the late phase of formalin-induced pain responses.

Perception of repeated pain relief with controllable and uncontrollable pain

BACKGROUND

The ultimate goal of pain research is to provide effective routes for pain relief. Nevertheless, the perception pain relief as a change in pain intensity and un-/pleasantness has only been rarely investigated. It has been demonstrated that pain relief has rewarding and reinforcing properties, but it remains unknown whether the perception of pain relief changes when pain reductions occur repeatedly. Further, it remains an open question whether the perception of pain relief depends on the controllability of the preceding pain.

METHODS

In this study, healthy volunteers (N = 38) received five cycles of painful heat stimulation and reduction of this stimulation to a non-painful warm stimulation once in a condition with control of the stimulation and once without control. Participants rated perceived intensity and un-/pleasantness on visual analogue scales during the heat stimulation and immediately after its reduction.

RESULTS

Results showed that perceived pain relief, estimated by the difference in ratings during ongoing heat stimulation and after its reduction, increased with repetitions. However, this increase levelled off after two to four repetitions. Further, perceived pain relief was larger in the condition without control compared to the condition with control.

CONCLUSION

The perception of pain relief can be modulated similar to the perception of pain by stimulus characteristics and psychological factors. Mechanistic knowledge about such modulating factors is important, because they can determine, e.g., the amount of requested pain killers in clinical settings and the efficacy of pain relief as a reinforcing stimulus.

SIGNIFICANCE

When in pain, pain relief can become an all-dominate goal. The perception of such pain relief can vary depending on external and internal characteristics and thus modulate, e.g., requests for pain killers in clinical settings. Here, we show that perceived intensity and pleasantness of pain relief changes with repetitions and whether the preceding pain is perceived as uncontrollable. Such mechanistic knowledge needs to be considered to maximize the effects of pain relief as a rewarding and reinforcing stimulus.

Phoneutria nigriventer Tx3-3 peptide toxin reduces fibromyalgia symptoms in mice

Fibromyalgia is characterized by the amplification of central nervous system pain with concomitant fatigue, sleep, mood disorders, depression, and anxiety. It needs extensive pharmacological therapy. In the present study, Swiss mice were treated with reserpine (0.25 mg/kg, s.c.) over three consecutive days, in order to reproduce the pathogenic process of fibromyalgia. On day 4, the administrations of the Tx3-3 toxin produced significant antinociception in the mechanical allodynia (87.16% ±12.7%) and thermal hyperalgesia (49.46% ± 10.6%) tests when compared with the PBS group. The effects produced by the classical analgesics (duloxetine 30 mg/kg, pramipexole 1 mg/kg, and pregabalin 30 mg/kg, p.o., respectively) in both of the tests also demonstrated antinociception. The administrations were able to increase the levels of the biogenic amines (5-HTP and DE) in the brain. The treatments with pramipexole and pregabalin, but not duloxetine, decreased the immobility time in the FM-induced animals that were submitted to the forced swimming test; however, the Tx3-3 toxin (87.45% ± 4.3%) showed better results. Taken together, the data has provided novel evidence of the ability of the Tx3-3 toxin to reduce painful and depressive symptoms, indicating that it may have significant potential in the treatment of FM.

5'UTR polymorphism in the serotonergic receptor HTR3A gene is differently associated with striatal Dopamine D2/D3 receptor availability in the right putamen in Fibromyalgia patients and healthy controls-Preliminary evidence

BACKGROUND

Extensive literature has investigated the role of serotonin (5-HT) in the control of the central dopamine (DA) systems, and their dysfunction in the pathological conditions. 5-HT stimulates the local DA release in striatal regions via activation of various receptors including serotonin receptor-3 (5-HT3). Several studies have related polymorphisms (SNPs) in the serotonin receptor-3 (HTR3) genes to be associated with the pain modulation and endogenous pain suppression. A few studies suggested a functional role of 5'UTR SNP in the serotonergic receptor HTR3A gene (rs1062613) in the development of the chronic pain and Fibromyalgia syndrome (FMS) in particular. Here, we investigated the effect of a 5'UTR SNP in the serotonergic receptor HTR3A gene (rs1062613) on striatal dopamine D2/D3 receptor (DRD2) availability and reward-associated DA release in response to unpredictable monetary rewards in 23 women with FMS and 17 age-matched healthy female controls. Furthermore, we aimed to examine if SNP rs1062613 is associated with thermal pain and pain tolerance thresholds.

METHODS

We used PET and [¹¹ C]raclopride to assess the DRD2 availability. In the same participants we used the [¹¹ C]raclopride PET bolus-plus-infusion method to measure the [¹¹ C]raclopride receptor binding potential (ΔBP) between an unpredictable reward condition and a sensorimotor control condition. DRD2 availability and ΔBP were assessed in MRI-based striatal regions of interest. Thermal pain and pain tolerance thresholds were assessed outside the scanner.

