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The aim of this study was to evaluate the biocompatibility in rat subcutaneous connective tissue of a new zinc oxide endodontic sealer (Endomethasone N) compared to those provided by Endofill and Sealer 26. Polyethylene tubes containing the test materials were implanted into dorsal subcutaneous connective tissue of Wistar albino rats. After 7 and 42 days, the implants with the surrounding tissue were collected, fixed, and processed for histologic evaluation. Sections were evaluated for the presence of inflammatory cells (poly or monomorfonuclear), blood vessels, necrosis area, and thickness of fibrous capsule. Comparisons between groups and time-periods were performed with Kruskal–Wallis and Mann–Whitney U non-parametric tests for 5% significance level. No differences in the biocompatibility patterns among the materials for the 2 experimental periods were observed. Independently of the sealer, the tissue behavior showed a tendency to decrease the irritation effect over time. It can be concluded that all sealers are irritant, but its toxicity decreased with time. Endomethasone N showed biocompatible characteristics comparable with those provided by Endofill and Sealer 26. Microsc. Res. Tech. 76:1292–1296, 2013. © 2013 Wiley Periodicals, Inc.

The peripheral injection of phorbol myristate acetate (PMA) into the mouse paw induces nociception mediated through activation of protein kinase C (PKC). In the present study, we examine the contribution of kinin B1 receptor to PMA-induced nociception. Nociception was assessed after intraplantar injection of PMA or the B1 receptor agonist des-Arg9-bradykinin in mice. Mechanisms of nociception were studied using the combination of knockout mice, selective drugs, and measurement of B1 receptor mRNA and protein levels. Peripheral injection of PMA (50 pmol/paw) induced a nociceptive behaviour that was abolished by selective B1 receptor antagonist des-Arg9-Leu8-bradykinin or by the B1 receptor gene deletion. Moreover, PMA treatment did not alter B1 receptor mRNA levels, but greatly increased B1 receptor protein levels in the mouse paw. The injection of des-Arg9-bradykinin did not cause nociception in naive mice, but produced marked nociception in animals previously treated with a low dose of PMA (0.5 nmol/paw). The co-treatment of PMA with selective PKC or protein synthesis inhibitors, but not with p38 mitogen activated protein kinase (MAPK) or transcription inhibitors significantly reduced des-Arg9-bradykinin-induced nociception. On the other hand, the co-administration of selective PKC or p38 MAPK inhibitors, but not of protein synthesis or transcription inhibitors, reduced des-Arg9-bradykinin-induced nociception when evaluated in PMA pre-injected animals. These results suggest that the B1 receptor exerts a critical role in the nociception caused by PKC activation in peripheral tissues. Since the PKC pathway is downstream of several pro-inflammatory mediators, B1 receptor stimulation appears to contribute to the acute inflammatory pain process.

Protein kinase C (PKC) is able to phosphorylate several cellular components that serve as key regulatory components in signal transduction pathways of nociceptor excitation and sensitisation. Therefore, the present study attempted to assess some of the mechanisms involved in the overt nociception elicited by peripheral administration of the PKC activator, phorbol 12-myristate 13-acetate (PMA), in mice. The intraplantar (i.pl.) injection of PMA (16-1600 pmol/paw), but not its inactive analogue alpha-PMA, produced a long-lasting overt nociception (up to 45 min), as well as the activation of PKCalpha and PKCepsilon isoforms in treated paws. Indeed, the local administration of the PKC inhibitor GF109203X completely blocked PMA-induced nociception. The blockade of NK1, CGRP, NMDA, beta1-adrenergic, B2 or TRPV1 receptors with selective antagonists partially decreased PMA-induced nociception. Similarly, COX-1, COX-2, MEK or p38 MAP kinase inhibitors reduced the nociceptive effect produced by PMA. Notably, the nociceptive effect promoted by PMA was diminished in animals treated with an antagonist of IL-1beta receptor or with antibodies against TNFalpha, NGF or BDNF, but not against GDNF. Finally, mast cells as well as capsaicin-sensitive and sympathetic fibres, but not neutrophil influx, mediated the nociceptive effect produced by PMA. Collectively, the results of the present study have shown that PMA injection into the mouse paw results in PKC activation as well as a relatively delayed, but long-lasting, overt nociceptive behaviour in mice. Moreover, these results demonstrate that PKC activation exerts a critical role in modulating the excitability of sensory neurons.

Objective: This study examines the pro-inflammatory action caused by subcutaneous (s.c.) injection of the bee venom (BV) Apis melifera in the rat paw.¶Methods: Male Wistar rats were used. The venom of Apis melifera was injected s.c. into the rat paw and the oedema formation and the activity of myeleperoxidase (MPO) were measured.¶Results: Subcutaneous injection of BV caused dose-and time-dependent paw oedema (ED50 of 1.5 μg/paw) with peak at 30 min. The MPO activity increased about 1.6, 4.2 and 8.9 folds at 0.5, 4 and 6 h after s.c. injection of BV. The mast cell degranulating drug 48/80, pyrilamine or metysergide, inhibited BV-mediated oedema formation (88, 62 and 96 %, respectively). Likewise, L-NAME, the NK1 antagonist FK 888, the B1 des-Arg9-[Leu8]-BK or B2 kinin antagonist Hoe 140 also antagonised the paw oedema induced by BV (60, 59, 49, and 49 %, respectively). SR48968 and SR14280, respectively NK2 and NK3 antagonists and also indomethacin, inhibited by 31, 29 and 22 %, respectively BV-induced oedema formation. In contrast, the PAF antagonist WEB 2086 or valeryl salycilate, did not affect the BV-induced paw oedema. The levels of MPO were inhibited by compound 48/80, cyproheptadine, Hoe 140, or by des-Arg9[Leu8]-BK (85, 61, 59, and 53 %, respectively) measured 6 h after.¶Conclusion: These results indicate that the BV from Apis melifera causes a marked dose-and time-dependent oedema formation in the rat paw, an effect that is accompanied by intense leukocyte migration. The pro-inflammatory response induced by BV is mediated by several mechanisms, namely the release of histamine and/or serotonin from mast cells, activation of H1 histamine receptor, production of nitric oxide, the involvement of kinins through the activation of B1 and B2 receptors, and also tachykinins acting at NK1 receptor or and to a lesser extent at NK2 and NK3 receptors.