Conditioned Pain Modulation Is Associated with Common Polymorphisms in the Serotonin Transporter Gene

BACKGROUND: Variation in the serotonin transporter (5-HTT) gene (SLC6A4) has been shown to influence a wide range of affective processes. Low 5-HTT gene-expression has also been suggested to increase the risk of chronic pain. Conditioned pain modulation (CPM)--i.e. 'pain inhibits pain'--is impaired in chronic pain states and, reciprocally, aberrations of CPM may predict the development of chronic pain. Therefore we hypothesized that a common variation in the SLC6A4 is associated with inter-individual variation in CPM. Forty-five healthy subjects recruited on the basis of tri-allelic 5-HTTLPR genotype, with inferred high or low 5-HTT-expression, were included in a double-blind study. A submaximal-effort tourniquet test was used to provide a standardized degree of conditioning ischemic pain. Individualized noxious heat and pressure pain thresholds (PPTs) were used as subjective test-modalities and the nociceptive flexion reflex (NFR) was used to provide an objective neurophysiological window into spinal processing. RESULTS: The low, as compared to the high, 5-HTT-expressing group exhibited significantly reduced CPM-mediated pain inhibition for PPTs (p = 0.02) and heat-pain (p = 0.02). The CPM-mediated inhibition of the NFR, gauged by increases in NFR-threshold, did not differ significantly between groups (p = 0.75). Inhibition of PPTs and heat-pain were correlated (Spearman's rho = 0.35, p = 0.02), whereas the NFR-threshold increase was not significantly correlated with degree of inhibition of these subjectively reported modalities. CONCLUSIONS: Our results demonstrate the involvement of the tri-allelic 5-HTTLPR genotype in explaining clinically relevant inter-individual differences in pain perception and regulation. Our results also illustrate that shifts in NFR-thresholds do not necessarily correlate to the modulation of experienced pain. We discuss various possible mechanisms underlying these findings and suggest a role of regulation of 5-HT receptors along the neuraxis as a function of differential 5-HTT-expression

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Cancer in inflammatory bowel disease 15 years after diagnosis in a population-based European Collaborative follow-up study

AIM OF THE STUDY: To determine the occurrence of intestinal and extraintestinal cancers in the 1993-2009 prospective European Collaborative Inflammatory Bowel Disease (EC-IBD) Study Group cohort. PATIENTS-METHODS: A physician per patient form was completed for 681 inflammatory bowel disease patients (445UC/236CD) from 9 centers (7 countries) derived from the original EC-IBD cohort. For the 15-year follow up period, rates of detection of intestinal and extraintestinal cancers were computed. RESULTS: Patient follow-up time was fifteen years. In total 62/681 patients (9.1%) [41 with ulcerative colitis/21 with Crohn's disease, 36 males/26 females] were diagnosed with sixty-six cancers (four patients with double cancers). Colorectal cancer was diagnosed in 9/681 patients [1.3%] (1 Crohn's disease and 8 ulcerative colitis). The remaining 53 cancers were extraintestinal. There was a higher prevalence of intestinal cancer in the Northern centers compared to Southern centers [p=NS]. Southern centers had more cases of extraintestinal cancer compared to Northern centers [p=NS]. The frequency of all observed types of cancers in Northern and in Southern centers did not differ compared to the expected one in the background population. CONCLUSIONS: In the fifteen-year follow up of the EC-IBD Study Group cohort the prevalence of cancer was 9.1% with most patients having a single neoplasm and an extraintestinal neoplasm. In Northern centers there were more intestinal cancers while in Southern centers there were more extraintestinal cancers compared to Northern centers. In this IBD cohort the frequency of observed cancers was not different from that expected in the background population

cGMP signalling in dorsal root ganglia and the spinal cord: Various functions in development and adulthood

Cyclic GMP (cGMP) is a second messenger that regulates numerous physiological and pathophysiological processes. In recent years, more and more studies have uncovered multiple roles of cGMP signalling pathways in the somatosensory system. Accumulating evidence suggests that cGMP regulates different cellular processes from embryonic development through to adulthood. During embryonic development, a cGMP-dependent signalling cascade in the trunk sensory system is essential for axon bifurcation, a specific form of branching of somatosensory axons. In adulthood, various cGMP signalling pathways in distinct cell populations of sensory neurons and dorsal horn neurons in the spinal cord play an important role in the processing of pain and itch. Some of the involved enzymes might serve as a target for future therapies. In this review, we summarise the knowledge regarding cGMP-dependent signalling pathways in dorsal root ganglia and the spinal cord during embryonic development and adulthood, and the potential of targeting these pathways. LINKED ARTICLES This article is part of a themed issue on cGMP Signalling in Cell Growth and Survival. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.11/issueto