Opioid peptides and arthritis

56 response by 52 _+12 (p 50.01) after 360 s occlusion. The effect of intradermal injection of saline vehicle and the nitric oxide synthesis inhibitor L-NMMA (1 x lo-’ moles/site) were also studied. L-NMMA, which reduced basal skin blood flow, partially inhibited hyperaemic responses after 90 s occlusion (-12%) but had no significant effect on hyperaemia following longer occlusions. The results show that sensory neuropeptide depletion using capsaicin can significantly inhibit reactive hyperaemia. This provides further evidence to suggest that postocclusion reactive hyperaemia in human skin is in part mediated by a local reflex involving sensory nerves.’ 1. Larkin, S. W. and Williams, T. J. Evidence for sensory nerve involvement in cutaneous reactive hyperemia in humans. Circ. Res. 1993: 73: 147-154. C9/4 Kinins and Tachykinins in Neurogenic Inflammation in the Airways P. Geppetti*, C. Bertrand?, F. L. M. Ricciardolo$ and J. A. Nadel: *Institute ofInternal Medicine IV, University ofFlorence, Italy, TDepartment of Asthma and Allergy, Ciba-Geigy, Base& Switzerland, fCardiovascular Research Institute, University of California, San Francisco, California, USA Tachykinins released from airway sensory nerves cause a series of in&mmatory responses similar to responses evoked by exposure to antigen. However, conflicting results have been reported on the role of sensory nerve activation and tachykinin release in the anaphylactic response in the airways. We provided evidence that tachykinins released from sensory nerves play a role in the plasma extravasation evoked by aerosolized ovalbumin in the trachea and nasal mucosa of sensitized guineapigs, because these responses were increased by the neutral endopeptidase inhibitor, phosphoramidon, and were reduced by the NK, tachykinin receptor antagonist, CP-96,345. The bradykinin Bz antagonist, HOE 140, reduced plasma extravasation evoked by ovalbumin in the trachea and nasal mucosa. The inhibition evoked by HOE 140 was similar to the inhibition evoked by the combination of HOE 140 and CP-96,345. Bradykinin is a powerful stimulant of sensory nerves, it releases sensory neuropeptides from airway tissue and kinins are released in the airway lumen after exposure to antigen. We propose that in the guinea-pig airways kinins released in an early phase of the anaphylactic reaction stimulate sensory nerves and release tachykinins that contribute in part to the plasma extravasation in response to antigen. C9/5 Modulation of Mucosal Exudation in the Mouse Airways by Capsaicin-sensitive Nerves T. L. Buckley and F. P. Nijkamp Department of Pharmacology, Faculty of Pharmacy, Utrecht University, 3508 TB Utrecht, The Netherlands

NEUROPEPTIDES

Mucosal exudation is the passage of plasma proteins across the epithelial barrier into the airway lumen. This process could be important in delivering leukocytes and bioactive mediators into the airway lumen under pathophysiological conditions (i.e. during an asthmatic reaction). In this study, mucosal exudation @l/lung) associated with a pulmonary delayed type-hypersensitivity (DTH) reaction was measured using Evans blue dye as a tracer molecule. The DTH reaction was induced by skin-sensitizing mice with dinitrofluorobenzene (DNFB; 0.5%). Control mice were treated with the vehicle solution (acetone: olive oil, 1:4). 5 days later all mice were challenged intranasally with dinitrobenzene sulphonic acid (DNS). A significant (p < 0.01) enhancement in mucosal leakage was observed 24 h after the challenge in DNFB-sensitized mice (vehicle group 9.19 + 1.37 pl: DNFB group 20.22 f 3.29 pl mean 4 SEM n = 6-8 mice/group). This increase in mucosal exudation was virtually abolished by the NK, antagonist RP67580 (5. 1O-9mol/site) which was administered 5 min before and 2 h after the challenge (vehicle group 12.54+ 1.37pl:DNFBgroup 13.96f2.91 plmean f SEM n = 5-6 mice/group). In contrast, the CGRP antagonist CGRP,, had no effect on this reaction. Surprisingly, capsaicin pretreatment (14 d before sensitization) markedly enhanced the mucosal leakage response 24 h after the challenge, however this increase was observed in vehicle- and DNFB-treated mice (vehicle group 46.5 f 6.5 ~1: DNFB group 73.68 + 9.9 ~1 mean f SEM n = 5 mice/group). In conclusion, tachykinins appear to be important in mediating leakage across the epithelial barrier, however other neural mediators could be involved in protecting the airways against mucosal exudation. We would like to thank Rhone-poulenc Rorer for the RP67580.

