Nanomolar oxytocin synergizes with weak electrical afferent stimulation to activate the locomotor CPG of the rat spinal cord in vitro.

Synergizing the effect of afferent fibre stimulation with pharmacological interventions is a desirable goal to trigger spinal locomotor activity, especially after injury. Thus, to better understand the mechanisms to optimize this process, we studied the role of the neuropeptide oxytocin (previously shown to stimulate locomotor networks) on network and motoneuron properties using the isolated neonatal rat spinal cord. On motoneurons oxytocin (1 nM-1 \u3bcM) generated sporadic bursts with superimposed firing and dose-dependent depolarization. No desensitization was observed despite repeated applications. Tetrodotoxin completely blocked the effects of oxytocin, demonstrating the network origin of the responses. Recording motoneuron pool activity from lumbar ventral roots showed oxytocin mediated depolarization with synchronous bursts, and depression of reflex responses in a stimulus and peptide-concentration dependent fashion. Disinhibited bursting caused by strychnine and bicuculline was accelerated by oxytocin whose action was blocked by the oxytocin antagonist atosiban. Fictive locomotion appeared when subthreshold concentrations of NMDA plus 5HT were coapplied with oxytocin, an effect prevented after 24 h incubation with the inhibitor of 5HT synthesis, PCPA. When fictive locomotion was fully manifested, oxytocin did not change periodicity, although cycle amplitude became smaller. A novel protocol of electrical stimulation based on noisy waveforms and applied to one dorsal root evoked stereotypic fictive locomotion. Whenever the stimulus intensity was subthreshold, low doses of oxytocin triggered fictive locomotion although oxytocin per se did not affect primary afferent depolarization evoked by dorsal root pulses. Among the several functional targets for the action of oxytocin at lumbar spinal cord level, the present results highlight how small concentrations of this peptide could bring spinal networks to threshold for fictive locomotion in combination with other protocols, and delineate the use of oxytocin to strengthen the efficiency of electrical stimulation to activate locomotor circuits

Effects of multiple-dose ponesimod, a selective S1P1 receptor modulator, on lymphocyte subsets in healthy humans

Stipo Jurcevic,1 Pierre-Eric Juif,2 Colleen Hamid,3 Roseanna Greenlaw,3 Daniele D’Ambrosio,2 Jasper Dingemanse2 1Department of Biomedical Sciences, University of Westminster, London, UK; 2Department of Clinical Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland; 3Division of Transplantation Immunology & Mucosal Biology, King’s College London, London, UK Abstract: This study investigated the effects of ponesimod, a selective S1P1 receptor modulator, on T lymphocyte subsets in 16 healthy subjects. Lymphocyte subset proportions and absolute numbers were determined at baseline and on Day 10, after once-daily administration of ponesimod (10 mg, 20 mg, and 40 mg each consecutively for 3 days) or placebo (ratio 3:1). The overall change from baseline in lymphocyte count was -1,292±340×106 cells/L and 275±486×106 cells/L in ponesimod- and placebo-treated subjects, respectively. This included a decrease in both T and B lymphocytes following ponesimod treatment. A decrease in naïve CD4+ T cells (CD45RA+CCR7+) from baseline was observed only after ponesimod treatment (-113±98×106 cells/L, placebo: 0±18×106 cells/L). The number of T-cytotoxic (CD3+CD8+) and T-helper (CD3+CD4+) cells was significantly altered following ponesimod treatment compared with placebo. Furthermore, ponesimod treatment resulted in marked decreases in CD4+ T-central memory (CD45RA-CCR7+) cells (-437±164×106 cells/L) and CD4+ T-effector memory (CD45RA-CCR7-) cells (-131±57×106 cells/L). In addition, ponesimod treatment led to a decrease of -228±90×106 cells/L of gut-homing T cells (CLA-integrin β7+). In contrast, when compared with placebo, CD8+ T-effector memory and natural killer (NK) cells were not significantly reduced following multiple-dose administration of ponesimod. In summary, ponesimod treatment led to a marked reduction in overall T and B cells. Further investigations revealed that the number of CD4+ cells was dramatically reduced, whereas CD8+ and NK cells were less affected, allowing the body to preserve critical viral-clearing functions. Keywords: ponesimod, multiple dose, S1P1 receptor, lymphocyte subsets, CD45RA/CCR

Oxytocin Signaling in Pain: Cellular, Circuit, System, and Behavioral Levels.

Originally confined to the initiation of parturition and milk ejection after birth, the hypothalamic nonapeptide oxytocin (OT) is now recognized as a critical determinant of social behavior and emotional processing. It accounts for the modulation of sensory processing and pain perception as OT displays a potent analgesic effect mediated by OT receptors (OTRs) expressed in the peripheral and central nervous systems. In our chapter, we will first systemically analyze known efferent and afferent OT neuron projections, which form the anatomical basis for OT modulation of somatosensory and pain processing. Next, we will focus on the synergy of distinct types of OT neurons (e.g., magno- and parvocellular OT neurons) which efficiently control acute inflammatory pain perception. Finally, we will describe how OT signaling mechanisms in the spinal cord control nociception, as well as how OT is able to modulate emotional pain processing within the central amygdala. In the conclusions at the end of the chapter, we will formulate perspectives in the study of OT effects on pain anticipation and pain memory, as well as propose some reasons for the application of exogenous OT for the treatment of certain types of pain in human patients

Host immune response determines visceral hyperalgesia in a rat model of post-inflammatory irritable bowel syndrome

Background: Irritable bowel syndrome (IBS) is associated with visceral hyperalgesia and frequently occurs after a transient gastrointestinal infection. Only a proportion of patients with acute gastroenteritis develop post-infectious IBS suggesting differences in host response to inflammatory stimuli. We aimed to investigate this concept by characterizing visceral sensitivity in two rat strains, following a chemically induced colitis. Methods: Colorectal instillation of trinitrobenzenesulfonic acid (TNBS) in aqueous ethanol was used to induce a transient colitis in Lewis and F344 rats. The colitis was characterized semiquantitatively by histology, as well as by quantitative methods using Tc-leukocytes (radioactive organ assay) and plasma IL-2 and IL-6 levels. Visceromotor response to colorectal distensions was assessed after 2 h and, 5, 14, and 28 days. Results: The colitis peaked on day 5 and dissipated to no visible mucosal damage on day 14. Cytokines were significantly increased in TNBS-treated rats at 2 h and on day 5. On day 14 cytokines were still significantly enhanced in Lewis but not Fisher rats. Both strains had a highly inflamed to non-inflamed tissue ratio at 3 h after TNBS instillation with increased uptake in Lewis compared to F344 rats. No Tc-tin-colloid-leukocytes were detected in colon samples on day 28. Visceromotor response was significantly elevated in both strains during the acute colitis (day 5), whereas only Lewis rats developed a postinflammatory (day 28) visceral hyperalgesia. Conclusion: Genetically determined host factors account for prolonged immune activation in response to a standardized inflammatory stimulus and are linked to susceptibility for a post-inflammatory visceral hyperalgesia