SummaryBuprenorphine is a potent analgesic commonly used clinically in humans and rodents experiencing severe pain. However, effects of therapeutic doses on locomotor activity and the cardiovascular system have not been studied in conscious animals. The effects of buprenorphine were therefore evaluated in this study using telemetric monitoring in conscious animals. Telemetry transmitters were implanted in the peritoneal cavity of Wistar rats with a pressure catheter in the aorta and electrodes for electrocardiogram (ECG) recording subcutaneously. After a single subcutaneous administration of saline, each rat was administered single subcutaneous doses of 0.006, 0.03 or 0.15 mg/kg body weight (bw) of buprenorphine. During a 10 h period after administration, buprenorphine induced a varying dose-dependent increase in body temperature, heart rate, dP/dt and systolic-diastolic blood pressure, as well as a corresponding decrease in QT time. At high dose, however, QT time was still decreased 24 h post-administration, but no arrhythmias or visual changes were observed in the ECG complex. Body temperature and heart rate increased at the high dose of buprenorphine, even at 20 -24 h after administration. Moreover, the high dose of buprenorphine induced a biphasic response in diastolic blood pressure, with an early and pronounced increase that, at 14 h after administration, reversed to a decrease, failing to normalize within 24 h post-dosage. The results indicate that buprenorphine induces long-lasting effects (such as body temperature and cardiovascular effects) in the rat after a single subcutaneous dose at 0.15 mg/kg bw.

BackgroundAtopic dermatitis (AD) is a chronic inflammatory skin disease characterized by highly pruritic eczematous lesions that are commonly treated with topical corticosteroids and calcineurin inhibitors. Side-effects and safety concerns associated with these agents restrict their use, and new, safe treatment options are therefore needed. Recent reports suggest that serotonin, i.e. 5-hydroxytryptamine (5-HT) and the 5-HT2 receptor family may contribute to inflammation and pruritus in the skin. The objective of this particular study was to investigate the 5HT2B receptor antagonist AM1030 with respect to its anti-inflammatory profile and potential.MethodsAM1030 was tested in a set of distinct human and rodent in vitro and in vivo models, differing with respect to e.g. T cell involvement, triggering stimulus, main read-outs and route of drug administration. The in vitro systems used were staphylococcal enterotoxin A (SEA)-stimulated human peripheral blood mononuclear cells, lipopolysaccharide (LPS)-stimulated human primary monocytes, LPS-stimulated human THP-1 monocytes and LPS-stimulated mouse primary macrophages. The in vivo systems used were LPS- and SEA-induced cytokine production in the mouse, antigen-induced arthritis in the rat, glucose-6-phosphate isomerase-induced arthritis in the mouse and delayed-type hypersensitivity reaction in the mouse. In addition, different cell populations were analyzed with respect to their expression of the 5-HT2B receptor at the mRNA level.ResultsAM1030 significantly reduced both T cell-dependent and T cell-independent inflammatory responses, in vivo and in vitro. Due to the low or absent expression of the 5-HT2B receptor on T cell populations, the influence of AM1030 in T cell-dependent systems is suggested to be mediated via an indirect effect involving antigen-presenting cell types, such as monocytes and macrophages.ConclusionBased on the wide range of model systems used in this study, differing e.g. with respect to species, T cell involvement, triggering stimuli, route of drug administration and read-outs, our results suggest a broad anti-inflammatory effect of AM1030 and identify the 5-HT2B receptor as a promising future target for anti-inflammatory intervention, e.g. in AD.

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Background Serotonin (5-HT) is well known as a central neurotransmitter, but has important functions also in the periphery, e.g. as a regulator of vascular tone, platelet aggregation and cytokine expression. Objectives The aim of this study was to investigate the potential influence of selective 5-HT2B receptor antagonists on inflammation and inflammatory pain. For this purpose, AnaMar´s proprietary compounds were studied in vitro and in vivo. Methods In vitro, IL-6 production: Primary synoviocytes were isolated from pannus tissue obtained from female, Dark Agouti rats with antigen-induced arthritis and used for experiments after seven days in culture. The cells were stimulated with 5-HT and LPS, in the presence of the 5-HT2B receptor antagonists (0.1-10 µM). After three days incubation, supernatants were collected and the IL-6 content measured with ELISA. In vivo, systemic inflammation: Female BALB/c mice were pre-treated perorally with the 5-HT2B receptor antagonists (3-30 mg/kg). Thirty minutes later, LPS was administered systemically by intra-peritoneal injection. After 90 minutes, blood was collected and cytokines measured in plasma with ELISA. In vivo, inflammatory pain: Male Sprague-Dawley rats were pre-treated perorally with the 5-HT2B receptor antagonists (3-30 mg/kg). Sixty minutes later, formalin was injected subcutaneously into the dorsum of the right hind paw to induce pain. Pain responses were recorded by measuring the cumulative time of nociceptive behaviour per unit of time. Results AnaMar´s 5-HT2B receptor antagonists dose-dependently decreased the production of IL-6 from primary rat synoviocytes. Further, the compounds potently decreased the production of TNF-α triggered by systemic LPS injection in mice. In the inflammatory pain model, the compounds significantly reduced the pain response. Conclusions The 5-HT2B receptor antagonists reduced inflammatory cytokine production and pain responses. The results strongly support that approaches targeting 5-HT2B receptor signaling could have therapeutic potential in conditions associated with inflammation and inflammatory pain. It remains to be investigated whether the effect on inflammatory pain is mediated through a suppressed production of inflammatory cytokines, a direct effect on peripheral neurons, or a combination of these. References Mössner R, Lesch KP: Role of serotonin in the immune system and in neuroimmune interactions, Brain Behav Immun 1998, 12 (4): 249-271. Disclosure of Interest N. Palmqvist Employee of: AnaMar AB, C. Wenglén Employee of: AnaMar AB, A. Sjödin Employee of: AnaMar AB, A.-C. Ryde Employee of: AnaMar AB, M. Siller Employee of: AnaMar AB, H. Arozenius Employee of: AnaMar AB, A. Mathisson Employee of: AnaMar AB, C. Klint Employee of: AnaMar AB, A. Pramhed Employee of: AnaMar AB, L. Pettersson Employee of: AnaMar AB, G. Ekström Employee of: AnaMar AB