C9/6 Opioid Peptides and Arthritis C. Stein, M. SchHfer, A. H. S. Hassan, I. Antonijevic and S. A. Mousa Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD 21287-5354, USA and Ludwig-MaximiliansUniversitat, Miinchen, Germany Neuropeptides are prominent in peripheral mechanisms not only sustaining but also counteracting inflammation and pain. The inhibitory role has emerged more recently during the discovery of peripheral analgesic effects of exogenous opioids, particularly in inflammatory conditions such as arthritis. In the course of these studies, opioid receptors located on peripheral terminals of sensory nerves have been identified and shown to mediate antinociceptive effects. In search of the endogenous ligands of these receptors, opioid peptides and messengerRNA encoding their precursors were discovered in immune-competent cells within inflamed tissue ofrats and arthritic synovia of humans. The fact that immunosup-

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pression entailed enhanced inflammatory pain led to the hypothesis that opioid peptides are released from immune cells, occupy their receptors on sensory nerves and elicit analgesia, presumably by inhibiting afferent and/or efferent functions of these nerves. This paper will give an overview of experimental and clinical studies expounding on this concept and will discuss current research into mechanisms of opioid release from immune cells, the passage of opioid peptides across the perineural barrier and the axonal transport of opioid receptors towards peripheral terminals of sensory nerves.

C9/7 Acute Monoarthritis

of the Cat’s Knee Joint Alters the Proportion of CGRPimmunoreactive Articular Afferents U. Hanesch, B. Heppelmarm and R. F. Schmidt Physiologisches Institut, Rontgenring 9, D-97070 Wtirzburg, Germany CGRP seems to play a role in the processing of nociceptive information and in pathophysiological aspects of neurogenic inflammation. Under normal conditions it is expressed in one third of cat’s articular afferents many of which are nociceptors. We therefore examined alterations in the number of CGRP synthetising articular afferents after inflammation-induced activation of nociceptors. Cat’s articular afferents were fluorescent labelled by injecting Fast Blue into the synovial cavities of both knee joints. After 4 d the inflammation was induced in the left knee joint by injecting kaolin and carrageenan. 32 h postinoculation the animals were perfused and the dorsal root ganglia L&L7 were cut. In control ganglia 41 .l% of 669 fluorescent labelled articular afferents showed a CGRP-like immunoreactivity. In cats with a unilateral inflammation CGRP was found on the unaffected side in 40.7% of 16 18 fluorescent cells. On the inflamed side the proportion of CGRP-synthetising perikarya increased to 52.3% of 1755 labelled cells representing an increase of about 29%. These data suggest that already in acute stages of inflammation the synthesis of CGRP is induced in a subgroup of articular afferents. In consequence the density of CGRP-containing and -releasing terminals is enhanced in the knee joint and in the spinal cord.

C9/8 Is Substance P the Mediator of Capsaicininduced Plasma Protein Extravasation? F. F. Y. Lam and J. K. M. Chan Department of Pharmacology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong This study investigates if substance mediator

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of capsaicin-induced

P (SP) could be the plasma protein extravasa-

tion (PE) in the rat knee joint by protein micro-turbidimetry.’ SP (4OOpmol/min)producedtransient PE (0.158 f0.03 mg/ml) whereas capsaicin (40 nrnohmin) produced sustained PE (0.129 + 0.0 14 mgml) when perfused into rat knee joints. Perfusion with 400 pmol/min FKK888 (NK, antagonist, Fujisawa, Japan) 40 min prior to co-perfusion with capsaicin (40 nmol/min) did not abolish the capsaicin-induced PE although it was significantly (p < 0.05) reduced. A similar reduction on the capsaicin response was observed when capsaicin was co-perfused with either 400 pmol/min SR48968 (NK, antagonist, Sanofi Recherche, France) or 400 pmol/min FK224 (NK,/NK, antagonist, Fujisawa, Japan). These findings indicate that capsaicin-induced PE in the rat knee joint is mediated partially by SP released, however, other neuropeptides released by capsaicin could also have significant contributions. 1. Scott, D. T., Lam, F. Y. and Ferrell, W. R. Time course of

substance P induced protein extravasation in the rat knee joint measured by micro-turbidimetry. Neurosci. Lett. 199I ; 129: 7476.

P9/1 Functional Ablation of Capsaicin Sensitive Afferent Nerves Impairs Healing of Chronic Gastric Ulcers in Rats D. Renzi*, M. Tramontanat, A. Calabrb*, C. Panerai*, S. Milani*, C. Surrenti* and S . Evangelistat *Gastroenterology Unit, Department of Clinical Pathophysiology, University of Florence and fMalesci Pharmaceuticals, Italy Current evidence indicates that capsaicin sensitive (nociceptive) afferent neurons play a crucial role in acute gastroprotection. However, whether they also influence healing of chronic gastric ulcers remains to be clarified. Therefore, the purpose of this study was to investigate the effects of ablation of sensory neurons on acetic acidinduced chronic gastric ulcers in rats. Functional ablation of sensory neurons was induced by a neurotoxic dose of capsaicin (50+50 mg/kg S.C.over 2 d) before the experiments and the effects of pretreatment were examined by computerized imaging analysis of the ulcerated area, histological examination, and neuropeptide radioimmunoassay. Afferent nerve ablation by capsaicin produced a significant increase in the ulcer area at 1 and 2 weeks after acetic acid injection @ C.0.05 at each time interval). The delay in ulcer healing was associated with a marked and persistent decrease in tissue CGRP-like immunoreactivity levels, whilst tissue concentrations of VIP, which in the stomach is almost completely ofintrinsic origin, were unaffected by capsaicin pretreatment. Histologically, as compared to control rats, capsaicin-desensitized animals only differed for a slight increase in the inflammatory infiltrate during the early phase of ulcer formation. These findings