RESULTS

The frequency of SNP rs1062613 genotype differed significantly between groups, indicating that CC homozygotes were more frequent in FMS patients (82.6%) than in healthy controls (41.3%). Our results showed a significant main effect of SNP rs1062613 on [¹¹ C]raclopride binding potential in the right caudate nucleus indicating a higher DRD2 receptor availability for CC-genotype of this SNP. Furthermore, we found a significant group × SNP interaction on [¹¹ C]raclopride binding potential in the right putamen, indicating a higher DRD2 availability in T-carriers compared to CC genotype of SNP rs1062613 in FMS patients, whereas this effect was not present in healthy controls. However, we did not find an influence of SNP rs1062613 on reward-related DA release. In addition, there was no association between SNP rs1062613 and pain threshold or pain tolerance threshold in our data.

CONCLUSION

These preliminary results indicate that SNP rs1062613 in the serotonergic receptor HTR3A gene possibly modulates the DRD2 receptor availability.

Acute anxiety disorder, major depressive disorder, bipolar disorder and schizophrenia are related to different patterns of nigrostriatal and mesolimbic dopamine dysfunction

Dopamine (DA) receptor and transporter dysfunctions play a major role in the pathophysiology of neuropsychiatric diseases including anxiety disorder (AD), major depressive disorder (MDD), bipolar disorder (BD) in the manic (BDman) or depressive (BDdep) state and schizophrenia (SZ). We performed a PUBMED search, which provided a total of 239 in vivo imaging studies with either positron emission tomography (PET) or single-proton emission computed tomography (SPECT). In these studies, DA transporter binding, D1 receptor (R) binding, D2R binding, DA synthesis and/or DA release in patients with the primary diagnosis of acute AD (n=310), MDD (n=754), BDman (n=15), BDdep (n=49) or SZ (n=1532) were compared to healthy individuals. A retrospective analysis revealed that AD, MDD, BDman, BDdep and SZ differed as to affected brain region(s), affected synaptic constituent(s) and extent as well as direction of dysfunction in terms of either sensitization or desensitization of transporter and/or receptor binding sites. In contrast to AD and SZ, in MDD, BDman and BDdep, neostriatal DA function was normal, whereas MDD, BDman, and BDdep were characterized by the increased availability of prefrontal and frontal DA. In contrast to AD, MDD, BDman and BDdep, DA function in SZ was impaired throughout the nigrostriatal and mesolimbocortical system with an increased availability of DA in the striatothalamocortical and a decreased availability in the mesolimbocortical pathway.

Altered prefrontal correlates of monetary anticipation and outcome in chronic pain

Chronic pain may alter both affect- and value-related behaviors, which represents a potentially treatable aspect of chronic pain experience. Current understanding of how chronic pain influences the function of brain reward systems, however, is limited. Using a monetary incentive delay task and functional magnetic resonance imaging (fMRI), we measured neural correlates of reward anticipation and outcomes in female participants with the chronic pain condition of fibromyalgia (N = 17) and age-matched, pain-free, female controls (N = 15). We hypothesized that patients would demonstrate lower positive arousal, as well as altered reward anticipation and outcome activity within corticostriatal circuits implicated in reward processing. Patients demonstrated lower arousal ratings as compared with controls, but no group differences were observed for valence, positive arousal, or negative arousal ratings. Group fMRI analyses were conducted to determine predetermined region of interest, nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC), responses to potential gains, potential losses, reward outcomes, and punishment outcomes. Compared with controls, patients demonstrated similar, although slightly reduced, NAcc activity during gain anticipation. Conversely, patients demonstrated dramatically reduced mPFC activity during gain anticipation-possibly related to lower estimated reward probabilities. Further, patients demonstrated normal mPFC activity to reward outcomes, but dramatically heightened mPFC activity to no-loss (nonpunishment) outcomes. In parallel to NAcc and mPFC responses, patients demonstrated slightly reduced activity during reward anticipation in other brain regions, which included the ventral tegmental area, anterior cingulate cortex, and anterior insular cortex. Together, these results implicate altered corticostriatal processing of monetary rewards in chronic pain.

Role of central oxytocin and dopamine systems in nociception and their possible interactions: suggested hypotheses

Central oxytocin and dopamine have an important role in the process of nociception at the spinal level as well as supraspinal structures, e.g. anterior cingulate cortex, insular cortex, amygdala, nucleus accumbens, and hypothalamus. Many studies have pointed out the importance of both systems in the pain descending modulatory system and in pain-related symptoms in some chronic disorders, e.g. Parkinson disease and fibromyalgia. The interaction between oxytocin and dopamine systems has been addressed in some motivational behaviors, e.g. maternal and sexual behaviors, pair bonding, and salience. In this aspect, we propose that an oxytocin-dopamine interaction could be present in nociception, and we also explain the possible hypotheses of such an interaction between these systems.